255 results about "Resistivity logging" patented technology

Well logging apparatus and methods for determining formation resistivity at multiple (>3) depths of investigation. At least one transmitter antenna and at least two receiver antennas are mounted in a logging tool housing, on substantially a common axis. The antennas are untuned coils of wire. Electromagnetic energy is emitted at multiple frequencies from the transmitter into the formation. The receiver antennas, which are spaced apart from each other and from the transmitter, detect reflected electromagnetic energy. Formation resistivity at multiple depths of investigation is determined using only phase differences in the reflected energy at the different frequencies, minimizing false indications of invasion due to mismatch of vertical response with attenuation measurements and also permitting correcting for the effects of varying dielectric constant of the formation. The apparatus minimizes the number of antennas, electronics complexity, required power, and measurement time required to determine resistivity at multiple depths of investigation.

A system and related method for obtaining electromagnetic resistivity logs of a formation having fixed depths of investigation that differ from the actual depths of investigation for the tool. The system and related method comprises calculating actual invaded zone and formation resistivities, and then using least-squares curve fitting techniques to find a function that models the relationship between the physical spacing of the transmitters and the depths of investigation. Using the function, it is possible to find a transmitter-to-receive spacing that, though not actually wed, would give the desired depth of investigation. This transmitter-to-receiver spacing is then used in combination with a second function, determined using least-squares curve fitting methods, which models the relationship between the transmitter-to-receiver physical spacing and the measured resistivity to obtain the resistivity reading at a fixed depth of investigation.

A resistivity logging sensor for logging while drilling a well using an oil-based mud includes a sensor body; a first current injector electrode disposed on the sensor body, wherein the first current injector electrode is electrically insulated from the sensor body; at least two current return electrodes disposed on the sensor body at a selected distance from the first current injector electrode, wherein the at least two current return electrodes are disposed proximate to each other and are electrically insulated from the sensor body; and an electrical source configured to energize the first current injector electrode with a current having a voltage of no less than 50 mvolts and a frequency of no less than 1 KHz.

Method for predicting physical properties of a source rock formation wherein an inclusion-based (103) mathematical rock physics model (101) is constructed that treats organic matter as solid inclusions, solid background, or both, and relates anisotropic elastic and electric properties of source rock to in-situ rock and fluid properties (102). The model is calibrated with well log data and may be used to forward model calculate effective anisotropic elastic (104.1) and electrical (104.2) properties of the source rock formation, or by inversion (441-442) of sonic and resistivity log data to calculate total organic carbon (423) in terms of a difference (421) between elastic and electrical properties of the source rock.

A resistivity logging tool suitable for downhole use includes a transmitter, two spaced apart receivers. The measured resistivities at the two receivers are corrected for differences in receiver characteristics based on measuring the responses of the receivers to a calibration signal passed through calibration circuits. The logging tool may be used in reservoir navigation. A calibration antenna positioned between the two receivers may be used to identify factors other than the distance to a bed boundary that may effect the receiver signals.

The invention discloses a method and device for checking scales of a resistivity logging instrument, and the method comprises a resistivity logging instrument calibrating step and a resistivity logging instrument checking step, wherein the resistivity logging instrument calibrating step is as follows: measuring the amplitude ratio R0 and the phase difference D0 of signals when the resistivity logging instrument is exposed in air, measuring the amplitude ratio Rn and the phase difference Dn of the signals when simulated formations with different resistivities are placed around the resistivity logging instrument, and confirming the amplitude ratio response function relationship and the phase difference response function relationship according to R0, D0, Rn and Dn; and the resistivity logging instrument checking step is as follows: measuring the amplitude ratio R and the phase difference D of the signals when a simulated formation with resistivity Rho is placed nearby the logging instrument, calculating the amplitude ratio resistivity and the phase difference resistivity as per R, D, the amplitude response function relationship and the phase difference response function relationship, and calculating difference values of the amplitude ratio resistivity and the phase difference resistivity with the resistivity Rho. If the difference values of the amplitude ratio resistivity and the phase difference resistivity with the resistivity Rho are both less than a preset measuring error of the instrument, the resistivity logging instrument passes through the checking.

The invention discloses a method for calculating the distances between a horizontal well borehole and the upper and lower interfaces of stratum. The method comprises the following steps: dividing the stratum of the whole well section of a target well and determining the initial resistivity value of each stratum; determining the initial stratum inclination angle value of each stratum; determining the initial resistivity value and the initial stratum inclination angle value of a target layer, and determining the resistivity logging curve while drilling corresponding to the target layer; calculating the distance values between a target well borehole trajectory and the upper and lower interfaces of the target layer; generating a resistivity well logging simulated response curve while drilling of the target layer; judging whether the resistivity well logging simulated response curve while drilling of the target layer is consistent with the resistivity logging curve while drilling corresponding to the target layer, interactively inversing and modifying the stratum resistivity value and the stratum inclination angle value of the target layer, and repeating the steps until the resistivity well logging simulated response curve while drilling of the target layer is consistent with the resistivity logging curve while drilling corresponding to the target layer. By the method, the factors of geological background, oil reservoir conditions, engineering environment and the like are fully taken into consideration; calculation results are more reasonable; basis is provided for a well completion design or reservoir reconstruction; perforation horizon optimization is facilitated; an oil-gas recovery ratio is improved.

The invention relates to an array coil system of an azimuthal electromagnetic wave resistivity logging instrument while drilling, wherein the array coil system (2) is wound in a corresponding hole or groove in a coil carrier (1) and comprises a plurality of groups of transmitting coils and a plurality of groups of receiving coils; the transmitting coils are symmetrically distributed longitudinal coils of different spacing; and the receiving coils are symmetrically distributed on the two sides of the center of the array coil system (2) and comprise longitudinal coils with coil system magnetic dipole direction coaxial with the instrument and transverse coils with coil system magnetic dipole direction vertical with the instrument. According to the array coil system, the characteristics of stratum azimuth, dip, resistivity and anisotropy can be achieved, and information such as stratum structure change and distance from a wellbore to the boundary of a reservoir stratum can also be achieved; and the array coil system has an important effect on accurate geological guidance and reservoir stratum evaluation in a well drilling process. The array coil system is suitable for the technical field of logging in oil and gas exploration.

In-situ calibration of a resistivity logging tool is accomplished using a variety of methods in which deep measurement signals are calibrated using acquired and simulated measurement signals.

A resistivity logging sensor for logging while drilling a well using an oil-based mud includes a sensor body; a first current injector electrode disposed on the sensor body, wherein the first current injector electrode is electrically insulated from the sensor body; at least two current return electrodes disposed on the sensor body at a selected distance from the first current injector electrode, wherein the at least two current return electrodes are disposed proximate to each other and are electrically insulated from the sensor body; and an electrical source configured to energize the first current injector electrode with a current having a voltage of no less than 50 mvolts and a frequency of no less than 1 KHz.

Multifrequency focusing is applied to measurements made with a multicomponent resistivity logging tool in an earth formation having resisitivity anisotropy. From knowledge of relative dip and azimuth of the borehole relative to the formation, two modes can be separated, one of which is dependent substantially on the horizontal resistivity. Alternatively, mode separation and angle determination can be made simultaneously.

The invention discloses a method for recognizing geological sweet spots in a shale stratum. The method includes the following steps that the kerogen volume content, the gas-bearing porosity and the water-filled porosity in the shale stratum are determined according to logging information; the gas saturation is determined according to the water-filled porosity and the gas-bearing porosity of the shale stratum; the total organic content is determined according to sound wave and resistivity logging information and the organic matter maturity; and according to the kerogen volume content, the gas-bearing porosity, the gas saturation and the total organic content of the shale stratum, the geological sweet spot coefficient of the shale stratum is determined through a radar map analyzing method, and the geological sweet spot coefficient is used for recognizing the geological sweet spots in the shale stratum. According to the method, the geological sweet spots in the shale stratum are represented through the four parameters of the organic content, the kerogen volume content, the gas-bearing porosity and the gas saturation, recognition completeness of the geological sweet spots in the shale stratum is fully considered, the quality of the geological sweet spots in the shale stratum is quantitatively represented through the geological sweet spot coefficient, and quantitative reference is provided for mining engineering of the shale stratum.

Disclosed is a method for calculating a shale content of high and low gamma interaction reservoirs. The method includes step one, influencing correction by means of a logging information environment; step two, calculating the shale content by means of spontaneous potential logging; step three, calculating the shale content by means of resistivity logging; step four, calculating the shale content by means of a compensated neutron-density method; step five, calculating the shale content by means of natural gamma-ray logging; step six, determining the shale content using a minimum value method on the basis of the shale contents calculated by using the previous four methods. According to the method for calculating the shale content of the high and low gamma interaction reservoirs, shale content calculations of a high gamma reservoir and a conventional reservoir are organically integrated, a calculated shale content curve basically overlaps with a shale content analyzed and tested by a lab, and accuracy of calculation of the shale content is greatly increased.

An azimuthal resistivity logging tool includes one or more pads for making azimuthal resistivity measurements of earth formation. Current from the pads, guard electrodes and a measure electrode are measured while monitoring the voltage difference between pairs of monitor electrodes. The pads and an adjacent portion of the tool body form a guard electrode. In addition, microelectrodes are provided on the pads for obtaining high resolution resistivity measurements.

Various systems and methods for implementing an azimuthally sensitive resistivity logging tool are disclosed. One such method involves transmitting a primary magnetic field from one or more coils placed on a drill collar and receiving several electrical signals, where each of the electrical signals is received from a respective one of several sensors. The sensors are distributed around a circumference of a drill collar, and an axis of at least one of the sensors is perpendicular to an axis of the drill collar. Each of the electrical signals indicates a respective magnitude of a measurement of a reflected magnetic field, where the reflected magnetic field is reflected from an anomalous geological formation. The method calculates a vector measurement of the reflected magnetic field, based upon the electrical signals.

A resistivity logging tool suitable for downhole use includes a transmitter, two spaced apart receivers. The measured signals are inverted to determine the distance to a boundary in the earth formation in the presence of a transition zone in resistivity. The direction of drilling may be controlled based on the determined distance.

A resistivity logging tool suitable for downhole use includes a transmitter and two spaced apart receivers. The measured signals are inverted to determine the distance to an overpressured zone in the earth formation. The overpressured zone may be a transition zone in resistivity. The direction of drilling may be controlled based on the determined distance. Optionally, seismic-while drilling measurements may be made from which a separate estimate of the distance can be obtained. The SWD® measurements may also be processed to estimate the pore pressure.

System and method for borehole compensation. The method includes simultaneously transmitting at least two modulated signals from one or more transmitters; receiving the at least two modulated signals by at least one receiver; and processing the received at least two modulated signals to determine a phase difference and an amplitude attenuation of the transmitted modulated signals, the processing providing borehole compensated data.

Provided is a recognition method of properties of complex reservoir stratum fluid in different mud systems. Based on the natural potential, resistivity logging data and sonic time difference calculation porosity, the ratio of a natural potential amplitude difference to mud resistivity and an apparent formation water resistivity crossplot are established through combination of mud resistivity and formation water resistivity in an industrial region and rock-electro parameters, the properties of fluid in complex reservoir stratums in different mud systems in the industrial region are recognized through the plot, and technological support of logging will be provided for improving the recognition precision of a low oil-resisting layer and a high water-resisting layer. The natural potential amplitude difference and a mud resistivity parameter are organically combined, a new path is provided for recognizing the low oil-resisting layer and the high water-resisting layer, and the problem that the fluid properties are recognized just through resistivity logging is also avoided.

The invention discloses a method and a device for determining true resistivity of a horizontal well / highly-deviated well. The method comprises steps as follows: logging-while-drilling resistivity information, auxiliary logging curve information, logging information of an adjoining well or a pilot hole well and seismic data of the neighboring area of the well are acquired; a target stratum drilled at the horizontal well section / the highly-deviated well section is determined, the target stratum is layered, an initial ground layer model is established, and a resistivity initial value of the initial ground layer model is determined, and a while-drilling resistivity simulation response curve of a corresponding layer is generated; whether the while-drilling resistivity simulation response curve of the corresponding layer is identical to a while-drilling resistivity original response curve of the corresponding layer is judged, the resistivity initial value of the initial ground layer model is taken as the true resistivity value of the ground layer to be output if the while-drilling resistivity simulation response curve of the corresponding layer is identical to the while-drilling resistivity original response curve of the corresponding layer, and otherwise, the resistivity initial value is modified through interactive inversion. According to the method and the device, the recognition capability of an oil layer and the oil saturation estimation accuracy are improved greatly, and firmer foundation is provided for perforation oil testing.

The invention discloses a resistivity anisotropy recognition method in a horizontal well stratum environment. Firstly, an azimuth natural GR and an azimuth resistivity logging are obtained through logging, and then a stratigraphic dip and a stratigraphic azimuth angle are extracted. Secondly, the instrument azimuthal resistivity logging response value at multiple spacings and different frequencies in a horizontal well are acquired through logging. Through the environmental correction and automatic layering process, a false layer is removed, and standardized logging data and a stratum layering interface are obtained. Thirdly, according to a stratigraphic dip extracting result, the layering interface, an apparent resistivity measured value and adjoining well data, a horizontal well stratum model is constructed. Finally, the stratum model is subjected to back calculation, and then an anisotropy coefficient and a stratum resistivity inversion result are outputted. According to the method, the real resistivity information and the anisotropy coefficient information of the stratum in the horizontal well environment are extracted based on azimuthal resistivity logging data while drilling, so that the existing logging evaluation data of the horizontal well are perfected. During the comprehensive interpretation and evaluation process of the logging data of the horizontal well, the reservoir oil saturation and the like can be accurately calculated based on the stratum real resistivity and the anisotropy coefficient. As a result, the method provides reliable parameters for reservoir evaluation.

The invention discloses a carbonate rock structure ingredient well logging quantitative recognition method and a purpose thereof. The method mainly comprises three parts including porosity and water saturation well logging calculation, rock structure number parameter calculation and rock structure ingredient identification. When RFN obtained through calculation is smaller than 0.3, the structure is a micrite structure; when the RFN is between 0.3 and 1.1, the structure is a powder crystal structure; when the RFN is greater than 1.1, the structure is a fine crystal or particle structure. The sound wave time difference logging curve is adopted for calculating the porosity, the deep lateral resistivity well logging curve and the porosity are utilized for calculating the stratum water content saturability, a rock structure number formula is utilized for calculating the rock structure number parameter, and different rock structure ingredients are identified through cutoff values. The method provided by the invention is practically applied to the stratum of Majiagou formation of Ordovician system in Wuqinan region of Ordos Basin, and a better effect is obtained.

Various systems and methods for implementing an azimuthally sensitive resistivity logging tool are disclosed. One such method involves transmitting a primary magnetic field from one or more coils placed on a drill collar and receiving several electrical signals, where each of the electrical signals is received from a respective one of several sensors. The sensors are distributed around a circumference of a drill collar, and an axis of at least one of the sensors is perpendicular to an axis of the drill collar. Each of the electrical signals indicates a respective magnitude of a measurement of a reflected magnetic field, where the reflected magnetic field is reflected from an anomalous geological formation. The method calculates a vector measurement of the reflected magnetic field, based upon the electrical signals.

The invention relates to a transient measurement method for the barefoot well formation resistivity. An emitting coil and a receiving coil of an induction logging instrument are coaxially placed in a formation; the emitting coil is controlled by a high power transistor in a full bridge converter, high-power and low-frequency bipolar rectangular waveforms are generated on the emitting coil, trigger signals trigger a receiving circuit at the moments of current disconnection and current connection, and transient voltage response waveforms inducted by the receiving coil are recorded; scale operation is conducted on transient response waveforms received by the tested formation and a set of received signals of a standard formation, and only a secondary field for reflecting the resistivity difference ratio of the tested formation is left; and the resistivity of the tested formation is obtained from response waveforms of the secondary field. According to the transient measurement method, the application range of a transient electromagnetic method to logging is widened, the method can be complementary to a common induction logging method, and obtained resistivity logging data can be used for formation evaluation and reservoir stratum division in the logging interpreting process, and also can be used for calculating the porosity, the saturability, the permeability and other parameters of reservoir stratums.

A resistivity logging tool includes one or more pads for making azimuthal resistivity measurements of earth formation. Current from the pads, guard electrodes and a measure electrode are measured while monitoring the voltage difference between pairs of monitor electrodes. In addition, microelectrodes are provided on the pads for obtaining high resolution resistivity measurements.

Measurements made by a multi-array / multi-frequency induction resistivity logging tool in a borehole are used for determining the length of fractures in an earth formation and the resistivity of the unfractured formation when the fractures have a resistive fluid. A look-up table based on modeling of a fracture by a pair of wings is used.

Methods for making calibrated microresistivity logging measurements in nonconductive drilling fluid are disclosed. A calibrated measurement parameter (e.g., a calibrated electrical impedance or a calibrated potential difference) is obtained and further utilized to compute a formation resistivity. The methods tend to be particularly well suited for drilling applications in which the borehole environment is highly resistive (i.e., boreholes in which both the drilling fluid and the formation have a high resistivity).

Induction and other resistivity well logging tools determine formation conductivity at various depths but these measurements contain pronounced errors when the tool is proximate to an inclined underground bed boundary. A method to correct tool measurements includes calculating an expected tool response at a relative dip angle of zero degree and at a particular depth based on an earth model of the underground formation. An expected tool response at the known dip is then calculated. Comparing the calculated zero-dip response with the calculated non-zero-dip response yields the dip effect. A response is also modeled to exclude the non-linearity of the shoulder effect. Comparing the calculated linear response (obtained, e.g. by the Born approximation) with the calculated zero-dip response yields the nonlinear shoulder effect. The nonlinear shoulder effect and / or the dip effect may then be corrected for by subtracting them from the raw or pre-processed measurements.