Electromagnetic tool using slotted point dipole antenna

Abstract

An electromagnetic tool using a slotted dipole antenna is presented. The dipole may be placed in a slot on the drill collar. The receiver or transmitter antenna is composed of one or more slots. The dipole consists of a ferrite rod together with electrical conductors placed above and below the ferrite. Wires may be connected such that wire current forms a loop around the ferrite rod. When a set of slots is used for an antenna, wire holes are formed between the slots. Effectively, a single wire can be used to travel over all of the ferrite bars in the group, and then steer to travel under all of the bars. The two wire sections are located in a wire hole connecting two adjacent slots. Current amplitudes in the two sections are the same and flow in opposite directions. No net current exists in the wire in the wire hole.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application number 202080089723.7, application date October 26, 2020, and invention name “Electromagnetic tool using slotted point dipole antenna”. Background Art

[0002] In recent years, information about the properties of the formations traversed by the wellbore has been collected during the drilling of oil and gas wells. This information is used to evaluate the geological characteristics of the formations. Recently, this information has also often been used specifically or primarily to determine the position of the well section being drilled relative to the formation geological structure. The position information relative to the geology is used to determine the next action of the drilling process so that the next section of the well is placed in the hydrocarbon area to maximize production. The process of measuring formation parameters during drilling and then using the measured values ​​to determine the formation structure relative to the borehole to help guide the well is called geosteering. Regional formation geological structures are called formation structures or formations. Even if the geometry is the same but one or more geometric volumes have different geology, the two formations are different. Thereafter, the formation characteristics or formation parameters include geological characteristics, geometric structure information, and the relative position between the well section and the formation geological structure.

[0003] The measurement of formation properties while drilling was first known as formation evaluation measurements while drilling (FEMWD). Later the term logging while drilling (LWD) was used.

[0004] One of the formation properties measured by LWD systems is resistivity. This parameter quantifies how difficult it is to conduct an electric current in a formation. The porous spaces in a potential hydrocarbon-bearing formation are filled with either hydrocarbon fluids or brine. Hydrocarbon fluids (i.e., oil and gas) are highly resistive, while brine is conductive. By measuring resistivity, an estimate of the percentage of porous space that contains oil and gas in a well section in a homogeneous formation can be determined.

[0005] Wave propagation resistivity tools have been used for LWD resistivity measurements. A transmitter antenna and a receiver antenna are built on a portion of the drill collar. Electromagnetic waves are transmitted from the transmitter antenna of the tool into the borehole. The waves propagate through space including the borehole environment and the formations surrounding the borehole. The wave signal is measured at the receiver antenna located on the drill collar at a certain distance from the transmitter. The phase delay and amplitude attenuation of the receiver wave signal relative to those of the transmitter are obtained from the measured values ​​of the wave signal at the receiver when a transmitter transmits at one frequency. The phase delay may be referred to as phase. The amplitude attenuation may be referred to as attenuation or amplitude. The phase and attenuation are functions of the frequency, the distance between the transmitter and the receiver, the borehole geometry and its properties, and the electromagnetic properties of the formations near the borehole.

[0006] In electronics, the term "gain" is used to refer to the scaling factor of power levels and phase shifts. The scaling factor can be greater or less than 1. Gain is usually represented by a complex number. In general, amplification or attenuation systems are often used in signal generation or signal detection processes. Gain is generated to improve signal quality and measurement accuracy. Uncontrolled gain exists in transmitters and receivers from antenna structures and circuits. Uncontrolled gain can also come from errors in the amplification or attenuation system that deviates from the designed behavior. Unless otherwise specifically stated below, the term gain only refers to uncontrolled gain.

[0007] In addition to being affected by borehole and formation parameters, phase and attenuation measurements are also affected by the gain in the transmitter and receiver. Using digital electronics, the transmitter is commanded to turn on at a known power level and phase. The actual power level and phase in the transmitter are offset by the gain in the analog portion of the antenna that transmits the electromagnetic wave. Similarly, there is gain between the wave signal at the receiver location and the analog-to-digital conversion stage of the receiver system. This gain drifts with temperature. Gain and the associated offsets were even more pronounced in early resistivity tools that used primarily analog electronics. The analog electronics had no knowledge of the nominal phase value of the transmitter signal. The frequency range and geometry used by the antennas on resistivity tools were such that the radiation resistance of the antennas was relatively small. Uncontrolled gain variations in the antennas depended primarily on small changes in the antenna's construction and the characteristics of the electronics components and materials used in the antenna. Gain drifts widely over the temperature range experienced by the resistivity tool. Gain can be non-repeatable between antennas and is not easily tracked and calibrated. The effects of gain on phase and attenuation must be eliminated in order to extract information about formation properties.

[0008] Multiple transmitter-receiver pairs operating at one or more frequencies are used to create measurement combinations. Each combination is designed to be most sensitive to specific characteristics of a specific area near the resistivity tool. For example, a LWD resistivity tool used in a drilling operation may include a transmitter and two receivers. The two receivers are closely spaced and are located a certain distance from the transmitter along the axis of the tool as part of the drill string. When the transmitter is powered on, the phase difference and amplitude ratio between the signals at the receivers are, in most cases, most sensitive to the resistivity of the formation area away from the borehole and are least affected by the characteristics of the borehole. This ideal characteristic is called borehole rejection in the industry.

[0009] These combinations are also used to overcome imbalance or drift in the electronics (i.e., gain in the transmitter and receiver antennas). The differential measurement between a pair of receivers described in the previous paragraph is not directly affected by the transmitter power level or phase. As long as the power level is above the signal-to-noise ratio requirement, the receiver differential measurement is not affected by the transmitter gain. Therefore, there is no need to calibrate the transmitter. The differential measurement also eliminates the effect of the common gain of the two receiver systems. However, the gain in the two receivers may be different and drift differently with temperature. To overcome the effect of imbalance in the receivers, a second transmitter with the same frequency is placed on the opposite side of the two receivers along the drill collar axis from the first transmitter. That is, the two receivers are between the two transmitters. The phase difference and amplitude ratio between the signals at the first receiver and the second receiver from the first transmitter are measured. The first transmitter is then turned off and the second transmitter on the other side of the receiver is turned on. The phase difference and amplitude ratio between the signals at the second receiver and the first receiver are obtained. The two phase differences in degrees and the two amplitude ratios in dB are averaged respectively. The phase error caused by the difference between the two receiver gains has the same amplitude in the two phase difference measurements, but opposite signs. The averaging of the two phase differences completely eliminates the error due to receiver gain differences. Errors in the amplitude ratio from the receiver gain differences are eliminated in a similar manner. The averaged phase difference is referred to as the compensated phase difference or compensated phase. The averaged amplitude ratio is referred to as the compensated amplitude ratio or compensated attenuation. Although the gain in an antenna varies from antenna to antenna and is very sensitive to temperature, the gain in a particular antenna is very stable over a measurement cycle. In a drilling environment where the temperature changes slowly relative to the tool measurement cycle, there is no measurable difference in the gain in the receiver between the first and second transmitter transmission sequences. The compensated measurements are not directly affected by the gain in either the transmitter or the receiver.

[0010] Even if systematic errors due to antenna gain are eliminated or greatly reduced through measurement combinations such as compensating phase and attenuation, random noise in the antenna electronics can cause measurement errors. Most LWD tools employ common techniques to improve the signal-to-noise ratio and widen the signal averaging window. The antenna is tuned to resonate at its operating frequency. This greatly increases the signal level and narrows the noise band. Transmitter power levels are limited by the limited power available for the operation of resistivity tools in the well. In addition, because LWD tools operate while the drill string moves, the signal averaging window needs to be small enough so that the tool moves only a small amount during the measurement cycle. Further improvements in the signal-to-noise ratio need to come from improvements in antenna design.

[0011] The raw tool measurements, including the measurement combination, are converted to measurements of formation properties by a conversion function. The conversion function is the inverse tool response function. In very limited cases, the tool response function consists of a table of experimental data. Since the structure and geology of the formations encountered by the LWD resistivity tool may be very large and complex in scale, it is impractical to establish a collection of experimental devices to obtain the response of the tool in all these environments. In most cases, the tool response function or data is generated by modeling how the electromagnetic waves generated by the transmitter propagate in various borehole and formation structures based on the physical laws governing the behavior of electromagnetic waves. The receiver output is calculated for each borehole and formation structure and for each transmitter-receiver antenna pair in the tool. The receiver signals (i.e., receiver voltage or receiver current or receiver reading) calculated from all antenna pairs are processed and combined in exactly the same way as they are done in the tool for each borehole and formation structure. The modeled tool response is compared with the tool measurement value. The best match is determined. The formation parameters associated with the best match in the model are considered as tool measurements.

[0012] The converted measurements are the output of the LWD system. They are tool measurements or data. The raw tool measurements (such as compensated phase and attenuation) are considered as intermediate results of the resistivity tool. The final tool data is derived from the intermediate results.

[0013] The impracticality of setting up extensive experimental setups to obtain tool response functions is one reason why theoretical modeling is used to calculate tool response functions for data conversion and interpretation. Another reason is that a laboratory experimental setup may not accurately replicate the environment that an LWD resistivity tool experiences in a well. An LWD resistivity tool is a precision instrument. At temperatures up to 175 degrees Celsius, several manufacturers achieve a resolution of 0.0002 decibels (dBs) in attenuation measurements. This is equivalent to 23 parts per million. Therefore, the amplitude measurement of the receiver voltage needs to have five significant digits in many cases. Similarly, the phase measurement also needs to have five significant digits. The accuracy of attenuation measurements achieved by some manufacturers is less than 0.005 dBs at temperatures below 175 degrees Celsius.

[0014] In a well, the LWD tool is installed near the bottom of the drill string. For example, it can be from a few meters to tens of meters from the bottom of the drill bit. The length of the drill string above the resistivity tool is approximately the entire length of the well that has been drilled at that time. In areas where resistivity measurements are important, the length of the well can be hundreds of meters to thousands of meters. Even if a resistive oil-based drilling fluid is used in the well, the tool is well grounded because the contact area between the drill string and the earth is very large. In the cylindrical model used to calculate the tool response, the drill string, borehole, and formation are assumed to extend infinitely in both directions in the axial direction of the well section near the tool. The tool is assumed to be perfectly grounded to the surrounding environment in the model. In terms of grounding, the model closely matches the operating environment of the LWD tool during drilling.

[0015] In the laboratory, the earth formation is usually simulated by a water tank. The resistivity of the water is determined by its salinity. The box resistivity is usually chosen at the lowest limit of the design resistivity range. This limit is usually equal to or close to 0.2Ohm-M. Salt is added to the water to achieve this resistivity. The receiver signal is lowest at this limit for a given transmitter power. The most challenging signal-to-noise ratio point is a good test for any tool. At this resistivity, the size of the box required to simulate an infinite earth formation is also minimal, because electromagnetic signals attenuate faster in a more conductive (lower resistivity) medium. Only a limited length of the tool segment is vertically immersed in the middle of the box to simulate the tool in the formation as part of an almost infinite length drill string. In the absence of any drilling structure, the tool surface has good electrical contact with the salt water body in the box. The tool segment itself can be considered an excellent ground rod. The tool is well electrically grounded to the water, which may otherwise be poorly grounded to the earth. This experimental setup with the lowest water resistivity can simulate the actual tool working environment in low resistivity formations. Axial dimensions of truncation in the drill string or earth formation in the setup do not directly affect the experimental results because the differential measurements between a pair of closely spaced receivers are insensitive to the electromagnetic properties of truncated and altered regions in the experimental setup. The truncated drill string and formation are replaced by air above the box and land below the box. A properly functioning tool is expected to produce results that match the model predictions. This experiment is performed frequently and its results are used as a quality assurance point.

[0016] To experimentally obtain the tool response of a borehole in the formation, a thin layer of plastic tubing can be used to simulate a borehole. The tube is mounted vertically in the middle of a box. The resistivity tool is placed in the middle of the tube, isolating the fluid inside the tube from the water in the box. The fluid acts as the drilling fluid (also called drilling mud) and the water in the box is the formation. The diameter of the tube can be selected to match the diameter of the borehole. The salinity of the fluid inside the tube is varied to produce various drilling mud resistivities for the drilling operation. This experimental setup would appear to accurately simulate the tool response of a borehole in the formation, or be a convenient way to test the quality of tool measurements in a borehole; however, this is not the case.

[0017] The plastic material of the tube is an electrical insulator. The thin insulating cylinder does not significantly affect the propagation of electromagnetic waves generated by the tool with an axial antenna in a cylindrically symmetrical environment. However, the insulation destroys the almost perfect direct grounding of the tool to the water in the box. This problem cannot be solved simply by electrically connecting one end of the wire to the tool and the other end to a small conductive rod immersed in the box. There may still be a small resistance between the tool and the water in the box. In addition, this grounding problem cannot be easily solved by grounding the water and the tool separately. The electronics used to power the tools in the laboratory are usually already grounded. The box is usually made of an electrically insulating material (such as fiberglass). The water in the box is not directly grounded if a relatively large metal structure that may interfere with the tool measurement is not used. As a precision instrument, the resistivity tool is designed to be very sensitive to small signals. In a low resistivity box, the receiver voltage signal may be drowned by the noise generated by the imperfect grounding of the tool to the water in the box.

[0018] For tool response, modeling results are more accurate than laboratory experimental data in many cases. Experimental setups may introduce noise that is not present in the downhole environment. Models, on the other hand, can match the real environment very well.

[0019] Tool response modeling can play a key role in all stages of the tool life cycle. In the R&D phase, model simulations can be used to determine tool parameters (such as frequency, antenna spacing, and measurement combinations). When the tool is manufactured, the modeling results are compared with data from tool testing to determine the quality of tool performance. In the commercial operation of the tool, modeling and its results are used for data conversion and interpretation.

[0020] Some factors that affect antenna gain are not included in the modeled tool response due to complexity and intractability. For example, the effect of antenna gain on tool measurements is eliminated by using a combination of measurements such as compensating for phase difference. Some tools have antenna configurations and / or measurement combinations that are not affected by antenna gain. For these tools, the output vs. temperature for each measurement is typically established by subjecting the tool to a range of temperatures. Each measurement is corrected for the effect of temperature based on a temperature function of the measurement. Temperature correction is appropriate for antenna systems where gain vs. temperature is repeatable and real-time temperature can be accurately measured.

[0021] Even though a great deal of the borehole and formation structure can be modeled, many details of the resistivity tool construction cannot be modeled on the computer. The structures of the tool's antenna in the tool model are much simpler than those of the actual hardware. In addition, the electrical and magnetic permeabilities of the materials used for the antenna structure may not be exactly constant over the temperature range of the tool. They also vary slightly from tool to tool and are not precisely known. In order to calculate the tool response on the computer, model simplifications may be necessary. The modeled tool is an approximation of the actual tool. Since the modeled tool response is used to convert the raw tool measurements into the final tool data, the difference between the modeled tool response and the response of the actual tool can cause errors in the measurements of formation properties.

[0022] Besides ruggedness and reliability, two other considerations when designing antennas for LWD wave propagation resistivity tools are efficiency and model tractability.

[0023] LWD tools are usually cylindrical in shape so that they can be installed into the drill string and become part of it. The cylindrical structure that is the base of the LWD tool is called a joint. The direction parallel to the centerline of the cylinder is the axial direction. The direction perpendicular to the centerline is called the transverse axial or transverse direction.

[0024] FIG1 is a schematic side view of a steel joint 1 and antenna wire 4 of an antenna section of one of the earliest resistivity tools in the prior art. FIG2 is a cross-sectional view of the structure of FIG1 plus the antenna in a plane containing the cylindrical axis of the joint 1. Typically, the steel joint 1 is the antenna section. A circumferential groove 2 is cut from the steel joint 1. Some insulating material 3 ( FIG2 ) is placed around the deepest surface 6 of the groove 2 to keep the antenna wire 4 at a distance from the deepest surface 6. The antenna wire 4 is covered and protected by a radome 5 made of a non-conductive material such as fiberglass.

[0025] In US Pat. No. 5,138,263 to Towle (hereinafter referred to as "Towle" and incorporated herein by reference in its entirety), ferrite material having high magnetic permeability and negligible hysteresis is used as insulating material 3 in Fig. 2. Ferrite greatly improves antenna efficiency.

[0026] In order to improve the mechanical reliability of the antenna section, a steel shell with several slots is used as the radome 5 in Figure 2. The shell covers the entire circumference and is fastened to the joint by bolts. The slots of the steel shell are along the axial direction of the joint.

[0027] The use of ferrite and steel housing greatly improves the reliability and efficiency of the antenna design depicted in Figures 1 and 2. However, the improvement is not significant enough.

[0028] The steel shell of the radome 5 may be damaged or the bolts may become loose. The antenna segments still require frequent repairs and rebuilding. The circumferential groove 2 in Figure 1 weakens the mechanical strength of the steel joint 1. This weakening makes it difficult to build resistivity tools with small cylinder diameters.

[0029] Faraday's law of induction and Ohm's law of conduction induce an alternating current in the antenna wire 4 in FIG. 1 to induce a current on the surface 6 of the steel joint 1 at the deepest part of the annular groove 2 below the antenna wire 4. Since steel has high conductivity, the current is in a thin layer at the surface. The induced current generally flows in the opposite direction to the current in the antenna wire 4. Therefore, the induced current can be qualitatively regarded as a line current on the surface 6 of the deepest part of the circumferential groove 2 below the antenna wire 4, and can be approximately equal in magnitude and opposite in sign to the current in the antenna wire 4. That is, the induced current roughly forms an image of the current in the antenna wire 4. However, the total amount and distribution of the actual induced current depends on the conductivity of the steel, the gap between the antenna wire 4 and the surface 6 of the deepest part of the circumferential groove 2 in FIG. 1 and FIG. 2. In addition, the shape of the antenna wire 4 may not be perfectly circular and / or concentric with the steel joint 1. The presence of ferrite between the antenna wire 4 and the surface of the steel joint 1 may also affect the induced current distribution.

[0030] For the transmitter antenna, the primary current in the antenna wire 4, the induced current in the steel joint 1, and the aligned magnetic dipoles in the ferrite material form the emission source of the antenna assembly. The total impedance of the transmitter antenna is affected by the presence of the induced current in the steel joint 1. In particular, the resistance of the antenna assembly is a combination of the resistance in the antenna wire 4 and the resistance seen by the induced current in the steel joint 1. For a given power output of the transmitter electronics, the current in the antenna wire 4 of the transmitter antenna is determined by the total impedance of the antenna assembly. Similarly, the current measured by the receiver electronics in the antenna wire 4 of the receiver antenna is determined by the electromagnetic field at the receiver location and the total impedance of the receiver antenna assembly.

[0031] The antenna is tuned to resonate at the operating frequency. Since the radiation losses are small, the peak of the resonance is almost entirely determined by the resistance of the antenna components. It is important to make the resistance of the antenna components as small as possible.

[0032] A steel joint 1 of an antenna segment, such as the one depicted in Figures 1 and 2, is modeled as a perfect cylinder without a circumferential groove 2 cut to accommodate the antenna wire 4. A schematic diagram of the modeled antenna segment is depicted in Figure 3 .

[0033] FIG3 illustrates an antenna segment 8 with a steel joint 9, an antenna wire 10 and a gap 11. The gap 11 is located between the antenna wire 10 and the surface of the steel joint 9. The transmitter is used as a perfect current source in the model. The receiver is used as a perfect sensor of voltage or electromagnetic force. Both the current of the steel joint 9 and the antenna wire 10 can be assumed to be perfectly circular and concentric. This model is called a Sleek-Collar Current-Loop (SCCL) model.

[0034] The simplification of the antenna segment 8 in the model allows the tool response to be calculated analytically in various borehole and formation environments. Because the wavelength of the electromagnetic signal used by the resistivity tool is much larger than the size of the antenna segment 8, the simplification used in the model is reasonable for the differential measurement between the two receivers. However, this reasonableness is based on the assumption that the antenna wire 10 is perfectly circular and concentric with the steel joint 9. In reality, the shape of the antenna wire 10 may be different from that of the model. The distribution of the induced current in the steel joint 9 may be different from the model prediction. This is a source of error.

[0035] Even if the antenna wire 10 is perfectly circular and concentric, the tool response is sensitive to the conductivity of the steel joint 9. The size of the gap 11 between the antenna wire 10 and the surface of the underlying steel joint 9 may also affect the tool response. Therefore, the conductivity of the steel and the gap must be accurately accounted for in the model used to calculate the tool response. Therefore, inaccuracies in the manufacturing process and inconsistencies in the material can lead to resistivity measurement errors.

[0036] The type of antenna depicted in Figure 1 has at least three major disadvantages. First, the steel joints 1 (antenna segments) can be easily damaged. Second, the induced current in the steel joints 1 experiences a higher resistance than the antenna wires 4 made of copper, limiting the antenna efficiency. Third, the distribution of the induced current is sensitive to the details of the antenna construction and the properties of the materials used for the antenna segments. This distribution is often unknown and not correctly accounted for in the model, which can lead to errors in the resistivity measurements.

[0037] Antenna reliability is greatly improved in the design of U.S. Patent No. 5,530,358 to Wisler et al. (hereinafter referred to as the "Wisler design" or "Wisler antenna"), which is incorporated herein by reference in its entirety.

[0038] FIG. 4 is a schematic, non-proportional side view of an antenna segment 13 using the design of Wisler et al. The antenna segment 13 includes a steel structure 14. The slots are cut parallel to the axis of the tool cylinder and are approximately evenly distributed in the circumferential direction. Nine slots can be seen in FIG. 4. For simplicity, only one slot with the label 15 is shown in FIG. 4. "Slot 15" or "slot" refers to any one of the nine slots shown and the slots not shown. "Multiple slots 15" refers to the collection of all slots. The wire hole is a passage between the slots 15 in the steel structure 14. The label 31 refers to a single wire hole segment connecting two adjacent slots. For simplicity, only one wire hole is labeled 31 in FIG. 4. However, "wire hole 31" or "wire hole" is used to refer to any one of the wire holes. "Multiple wire holes 31" refers to the collection of all slots. The slots 15 and the wire holes 31 form a circumferential passage for the antenna wire (not shown).

[0039] FIG. 5 is a cross-sectional view of the antenna segment 13 in a plane perpendicular to the cylindrical axis of the antenna segment 13 and at the antenna wire 32 in the Wisler antenna. The antenna wire 32 in FIG. 5 is shown as a dotted line. The wire hole 31 is positioned at a distance from the surface of the joint. The insulating material 33 may include a magnetic ferrite rod in a segment (e.g., a bottom segment) of the slot 15 positioned below the antenna wire 32. The insulating material 33 (e.g., a ferrite rod) may be made of a material with high magnetic permeability and no hysteresis. Although only one mark 33 is shown in FIG. 5 for simplicity, the mark applies to all 16 pieces of insulating material. Non-conductive and non-magnetic filling material 49 is used to fill the space in the slot 15 above the antenna wire 32 for protection of the antenna. The wire channel 65 provides a path for the antenna wire 32 to the electronic circuit. Here, in the slot 15, object A is above or above object B, which means that A is closer to the surface of the joint than B in the radial direction. Conversely, object A is below or beneath object B means that A is radially closer to the centerline of the joint than B is.

[0040] FIG6 is an enlarged view of the antenna conductor 32 and the ferrite rod 33. The steel structure and other components in the antenna structure are not shown in FIG6. Wire segments 66 and 67 connect the antenna conductor 32 to the electronic circuit 68 and the electronic circuit 68 to the antenna conductor 32. The antenna conductor 32 and the wire segments 66 and 67 can be made of a single continuous wire. The wire segments 66 and 67 can be twisted. The currents in the wire segments 66 and 67 have substantially the same amplitude and are in opposite directions. The wire segments 66 and 67 together may not contribute substantially to the receiving or transmitting function of the antenna structure, especially when well twisted.

[0041] Referring to FIG5 , for the transmitter antenna, the current in the antenna wire 32 forms a current loop. The current induces current at the bottom of the slot below the ferrite rod, the walls of the wire passage 31, the side walls of the slot, and the surface of the antenna connector. The total strength of the induced current in the azimuth direction is approximately equal to the total strength of the current in the antenna wire 32, as in the case of the antenna depicted in FIGS. 1 and 2 . Even if the main antenna transmit power comes from the ferrite rod, the induced current is still a factor. The resistance encountered by the induced current is also important in limiting the height of the antenna resonance.

[0042] The Wisler design is one of the strongest antenna structures and virtually eliminates the need for mechanical maintenance and repair of the antenna segments. Mechanically, the antenna structure is easy to manufacture. There are still large amounts of induced currents in the steel structure surrounding the antenna wires. The resistance in the steel still limits the resonant height of the tuned antenna assembly. More importantly, the distribution of the induced currents is still not explicitly accounted for in the model. Due to variations in the conductivity of the steel and the details of the antenna construction, the distribution can vary from antenna to antenna and from tool to tool. Typically, the model used for tool response, data processing, and log interpretation in a drilling environment is the Circular Shaft Ring Current Model (SCLC) depicted in Figure 3.

[0043] In Wu (U.S. Pat. No. 5,331,331 and U.S. Pat. No. 5,491,448, both of which are incorporated herein by reference in their entirety), each antenna is made of one or more magnetic dipoles (point dipole antennas, or Wu antennas). The dipoles are placed in pocket-shaped cutouts on the surface of a steel joint. Each magnetic dipole consists of or can be considered to be a current loop. In particular, the dipole is made of a current wire wound around a ferrite rod with high magnetic permeability. The current loop in this case is much smaller than the diameter of the steel joint and the wavelength of the electromagnetic waves used in the resistivity tool. With the same current in the dipole and in the circumferential loop, the dipole induced current in the steel joint is much smaller than the current in the circumferential current loop around the steel joint in the Wisler design or the groove structure depicted in FIG. 1. Smaller induced current means that the conductivity of the steel joint has less impact on the antenna efficiency. In turn, the correct modeling of the detailed distribution of the induced current becomes less important. The simplified structure of the antenna can be used to approximate the real antenna in the model so that the model calculation can be performed. An axial antenna segment for a model of the tool response for an antenna consisting of three point dipoles in a homogeneous medium or borehole environment is depicted in FIG. 7 .

[0044] In FIG7 , the axial antenna section 69 includes a steel joint 70 extending in two directions with a constant outer diameter. The magnetic point dipoles 71, 72 and 73 are in the axial direction of the steel joint 70. There is a distance d between the surface of the steel joint 70 and the magnetic point dipoles 71, 72 and 73. This antenna is called a circular shaft ring point dipole (SCPD) model. The point dipole antenna in the non-axial direction is also modeled by SCPD. For the reasons mentioned above, SCPD uses a point dipole antenna to model the tool response much better than the SCLC designed by Wisler.

[0045] There is a need in the art for an antenna for LWD tools that has efficiency and model tractability while ensuring mechanical structural integrity, manufacturability, and / or zero maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Like reference numerals in the figures represent and refer to the same or similar elements or functions. The embodiments of the present disclosure may be better understood when considering the following detailed description thereof. This description makes reference to the attached illustrations, schematic diagrams, charts, drawings and appendices. In the drawings:

[0047] FIG. 1 is a schematic side view of a steel structure of an antenna segment and an antenna wire according to the prior art.

[0048] 2 is a cross-sectional view of the structure of FIG. 1 with the components of the antenna in a plane containing the cylindrical axis of the joint.

[0049] FIG. 3 is a schematic diagram of a model for the antenna depicted in FIGS. 1 and 2 .

[0050] 4 is a schematic, not-to-scale side view of an antenna segment in the prior art design of Wisler et al.

[0051] FIG. 5 is a cross-sectional view of the antenna structure at the antenna conductor.

[0052] FIG. 6 is an enlarged schematic diagram of the antenna wire and the ferrite rod of FIG. 5 .

[0053] FIG. 7 is an axial antenna segment of a prior art model for a point dipole.

[0054] Figure 8 is a schematic cross-sectional view of an antenna wire segment of an antenna using an embodiment of the present disclosure.

[0055] Fig. 9 yes Figure 8 A magnified view of the antenna wire and ferrite rod.

[0056] Fig.10 is a schematic cross-sectional diagram of the net current of an antenna wire segment of an antenna having an embodiment of the present disclosure.

[0057] FIG. 11 is a schematic side view of the steel structure of the transverse axial antenna section.

[0058] FIG. 12 is a schematic diagram showing the antenna segment shown in FIG. 11 rotated 90 degrees around its cylindrical axis.

[0059] 13 shows a cross-sectional view of a prior art transverse axial antenna in a plane containing the tool spindle and perpendicular to the axis of the transverse axial antenna.

[0060] Fig.14 A cross-sectional view of the transverse-axial antenna is shown in a plane containing the tool spindle and perpendicular to the axis of the transverse-axial antenna.

[0061] Fig.15 A cross-sectional view of the net current in the antenna wire in the transverse axial antenna is shown in a plane containing the tool spindle and perpendicular to the axis of the transverse axial antenna.

[0062] FIG. 16 is a schematic diagram of one half of an antenna conductor in a prior art axial and transverse axial combination antenna.

[0063] Fig.17 It is a schematic diagram of one half of the antenna wire in the axial-transverse axial combination antenna.

[0064] Fig.18 Schematic diagram of the two halves of the antenna wire in an axial-transverse axial combination antenna.

[0065] Fig.19 is a diagram of the antenna wire in a transverse axial antenna.

[0066] Fig. 20 It is a side view of the bare steel structure of the transverse axial antenna section.

[0067] Fig.21 A cross-sectional view of a dipole antenna showing a segment of antenna wire.

[0068] Fig. 22 It is the antenna wire diagram of a dipole antenna.

[0069] Fig.23 is a schematic flow chart of a transceiver electronic system according to the present disclosure. DETAILED DESCRIPTION

[0070] Typically, multiple slots are cut around the surface of the antenna segment. For axial antennas, the slots are in the direction of the cylindrical axis of the tool and distributed circumferentially. Below the sub-surface, wire holes perpendicular to the slots are made to connect the slots, thereby forming a circumferential wire channel. A high-permeability ferrite rod is positioned in the slot. The antenna wire is positioned around the wire path above the ferrite rod in a first direction. The antenna wire is then positioned in a second direction opposite to the first position so that the antenna wire is located below the ferrite rod. The net current in the wire hole connecting two adjacent slots is zero. The net current around each ferrite rod forms a closed loop. Each ferrite rod can be used as a point dipole. A group of point dipoles forms an antenna. The slot structure makes the antenna structure durable. The current in and around the wire hole and slot induced by the antenna current is much smaller than that of any prior art antenna structure. The antenna efficiency is improved. Models with point dipole antennas can track the antenna response well. Antennas in non-axial directions can be made by a group of slots cut along a pre-designed direction on the joint surface. The wire holes, ferrite rods and antenna wires are arranged in a manner similar to the axial antenna.

[0071] Before explaining at least one embodiment of the present disclosure in detail, it should be understood that the embodiments of the present disclosure are not limited in their application to the details of the construction and arrangement of the components or steps or methods described in the following description or illustrated in the accompanying drawings. The inventive concepts in the present disclosure can have other embodiments or can be practiced or executed in various ways. In addition, it should be understood that the words and terms used herein are for descriptive purposes and should not be considered as limiting.

[0072] In the detailed description of the embodiments of the inventive concept, many specific details are set forth in order to provide a more thorough understanding of the inventive concept. However, it is apparent to one of ordinary skill in the art that the inventive concept disclosed and claimed herein can be practiced without these specific details. In other cases, well-known features are not described in detail to avoid unnecessarily complicating the disclosure.

[0073] As used herein, language such as "including," "comprising," "having," "containing," or "involving," and variations thereof, are intended to be comprehensive and encompass the subject matter listed thereafter, equivalents, and additional subject matter not mentioned or inherently present therein.

[0074] Unless expressly stated to the contrary, "or" refers to an inclusive or and not to an exclusive or. For example, condition A or B is satisfied by any of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist).

[0075] In addition, the use of "a" or "an" is used to describe the elements and components of the embodiments herein. This is done only for convenience and to give a general sense of the inventive concept. The description should be understood to include one or at least one, and the singular also includes the plural unless it is obvious that it has a different meaning.

[0076] Throughout this disclosure and claims, the terms "about," "approximately," and "substantially" are intended to indicate that the quantified item is not limited to the exact value specified, but includes slight variations or deviations therefrom (e.g., resulting from measurement error, manufacturing tolerances, stress on various components, wear, or a combination thereof).

[0077] The use of the term "at least one" will be understood to include any number of one and more than one, including but not limited to any of 2, 3, 4, 5, 10, 15, 20, 30, 40, 50, 100 and all integers therebetween. The term "at least one" may extend to as many as 100 or 1000 or more, depending on the term to which it is attached; furthermore, the number of 100 / 1000 should not be considered limiting, as higher limits may also produce satisfactory results. Unless otherwise specified, singular terms shall include pluralities and plural terms shall include the singular.

[0078] As used herein, the term "or combinations thereof" refers to all permutations and / or combinations of the items listed before the term. For example, "A, B, C, or combinations thereof" is intended to include at least one of the following: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, BA, CA, CB, CBA, BCA, ACB, BAC, or CAB. Continuing with this example, expressly included are combinations containing repetitions of one or more items or terms, such as BB, AAA, AAB, BBC, AAABCCCC, CBBAAA, CABABB, and the like. Those skilled in the art will understand that there is generally no limit to the number of items or terms in any combination, unless otherwise apparent from the context.

[0079] As used herein, a circuit can be an analog and / or digital component, or one or more appropriately programmed microprocessors and associated hardware and software, or hardwired logic. In addition, some parts of the embodiments may be described as "components" that perform one or more functions. The term "component" may include hardware (such as a processor, an application specific integrated circuit (ASIC), or a field programmable gate array (FPGA)), or a combination of hardware and software. Software includes one or more computer executable instructions that, when executed by one or more components, cause the component to perform a specified function. It should be understood that the algorithms described herein are stored on one or more non-transient memories. Exemplary non-transient memories include random access memory, read-only memory, flash memory, etc. This non-transient memory may be electrical or optical.

[0080] As used herein, any reference to "one embodiment" or "an embodiment" means that a particular element, feature, structure, or characteristic described in the embodiment is included in at least one embodiment. The appearance of the phrase "in one embodiment" in different places in the specification does not necessarily refer to the same embodiment, although the inventive concepts disclosed herein are intended to cover all combinations and permutations of one or more features of the described embodiments.

[0081] In the present disclosure, LWD may mean both FEMWD and LWD.

[0082] Resistivity tools in this disclosure refer exclusively to LWD wave propagation resistivity tools unless otherwise specified.

[0083] refer to Figure 8 , wherein a schematic cross-sectional view of an exemplary embodiment of an antenna conductor 75 of an antenna segment according to the present disclosure is illustrated. The view is located in a plane perpendicular to the cylindrical axis of the antenna segment and the plane is located at the location of the antenna conductor 75. Figure 8 There are 16 slots in the ferrite rod. For simplicity, only one is explicitly marked as 15a. "Slot 15a" can refer to any of the sixteen. Similarly, a mark 33a and a mark 31a are explicitly marked in the ferrite rod for any of the sixteen ferrite rods and any of the sixteen wire hole segments, respectively. Figure 8 5 . The antenna wire 75 runs above each ferrite rod 33a. This section of the antenna wire 75 is similar to the antenna wire 32 shown in FIG. 5 . The antenna wire 75 turns around and runs under each ferrite rod 33a in the opposite direction. Two wire sections 76 and 77 of the antenna wire 75 are located in the wire hole 31a between two adjacent slots 15a. Although only one pair of wire sections in one wire hole is shown for simplicity, Figure 876 and 77, respectively, but each pair of wire segments in each of the 16 wire holes is referred to as 76 and 77. For example, the currents in a pair of wire segments 76 and 77 have the same magnitude but opposite directions. It should be noted that wire segments 76 and 77 can be more than one in wire hole 31. Figure 8 15a. The antenna wire 75 is closer and more tightly combined than shown in . The net current in the wire hole 31a connecting two adjacent slots 15a is zero. During the manufacturing process, a portion of the antenna wire 75 (for example, the bottom portion) can be laid through the slot 15a and the wire hole 31a first. Then, the ferrite rod 33a can be placed in the slot 15a, on top of the wire 75 segment already in the slot 15a. Finally, the antenna wire 75 turns around and passes through the wire hole 31a and travels around the top of the ferrite rod 33a. The antenna wire 75 can be composed of a single continuous wire segment or multiple wire segments that are electrically connected together in sequence.

[0084] Figure 8 An enlarged view of the antenna conductor 75 and the ferrite rod 33a is schematically shown in Fig. 9 Reference Figure 8 and Fig. 9 , the wire sections 76 and 77 are positioned in the section where the wire hole 31a is located between two adjacent slots 15a having the ferrite rod 33a. It should be noted that the wire sections 76 and 77 may be Figure 8 and Fig. 9 For example, in some embodiments, the outer sheaths of the wire insulation of the two wire segments 76 and 77 may touch each other. The antenna wire 75 may also be positioned closer than Figure 8 and Fig. 9 The one shown in FIG. 3 is closer to the ferrite rod 33a.

[0085] Fig.10 yes Figure 8 31a. The net current 79 of the antenna wire 75 is shown in cross section. The wire segments 76 and 77 in the wire hole 31a carry equal amounts of current in opposite directions. The net current 79 in the wire segments 76 and 77 in any wire hole 31a is zero. The net current 79 around each ferrite rod 33a forms a closed loop around the ferrite rod 33a. The ferrite rod 33a then becomes a point dipole. The separation between the wire segments 76 and 77 in the wire hole 31a causes a closed current loop 80 to form in the wire hole 31a, as shown in FIG. Fig.10 However, the separation is limited by the diameter of the wire hole 31a. Therefore, the area surrounded by the closed current loop 80 means that the net current 79 is small, so that the magnetic dipole moment associated with the closed current loop 80 is negligible relative to the dipole moment of the ferrite rod 33a with high magnetic permeability. It should be noted that the closed current loop 80 around the ferrite rod 33a does not have to be as large as Fig.1033a. The closed current loop 79 can be loosely wrapped around the ferrite rod 33a. The magnetic dipole moment of the ferrite rod 33a is insensitive to how tightly the closed current loop 79 surrounds the ferrite rod 33a. Therefore, no restrictions need to be placed on how the wire segments 76 and 77 are positioned around the ferrite rod 33a during the manufacturing process.

[0086] Point dipoles can point in the same direction, e.g. Figure 8 , 9 and 10, thereby acting in unison. The collection of all magnetic point dipoles forms a composite magnetic dipole in the axial direction. This composite dipole is an axial antenna. Hereafter, when the dipoles based on parallel slots point in the same direction as each other, they are said to be in phase. When the direction of the dipoles of one group is opposite to that of the dipoles of the other group at any time, the two groups of parallel dipoles are completely out of phase. For a group including subgroups of parallel dipoles in different orientations, if each subgroup in one orientation is in phase, the group is in phase.

[0087] Wu antennas include designs for non-axial antennas made from a collection of coherent point dipoles pointing in a desired direction. Wisler et al. (U.S. Pat. No. 9,885,900, referred to herein as Wisler 2006 and incorporated by reference in its entirety) teach designs for transverse axial and other non-axial antennas with slots and slot-like structures (Wisler 2006).

[0088] FIG. 11 is a prior art transverse axial antenna segment 89 including a steel structure 91 as described by Wisler 2006. Coordinate system 94 shows that the Z axis is the central axis of the steel structure 91. The Y axis of coordinate system 94 points outward. A plurality of holes 92 on the steel structure are positioned in the X direction of coordinate system 94. The plurality of holes 92 are connected by slot openings 93 on the steel structure. Typically, the slot openings 93 must be narrower than the openings of a typical axial slot so that the non-conductive material filling the slot openings 93 is not damaged by abrasive drilling mud when the tool is rotated. The holes 92 are formed by drilling through the joint surface of the steel structure 91 in the X direction. The diameter of each hole 92 is greater than the width of the surface opening of the adjacent slot opening 93, so that a relatively large ferrite rod can be placed in the hole 92. The dipole moment of the ferrite rod is proportional to its cross-sectional area. The dipole moment of the ferrite rod is insensitive to the cross-sectional shape. The use of ferrite rods with rectangular and circular cross sections for axial and transverse axial antennas, respectively, is simply due to the machining method of the slot 15 and the hole 92. Although the axial groove 15 in FIG. 4 and FIG. 5 or Figure 8 , Fig.10 The geometric shapes of the axial groove 15a and the combination of the hole 92 and the slot opening 93 are different, but each can play the role of a slot. Hereinafter, the combination of a hole 92 and an adjacent slot opening 93 is referred to as a slot.

[0089] The actual width of the slot opening 93 can be made smaller than the width shown in the schematic diagram of FIG11. The slot opening 93 can be cut, for example, by a minimal mechanical knife during the machining process. Due to the low frequencies (<=10 MHz) used in the LWD resistivity tool, the capacitive impedance of the slot opening 93 is very large. For example, there is no closed loop for the sense current to eliminate the ferrite signal.

[0090] Figure 12 is another side view of the prior art steel structure 91 shown in Figure 11. In this view, the steel structure 91 is rotated 90 degrees about its cylindrical axis from its position in the transverse-axial antenna section 89 of Figure 11. The X-axis of the coordinate system 94 points into the paper.

[0091] FIG. 13 illustrates an enlarged view 95 on a section of the antenna section 89 of FIG. 12 . Coordinate system 100 is at the X=0 plane in coordinate system 94 in FIG. 11 and FIG. 12 . Antenna 95 includes a ferrite rod 96, a wire hole 98, and an antenna wire 99. Non-conductive and non-magnetic material 97 is positioned within slot opening 93. Similar to the axial antenna of the Wisler design, currents are induced in the wall of the steel structure 91 and in the wire hole 98 around the ferrite rod 96. As in the case of the axial antenna, the main transmit or receive power comes from the ferrite rod 96. The induced current still plays a role in the transmit or receive function of the antenna 95. The conductivity of the steel plays a large role in the impedance of the antenna 95. The geometry of the ferrite rod 96 and the details of the wire placement in the wire hole 98 affect the distribution of the induced current and the impedance of the antenna 95. Therefore, the model used to calculate the tool response in various drilling and formation environments cannot track the induced current well.

[0092] Fig.14 1 is an exemplary embodiment of a transverse axial antenna 101. Antenna wires 102 are positioned in opposite directions around ferrite rods 96a. Two wire segments 76a and 77a in wire hole 98a connect two adjacent slots 93a. The currents in the two wire segments 76a and 77a are substantially equal in magnitude and opposite in direction. The net current in wire hole 98a between slots 93a is zero.

[0093] Fig.15 is a schematic diagram of a transverse axial antenna 101 illustrating a net current 104. The net current 104 around each ferrite rod 96a forms a closed loop around the ferrite rod 96a. Each ferrite rod 96a becomes a point dipole. Therefore, the collection of point dipoles forms a transverse axial antenna.

[0094] FIG. 16 is a schematic antenna wire diagram of one half of the XZ antenna combination 150 in Wisler 2006. The antenna wire 111 consists of two semicircles and two straight lines. The tuning circuit 112 is connected to the transceiver circuit (not shown) via a connector 113. Ferrite rods (not shown) are placed in slots perpendicular to the antenna wire 111 (in the circular and straight segments). Each ferrite rod is located between the section of the antenna wire 111 in the slot (not shown) and the steel bottom of the slot. The steel structure, ferrite rods, non-conductive material filling the slot between the surface of the antenna wire 111 and the antenna connector are not shown so that the approximate wire path can be clearly depicted. The diagram of the antenna wire of the other half of the XZ antenna combination is very similar. The main transmission or reception power comes from the ferrite rods. The wire sections that are not in the slot and the steel structure still affect the antenna power. The wires from the two halves are connected to a single transceiver circuit. The transceiver circuit operates the two halves simultaneously in the desired mode.

[0095] Fig.17 is a schematic wire diagram of one half of an XZ antenna assembly 152. The antenna wire 114 extends through a path under a ferrite rod (not shown) and then turns around and passes through the path again in the opposite direction over the ferrite rod. The net current is zero everywhere except in any slot (not shown) where the ferrite rod is sandwiched between two opposing wire segments in the slot. The net current around the ferrite rod forms a closed loop. Only the ferrite rod and the immediate surroundings perform the transmit or receive function of the antenna. The wire hole segments connecting the slot to the slot and the slot to the electronic device do not directly participate in the transmit or receive function. The SCPD model without the wire hole segments simulates the antenna structure.

[0096] Fig.17 The tuning circuit 112a illustrated in FIG. 16 may be similar to the tuning circuit 112 in FIG. 16. In some embodiments, the tuning circuit 112a may include different electronic components (such as capacitors) because the antenna conductor 111 and the antenna conductor 112 in FIG. 16 may be different from the antenna conductor 111 and the antenna conductor 112 in FIG. 16. Fig.17 The antenna conductors 114 in the embodiment may have different inductances.

[0097] In some embodiments, the antenna mechanical structure and the structure for housing the antenna tuning circuit and the transceiver circuit and the wire paths between the different locations can be very similar to those of the prior art. Existing tools can be updated to include embodiments of the present invention with no or minor modifications to the mechanical structure.

[0098] The structure including the slots and wire holes for the two halves of the XZ antenna assembly 152 is hereinafter referred to as an XZ steerable antenna structure or simply a steerable antenna structure. The position and orientation of the slots and wire holes are also hereinafter referred to as being in a steerable antenna mode. Fig.17The conductor path in, and a similar path for the other half of the XZ antenna assembly 152, is referred to as a steerable antenna path.

[0099] Fig.18 Two antenna conductors 114 and 114a for two halves of an XZ steerable antenna 154 are depicted in a steerable path. The X and Z directions are defined in a coordinate system 116. The Z axis coincides with the cylindrical axis of the section of the XZ steerable antenna 154. The transverse axial slot (not shown) is in the X direction. Typically, the path of the second antenna conductor 114a is a 180 degree rotation of the first conductor 114 about the tool cylindrical axis, except where the antenna conductors 114 and 114a are connected to tuning circuits 112 and 112a. Both antenna conductors 114 and 114a are connected to transceiver circuitry 140 via connectors 113 and 113a, respectively. Positioned at Fig.18 The transverse axial ferrite rod (not shown) of the straight section in the XZ steerable antenna 154 is powered (when the XZ steerable antenna 154 is a transmitter) or sensed (when the XZ steerable antenna 154 is a receiver) by both antenna wires 114 and 114a. The net current around the transverse axial ferrite rod forms two closed loops from the two antenna wires 114 and 114a. There are four wire segments in each wire hole connecting two adjacent transverse axial ferrite rods. Two of the wire segments come from the first antenna wire 114, and the other two segments come from the second antenna wire 114a. The net current in the wire hole is zero. Any axial ferrite rod in a circular cross-section is powered or sensed by one wire. The net current in the axial ferrite rod forms a closed loop. One half of the axial ferrite rod on a complete circular cross-section is powered or sensed by one wire, and the other half is powered or sensed by another wire.

[0100] As a transmitter, the XZ steerable antenna 154 can be made as a pure axial dipole or a pure transverse axial dipole or a tilted dipole pointing in a direction between Z and X. If the current amplitudes in the two antenna wires 114 and 114a are the same (zero relative amplitude, or unity amplitude ratio), and the phase is such that the two closed net current loops around the transverse axial ferrite rods are exactly 180 degrees out of phase, then the total net current around the transverse axial ferrite rods is zero. The net currents on all axial ferrite rods are the same and in phase. The transmitter is a pure axial magnetic dipole antenna. If the two closed net current loops on the transverse axial ferrite rods are in phase, then the net current loops around the axial ferrite rods powered by the first antenna wire 114 are 180 degrees out of phase with those of the second antenna wire 114a. One half of the axial ferrite rod on one half turn is 180 degrees out of phase with the other half. If the amplitude ratio between the two wire currents is 1, then the net axial dipole moment of each turn is zero. The axial ferrite rods on one turn form a quadrupole. The second quadrupole is formed by another turn of the axial ferrite rod. The two quadrupoles are completely out of phase. The total quadrupole moment is also zero. The two quadrupoles are separated by the distance between the two turns. There is a small octopole whose effect on the antenna is negligible. The transmitter behaves like a transverse axial magnetic dipole antenna.

[0101] The phase of the transmitting ferrite rod without hysteresis is the phase of the wire current. The relative phase between the magnetic dipole components excited by the two wire currents is the relative phase of the two wire currents. Fig.18 The total magnetic dipole in the transverse axial direction in the XZ steerable antenna 154 depicted in is:

[0102]

[0103] Where x is the transverse axial axis defined by the transverse axial slot in the XZ steerable antenna 154, 1 is the current in wire 114, M x is the magnetic dipole moment in the x direction, the product CI 1 is the magnitude of the total magnetic dipole moment in the x direction powered by the current in antenna conductor 114, B is the magnitude ratio of the current in conductor 114a to the current in conductor 114, ω is the current frequency, sin() is the sine function, and is the relative phase between the two currents.

[0104] Each transverse axial ferrite rod is powered by both a first current and a second current. The first term on the right hand side of equation 1 is the magnetic dipole generated by the first current. The second term is the magnetic dipole generated by the second current. Without loss of generality, the phase of the collective transverse axial dipole is defined as the phase relative to the first current. Therefore, the phase of the first term is zero and the phase of the second term is the relative phase between the two terms.

[0105] Equation 1 can be rewritten as:

[0106]

[0107] where cos() is the cosine function and ATAN2[] is the inverse tangent function with two parameters. The amplitude and phase of the collective transverse axial dipole are and

[0108]

[0109] The total magnetic moment in the axial direction is:

[0110]

[0111] Where z is the axial axis defined by the axial slot in the XZ steerable antenna 154, M z is the total magnetic dipole moment in the z direction, AI 1 is the magnitude of the total magnetic dipole moment in the z direction supplied by the first current.

[0112] Each axial ferrite rod is powered by either the first current or the second current, but not both. The first term on the right-hand side of Equation 3 is the total axial magnetic moment powered by the first current. The second term is the total axial magnetic moment powered by the second current. The minus sign between the two terms is the result of the addition of the two transverse axial dipole components powered by the two currents, the subtraction of the two axial dipole components powered by the two currents, and vice versa. This characteristic is determined by the designed steerable wire path. Therefore, the two signs between the two terms in Equations 1 and 3 are opposite. Which of the two signs is the plus sign is a choice about how to define the relative phase between the two currents. If the relative phase between the two currents is defined as Rather than Then the two signs between the two terms in equations 1 and 3 are reversed. Both choices for the relative phase are equally valid. The antenna characteristics and behavior do not depend on the choice used in the equations. In the following, the relative phase between the two currents used in equations 1 and 3 is The phase of the collective axial dipole is also defined relative to the phase of the first current.

[0113] Equation 3 can be rewritten as:

[0114]

[0115] The amplitude and phase of the collective axial dipole are and The relative phase between the collective transverse axial dipole and the collective axial dipole is

[0116] The total collective dipole vector is M x and M z is the vector sum such that there is a magnetic dipole (linear dipole) in a constant direction, and the relative phase between the transverse axial component M x and the axial component M z must be zero or a multiple of 180 degrees. So that:

[0117]

[0118] where n = 0, ±1, and π is Archimedes' constant (the ratio of the circumference of a circle to its diameter).

[0119] Equation 5 applies only when both M x and M z have non-zero amplitudes. When the amplitude of M z is zero, the resulting collective dipole is a linear dipole in the transverse axial direction, regardless of its phase. Similarly, when the amplitude of M x is zero, the resulting collective dipole is a linear dipole in the axial direction, regardless of its phase. It can be shown that the necessary and sufficient condition for the amplitude of M x or M z to be zero is (B = 1 and (B = 1 and degrees) condition results in the emitter being a transverse axial dipole with zero axial dipole moment. (B = 1 and degrees) condition results in the emitter being an axial dipole with zero transverse axial dipole moment.

[0120] If B = 1 and then the relative phase between the two dipole components is 90 or -90 degrees. This violates Equation 5. Thus, (B = 1 and condition results in the emitter being a non-linearly polarized dipole. The resulting emitter is an elliptically polarized magnetic dipole. The eccentricity of the ellipse is a function of the relative phase between the first current and the second current. When (where ATAN() is the arctangent function), the ellipse becomes a circle. The emitter becomes a circularly polarized magnetic dipole antenna. When is zero, the ellipse degenerates into a line. The resulting emitter is a linearly polarized dipole. For B = 1, the emitter can be made into an elliptically polarized magnetic dipole when , or the emitter can be made into a linearly polarized magnetic dipole in the transverse axial direction when , or the emitter can be made into a linearly polarized magnetic dipole in the axial direction when degrees. To make the steerable emitter form a linearly polarized magnetic dipole antenna in the direction between the axial axis and the transverse axial axis, the two wire currents must be different.

[0121] For B ≠ 1, Equation 5 gives:

[0122]

[0123] Equation 6 has four solutions: B = 0; B = ∞,; as well as degrees. B being zero means that the second current is zero and the first current is non-zero. The resulting emitter is a tilted linear dipole. The dipole's tilt angle relative to the axial axis is B is infinite, indicating that the first current is zero and the second current is non-zero. The resulting emitter is tilted at an angle of The tilt angle in the XZ plane is The linear dipole has a phase difference of 180 degrees. linear dipole. The path of wire 114 and the path of wire 114a in the path of steerable antenna 154 are identical, except that they are separated in azimuth by 180 degrees about the antenna cylindrical axis. The azimuth of the tool about its cylindrical axis (the drill string axis) is called the tool face. Rotating the antenna cylinder 180 degrees in the tool face causes the two wire paths to switch positions. Because the axial slot structure and the ferrite rods are identical to each other, the amplitude ratio between the total transverse axial and axial dipoles when only current 2 is non-zero (B=∞) is the same as when only current 1 is non-zero (B=0). The absolute value of the tilt angle is the same in both cases. The only difference between the two cases is that the two tilted dipoles are separated by 180 degrees in both the tool face and the dipole phase. Ratio It is independent of the amplitude of the conductor current. It is determined by the structure of the steerable antenna.

[0124] when When the XZ steerable antenna 154 changes to have a tilt angle from the cylindrical axis of the steerable antenna 154 A linearly polarized magnetic dipole of θ, where ACOS() is the arccosine function. The tilt angle is a function of B. B can be chosen to be a value in the domain [0, +∞). s The range is and between.

[0125] when degrees, the steerable antenna 154 has an inclination angle of 1.1° from the cylindrical axis of the steerable antenna 154. The linearly polarized magnetic dipole of θ is θ, where ASIN() is the inverse sine function. s The range is and By Selecting 0 or 180 degrees can make the tilt angle θs Between and Any position between. The entire range of tilt angles is 180 degrees. A linearly polarized magnetic dipole antenna in any direction in the XZ plane can be embodied in the steerable antenna 154. For example, by setting B to And will Set to 0 (when A≥C) or 180 degrees (when A<C), Fig.18 The steerable antenna 154 depicted in FIG. 1 is embodied as a linear dipole antenna having a tilt angle of 45 degrees from the cylindrical axis of the antenna section.

[0126] The receiving linearly polarized magnetic dipole antenna can be implemented in the steerable antenna in the same way as the transmitting magnetic dipole antenna having the same linear polarization characteristics. The receiving steerable antenna is made into a magnetic dipole with the same linear polarization and tilt angle. Therefore, the embodiments of this article can be applied to the steerable antenna to create an axial dipole, or a transverse axial dipole, or a tilted linear polarized dipole, or an elliptically polarized dipole receiver.

[0127] Embodiments herein may be used to construct a purely transverse axial antenna without any axial component. Fig.19 and Fig. 20 An exemplary pure transverse axial antenna 156 is shown. The steel structure and other parts are very similar to those of the XZ antenna combination 152, except that only one arcuate wire segment 158 ​​is provided. The steel structure is not shown in the figure. Ferrite rods (not shown) are placed in the transverse axial slots of the straight segments and sandwiched between the two wire segments in each slot. There are no slots in the arcuate segments of the wire. There is no axial component in this design.

[0128] Fig. 20 Shows Fig.19 158. A side view of a pure transverse axial antenna 156 in FIG. 159. The arcuate segments of the wire holes are embedded and cannot be observed. The tuning circuit 112 is positioned in the tuning port 123 and is connected during the construction of the pure transverse axial antenna 156. A metal cover can be used to protect the tuning port 123. Optional holes 124 can be drilled radially inward from the connector surface to reach the arcuate wire segments 158. During the manufacturing process, the holes 124 can be used to help pass the antenna wires through the arcuate wire segments 158. These holes 124 can then be twisted or plugged with conductive material. For example, these holes 124 are generally not a functional part of the pure transverse axial antenna 156 and can only be used during the manufacturing and maintenance stages.

[0129] Measurements from a pair of axial transmitter-receiver antennas on an LWD tool are invariant under toolface rotation. These measurements cannot be used to sense azimuthal variations in formation properties about the drill string axis. Measurements from a pair of transmitter-receiver antennas, one antenna being axial and the other transaxial, may be sensitive to the toolface angle about the transaxial axis. Some azimuthal variations in formation properties can be determined from the measurements. If the formation is not azimuthal invariant, then the receiver readings are a function of the toolface about the transaxial axis. By measuring the toolface angle for each receiver reading, a distribution of receiver data can be obtained on the toolface after the tool has been rotated at least 360 degrees. A transmitter-receiver antenna pair, both in the transaxial direction, produces measurements that are sensitive to azimuthal variations in formation properties.

[0130] Each resistivity measurement is made using a constant sampling window. The measurements are made at constant time intervals. During drilling operations, the rotational speed of the drill string can change. The constant time interval between measurements does not translate into constant tool face increments. The data distribution on the tool face can be on unevenly spaced tool face angles. To facilitate data processing and interpretation, the data distribution on the tool face is usually acquired or converted to data on a constantly spaced tool face grid or bins. The conversion is done by dividing the entire 0 to 360 degree tool face space into multiple equally sized bins. The receiver reading is assigned to the bin where the tool face angle lies at the time of the reading. If multiple readings fall into a bin, all readings in the bin are averaged into the reading for the bin. After collecting measurement data for all bins, a set of data distributions on the tool face is obtained. A complete set of binned data can be directly stored together with the time in the middle of the measurement cycle of the complete set of binned data (cycle time). The set of binned data can be further processed and the results of the processing are stored in memory together with the cycle time. Then, all bins are cleared for the next set of distribution data. Variable drill string rotation speed results in a variable measurement cycle. The measurement cycle is managed dynamically by the resistivity tool's electronics.

[0131] The distribution of measured data on the tool face in binned format can be used directly for imaging logs (which are two-dimensional plots of well depth and tool face angle). The distribution on the tool face is plotted at the average depth of the tool during the time period over which data in all bins were collected for that distribution. The average depth is the tool depth at the cycle time. The time-depth correlation is performed by a logging system including a resistivity tool.

[0132] The frequencies used by LWD tools are much higher than the rotational frequency of the drill string during drilling. For modeling the tool response and interpreting data for the tool at the tool face angle, the tool can be considered stationary at this position.

[0133] The electromagnetic field generated by the transmitter on the wave propagation resistivity tool is a linear field and has superposition characteristics. The transverse axial transmitter dipole is a vector in the XY plane in a Cartesian coordinate system at rest relative to the earth (derrick), where the z axis is the cylindrical axis of the antenna cylinder and the drill string. On any tool face, the dipole can be viewed as a vector consisting of two component vectors in the X and Y directions. The dipole is the vector sum of the two component vectors. That is, the dipole vector is given by:

[0134]

[0135] in is the tool face angle of the launcher in the transverse direction, It's a tool surface The emitter dipole vector at , D is the emitter's dipole moment, and are the unit vectors of the X-axis and Y-axis of the derrick respectively.

[0136] The superposition principle states that the electromagnetic field generated by the transverse axial transmitter dipole at the tool face angle is the same as the vector sum of the fields generated by the two component vectors separately. The axial component of the field at a distance in the z-axis measured by the axial dipole receiver is:

[0137]

[0138] in It means that when the axial transmitter is at the tool face angle The phase and amplitude of the complex receiver voltage, V zx and V zy is the axial receiver voltage when the tool face of the transverse axial transmitter is at zero and ninety degrees, respectively.

[0139] The receiver voltages of the transverse-axial receivers on the electromagnetic field generated by the axial transmitter dipole are also simple sinusoidal functions of the tool face similar to those of Eq. 8.

[0140] The receiver measurements from the axial and transaxial transmitter-receiver pairs vary sinusoidally with the toolface. As a Fourier series of the toolface, the measurements have only two non-zero coefficients.

[0141] The measurement of the electromagnetic field generated by the tilted linear magnetic dipole transmitter by the tilted linear magnetic dipole receiver is given by:

[0142]

[0143]

[0144] in is the tool face angle, are the receiver inclination angle and tool face offset, is the launcher inclination angle and tool face offset, the matrix element V ij is the receiver voltage with the receiver in the i direction and the transmitter in the j direction in the derrick.

[0145] The matrix V in Equation 9 is called the transfer matrix or transfer function. It can be shown that the tool face angle middle The coefficients of the third and all higher order harmonics of the Fourier transform are zero. For a pair of linear magnetic dipole transmitters and receivers, there are at most five non-zero coefficients in the Fourier series of the receiver measurements at the toolface. Therefore, the toolface variation of the receiver voltage can be characterized by a function with at most five complex parameters. The minimum number of bins required to extract the five parameters is five.

[0146] With five bins, each bin spans 72 degrees in the tool face. The tool face angle of a piece of data can be anywhere within that tool face interval. Errors from sampling jitter can be large (e.g., 36 degrees in the tool face). Jitter errors can be reduced by using more bins than necessary (e.g., a minimum of five in the data binning process). Oversampling the data also reduces random measurement errors. Increasing the number of bins will increase data storage requirements. The choice of the number of bins is a balance between minimizing jitter and random errors and minimizing data storage requirements.

[0147] In some embodiments, each bin is divided into multiple smaller sub-bins. After collecting the data of all sub-bins in each bin, the data collection of a tool face distribution is considered complete. The data from all sub-bins in the bin are averaged or added as the data of the bin. Only this data can be stored. Therefore, the sub-bin size limits the jitter error. A larger number of sub-bins can also reduce random errors. A smaller number of bins will not burden the data storage system.

[0148] In some embodiments, receiver measurements and the tool face angle at which the receiver measurements are made are temporarily recorded during the measurement process. After data is collected for all bins, the complete set of binned data is stored in memory or processed into Fourier series coefficients (Fourier decomposition) for storage in memory. Since the tool face angles are not on a uniformly spaced grid, the Fourier decomposition is performed using techniques designed for irregularly sampled data. As discussed herein, for the measurements from each linear dipole transmitter-receiver pair, the Fourier coefficients of the third or higher order harmonics are zero. There are only five non-zero coefficients. These five non-zero coefficients can be determined in a direct data fitting optimization method (such as the least squares method). Since the exact value of the tool face angle associated with each receiver measurement is used, there is no jitter error. To minimize jitter error, the number of bins or sub-bins does not have to be large. A set of coarse bins can be used.

[0149] Random noise and other errors in the binned data can cause the Fourier coefficients of the third and higher order harmonics to be non-zero. The third and higher order Fourier coefficients can be calculated and stored to memory. The values ​​of these coefficients can be used to measure the quality of the measurement of the binned data.

[0150] Five or more measurements over the tool face angle may be used to determine the possible five non-zero Fourier coefficients. If the measurements are over a small range of tool faces (azimuths), then the emergent azimuth changes to be measured may be small compared to the systematic measurement error. The signal to noise ratio may be poor. In this embodiment, this problem is avoided by requiring the presence of measurement data in each bin.

[0151] In directional wells, the gravity tool face is used for tool face measurements. It is given by:

[0152]

[0153] Among them G x and G y It is the gravity component in the X and Y directions of the Cartesian coordinate system fixed to the tool section (sensor frame), with the drill string axis as the Z axis. The gravity component is measured by the accelerometer in the direction sensing system when the drill string is at rest. This is done during the pipe change period, when drill string sections are added to or removed from the drill string, and the downhole section of the drill string is at rest.

[0154] In some embodiments, the magnetic tool face is measured dynamically during the drilling process. The gravity tool face is derived from the magnetic tool face. The magnetic tool face is measured by a magnetometer and is not affected by mechanical factors during the drilling process that would corrupt gravity measurements made using accelerometers. for

[0155]

[0156] Among them, M x and M y are the geomagnetic field components in the X and Y transverse axial directions of the sensor frame, respectively.

[0157] The Difference Between Magnetic and Gravity Toolfaces is a function of the geomagnetic field inclination, the inclination of the drill string section where the directional sensor is located, and the azimuth. It is not a function of the tool face. If the attitude of the drill string remains unchanged, it remains unchanged as the drill string rotates. In this embodiment, the instantaneous gravity tool face of the x-axis of the magnetometer used for dynamic measurement of the geomagnetic field is given by:

[0158]

[0159] in and is the instantaneous gravity and magnetic tool face when the drill string rotates, is the static gravity and geomagnetic toolface difference obtained from the most recent directional sensor survey conducted during the pipe change period when the drill string is at rest. The approximation used in deriving Equation 12 is that the attitude of the drill string and well changes very little between two static surveys. The gravity toolface error associated with this approximation is much less than the toolface accuracy requirement for the data binning.

[0160] The magnetometers used to dynamically measure the geomagnetic field component in the transverse axial direction during the drilling process may be different from the magnetometers used for static directional surveys. The two sets of transverse axial magnetometers may be offset in azimuth around the drill string axis. Equation 12 is still valid and can be used to obtain the gravity tool face angle of the transverse X axis of the dynamic magnetometer system.

[0161] The transverse axial component of the linear dipole antenna may be offset in the tool face from the X-axis of the sensor frame of the dynamic magnetometer system. This offset is a known constant. The instantaneous gravity tool face of the transverse axial component of the linear dipole antenna is:

[0162]

[0163] in, is the gravity tool face in the transverse axis of the antenna, is the tool face offset between the X-axis of the antenna and the dynamic magnetometer system.

[0164] The directional sensor system may be part of an electronic system of a resistivity tool having a transverse axial antenna component.The cylindrical section housing the directional sensor system may be part of a resistivity tool section.

[0165] Prior art LWD tools with transverse axial antennas have been used to measure one or more parameters of formation properties. LWD tools with transverse axial antennas using embodiments described herein may be more efficient and accurate than those of the prior art.

[0166] refer to Figure 8 and Fig.21 Compared with the prior art, the embodiments described herein can be used to conveniently manufacture magnetic quadrupole antennas. Figure 8 By crossing the wires (half-turn twisting) in the wire holes diametrically opposite to the wire channel 65, an antenna can be obtained in which one half of the dipole points in the opposite direction to the other half of the dipole. A schematic cross-sectional view of an exemplary quadrupole antenna 160 is shown in FIG. Fig.21 The quadrupole antenna 160 is similar to Figure 8 , except that the two wire sections 76a and 77a in the wire hole 31a opposite to the wire channel 65 intersect at 128. The intersection at 128 can be anywhere in the wire hole 31a. It can also be at the intersection of the groove 15a and the Fig.21 The cross-axial direction is shown as 126. The cross section at 128 divides the dipole based on the ferrite rod 33a into two groups. Fig.21 The ferrite dipole on the left half is 180 degrees out of phase with the right half. The total dipole moment is zero. The quadrupole moment is not zero. In a coordinate system where the Z axis is the centerline of the joint cylinder, the Y axis passes through Fig.21 With the center of the wire channel 65 in the middle and the X-axis pointing in the direction of 126, the XZ component of the quadrupole moment Qxz is approximately given by:

[0167]

[0168] Where R is the radial distance from the middle of the ferrite rod 33a to the centerline of the steel joint, d is the axial magnetic dipole moment of each ferrite rod 33a, and N is the total number of ferrite rods 33a. The approximation used in obtaining Equation 14 is: Assuming N is large, it is assumed that the ferrite rod dipoles are uniformly and continuously distributed along the circumference. For an exact value, if N is an even number and the slots 15a are uniformly distributed, such as Fig.21 As shown, the factor in equation 14 is It is replaced by the average value of the absolute values ​​of the X coordinates of all ferrite rods 33a in the coordinate system.

[0169] According to the definition of quadrupole moment, the ZX component Q zx Equal to Q xz . All other components of the quadrupole tensor are zero.

[0170] The antenna includes both dipole and quadrupole moments by crossing antenna wire segments in wire bores 31a that are not diametrically opposed to wire passage 65. Multiple antenna wire crossings can be used to create an antenna with non-zero dipole and quadrupole moments centered about the cylindrical axis of the resistivity tool.

[0171] Fig. 22 A schematic wire diagram of an exemplary quadrupole antenna segment 162 having transverse axial slots is shown. The steel structure (not shown) with the slots is almost identical to the Fig. 20 The steel structure of the antenna 131 is the same as that of the antenna 132. The ferrite rods (not shown) are placed in the transverse axial slots in the straight segments and are sandwiched between two wire segments in each slot. There are no slots in the arcuate segments of the wire. The antenna wire 131 can be similar to Fig.19 Continuous wire of antenna wire 115 for a pure transverse axial dipole antenna. Segments of antenna wire 131 cross in arc segment 164 of the wire hole shown at 132. Wire intersection 132 can be anywhere on arc segment 164, or at the beginning of a straight segment before the first ferrite rod closest to arc segment 164. Wire intersection 132 makes the two sets of ferrite dipoles on the two straight wire segments 180 degrees from each other in polarity. The total dipole moment is zero. In a coordinate system parallel to 133 (with its origin at the center between the two straight segments), the non-zero components of the quadrupole are:

[0172]

[0173] Where l is the distance between two straight wire hole segments ( is the radius of the antenna joint cylinder minus the depth of the centerline of the ferrite rod from the joint surface), d is the dipole moment of the ferrite rod structure in the direction of the rod (the X direction in coordinate system 133), and N is the total number of transverse ferrite rods in the two straight line segments and is assumed to be an even number. All other components of the quadrupole are zero.

[0174] In some embodiments, similar to Fig. 22 Another wire intersection 132 in the wire intersection 132 can be positioned to create two sets of dipoles with unequal numbers of slot-based dipoles in them. The dipoles in each set are in phase, and the two sets are 180 degrees out of phase. The total dipole moment is not zero. The antenna has both a dipole moment and a quadrupole moment. As with the case of the axial dipole, multiple wire intersections 132 can be used in one embodiment to create an antenna with all moments centered on the cylindrical axis of the resistivity tool.

[0175] In the prior art, the orientation of the wire hole segment is important because a single wire segment in the segment induces a current around the wire hole structure and the induced current becomes the active part of the antenna. The antenna structure using the embodiments described herein has no strict requirements on the orientation of the wire hole because there are two wire segments in the wire hole and the net current of the two segments is zero. The wire segments in the wire hole do not participate in the transmit or receive function of the antenna constructed in the embodiments described herein. The angle at which the wire segments cross or pass through the ferrite rod may affect the behavior of the antenna. In the following, unless otherwise stated, it is assumed that the wire passes above / below the ferrite rod at right angles to the long axis of the ferrite rod.

[0176] The two wire segments in the wire hole can be twisted several full turns without changing the polarity of the dipole. A half turn twist intersects the two wire segments and causes a change in polarity in adjacent slots. It will be appreciated that the two wire segments can be twisted in the wire hole to minimize any magnetic moment from the two segments.

[0177] refer to Fig.23 , the operation of the resistivity tool is managed by a transceiver electronics system 165. The transceiver electronics system 165 is housed in the drill collar section of the tool. The transceiver electronics system 165 may include an electronic control unit 166, a receiver electronics unit 167, and a transmitter electronics unit 168. The antenna tuning and signal measurement electronics of the receiver are part of the receiver electronics unit 167. The receiver antenna 175 is connected to the receiver electronics unit 167 by electrical conductors 172. The electronic control unit 166 powers, controls, and collects receiver measurements from the receiver electronics unit 167 via an electrical connection system 170. The electronic control unit 166 powers and commands the transmitter electronics unit 168 through a connection system 171. The transmitter electronics unit 168 includes a tuning circuit and other transmitter electronics. The transmitter electronics unit 168 powers the transmitter antenna 176 through a connection system 173. Fig.23 is a schematic functional diagram. In some embodiments, part or all of the electronic control unit 166 and the receiver electronic unit 167 may be fabricated on a single electronic board. A portion of the transmitter electronic unit 168 may be on an electronic board on which most of the electronics of the electronic control unit 166 are located. In some embodiments, the antenna tuning circuits of the receiver electronic unit 167 or the transmitter electronic unit 168 are located next to the antennas 175 and 176 and are not on the electronic board for the rest of the unit to which they belong.

[0178] The electronic control unit 166 may be connected to the rest of the downhole system via a connection system 169. The electronic control unit 166 may include a directional sensing subsystem. The transceiver electronics 165 and antennas 175 and 176 may be housed in different sections of the drill collar. Hereinafter, the collection of all sections of the drill collar that house all components of the resistivity tool may be referred to as a drill collar segment.

[0179] It should also be understood that the embodiments described herein also describe embodiments in which the wire passing over / under the ferrite rod in the slot may be wrapped around the rod one or more times before exiting the slot. The twisting of the wire in the wire hole and the wrapping of the wire around the ferrite rod in the slot may not change the net current in the wire hole to be zero and the net current forms a complete loop around the ferrite rod.

[0180] Furthermore, the ferrite or ferrite rod may be made from a single volume of magnetic material, or may be composed of several pieces joined together linearly or packed in parallel.

[0181] While certain embodiments have been shown and described, various modifications and substitutions may be made without departing from the spirit and scope of the invention.

[0182] Techniques for providing one or more antennas within a drilling assembly are disclosed in the following U.S. patents:

[0183] U.S. Patent No. 5,001,675 (March 1991), Woodward;

[0184] U.S. Patent No. 5,138,263 (August 1992), Towle;

[0185] U.S. Patent No. 5,331,331 (July 1994), Wu;

[0186] U.S. Patent No. 5,491,488 (February 1996), Wu;

[0187] U.S. Patent No. 5,530,358 (June 1996), Wisler et al.;

[0188] U.S. Patent No. 6,181,138 (January 1999), Hagiwara;

[0189] U.S. Patent No. 6,163,155 (December 2000), Bittar;

[0190] U.S. Patent No. 8,378,908 (February 2013), Wisler et al.;

[0191] U.S. Patent No. 8,471,563 (June 2013), Wisler et al.;

[0192] U.S. Patent No. 8,604,796 (December 2013), Wisler et al.;

[0193] U.S. Patent No. 9,140,817 (September 2015), Wisler et al.

[0194] U.S. Patent No. 9,366,780 (June 2016), Wisler et al.; and

[0195] U.S. Patent No. 9,885,900 (February 2018), Wisler et al.

[0196] The following is a numbered list of non-limiting illustrative embodiments of the inventive concepts disclosed herein:

[0197] 1. An electromagnetic wave propagation tool, comprising:

[0198] a drill collar section having an outer surface;

[0199] An antenna system is disposed on the drill collar section, the antenna system comprising at least one transmitter antenna and at least one receiver antenna, at least one of the transmitter antenna or the receiver antenna in the antenna system is a magnetic dipole-based antenna, the magnetic dipole-based antenna comprises a slot-based magnetic dipole, and the slot-based magnetic dipole comprises:

[0200] at least one guide wire hole positioned below an outer surface of the drill collar section;

[0201] at least two grooves positioned in the outer surface of the drill collar, the at least one wire hole connecting the plurality of grooves to each other;

[0202] a ferrite rod placed in each slot; and,

[0203] a continuous antenna wire that passes through the slots and wire holes via a first path, the continuous wire reversed and re-passed through the slots and wire holes via a second path so that two wire sections in each slot are positioned above and below each ferrite rod;

[0204] a transceiver electronics system disposed on the drill collar section, the transceiver electronics system comprising a receiver electronics unit, a transmitter electronics unit, and an electronic control unit, the electronic control unit comprising electronic hardware, software, and firmware for scheduling and managing measurement sequences at at least one frequency and for processing receiver data into an output; and,

[0205] The at least one wire hole further connects the slot to the transceiver electronic system, and the continuous wire is further connected to the transceiver system through the wire hole.

[0206] 2. The electromagnetic wave propagation tool of illustrative embodiment 1, wherein the magnetic dipole antenna is a transmitter antenna.

[0207] 3. The electromagnetic wave propagation tool of illustrative embodiment 1, wherein the magnetic dipole antenna is a receiver antenna.

[0208] 4. An electromagnetic wave propagation tool according to illustrative embodiments 1, 2 or 3, wherein the slots and the slot-based magnetic dipoles are located in the axial direction and are basically evenly distributed in azimuth around the axis of the drill collar section, and the slot-based magnetic dipoles are located at an axial position on the drill collar section and are in phase, thereby forming a collective axial antenna.

[0209] 5. An electromagnetic wave propagation tool according to illustrative embodiments 1, 2 or 3, wherein the slots and the slot-based magnetic dipoles are located in the axial direction and are basically evenly distributed in azimuth around the axis of the drill collar section, and the magnetic dipole is located at an axial position on the drill collar section, wherein the continuous wire is arranged to form two groups of slot-based dipoles, the magnetic dipoles in each group are in phase and the two magnetic dipole groups are 180 degrees out of phase.

[0210] 6. An electromagnetic wave propagation tool according to illustrative embodiments 1, 2 or 3, wherein the slots and the magnetic dipoles based on the slots are located in the axial direction and are arranged in three groups distributed in azimuth around the axis of the drill collar section, and the magnetic dipoles are located at an axial position on the drill collar section.

[0211] 7. An electromagnetic wave propagation tool according to illustrative embodiments 1, 2 or 3, wherein the slots and the magnetic dipoles based on the slots are parallel and in phase in the transverse axial direction to form a collective transverse axial antenna, and the transceiver electronic system also includes a subsystem for obtaining the tool face angle of the transverse axial axis.

[0212] 8. The electromagnetic wave propagation tool of illustrative embodiment 7, wherein the slot-based magnetic dipoles are arranged in two axially distributed groups, wherein the two axially distributed groups are azimuthally separated by 180 degrees around the central axis of the drill collar section.

[0213] 9. An electromagnetic wave propagation tool according to illustrative embodiments 1, 2 or 3, wherein the slots and the slot-based magnetic dipoles are located in the transverse axial direction, and wherein the continuous wire is arranged so as to form two dipole groups of slot-based magnetic dipoles, the slot-based magnetic dipoles in each group are in phase, and the two dipole groups are 180 degrees out of phase.

[0214] 10. An electromagnetic wave propagation tool according to illustrative embodiments 1, 2 or 3, wherein the slot-based magnetic dipoles consist of two groups, wherein the first group consists of dipoles based on axial slots, and the second group consists of dipoles based on transverse axial slots in the transverse axial direction, the first group and the second group are in phase, thereby forming a collective tilted antenna; and wherein the transceiver electronic system also includes a subsystem for obtaining a tool face angle.

[0215] 11. An electromagnetic wave propagation tool according to illustrative embodiment 10, wherein a first group of dipoles based on axial grooves are arranged at two axial dipole positions on the drill collar section, and a second group of dipoles based on transverse axial grooves are arranged between two axial dipole positions on the drill collar section, so that the center of the collective axial dipole moment coincides with the center of the collective transverse axial dipole moment.

[0216] 12. The electromagnetic wave propagation tool of illustrative embodiment 10, wherein the transceiver electronic system further comprises a subsystem for spatially partitioning the surface of the electromagnetic wave propagation tool into a number of bins and collecting and averaging receiver data in each bin.

[0217] 13. The electromagnetic wave propagation tool of illustrative embodiment 12, wherein the transceiver electronics system further comprises a subsystem for processing the binned data into a distribution of data over a tool face angle.

[0218] 14. The electromagnetic wave propagation tool of illustrative embodiment 12, wherein the transceiver electronic system further comprises a subsystem for processing the binned data into parameters indicative of azimuthal properties of the formation.

[0219] 15. The electromagnetic wave propagation tool of illustrative embodiment 12, wherein the transceiver electronics system further comprises a subsystem for converting the binned data into coefficients of a Fourier series of tool face angles.

[0220] 16. A method of sensing formation properties while drilling a well, the method comprising:

[0221] providing an antenna system on the drill collar section, the antenna system comprising at least one transmitter antenna for creating an electromagnetic field and at least one receiver antenna for detecting the electromagnetic field;

[0222] providing a transceiver electronics system on the drill collar section, the transceiver electronics system comprising a receiver electronics unit, a transmitter electronics unit and an electronic control unit, the electronic control unit comprising electronic hardware, software and firmware for scheduling and managing measurement sequences at at least one frequency and for processing receiver data into an output;

[0223] Wherein, at least one antenna in the antenna system is a magnetic dipole-based antenna for creating or detecting an electromagnetic field, the magnetic dipole-based antenna comprising at least two slot-based magnetic dipoles, the slot-based magnetic dipole comprising:

[0224] a groove in an outer surface of the drill collar section;

[0225] wire holes below the outer surface, the wire holes connecting the slots to each other and to the transceiver electronics system,

[0226] a ferrite rod placed in each slot; and,

[0227] A continuous antenna wire passes through the slots and the wire holes via a first path, and turns around and passes through the slots and the wire holes again via a second path, wherein two wire sections in each slot pass over and under the ferrite rod, the continuous wire also being connected to and from the transceiver electronic system through one or more wire holes.

[0228] 17. A method according to illustrative embodiment 16, wherein the slots and slot-based magnetic dipoles are located in the axial direction and are substantially uniformly distributed in azimuth around the axis of the drill collar section, and the slot-based magnetic dipoles are located at an axial position on the drill collar section and are in phase, thereby forming a collective axial antenna.

[0229] 18. A method according to illustrative embodiment 16, wherein the slots and slot-based magnetic dipoles are located in the axial direction and are substantially uniformly distributed in azimuth around the axis of the drill collar section, the slot-based magnetic dipole is located at an axial position on the drill collar section, and wherein the continuous wire is arranged so as to form two groups of slot-based dipoles, the magnetic dipoles in each group are in phase and the two slot-based dipole groups are 180 degrees out of phase.

[0230] 19. The method of illustrative embodiment 16, wherein the slots and slot-based magnetic dipoles are located in an axial direction and are arranged in three groups distributed azimuthally around the axis of the drill collar section, and the slot-based magnetic dipole is located at an axial position on the drill collar section.

[0231] 20. The method of illustrative embodiment 16, wherein the slots and slot-based magnetic dipoles are parallel and in phase in the transverse-axial direction to form a collective transverse-axial antenna, and the transceiver electronic system further comprises a subsystem for obtaining a tool face angle of the transverse-axial axis.

[0232] 21. The method of illustrative embodiment 20, wherein the slot-based magnetic dipoles are arranged in two axially distributed groups, wherein the two axially distributed groups are azimuthally separated by 180 degrees about a central axis of the drill collar section.

[0233] 22. The method of illustrative embodiment 16, wherein the slots and slot-based magnetic dipoles are located in a transverse axial direction, wherein the continuous wire is arranged so as to form two groups of slot-based dipoles, the slot-based magnetic dipoles in each group are in phase, and the two slot-based dipole groups are 180 degrees out of phase, and the transceiver electronic system further comprises a subsystem for obtaining a tool face angle of the transverse axial axis.

[0234] 23. A method according to illustrative embodiment 16, wherein the slot-based magnetic dipoles consist of two groups, wherein a first group of axial slot-based dipoles and a second group of transverse-axial dipoles located in a transverse-axial direction are in phase, thereby forming a collectively tilted antenna; and the transceiver electronic system also includes a subsystem for obtaining a tool face angle.

[0235] 24. A method according to illustrative embodiment 23, wherein a first set of dipoles based on axial grooves are arranged at two axial dipole positions on the drill collar segment, and a second set of dipoles based on transverse axial grooves are arranged between the two axial dipole positions on the drill collar segment, so that the center of the collective axial dipole moment coincides with the center of the collective transverse axial dipole moment.

[0236] 25. The method of illustrative embodiment 23, wherein the transceiver electronic system further comprises a subsystem for dividing the face space into a number of bins and collecting and averaging receiver data in each bin.

[0237] 26. The method of illustrative embodiment 25, wherein the transceiver electronics system further comprises a subsystem for processing the binned data into a distribution of data over tool face angles.

[0238] 27. The method of illustrative embodiment 25, wherein the transceiver electronics system further comprises a subsystem for processing the binned data into parameters indicative of azimuthal properties of the formation.

[0239] 28. The method of illustrative embodiment 25, wherein the transceiver electronics system further comprises a subsystem for converting the binned data into coefficients of a Fourier series of tool face angles.

[0240] 29. An electromagnetic wave propagation tool, comprising:

[0241] Drill collar section;

[0242] an antenna system disposed on an outer surface of the drill collar section, the antenna system comprising at least one transmitter antenna and at least one receiver antenna;

[0243] a transceiver electronics system disposed on the drill collar section, the transceiver electronics system comprising a receiver electronics unit, a transmitter electronics unit, and an electronic control unit, the electronic control unit comprising electronic hardware, software, and firmware for scheduling and managing measurement sequences at at least one frequency and for processing receiver data into an output;

[0244] Wherein, at least one of the transmitter antenna or the receiver antenna in the antenna system is a magnetic dipole-based antenna, and the magnetic dipole-based antenna includes:

[0245] a plurality of slot-based magnetic dipoles comprising two or more slots in an outer surface of the drill collar segment and a wire bore beneath the outer surface, the wire bore connecting adjacent slots and connecting the slots with the transceiver electronics system;

[0246] a ferrite rod positioned in a plurality of slots;

[0247] a first continuous antenna wire that passes through the first set of slots via the wire holes in a first path and reverses direction to re-pass through the first set of slots and the wire holes via a second path, wherein two wire sections of the first continuous wire in each slot are positioned above and below each ferrite rod in each slot, the first continuous wire also being connected to and from the transceiver electronics system;

[0248] a second continuous antenna wire that passes through the second set of slots via the wire eyelets in a third path and reverses direction to re-pass through the second set of slots and the wire eyelets in a fourth path, wherein two wire segments of the second continuous wire in each slot are positioned above and below each ferrite rod in each slot, the second continuous wire also being connected to and from the transceiver electronics system; and,

[0249] The transceiver electronic system further includes a subsystem for maintaining a relative amplitude and phase between currents in the first continuous conductive line and the second continuous conductive line.

[0250] 30. The electromagnetic wave propagation tool of illustrative embodiment 29, wherein the magnetic dipole-based antenna is a transmitter antenna.

[0251] 31. The electromagnetic wave propagation tool of illustrative embodiment 29, wherein the magnetic dipole-based antenna is a receiver antenna.

[0252] 32. The electromagnetic wave propagation tool of illustrative embodiment 29, 30 or 31, wherein the relative amplitude and phase between the first continuous wire and the second continuous wire results in the formation of an axial dipole antenna.

[0253] 33. The electromagnetic wave propagation tool of illustrative embodiment 29, 30 or 31, wherein the relative amplitude and phase between the first continuous wire and the second continuous wire results in a transverse axial dipole antenna.

[0254] 34. The electromagnetic wave propagation tool of illustrative embodiment 29, 30 or 31, wherein:

[0255] The slot and wire aperture are in a steerable antenna mode;

[0256] The first continuous wire and the second continuous wire follow a steerable antenna path; and,

[0257] The transceiver electronics system also includes a subsystem for acquiring a tool face.

[0258] 35. The electromagnetic wave propagation tool of illustrative embodiment 34, wherein the relative amplitude and phase between the first continuous wire and the second continuous wire results in a tilted dipole antenna located between the axial direction and the transverse axial direction.

[0259] 36. The electromagnetic wave propagation tool of illustrative embodiment 35, wherein the transceiver electronic system further comprises a subsystem for dividing the surface space into a number of bins and collecting and averaging receiver data in each bin.

[0260] 37. The electromagnetic wave propagation tool of illustrative embodiment 36, wherein the transceiver electronics system further comprises a subsystem for processing the binned data into a distribution of data over a tool face angle.

[0261] 38. The electromagnetic wave propagation tool of illustrative embodiment 36, wherein the transceiver electronic system further comprises a subsystem for processing the binned data into parameters indicative of azimuthal properties of the formation.

[0262] 39. The electromagnetic wave propagation tool of illustrative embodiment 36, wherein the transceiver electronics system further comprises a subsystem for converting the binned data into coefficients of a Fourier series of tool face angles.

[0263] 40. A method of sensing formation properties while drilling a well, the method comprising:

[0264] providing an antenna system on the drill collar section, the antenna system comprising at least one transmitter antenna for creating an electromagnetic field and at least one receiver antenna for detecting the electromagnetic field;

[0265] providing a transceiver electronics system on the drill collar section, the transceiver electronics system comprising a receiver electronics unit, a transmitter electronics unit and an electronic control unit, the electronic control unit comprising electronic hardware, software and firmware for scheduling and managing measurement sequences at at least one frequency and for processing receiver data into an output;

[0266] Wherein, at least one of the transmitter antenna or the receiver antenna in the antenna system is a magnetic dipole-based antenna, and the magnetic dipole-based antenna includes a plurality of slot-based magnetic dipoles, and the slot-based magnetic dipole includes:

[0267] a plurality of grooves in an outer surface of the drill collar section;

[0268] a plurality of wire holes located below the outer surface, the plurality of wire holes connecting adjacent slots and connecting the slots to the transceiver electronic system,

[0269] a ferrite rod positioned in the plurality of slots;

[0270] a first continuous wire that passes through a first set of slots via a wire eyelet in a first path and reverses direction to re-pass through the first set of slots and the wire eyelet in a second path, wherein a first wire segment is positioned below each ferrite rod in each slot and a second wire segment is positioned above each ferrite rod in each slot;

[0271] a second continuous wire passing through the second set of slots via the wire eyelets in a third path and reversing direction to re-pass through the second set of slots and the wire eyelets in a fourth path, wherein a first wire segment of the second continuous wire is positioned below each ferrite rod in each slot and a second wire segment is positioned above each ferrite rod in each slot; and,

[0272] The transceiver electronic system further includes a subsystem for maintaining a relative amplitude and phase between currents in the first continuous conductive line and the second continuous conductive line.

[0273] 41. The method of illustrative embodiment 40, wherein:

[0274] The slot and wire aperture are in a steerable antenna mode;

[0275] The first continuous wire and the second continuous wire follow a steerable antenna path; and,

[0276] The transceiver electronics system also includes a subsystem for acquiring a tool face.

[0277] 42. The method of illustrative embodiment 41, wherein the relative magnitude and phase between the currents in the first continuous wire and the second continuous wire results in the formation of an axial dipole antenna.

[0278] 43. The method of illustrative embodiment 41, wherein the relative amplitude and phase between the currents in the first continuous conductive line and the second continuous conductive line results in the formation of a transverse axial dipole antenna.

[0279] 44. The method of illustrative embodiment 41, wherein the relative amplitude and phase between the currents in the first continuous wire and the second continuous wire results in the formation of a tilted dipole antenna located between an axial direction and a transverse axial direction.

[0280] 45. The method of illustrative embodiment 44, wherein the transceiver electronic system further comprises a subsystem for dividing the face space into a number of bins and collecting and averaging receiver data in each bin.

[0281] 46. ​​The method of illustrative embodiment 45, wherein the transceiver electronics system further comprises a subsystem for processing the binned data into a distribution of data over tool face angles.

[0282] 47. The method of illustrative embodiment 45, wherein the transceiver electronic system further comprises a subsystem for processing the binned data into parameters indicative of azimuthal properties of the formation.

[0283] 48. The method of illustrative embodiment 45, wherein the transceiver electronics system further comprises a subsystem for converting the binned data into coefficients of a Fourier series of tool face angles.

Claims

1. An electromagnetic wave propagation tool, comprising: An antenna system disposed on a drill collar section, the antenna system comprising a magnetic dipole antenna, the magnetic dipole antenna comprising a slot-based magnetic dipole, the slot-based magnetic dipole comprising: a plurality of guide wire holes positioned below an outer surface of the drill collar section; at least two grooves positioned in the outer surface of the drill collar section, the guide wire holes connecting the plurality of grooves to each other; a ferrite rod placed in each slot; and, A continuous antenna wire that passes through the slots and wire holes via a first path is turned around and re-passed through the slots and wire holes via a second path so that two wire sections in each slot are positioned above and below each ferrite rod.

2. The electromagnetic wave propagation tool according to claim 1, wherein: The magnetic dipole antenna is the transmitter antenna.

3. The electromagnetic wave propagation tool according to claim 1, wherein: The magnetic dipole antenna is the receiver antenna.

4. The electromagnetic wave propagation tool according to claim 1, wherein: The slots and slot-based magnetic dipoles are located in an axial direction and are substantially evenly distributed in azimuth about the axis of the drill collar section, the slot-based magnetic dipoles being located at one axial position on the drill collar section and in phase, thereby forming a collective axial antenna.

5. The electromagnetic wave propagation tool according to claim 1, wherein: The slots and slot-based magnetic dipoles are located in an axial direction and are substantially evenly distributed azimuthally about the axis of the drill collar section.

6. The electromagnetic wave propagation tool according to claim 1, wherein: The slots and slot-based magnetic dipoles are located in the axial direction and are arranged in three groups distributed azimuthally about the axis of the drill collar section.

7. The electromagnetic wave propagation tool according to claim 1, wherein: The slots and the magnetic dipoles based on the slots are parallel and in phase in the transverse-axial direction to form a collective transverse-axial antenna, and the electromagnetic wave propagation tool also includes a subsystem for obtaining a tool face angle of the transverse-axial axis.

8. The electromagnetic wave propagation tool according to claim 7, wherein: The slot-based magnetic dipoles are arranged in two axially distributed groups positioned 180 degrees azimuthally apart about a central axis of the drill collar section.

9. The electromagnetic wave propagation tool according to claim 1, wherein: The slots and slot-based magnetic dipoles are located in a transverse axial direction, and the continuous antenna wire is arranged so as to form two dipole groups of slot-based magnetic dipoles, the slot-based magnetic dipoles in each group are in phase, and the two dipole groups of slot-based magnetic dipoles are 180 degrees out of phase.

10. The electromagnetic wave propagation tool according to claim 1, wherein: The slot-based magnetic dipoles are composed of two groups, wherein the first group is composed of dipoles based on axial slots, and the second group is composed of dipoles based on transverse axial slots in the transverse axial direction, the first group and the second group are in phase, thereby forming a collective tilted antenna; and wherein the electromagnetic wave propagation tool also includes a subsystem for obtaining a tool face angle.

11. The electromagnetic wave propagation tool according to claim 10, wherein: A first set of dipoles based on axial grooves is arranged at two axial dipole positions of the drill collar section, and a second set of dipoles based on transverse axial grooves is arranged between the two axial dipole positions on the drill collar section, so that the center of the collective axial dipole moment coincides with the center of the collective transverse axial dipole moment.

12. The electromagnetic wave propagation tool according to claim 10, wherein: The electromagnetic wave propagation tool also includes a transceiver electronics system configured to spatially divide the face of the electromagnetic wave propagation tool into a number of bins and to collect and average receiver data in each bin.

13. The electromagnetic wave propagation tool according to claim 12, wherein: The transceiver electronics system also includes a subsystem for processing the binned data into a distribution of data over the tool face angle.

14. The electromagnetic wave propagation tool according to claim 12, wherein: The transceiver electronics system also includes a subsystem for processing the binned data into parameters indicative of azimuthal properties of the formation.

15. The electromagnetic wave propagation tool according to claim 12, wherein: The transceiver electronics system also includes a subsystem for converting the binned data into coefficients of a Fourier series of tool face angle.

16. An electromagnetic wave propagation tool, comprising: A transceiver electronics system disposed on the drill collar section, the transceiver electronics system including a magnetic dipole-based antenna having: a plurality of slot-based magnetic dipoles comprising at least two slots in the outer surface of the drill collar segment and a wire bore beneath the outer surface of the drill collar segment, the wire bore connecting adjacent slots; a ferrite rod positioned in the slot; a first continuous antenna wire that passes through the first set of slots via the wire holes in a first path and reverses direction to re-pass through the first set of slots and the wire holes via a second path, wherein two wire sections of the first continuous antenna wire in each slot are positioned above and below each ferrite rod in each slot, the first continuous antenna wire also being connected to and from the transceiver electronics system; a second continuous antenna wire passing through the second set of slots via the wire eyelets in a third path and reversing direction to re-pass through the second set of slots and the wire eyelets in a fourth path, wherein two wire segments of the second continuous antenna wire in each slot are positioned above and below each ferrite rod in each slot, the second continuous antenna wire also being connected to and from the transceiver electronics system; and, The transceiver electronic system further includes a subsystem for maintaining a relative amplitude and phase between currents in the first continuous antenna conductor and the second continuous antenna conductor.

17. The electromagnetic wave propagation tool according to claim 16, wherein: The relative amplitude and phase between the first continuous antenna wire and the second continuous antenna wire results in the formation of an axial dipole antenna.

18. The electromagnetic wave propagation tool according to claim 16, wherein: The relative amplitude and phase between the first continuous antenna conductor and the second continuous antenna conductor results in a transverse axial dipole antenna.

19. The electromagnetic wave propagation tool according to claim 16, wherein: The slot and wire aperture are in a steerable antenna mode; The first continuous antenna conductor and the second continuous antenna conductor follow a steerable antenna path; and, The transceiver electronics system also includes a subsystem for acquiring a tool face.

20. A magnetic dipole based antenna for use in an antenna system disposed on a drill collar section, comprising: a plurality of slot-based magnetic dipoles comprising at least two slots in the outer surface of the drill collar segment and a wire bore beneath the outer surface of the drill collar segment, the wire bore connecting adjacent slots; a ferrite rod positioned in the slot; as well as, A continuous antenna wire that passes through the slots and wire holes via a first path is turned around and re-passed through the slots and wire holes via a second path so that two wire sections in each slot are positioned above and below each ferrite rod.

21. A method for manufacturing an electromagnetic wave propagation tool, the method comprising: Passing a bottom portion of the antenna wire through a plurality of wire holes positioned below an outer surface of a drill collar segment and through a plurality of slots positioned in the outer surface of the drill collar segment, the plurality of wire holes connecting the plurality of slots to one another; In each of the plurality of slots, a ferrite rod is placed on top of a bottom portion of the antenna wire in the plurality of slots; as well as The antenna wire is turned around and the top portion of the antenna wire is passed through the plurality of wire holes and slots and positioned on top of the ferrite rods in each of the plurality of slots so that each of the ferrite rods forms a point dipole, thereby forming a magnetic dipole antenna.

22. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The magnetic dipole antenna is the transmitter antenna.

23. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The magnetic dipole antenna is the receiver antenna.

24. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The slots and point dipoles are located in an axial direction and are substantially evenly distributed in azimuth about the axis of the drill collar section, the point dipoles being located at one axial position on the drill collar section and in phase, thereby forming a collective axial antenna.

25. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The slots and point dipoles are located in an axial direction and are substantially evenly distributed in azimuth about the axis of the drill collar section.

26. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The slots and point dipoles are located in the axial direction and are arranged in three groups distributed azimuthally around the axis of the drill collar section.

27. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The slots and the point dipoles are parallel and in phase in the transverse-axial direction to form a collective transverse-axial antenna, and wherein the electromagnetic wave propagation tool further comprises a subsystem for obtaining a tool face angle of the transverse-axial axis.

28. The method for manufacturing an electromagnetic wave propagation tool according to claim 27, wherein: The point dipoles are arranged in two axially distributed groups located 180 degrees azimuthally apart about a central axis of the drill collar section.

29. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The slots and the point dipoles are located in the transverse axial direction, and the antenna wires are arranged so as to form two dipole groups of point dipoles, the point dipoles in each group are in phase, and the two dipole groups of point dipoles are 180 degrees out of phase.

30. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The point dipoles are composed of two groups, wherein the first group is composed of point dipoles based on axial slots, and the second group is composed of point dipoles based on transverse axial slots located in the transverse axial direction, and the first group and the second group are in phase, thereby forming a collectively tilted antenna; and wherein the electromagnetic wave propagation tool also includes a subsystem for obtaining a tool face angle.

31. The method for manufacturing an electromagnetic wave propagation tool according to claim 30, wherein: A first group of point dipoles based on axial grooves are arranged at two axial dipole positions of the drill collar section, and a second group of point dipoles based on transverse axial grooves are arranged between the two axial dipole positions on the drill collar section, so that the center of the collective axial dipole moment coincides with the center of the collective transverse axial dipole moment.

32. The method for manufacturing an electromagnetic wave propagation tool according to claim 30, wherein: The electromagnetic wave propagation tool also includes a transceiver electronics system configured to spatially divide the surface of the electromagnetic wave propagation tool into a number of bins to collect and average receiver data in each bin.

33. The method for manufacturing an electromagnetic wave propagation tool according to claim 32, wherein: The transceiver electronics system also includes a subsystem for processing the binned data into a distribution of data over the tool face angle.

34. The method for manufacturing an electromagnetic wave propagation tool according to claim 32, wherein: The transceiver electronics system also includes a subsystem for processing the binned data into parameters indicative of azimuthal properties of the formation.

35. The method for manufacturing an electromagnetic wave propagation tool according to claim 32, wherein: The transceiver electronics system also includes a subsystem for converting the binned data into coefficients of a Fourier series of tool face angle.

36. The method of manufacturing an electromagnetic wave propagation tool according to claim 21, the method comprising: Connect a tuning circuit to the antenna wire.

37. The method of manufacturing an electromagnetic wave propagation tool according to claim 36, the method comprising: The tuning circuit is positioned in a tuning port of the drill collar section.

38. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The antenna wire has a wire insulating outer covering, and wherein the outer covering of the top portion of the antenna wire and the outer covering of the bottom portion of the antenna wire may be positioned to contact each other in one or more of the plurality of wire holes.

39. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: Passing a top portion of the antenna wire through the top of the ferrite rod in each of the plurality of slots together with a bottom portion of the antenna wire creates a closed current loop around the ferrite rod.

40. The method for manufacturing an electromagnetic wave propagation tool according to claim 21, wherein: The top portion of the antenna wire and the bottom portion of the antenna wire are configured to carry equal amounts of current in opposite directions through the plurality of slots and the plurality of wire holes.

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