Geosteering method based on formation dielectric properties estimated from logging-while-drilling measurements

Abstract

A drilling system performs a method for identifying a reservoir in a formation. The processor measures a first dielectric constant of the formation at a selected depth or depth interval using a first electromagnetic wave or signal emitted through the formation at the selected depth or depth interval in a borehole in the formation at a first frequency; measuring a second dielectric constant of the formation at a selected depth or depth interval using a second electromagnetic wave or signal emitted through the formation at a second frequency at the selected depth or depth interval in the borehole in the formation; and identifying a reservoir in the formation based on the first dielectric constant at the selected depth or depth interval and the second dielectric constant at the selected depth or depth interval.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit of an earlier filing date of U.S. Provisional Application Serial No. 63 / 547,427, filed on November 6, 2023, the entire disclosure of which is incorporated herein by reference. Background Technology

[0003] In the resource recovery industry, drill strings are used to bore into formations and locate the presence of hydrocarbons within them. Drill strings may incorporate logging-while-drilling (LWD) tools, which include various sensors that can be used to determine formation parameters. Specifically, power tools can be used to measure formation resistivity, which can be used to determine the depth at which hydrocarbons are present in the formation. However, for some formations, resistivity is not a useful parameter for determining the presence of hydrocarbons, particularly when the resistivity difference between hydrocarbon-bearing and non-hydrocarbon-bearing zones is minimal or when prior knowledge of formation characteristics, such as fluid resistivity and formation porosity, is unknown. Therefore, it is desirable to provide a method for employing power tools that can be used to determine parameters other than resistivity, which can be used to identify hydrocarbons in these formations. Summary of the Invention

[0004] This paper discloses a method for identifying pay zones in a formation. A first dielectric constant of the formation at a selected depth or depth interval is measured by transmitting a first electromagnetic wave or signal through the formation at a first frequency in a borehole within the formation. A second dielectric constant of the formation at a selected depth or depth interval is measured by transmitting a second electromagnetic wave or signal through the formation at a second frequency in a borehole within the formation. The pay zone is identified based on the first and second dielectric constants at the selected depths or depth intervals.

[0005] This document discloses a drilling system including a processor. The processor is configured to: measure a first dielectric constant of the formation at a selected depth or depth interval by transmitting a first electromagnetic wave or signal through the formation at a first frequency in a borehole in the formation; measure a second dielectric constant of the formation at the selected depth or depth interval by transmitting a second electromagnetic wave or signal through the formation at a second frequency in the borehole in the formation; and identify an oil-producing layer in the formation based on the first dielectric constant and the second dielectric constant at the selected depth or depth interval. Attached Figure Description

[0006] The following description should not be considered as limiting in any way. Referring to the accompanying drawings, similar element numbers are similar:

[0007] Figure 1 A drilling system in an exemplary embodiment is shown;

[0008] Figure 2 A power tool for a drill string of a drilling system in an exemplary embodiment is shown;

[0009] Figures 3A to 3D An exemplary logging profile obtained from the formation using a formation sensor that can be used with a drill string is shown;

[0010] Figure 4 The graph shows the relationship between the dielectric constant and frequency at different depths in the borehole.

[0011] Figures 5A to 5D Various logging profiles obtained from the formation are shown for illustrative purposes, where resistivity is not applicable for determining the presence of hydrocarbons;

[0012] Figure 6 This is a flowchart of a method for detecting hydrocarbon-bearing reservoirs at a certain depth in a borehole; and

[0013] Figure 7 This is a flowchart of another method for detecting hydrocarbons at a certain depth in a borehole. Detailed Implementation

[0014] Specific embodiments of one or more implementations of the devices and methods disclosed herein are presented by way of example rather than limitation, with reference to the accompanying drawings.

[0015] refer to Figure 1A drilling system 100 is disclosed in an exemplary embodiment. The drilling system 100 includes a borehole 102 penetrating a subsurface formation 104. A drill string 106 is disposed within the borehole 102. The drill string 106 includes a fitting 108 extending from a drilling platform 110 at a surface location 112. The fitting 108 includes a bottom hole assembly (BHA) 114, which includes a guide unit 116, a drill bit 118, and one or more formation sensors 120 for measuring various properties of the formation. The formation sensors 120 may include power tools for measuring electrical properties of the formation 104, such as resistivity, conductivity, dielectric constant, etc. Other formation sensors may include, for example, gamma-ray sensors. A controller 122 receives data from the formation sensors and determines the location of hydrocarbons in the formation based on the data. The controller 122 includes a processor 124 for performing various operations of the controller disclosed herein. Controller 122 can send signals to steering unit 116 to guide drill string 106 based on the presence or location of hydrocarbons, such as by guiding the drill string toward hydrocarbon-producing layers (i.e., the depth, depth interval, or depth range in the borehole where the hydrocarbons to be located are located). Additionally or alternatively, controller 122 can send signals to surface equipment for a human operator to command steering unit 116 to guide drill string 106 based on signals from controller 122. Controller 122 can also send signals to surface equipment that controls other drilling parameters, such as revolutions per minute (RPM) and weight on bit (WOB) of drill string 106. Controller 122 can be mounted on drill string 106 or on drilling platform 110 at surface location 112.

[0016] Figure 2 A power tool 200 for a drill string 106 in an exemplary embodiment is shown. The power tool 200 includes a pair of transmitters TX1, TX2 and receivers RX1, RX2. The transmitters TX1, TX2 are positioned at opposite ends along the longitudinal axis of the power tool 200. The receivers RX1, RX2 are positioned between the transmitters TX1, TX2 on the power tool 200 and separated from each other by a gap. The transmitters TX1, TX2 generate one or more electromagnetic waves or signals that propagate through the formation 104. After propagation through the formation 104, the electromagnetic waves or signals are received at the receivers RX1, RX2. The received signals can be sent to a processor 124. The processor 124 determines various characteristics of the formation 104 and, based on these characteristics, transmits information for controlling the operation of the drill string, such as guidance. Figure 2 Two transmitters and two receivers are shown, but it should be understood that in alternative embodiments, the power tool 200 may have any number of transmitters and any number of receivers in various configurations and arrangements (e.g., asymmetric configurations).

[0017] For illustrative purposes, Figures 3A to 3D Various logging profiles 300 obtained from the formation using formation sensor 120 are shown. Logging profile 300 includes resistivity logging profile 302 (…). Figure 3A ), dielectric constant logging curve 304 ( Figure 3B (Obtained from both logging while drilling (LWD) and wireline measurement results), Wireline porosity logging curve 306 ( Figure 3C ) and dielectric constant slope logging curve 308 ( Figure 3D (Obtained from LWD measurements). Although resistivity and dielectric constant are chosen in this disclosure to describe electrical measurement results, those skilled in the art will understand that various ways exist to describe electrical measurement results depending on the definitions used. For example, it is well known that resistivity is the reciprocal of conductivity, and therefore, when using resistivity, it can be replaced by conductivity to produce the same or similar information. Furthermore, in some embodiments, electrical measurements do not use resistivity / conductivity and dielectric constant, but may instead be referred to as the imaginary and real parts of permittivity (sometimes also called dielectric constant), and / or as the real and imaginary parts of conductivity, or related to these real and imaginary parts. It is worth noting that the dielectric constant used is merely the name of a physical quantity and does not imply that the physical quantity is constant in any respect, particularly with respect to variations in one or more of frequency, resistivity / conductivity, temperature, pressure, and / or one or more material properties (such as material properties of underground formations).

[0018] Cable porosity logging profile 306 can be used to determine the presence of hydrocarbons at a specific depth in a formation. Cable porosity logging profile 306 includes a water porosity profile 310 and a total porosity profile 312. The water porosity profile 310 (PORW) can be obtained using a cable multi-frequency multi-array dielectric tool, and the total porosity profile (PORT) can be obtained using a neutron / density tool.

[0019] Total porosity is the sum of water porosity and hydrocarbon porosity. Therefore, the difference or spacing between the water porosity curve 310 and the total porosity curve 312 at a given depth can indicate the presence of hydrocarbons at that depth. Thus, the wireline porosity logging curve 306 indicates a first hydrocarbon-producing layer 314 extending from a depth of approximately 450 feet to approximately 500 feet. The wireline porosity logging curve 306 also indicates a second hydrocarbon-producing layer 316 extending from a depth of approximately 510 feet to approximately 580 feet, and a third hydrocarbon-producing layer 318 extending from a depth of approximately 650 feet to approximately 720 feet.

[0020] The resistivity logging profile 302 can also be used to determine the presence of hydrocarbon-bearing oil-bearing layers in the formation or to confirm the presence of oil-bearing layers indicated by the porosity logging profile. The resistivity logging profile 302 includes resistivity measurements obtained using electromagnetic waves or signals transmitted into the formation 104 at various frequencies. Resistivity typically increases in the presence of hydrocarbons. Therefore, regions 320, 322, and 324 with increased resistivity indicate the presence of hydrocarbons at oil-bearing layers 314, 316, and 318. The resistivity logging profile 302 can be used alone or in conjunction with the wireline porosity logging profile 306 to confirm the presence of hydrocarbon-bearing oil-bearing layers 314, 316, and 318 indicated by the wireline porosity logging profile 306.

[0021] Referring now to dielectric constant logging curve 304, seven dielectric curves are shown. Each dielectric curve includes dielectric constant values ​​obtained over a depth range and at a specified frequency. Five dielectric curves 326 are obtained after drilling using a wireline dielectric tool (not shown). Curves 328 and 330 are dielectric constant values ​​obtained using an LWD power tool with drill string 106 at the LWD operating frequency. For illustrative purposes, curve 330 is obtained using an electromagnetic wave or signal with a frequency of approximately 400 kHz, and curve 328 is obtained using an electromagnetic wave or signal with a frequency of approximately 2 MHz. LWD dielectric constant curves can be used to determine the presence of oil-producing formations using the methods disclosed herein.

[0022] Figure 4 Graph 400 shows the relationship between dielectric constant values ​​and frequency at various depths. The data shown is from [source missing]. Figures 3A to 3D The same dataset is shown. Frequency is shown on a logarithmic scale along the horizontal axis, and the relative permittivity value is shown on the vertical axis (the relative permittivity is the ratio of the measured permittivity to the permittivity of free space, and is therefore a dimensionless quantity). Dielectric profiles of data obtained at different depths within the borehole are shown. Each profile includes data obtained via cable (such as...). Figure 3B Curve 326 in the middle) and LWD (such as Figure 3B The dielectric constant values ​​obtained from curves 328 and 330 are shown in Figure 402. First dielectric curve 402 includes dielectric constant values ​​obtained at a depth of approximately 600 feet. Second dielectric curve 404 includes dielectric constant values ​​obtained at a depth of approximately 700 feet. Third dielectric curve 406 includes dielectric constant values ​​obtained at a depth of approximately 750 feet.

[0023] refer to Figure 3A Image to Figure 3D At a depth of 600 feet (line 332), there is an oil-producing layer outside the hydrocarbon-producing layer, and at a depth of 750 feet (line 336), there is an oil-producing layer inside the layer (i.e., within the third hydrocarbon-producing layer 318).

[0024] Re-reference Figure 4 The slope of the curve indicates whether the associated depth is within an oil-producing layer. Specifically, a curve with a flat or shallow slope corresponds to a depth where a hydrocarbon-bearing oil-producing layer exists. The dielectric constant slope (of the dielectric curve) can be determined using dielectric constant values ​​at multiple frequencies. The frequencies can be selected from a range of about 1 kHz to about 30 MHz. In one embodiment, dielectric constant measurements can be obtained at 100 kHz, 400 kHz, and 2 MHz. In another embodiment, measurements can be obtained at 1 kHz, 2 kHz, 5 kHz, 8 kHz, 10 kHz, 20 kHz, 50 kHz, and 80 kHz. The dielectric constant slope can be calculated based on the dielectric constant values ​​at these frequencies. In one embodiment, the slope line can be determined using regression analysis.

[0025] For illustrative purposes, the dielectric constant slope is determined with respect to dielectric constant values ​​obtained at the first and second frequencies. Those skilled in the art will understand that waves or signals having the first and second frequencies can be simultaneously emitted through the formation, generating waves or signals containing both the first and second frequencies. Alternatively, waves or signals having the first frequency can be emitted through the formation alternately with waves or signals having the second frequency. In a non-limiting embodiment, the dielectric constant slope can be defined as shown in formula (1):

[0026]

[0027] Where DS is the slope of the dielectric constant, and ε f1 It is the dielectric constant at frequency f1, ε f2 It is the dielectric constant at frequency f2. For example, ε f1 and ε f2The dielectric constant can be a measured value or a value calculated from a measured value, such as, but not limited to, an average, a maximum, a minimum, etc. For the exemplary embodiments disclosed herein, the first frequency is 400 kHz and the second frequency is 2 MHz. To determine the presence of an oil-bearing layer, DS can be compared to one or more slope thresholds. An oil-bearing layer is determined to exist at a depth when the slope of the dielectric constant of the curve associated with a certain depth is less than a first slope threshold, and as long as the slope exceeds a second slope threshold. In one embodiment, the first slope threshold and the second slope threshold are the same. In other embodiments, the first and second thresholds may be different, and the second slope threshold may be greater than the first threshold. The dielectric constant slope is expressed as the difference between the logarithm of a first value of the dielectric constant for a first frequency and the logarithm of a second value of the dielectric constant for a second frequency. In other embodiments, the dielectric constant slope can be calculated using a logarithm with one or more different bases, or by using the difference between different values ​​without using a logarithm. In different embodiments, the subtraction of the dielectric constant (logarithm) can be replaced by a ratio of the dielectric constant (logarithm). Alternatively or additionally, the difference between a first value of the dielectric constant for a first frequency and a second value (logarithm) of the dielectric constant for a second frequency may not be relative to... It refers not to a value, but to one or more distinct values, for example Or any other value, such as, for example, a constant or independent of Instead, it depends on constants of other quantities or parameters, such as conductivity, resistivity (e.g., conductivity or resistivity measured at one or both of a first and second frequency), temperature, pressure, etc. In another embodiment, there might be an assignment method that is not... Instead of an analytical function, it is defined, for example, by a table that provides each pair of... The value defines a DS parameter, which can approximate one or more of the analytic functions discussed above. Those skilled in the art will understand that such tables can be generated by computer programs or for each pair... This can be achieved using tools similar to those that assign values ​​to predefined DS parameters.

[0028] The first dielectric curve 402 has the highest dielectric constant slope among the three curves 402, 404, and 406, and the third dielectric curve 406 also has a high dielectric constant slope, although not as steep as the first dielectric curve 402. The second dielectric curve 404 has a relatively flat dielectric constant slope. A slope threshold is selected to distinguish between dielectric constant slopes indicating oil-producing layers (e.g., the second dielectric curve 404) and dielectric constant slopes not associated with oil-producing layers (e.g., the first dielectric curve 402 and the third dielectric curve 406).

[0029] Re-reference Figures 3A to 3D Dielectric constant slope logging curve 308 shows the value of the dielectric constant slope at each logging depth, determined using formula (1). Curve 340 shows the relationship between the dielectric constant slope value and depth. Line 342 is the slope threshold. Dielectric constant slope logging curve 308 shows that in each of the first hydrocarbon-producing layer 314, the second hydrocarbon-producing layer 316, and the third hydrocarbon-producing layer 318, the dielectric constant slope value (curve 340) is substantially lower than the slope threshold (line 342). It is noteworthy that dielectric constant slope logging curve 308 provides this information using only one curve instead of multiple curves to derive the layer distribution of the oil reservoir. Furthermore, dielectric constant slope logging curve 308 can be measured using the same tools as, for example, resistivity logging curve 300, such as power tool 200 using the same sensor assembly used to generate resistivity logging curve 300. This means that the dielectric constant slope logging curve 308 can be measured while the drilling system 100 is drilling, and therefore the drilling system 100 can be guided through the formation 104 using the stratigraphic distribution (e.g., stratigraphic information including hydrocarbon-producing layers 314, 316, 318). In one or more embodiments, the analysis of whether to drill into hydrocarbon-producing layers is performed downhole, such as in the bottom hole assembly 114, and only this information, not the actual DS value, is sent to the drilling platform 110, where it is used to generate guidance commands sent to the bottom hole assembly 114 and the steering unit 116. In other embodiments, information regarding whether to drill into hydrocarbon-producing layers is sent to the downhole processor 124 to automatically generate guidance commands, which are then sent to the steering unit 116. Thus, an automated steering system based on DS measurements is created.

[0030] Figures 5A to 5D Various logging profiles 500 of formations obtained in exemplary embodiments are shown, where the resistivity is insufficient to determine the presence of hydrocarbons (low-resistivity oil-producing layers). Logging profile 500 includes resistivity logging profile 502 (…). Figure 5A ), dielectric constant logging curve 504 ( Figure 5B ), Porosity logging curve 506 ( Figure 5C ) and dielectric constant slope logging curve 508 ( Figure 5D ).

[0031] In porosity logging 506, water porosity logging 510 and total porosity logging 512 indicate the presence of a hydrocarbon-bearing layer 514 at depths of approximately 300 feet to approximately 415 feet. However, resistivity logging 502 shows low resistivity at these depths, making it impossible to confirm the presence of the hydrocarbon-bearing layer 514.

[0032] Dielectric constant slope logging curve 508 shows the dielectric constant slope curve 518 determined at each logging depth using formula (1) based on the curve of dielectric constant logging curve 504. Dielectric constant slope logging curve 508 includes dielectric constant slope curve 518 and slope threshold 520. Dielectric constant slope curve 518 is smaller than slope threshold 520 at depths within the hydrocarbon producing layer 514. Therefore, even when resistivity logging curve 502 cannot identify the producing layer, dielectric constant slope curve 518 can be used to identify the hydrocarbon producing layer.

[0033] Figure 6 This is a flowchart 600 of a method for detecting hydrocarbon-bearing formations at a certain depth in a borehole. In block 602, an electromagnetic signal is emitted through the formation at a certain depth in the borehole, and multiple values ​​of the dielectric constant of the formation at that depth are measured. Each measured value of the dielectric constant corresponds to a selected frequency of the electromagnetic signal. In block 604, a dielectric constant slope is calculated based on the multiple dielectric constant values ​​using regression analysis or other methods. In block 606, the dielectric constant slope is compared with a slope threshold to determine whether a hydrocarbon-bearing formation is present at the selected depth. In block 608, the drill string (such as drill string 106) is controlled to guide the drill string based on the presence of the hydrocarbon-bearing formation.

[0034] Figure 7 This is a flowchart 700 of another method for detecting hydrocarbon-bearing formations at a certain depth in a borehole. In block 702, a first electromagnetic wave or signal is emitted from a transmitter of a power tool through the formation at the selected depth and received at a receiver of the power tool. The first electromagnetic wave or signal has a first frequency. The received signal is used to determine a first value of the dielectric constant (real part) of the formation at the first frequency. In block 704, a second electromagnetic wave or signal is emitted from the transmitter at a second frequency through the formation at the selected depth. The second electromagnetic wave or signal is received at the receiver and used to determine a second value of the dielectric constant of the formation at the second frequency. In block 706, a dielectric constant slope is calculated based on the first and second values ​​using, for example, formula (1) disclosed herein. In block 708, the dielectric constant slope is compared with a slope threshold to determine whether a hydrocarbon-bearing formation exists at the selected depth. In block 710, the drill string is controlled to guide the drill string based on the presence of the hydrocarbon-bearing formation.

[0035] Various methods can be used to determine the slope threshold. In one implementation, the slope threshold can be determined by comparing a measurement of the dielectric constant slope at a given depth with known characteristics of the formation from any available logging or characterization method, such as porosity well characterized during drilling or wireline logging (e.g., in...). Figure 3CCuttings obtained at depth in the case of (as shown in cable porosity logging curve 306). This can be performed in the same drilled borehole, in a nearby borehole, or in a pilot hole in the same oil reservoir. Alternatively, the slope threshold can be determined via a simulation process, where the dielectric constant at various frequencies is calculated from a medium in which formation characteristics and hydrocarbon porosity are known and representative of the drilled formation. In another embodiment, the dielectric constant in a first section of a borehole containing hydrocarbons can be measured to determine a suitable slope threshold. This slope threshold can then be used for a second section of the borehole (typically a subsequently drilled section). The slope threshold can be used to determine the presence of a hydrocarbon-bearing reservoir in the second section based on the dielectric constant measurements obtained in the second section. The slope threshold can be stored in a memory location or a lookup table. The slope threshold can also be determined using other methods, such as correlation with a template or pattern recognition using machine learning.

[0036] The following are some of the aforementioned publicly disclosed implementation schemes:

[0037] Implementation Scheme 1. A method for identifying oil-producing layers in a formation. A first dielectric constant of the formation at a selected depth or depth interval is measured by transmitting a first electromagnetic wave or signal through the formation at a first frequency in a borehole within the formation. A second dielectric constant of the formation at the selected depth or depth interval is measured by transmitting a second electromagnetic wave or signal through the formation at a second frequency in the borehole within the formation. The oil-producing layer is identified based on the first dielectric constant at the selected depth or depth interval and the second dielectric constant at the selected depth or depth interval.

[0038] Implementation Scheme 2. The method according to any of the foregoing implementation schemes further includes determining a dielectric constant slope based on the first dielectric constant and the second dielectric constant, and identifying the oil-producing layer based on the dielectric constant slope.

[0039] Implementation Scheme 3. The method according to any of the foregoing implementation schemes further includes identifying the oil-producing layer based on a comparison of the dielectric constant slope with a dielectric constant slope threshold.

[0040] Implementation Scheme 4. The method according to any of the preceding embodiments, wherein the oil-producing layer is identified by using a processor in the borehole.

[0041] Implementation Scheme 5. The method according to any of the foregoing embodiments, wherein the first frequency or the second frequency is in the range of about 1 kHz to about 30 MHz.

[0042] Implementation Scheme 6. The method according to any of the preceding embodiments, wherein the dielectric constant slope is determined by using a processor in the borehole.

[0043] Implementation Scheme 7. The method according to any of the foregoing embodiments, wherein the first frequency or the second frequency is in the range of about 100 kHz to about 10 MHz.

[0044] Implementation Scheme 8. The method according to any of the foregoing embodiments further includes determining the dielectric constant slope threshold using measurements obtained in a first section of the borehole, wherein the selected depth or depth interval is located in a second section of the borehole that is different from the first section.

[0045] Implementation Scheme 9. The method according to any of the foregoing implementation schemes further includes guiding the drill string based on the identification of the oil-producing layer.

[0046] Implementation Scheme 10. A drilling system comprising a processor configured to: measure a first dielectric constant of the formation at a selected depth or depth interval by emitting a first electromagnetic wave or signal through the formation at a first frequency in a borehole in the formation; measure a second dielectric constant of the formation at the selected depth or depth interval by emitting a second electromagnetic wave or signal through the formation at a second frequency in the borehole in the formation; and identify an oil-producing layer in the formation based on the first dielectric constant at the selected depth or depth interval and the second dielectric constant at the selected depth or depth interval.

[0047] Implementation Scheme 11. A drilling system according to any of the foregoing embodiments, wherein the processor is further configured to determine a dielectric constant slope based on the first dielectric constant and the second dielectric constant, and to identify the oil-producing layer based on the dielectric constant slope.

[0048] Implementation Scheme 12. A drilling system according to any of the foregoing embodiments, wherein the processor is further configured to identify the oil-producing layer based on a comparison of the dielectric constant slope with a dielectric constant slope threshold.

[0049] Implementation Scheme 13. The drilling system according to any of the foregoing embodiments, wherein the processor is located in the borehole.

[0050] Implementation Scheme 14. The drilling system according to any of the foregoing embodiments, wherein the first frequency or the second frequency is in the range of about 1 kHz to about 30 MHz.

[0051] Implementation Scheme 15. A drilling system according to any of the foregoing embodiments, wherein the dielectric constant slope is determined by using a processor in the borehole.

[0052] Implementation Scheme 16. The drilling system according to any of the foregoing embodiments, wherein the first frequency or the second frequency is in the range of about 100 kHz to about 10 MHz.

[0053] Implementation Scheme 17. A drilling system according to any of the foregoing embodiments, wherein the processor is further configured to determine the dielectric constant slope threshold using measurements obtained in a first segment of the borehole, and wherein the selected depth or depth interval is located in a second segment of the borehole that is different from the first segment.

[0054] Implementation Scheme 18. The drilling system according to any of the foregoing embodiments, wherein the processor is further configured to guide the drill string based on the identification of the oil-producing layer.

[0055] In the context of describing the invention (particularly in the context of the appended claims), the terms “an” and “the”, and similar designations, should be interpreted to cover both singular and plural forms, unless otherwise specified herein or clearly contradicted by the context. Furthermore, it should be noted that the terms “first,” “second,” etc., used herein do not indicate any order, quantity, or importance, but are used to distinguish one element from another. The terms “about,” “substantially,” and “generally” are intended to include a degree of error associated with a specific number of measurements based on the equipment available at the time of filing. For example, “about” and / or “substantially” and / or “generally” can include a range of ±8% for a given value.

[0056] Although the invention has been described with reference to one or more exemplary embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for elements therein without departing from the scope of the invention. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of the invention without departing from the basic scope of the invention. Therefore, it is contemplated that the invention is not limited to the specific embodiments disclosed as the best mode contemplated for carrying out the invention, but rather that the invention will encompass all embodiments falling within the scope of the claims. Additionally, exemplary embodiments of the invention have been disclosed in the drawings and detailed descriptions, and although specific terminology has been used, it is used in a general and descriptive sense only, and not for limiting purposes, unless otherwise specified; therefore, the scope of the invention is not limited thereto.

Claims

1. A method for identifying oil-producing layers in a formation (104), the method being characterized in that: Using a first electromagnetic wave or signal emitted at a selected depth or depth interval in a borehole (102) in the formation (104) at a first frequency, a first dielectric constant of the formation (104) at the selected depth or depth interval is measured. Using a second electromagnetic wave or signal emitted at a second frequency at a selected depth or depth interval in the borehole (102) within the formation (104) through the formation (104), a second dielectric constant of the formation (104) at the selected depth or depth interval is measured; and The oil-producing layer is identified based on the first dielectric constant at the selected depth or depth interval and the second dielectric constant at the selected depth or depth interval.

2. The method according to claim 1, further characterized in that, The dielectric constant slope is determined based on the first dielectric constant and the second dielectric constant, and the oil-producing layer is identified based on the dielectric constant slope.

3. The method according to claim 2, further characterized in that, The oil-producing layer is identified by comparing the dielectric constant slope with the dielectric constant slope threshold.

4. The method according to claim 1, wherein, The oil-producing layer is identified by using a processor (124) in the borehole (102).

5. The method according to claim 1, wherein, The first frequency or the second frequency is in the range of about 1 kHz to about 30 MHz.

6. The method according to claim 5, wherein, The first frequency or the second frequency is in the range of about 100 kHz to about 10 MHz.

7. The method according to claim 3, further characterized in that, The dielectric constant slope threshold is determined using measurements obtained in a first section of the borehole (102), wherein the selected depth or depth interval is located in a second section of the borehole (102) that is different from the first section.

8. The method according to claim 1, further characterized in that, The drill string (106) is guided based on the identification of the oil-producing layer.

9. A drilling system (100), characterized in that: Processor (124), the processor being configured to: Using a first electromagnetic wave or signal emitted at a first frequency at a selected depth or depth interval in a borehole (102) in the formation (104) through the formation (104), a first dielectric constant of the formation (104) at the selected depth or depth interval is measured. Using a second electromagnetic wave or signal emitted at a second frequency at a selected depth or depth interval in the borehole (102) within the formation (104) through the formation (104), a second dielectric constant of the formation (104) at the selected depth or depth interval is measured; and The oil-producing layer in the formation (104) is identified based on the first dielectric constant at the selected depth or depth interval and the second dielectric constant at the selected depth or depth interval.

10. The drilling system (100) according to claim 9, wherein, The processor (124) is further configured to determine a dielectric constant slope based on the first dielectric constant and the second dielectric constant, and to identify the oil-producing layer based on the dielectric constant slope.

11. The drilling system (100) according to claim 10, wherein, The processor (124) is further configured to identify the oil-producing layer based on a comparison of the dielectric constant slope with a dielectric constant slope threshold.

12. The drilling system (100) according to claim 9, wherein, The processor (124) is located in the borehole (102).

13. The drilling system (100) according to claim 9, wherein, The first frequency or the second frequency is in the following ranges: (i) about 1 kHz to about 30 MHz; and (ii) about 100 kHz to about 10 MHz.

14. The drilling system (100) according to claim 11, wherein, The processor (124) is further configured to determine the dielectric constant slope threshold using measurements obtained in a first segment of the borehole (102), wherein the selected depth or depth interval is located in a second segment of the borehole (102) that is different from the first segment.

15. The drilling system (100) according to claim 9, wherein, The processor (124) is further configured to guide the drill string (106) based on the identification of the oil-producing layer.

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