CN107861162B - Microelectrode logging data-based natural crack identification method and system - Google Patents
Microelectrode logging data-based natural crack identification method and system Download PDFInfo
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Abstract
A natural crack identification method and system based on microelectrode logging information are disclosed. The method can comprise the following steps: determining the matrix resistivity characteristics of the crack-free formation; obtaining the resistivity characteristics of the fractured stratum, and determining the resistivity response characteristics of the fractured stratum, a microelectrode logging resistivity fracture identification threshold, a micro-potential and micro-gradient fracture resistivity difference threshold; performing inflection point analysis on the microelectrode logging resistivity curve to obtain microelectrode logging resistivity inflection point data and extracting the depth position of crack development; and identifying the crack according to the matrix resistivity characteristics of the crack-free stratum, the microelectrode logging resistivity crack identification threshold, the micro-potential and micro-gradient crack resistivity difference threshold and the microelectrode logging resistivity inflection point data, and calculating the logging response index of the crack. The method realizes the identification and evaluation of the single crack, reduces the uncertainty factor of the traditional method, improves the precision and provides a reliable data base for the three-dimensional crack modeling of the fractured oil-gas reservoir.
Description
Technical Field
The invention relates to the field of geophysical exploration and oil field development, in particular to a natural crack identification method and system based on microelectrode logging data.
Background
The fractured reservoir is a type of oil-gas reservoir commonly encountered in oil-gas exploration and development, and how to effectively identify natural fractures has important significance for reasonably and efficiently developing the type of oil-gas reservoir. At present, the mainstream method for identifying cracks by using conventional well logging is to identify cracks by using conventional well logging acoustic logging, lateral logging and induction logging, but due to the influences of longitudinal resolution and transverse detection depth of the well logging instruments, the well logging series can only identify crack development zones qualitatively in a macroscopic view, and the identification of a single crack is greatly limited. The invention provides a method for identifying the development law of natural cracks of a stratum by utilizing microelectrode logging information and combining conventional logging, a well drilling well body structure and the properties of drilling mud. Belonging to the field of natural crack research. The method comprises the steps of analyzing micro-gradient and micro-potential curve response characteristics of micro-electrode logging information and the mutual relation between micro-potential and micro-gradient, combining rock core and imaging logging information, and simultaneously referring to the structure of a well drilling body and the properties of drilling mud to identify natural cracks encountered by drilling one by one so as to judge the crack development characteristics of the stratum. The method has a good application effect on the identification of the single crack. The identified single crack indication may be applied directly in the three-dimensional stochastic modeling of the crack. Therefore, there is a need to develop a method and system for identifying natural fractures based on microelectrode well logging data.
The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention provides a natural fracture identification method and system based on microelectrode logging information, which realizes effective identification and evaluation of single fracture, reduces uncertainty factors of the traditional method, improves precision and provides a reliable data basis for three-dimensional fracture modeling of fractured oil and gas reservoirs.
According to one aspect of the invention, a method for identifying natural fractures based on microelectrode logging information is provided. The method may include: determining the matrix resistivity characteristics of the crack-free formation; obtaining the resistivity characteristics of the fractured stratum according to the substrate resistivity characteristics of the non-fractured stratum, and further determining the resistivity response characteristics of the fractured stratum, a microelectrode logging resistivity fracture identification threshold, a micro-potential and micro-gradient fracture resistivity difference threshold; performing inflection point analysis on the microelectrode logging resistivity curve to obtain microelectrode logging resistivity inflection point data, and further extracting the depth position of crack development; and identifying the crack according to the matrix resistivity characteristics of the crack-free stratum, the microelectrode logging resistivity crack identification threshold, the micro-potential and micro-gradient crack resistivity difference threshold and the microelectrode logging resistivity inflection point data, and calculating the logging response index of the crack.
Preferably, determining the matrix resistivity characteristics of the fracture-free formation comprises: selecting a measuring well section without borehole collapse and borehole collapse as a well section for extracting the matrix resistivity characteristics of the crack-free stratum according to the well diameter curve; and determining a lower matrix resistivity value of the non-fractured stratum in the characteristic well section of the matrix resistivity of the non-fractured stratum.
Preferably, determining the resistivity response characteristic of the fracture formation, the microelectrode logging resistivity fracture identification threshold, the micro-potential and micro-gradient fracture resistivity variance thresholds comprises: obtaining the resistivity characteristics of the fractured stratum according to the matrix resistivity characteristics of the non-fractured stratum; calculating the resistivity of the fracture simulation based on the resistivity model of the fracture stratum so as to obtain the resistivity response characteristic of the fracture; and simulating the fracture resistivity response characteristics of different strata and different lithologies to obtain the microelectrode logging resistivity fracture identification threshold and the micro-potential and micro-gradient fracture resistivity difference threshold.
Preferably, the fracture simulation resistivity is:
where ρ is the resistivity of the fracture simulation, ρvAnd ρHVertical and horizontal formation resistivities, p, respectively1For the matrix resistivity of a crack-free formation, pmfIs mud filtrate resistivity, pmcThe resistivity of the mud cake, H the longitudinal resolution of the microelectrode logging, L the transverse detection depth of the microelectrode logging, LmcThe thickness of the mud cake and the width of the crack are M.
Preferably, the log response index of the fracture is:
where ρ isbaseLower matrix resistivity value, rho, for a fracture-free formationRMLIs the microelectrode resistivity.
According to another aspect of the present invention, a natural fracture identification system based on microelectrode logging information is provided, which may include: a memory storing computer-executable instructions; a processor executing computer executable instructions in the memory to perform the steps of: determining the matrix resistivity characteristics of the crack-free formation; obtaining the resistivity characteristics of the fractured stratum according to the substrate resistivity characteristics of the non-fractured stratum, and further determining the resistivity response characteristics of the fractured stratum, a microelectrode logging resistivity fracture identification threshold, a micro-potential and micro-gradient fracture resistivity difference threshold; performing inflection point analysis on the microelectrode logging resistivity curve to obtain microelectrode logging resistivity inflection point data, and further extracting the depth position of crack development; and identifying the crack according to the matrix resistivity characteristics of the crack-free stratum, the microelectrode logging resistivity crack identification threshold, the micro-potential and micro-gradient crack resistivity difference threshold and the microelectrode logging resistivity inflection point data, and calculating the logging response index of the crack.
Preferably, determining the matrix resistivity characteristics of the fracture-free formation comprises: selecting a measuring well section without borehole collapse and borehole collapse as a well section for extracting the matrix resistivity characteristics of the crack-free stratum according to the well diameter curve; and determining a lower matrix resistivity value of the non-fractured stratum in the characteristic well section of the matrix resistivity of the non-fractured stratum.
Preferably, determining the resistivity response characteristic of the fracture formation, the microelectrode logging resistivity fracture identification threshold, the micro-potential and micro-gradient fracture resistivity variance thresholds comprises: obtaining the resistivity characteristics of the fractured stratum according to the matrix resistivity characteristics of the non-fractured stratum; calculating the resistivity of the fracture simulation based on the resistivity model of the fracture stratum so as to obtain the resistivity response characteristic of the fracture; and simulating the fracture resistivity response characteristics of different strata and different lithologies to obtain the microelectrode logging resistivity fracture identification threshold and the micro-potential and micro-gradient fracture resistivity difference threshold.
Preferably, the fracture simulation resistivity is:
where ρ is the resistivity of the fracture simulation, ρvAnd ρHVertical and horizontal formation resistivities, p, respectively1For the matrix resistivity of a crack-free formation, pmfIs mud filtrate resistivity, pmcIs mud cake resistivity, and H is microelectrode logging longitudinalThe lateral resolution, L, is the transverse detection depth of microelectrode logging, LmcThe thickness of the mud cake and the width of the crack are M.
Preferably, the log response index of the fracture is:
where ρ isbaseLower matrix resistivity value, rho, for a fracture-free formationRMLIs the microelectrode resistivity.
The method and apparatus of the present invention have other features and advantages which will be apparent from or are set forth in detail in the accompanying drawings and the following detailed description, which are incorporated herein, and which together serve to explain certain principles of the invention.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent by describing in more detail exemplary embodiments thereof with reference to the attached drawings, in which like reference numerals generally represent like parts.
FIG. 1 shows a flow chart of the steps of a method for microelectrode log based natural fracture identification according to the present invention.
FIG. 2 shows a schematic of a numerically simulated microelectrode log fracture response feature according to one embodiment of the present invention.
FIG. 3 shows a schematic diagram of crack identification according to an embodiment of the invention.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.
FIG. 1 shows a flow chart of the steps of a method for microelectrode log based natural fracture identification according to the present invention.
In this embodiment, the method for identifying natural fractures based on microelectrode well log data according to the present invention may include: step 101, determining the matrix resistivity characteristics of a crack-free stratum; 102, obtaining the resistivity characteristics of the fractured stratum according to the substrate resistivity characteristics of the non-fractured stratum, and further determining the resistivity response characteristics of the fractured stratum, a microelectrode logging resistivity fracture identification threshold, a micro-potential and micro-gradient fracture resistivity difference threshold; 103, performing inflection point analysis on the microelectrode logging resistivity curve to obtain microelectrode logging resistivity inflection point data, and further extracting the depth position of crack development; and step 104, identifying the crack according to the substrate resistivity characteristics of the crack-free stratum, the microelectrode logging resistivity crack identification threshold, the micro-potential and micro-gradient crack resistivity difference threshold and the microelectrode logging resistivity inflection point data, and calculating the logging response index of the crack.
In one example, determining a matrix resistivity characteristic of a fracture-free formation includes: selecting a measuring well section without borehole collapse and borehole collapse as a matrix resistivity characteristic well section for extracting a non-fractured stratum according to the well diameter curve; and determining a lower limit value of the matrix resistivity of the non-fractured stratum in the matrix resistivity characteristic well section of the non-fractured stratum.
In one example, determining a resistivity response characteristic of the fracture formation, a microelectrode logging resistivity fracture identification threshold, a micro-potential and micro-gradient fracture resistivity variance threshold comprises: obtaining the resistivity characteristics of the fractured stratum according to the matrix resistivity characteristics of the non-fractured stratum; calculating the resistivity of the fracture simulation based on the resistivity model of the fracture stratum so as to obtain the resistivity response characteristic of the fracture; by simulating the fracture resistivity response characteristics of different stratums and different lithologies, a microelectrode logging resistivity fracture identification threshold value and a micro-potential and micro-gradient fracture resistivity difference threshold value are obtained.
In one example, the resistivity for the fracture simulation is:
where ρ is the resistivity of the fracture simulation, ρvAnd ρHVertical and horizontal formation resistivities, p, respectively1For the matrix resistivity of a crack-free formation, pmfIs mud filtrate resistivity, pmcThe resistivity of the mud cake, H the longitudinal resolution of the microelectrode logging, L the transverse detection depth of the microelectrode logging, LmcThe thickness of the mud cake and the width of the crack are M.
In one example, the log response index of the fracture is:
where ρ isbaseLower matrix resistivity value, rho, for a fracture-free formationRMLIs the microelectrode resistivity.
Specifically, the mechanism of response of microelectrode logging to fractures is based on fractures, particularly resistivity abnormality at the fractures due to mud invasion in the drilling process of a fracture, the abnormality has obvious difference characteristics relative to surrounding rock strata, and the response of microelectrode logging to the fractures depends on factors such as mud performance, filling conditions of the fractures, production states of the fractures, fracture width and well conditions during logging. And analyzing the matrix resistivity of the non-fractured stratum and the resistivity response characteristic of the fractured stratum by utilizing the logging response characteristic of microelectrode logging through core observation description and numerical simulation, and determining the resistivity response characteristic of the fracture so as to evaluate the fracture development characteristic of the stratum.
Determining the matrix resistivity characteristics of a non-fractured stratum, selecting a measuring well section without borehole collapse and borehole collapse as a matrix resistivity characteristic well section for extracting the non-fractured stratum according to a well diameter curve, wherein the resistivity characteristic performance of the stratum is relatively stable and unchanged under the conditions of the same lithology and relatively unchanged stratum fluid property of the non-fractured stratum; counting the numerical distribution characteristics of the micro-potential and the micro-gradient through a histogram in a matrix resistivity characteristic well section of the crack-free stratum, and determining the lower limit value of the micro-potential and micro-gradient matrix resistivity of the crack-free stratum; obtaining the resistivity characteristics of the fractured stratum by combining the properties of drilling mud and utilizing numerical simulation according to the matrix resistivity characteristics of the non-fractured stratum; calculating the resistivity of the fracture simulation to be a formula (1) based on a resistivity model of the fracture stratum so as to obtain the resistivity response characteristic of the fracture; simulating the fracture resistivity response characteristics of different strata and different lithologies to obtain a microelectrode logging resistivity fracture identification threshold and a micro-potential and micro-gradient fracture resistivity difference threshold; performing inflection point analysis on the microelectrode logging resistivity curve by a secondary derivation method to obtain microelectrode logging resistivity inflection point data, and further extracting the depth position of crack development, wherein the low resistivity characteristic of crack response appears at the maximum value of the secondary derivation; identifying the crack according to the substrate resistivity characteristics of the crack-free stratum, the microelectrode logging resistivity crack identification threshold, the micro-potential and micro-gradient crack resistivity difference threshold and the microelectrode logging resistivity inflection point data, wherein the crack identification conditions are as follows: 1) rho < rho _ frac, 2) micro potential/micro gradient resistivity difference < rho _ diff, 3) microelectrode curve inflection point value >0, and identifying the fracture when the conditions 1) -3) are met, wherein rho _ frac is a microelectrode logging resistivity fracture identification threshold, rho _ diff is a micro potential and micro gradient fracture resistivity difference threshold, and the logging response index of the fracture is calculated to be formula (2).
The method realizes effective identification and evaluation of the single crack, reduces uncertainty factors of the traditional method, improves precision, and provides a reliable data base for three-dimensional crack modeling of the fractured oil-gas reservoir.
Application example
To facilitate understanding of the solution of the embodiments of the present invention and the effects thereof, a specific application example is given below. It will be understood by those skilled in the art that this example is merely for the purpose of facilitating an understanding of the present invention and that any specific details thereof are not intended to limit the invention in any way.
Determining the matrix resistivity characteristics of a non-fractured stratum, selecting a measuring well section without borehole collapse and borehole collapse as a matrix resistivity characteristic well section for extracting the non-fractured stratum according to a well diameter curve, wherein the resistivity characteristic performance of the stratum is relatively stable and unchanged under the conditions of the same lithology and relatively unchanged stratum fluid property of the non-fractured stratum; counting the numerical distribution characteristics of micro-potential and micro-gradient through a histogram in a matrix resistivity characteristic well section of the crack-free stratum, and determining a matrix resistivity lower limit value of the crack-free stratum; obtaining the resistivity characteristics of the fractured stratum by combining the properties of drilling mud and utilizing numerical simulation according to the matrix resistivity characteristics of the non-fractured stratum; and (3) calculating the resistivity of the fracture simulation into a formula (1) based on the resistivity model of the fracture stratum, and further obtaining the resistivity response characteristic of the fracture.
FIG. 2 shows a graphical representation of a numerically modeled microelectrode log fracture response characteristic based on a micro-potential substrate resistivity of 10 ohm-meters, a micro-gradient resistivity of 8 ohm-meters, a mud filtrate resistivity of 0.83 ohm-meters, a mudcake resistivity of 2.49 ohm-meters, and a mudcake thickness of 0.5 centimeters, in accordance with an embodiment of the present invention. As can be seen from the figure, the micro-potential and micro-gradient resistivity exhibited very significant descending characteristics with increasing crack width, while the resistivity difference of the micro-electrode and the micro-gradient was significantly reduced.
Simulating the fracture resistivity response characteristics of different strata and different lithologies to obtain a microelectrode logging resistivity fracture identification threshold and a micro-potential and micro-gradient fracture resistivity difference threshold; performing inflection point analysis on the microelectrode logging resistivity curve by a secondary derivation method to obtain microelectrode logging resistivity inflection point data, and further extracting the depth position of crack development, wherein the low resistivity characteristic of crack response appears at the maximum value of the secondary derivation; identifying the crack according to the substrate resistivity characteristics of the crack-free stratum, the microelectrode logging resistivity crack identification threshold, the micro-potential and micro-gradient crack resistivity difference threshold and the microelectrode logging resistivity inflection point data, wherein the crack identification conditions are as follows: 1) rho < rho _ frac, 2) micro potential/micro gradient resistivity difference < rho _ diff, 3) microelectrode curve inflection point value >0, and identifying the fracture when the conditions 1) -3) are met, wherein rho _ frac is a microelectrode logging resistivity fracture identification threshold, rho _ diff is a micro potential and micro gradient fracture resistivity difference threshold, and the logging response index of the fracture is calculated to be formula (2).
FIG. 3 shows a schematic diagram of crack identification according to an embodiment of the invention. The well drilling is in low-hole sandstone stratum and adopts water-based mud. From right to left, respectively, deep medium induction and eight lateral resistivities, a micro-gradient resistivity statistical histogram, a micro potential/micro gradient/sound wave time difference curve, a micro electrode crack response index, a micro potential/micro gradient resistivity difference statistical histogram, a micro potential/micro gradient resistivity difference, micro electrode logging curve inflection point analysis, a stratum lithology section, an imaging logging interpretation result, an imaging logging dynamic diagram, a depth channel, an imaging logging static diagram and a well diameter/natural gamma ray logging. As can be seen from the figure, in the fracture development well section, the acoustic wave time difference and the deep, medium and shallow resistivity values of the conventional well have no obvious change characteristics, so that a single fracture cannot be effectively identified. The microelectrode logging curve has good difference characteristics in a crack development well section, the microelectrode logging crack identification method is used for calculating the logging response index of the microelectrode logging to cracks, and the microelectrode logging response index is compared with the imaging logging crack explanation, so that compared with the traditional conventional logging crack identification method, the microelectrode logging method can be used for more effectively identifying and evaluating single cracks.
In conclusion, the method and the device realize effective identification and evaluation of the single fracture, reduce the uncertainty factor of the traditional method, improve the precision and provide a reliable data base for the three-dimensional fracture modeling of the fractured oil and gas reservoir.
It will be appreciated by persons skilled in the art that the above description of embodiments of the invention is intended only to illustrate the benefits of embodiments of the invention and is not intended to limit embodiments of the invention to any examples given.
According to an embodiment of the present invention, there is provided a natural fracture identification system based on microelectrode well log data, which may include: a memory storing computer-executable instructions; a processor executing computer executable instructions in the memory to perform the steps of: determining the matrix resistivity characteristics of the crack-free formation; obtaining the resistivity characteristics of the fractured stratum according to the matrix resistivity characteristics of the non-fractured stratum, and further determining the resistivity response characteristics of the fractured stratum, a microelectrode logging resistivity fracture identification threshold, a micro-potential and micro-gradient fracture resistivity difference threshold; performing inflection point analysis on the microelectrode logging resistivity curve to obtain microelectrode logging resistivity inflection point data, and further extracting the depth position of crack development; and identifying the crack according to the matrix resistivity characteristics of the crack-free stratum, the microelectrode logging resistivity crack identification threshold, the micro-potential and micro-gradient crack resistivity difference threshold and the microelectrode logging resistivity inflection point data, and calculating the logging response index of the crack.
In one example, determining a matrix resistivity characteristic of a fracture-free formation includes: selecting a measuring well section without borehole collapse and borehole collapse as a matrix resistivity characteristic well section for extracting a non-fractured stratum according to the well diameter curve; and determining a lower limit value of the matrix resistivity of the non-fractured stratum in the matrix resistivity characteristic well section of the non-fractured stratum.
In one example, determining a resistivity response characteristic of the fracture formation, a microelectrode logging resistivity fracture identification threshold, a micro-potential and micro-gradient fracture resistivity variance threshold comprises: obtaining the resistivity characteristics of the fractured stratum according to the matrix resistivity characteristics of the non-fractured stratum; calculating the resistivity of the fracture simulation based on the resistivity model of the fracture stratum so as to obtain the resistivity response characteristic of the fracture; by simulating the fracture resistivity response characteristics of different stratums and different lithologies, a microelectrode logging resistivity fracture identification threshold value and a micro-potential and micro-gradient fracture resistivity difference threshold value are obtained.
In one example, the resistivity for the fracture simulation is:
where ρ is the resistivity of the fracture simulation, ρvAnd ρHVertical and horizontal formation resistivities, respectively, ρ 1 is crack-freeFormation matrix resistivity, ρmfMud filtrate resistivity, rho mc mud cake resistivity, H microelectrode logging longitudinal resolution, L microelectrode logging transverse detection depth, LmcThe thickness of the mud cake and the width of the crack are M.
In one example, the log response index of the fracture is:
where ρ isbaseLower matrix resistivity value, rho, for a fracture-free formationRMLIs the microelectrode resistivity.
The method realizes effective identification and evaluation of the single crack, reduces uncertainty factors of the traditional method, improves the precision, and provides a reliable data base for three-dimensional crack modeling of the fractured oil-gas reservoir.
It will be appreciated by persons skilled in the art that the above description of embodiments of the invention is intended only to illustrate the benefits of embodiments of the invention and is not intended to limit embodiments of the invention to any examples given.
Having described embodiments of the present invention, the foregoing description is intended to be exemplary, not exhaustive, and not limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.
Claims (6)
1. A natural crack identification method based on microelectrode logging information comprises the following steps:
determining the matrix resistivity characteristics of the crack-free formation;
obtaining the resistivity characteristics of the fractured stratum according to the substrate resistivity characteristics of the non-fractured stratum, and further determining the resistivity response characteristics of the fractured stratum, a microelectrode logging resistivity fracture identification threshold, a micro-potential and micro-gradient fracture resistivity difference threshold;
performing inflection point analysis on the microelectrode logging resistivity curve to obtain microelectrode logging resistivity inflection point data, and further extracting the depth position of crack development;
identifying the crack according to the substrate resistivity characteristic of the crack-free stratum, the microelectrode logging resistivity crack identification threshold, the micro-potential and micro-gradient crack resistivity difference threshold and the microelectrode logging resistivity inflection point data, and calculating the logging response index of the crack;
wherein determining the resistivity response characteristic of the fracture formation, the microelectrode logging resistivity fracture identification threshold, and the micro-potential and micro-gradient fracture resistivity difference thresholds comprises:
obtaining the resistivity characteristics of the fractured stratum according to the matrix resistivity characteristics of the non-fractured stratum;
calculating the resistivity of the fracture simulation based on the resistivity model of the fracture stratum so as to obtain the resistivity response characteristic of the fracture;
obtaining a microelectrode logging resistivity crack identification threshold value and a micro-potential and micro-gradient crack resistivity difference threshold value by simulating the crack resistivity response characteristics of different strata and different lithologies;
wherein the fracture simulated resistivity is:
where ρ is the resistivity of the fracture simulation, ρvAnd ρHVertical and horizontal formation resistivities, p, respectively1For the matrix resistivity of a crack-free formation, pmfIs mud filtrate resistivity, pmcThe resistivity of the mud cake, H the longitudinal resolution of the microelectrode logging, L the transverse detection depth of the microelectrode logging, LmcThe thickness of the mud cake and the width of the crack are M.
2. The microelectrode log-based natural fracture identification method of claim 1, wherein determining a matrix resistivity characteristic of the fracture-free formation comprises:
selecting a measuring well section without borehole collapse and borehole collapse as a well section for extracting the matrix resistivity characteristics of the crack-free stratum according to the well diameter curve;
and determining a lower matrix resistivity value of the non-fractured stratum in the characteristic well section of the matrix resistivity of the non-fractured stratum.
3. The method for identifying natural fractures based on microelectrode log data of claim 2, wherein the log response index of the fracture is:
where ρ isbaseLower matrix resistivity value, rho, for a fracture-free formationRMLIs the microelectrode resistivity.
4. A microelectrode logging data-based natural fracture identification system, the system comprising:
a memory storing computer-executable instructions;
a processor executing computer executable instructions in the memory to perform the steps of:
determining the matrix resistivity characteristics of the crack-free formation;
obtaining the resistivity characteristics of the fractured stratum according to the substrate resistivity characteristics of the non-fractured stratum, and further determining the resistivity response characteristics of the fractured stratum, a microelectrode logging resistivity fracture identification threshold, a micro-potential and micro-gradient fracture resistivity difference threshold;
performing inflection point analysis on the microelectrode logging resistivity curve to obtain microelectrode logging resistivity inflection point data, and further extracting the depth position of crack development;
identifying the crack according to the substrate resistivity characteristic of the crack-free stratum, the microelectrode logging resistivity crack identification threshold, the micro-potential and micro-gradient crack resistivity difference threshold and the microelectrode logging resistivity inflection point data, and calculating the logging response index of the crack;
wherein determining the resistivity response characteristic of the fracture formation, the microelectrode logging resistivity fracture identification threshold, and the micro-potential and micro-gradient fracture resistivity difference thresholds comprises:
obtaining the resistivity characteristics of the fractured stratum according to the matrix resistivity characteristics of the non-fractured stratum;
calculating the resistivity of the fracture simulation based on the resistivity model of the fracture stratum so as to obtain the resistivity response characteristic of the fracture;
obtaining a microelectrode logging resistivity crack identification threshold value and a micro-potential and micro-gradient crack resistivity difference threshold value by simulating the crack resistivity response characteristics of different strata and different lithologies;
wherein the fracture simulated resistivity is:
where ρ is the resistivity of the fracture simulation, ρvAnd ρHVertical and horizontal formation resistivities, p, respectively1For the matrix resistivity of a crack-free formation, pmfIs mud filtrate resistivity, pmcThe resistivity of the mud cake, H the longitudinal resolution of the microelectrode logging, L the transverse detection depth of the microelectrode logging, LmcThe thickness of the mud cake and the width of the crack are M.
5. The microelectrode log-based natural fracture identification system of claim 4, wherein determining a matrix resistivity characteristic of the fracture-free formation comprises:
selecting a measuring well section without borehole collapse and borehole collapse as a well section for extracting the matrix resistivity characteristics of the crack-free stratum according to the well diameter curve;
and determining a lower matrix resistivity value of the non-fractured stratum in the characteristic well section of the matrix resistivity of the non-fractured stratum.
6. The microelectrode log-based natural fracture identification system of claim 5, wherein the log response index of the fracture is:
where ρ isbaseLower matrix resistivity value, rho, for a fracture-free formationRMLIs the microelectrode resistivity.
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| CN110007364B (en) * | 2018-11-21 | 2020-06-30 | 中国石油大学(华东) | Natural fracture logging comprehensive identification method based on geological pattern guidance |
| CN110500089B (en) * | 2019-08-15 | 2022-11-01 | 中石化石油工程技术服务有限公司 | Shale gas horizontal well bedding crack evaluation method based on array induction logging data |
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| CN105507890A (en) * | 2014-09-26 | 2016-04-20 | 中国石油化工股份有限公司 | Logging evaluation method suitable for shale gas reservoir geological model |
| WO2017127058A1 (en) * | 2016-01-20 | 2017-07-27 | Halliburton Energy Services, Inc. | Fracture interpretation with resistivity and sonic logs in biaxial anisotropic formations |
| CN106526693A (en) * | 2016-09-30 | 2017-03-22 | 中国石油天然气股份有限公司 | crack identification method and device |
| CN107092036A (en) * | 2017-04-10 | 2017-08-25 | 中国科学院大学 | A kind of Stratum of Volcanic Rocks Fluid Identification Method and system based on reservoir true resistivity inverting |
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