Method and device for distinguishing reverse faults using conventional logging curves

Abstract

The present invention provides a method for identifying reverse faults using conventional well logging curves, which comprises: step one: studying known reverse faults in a target area, and calibrating the known reverse faults on nine conventional well logging curves; step two: summarizing the material characteristics of reverse faults based on the formation principle and pattern diagram of reverse faults, combined with the identification of known reverse faults and the genetic characteristics of reverse faults; step three: determining the correspondence between the material structure of the upper and lower plates of the reverse faults and the response mechanism of the well logging curves based on the analysis results of step one and step two; step four: guiding the identification of reverse faults in the target area through the correspondence. The present invention is applicable to reverse fault-prone areas of dense and ultra-dense reservoirs. It directly identifies reverse faults using nine conventional well logging curves, which is an important means of discovering oil and gas and determining the economic sweet spots in such reservoirs, and can provide an accurate basis for improving the effect of oil and gas exploration and development and reducing investment risks; it has low cost, is easy to implement, has a wide coverage, and is highly operable.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field exploration and development, and in particular to a method and device for distinguishing reverse faults using conventional well logging curves. Background Art

[0002] A reverse fault is a type of fault in earthquake structures, where the upper plate rises and the lower plate falls relatively, and is mainly formed by horizontal compression. As for a fault, it is when the underground rock strata are subjected to a certain strength and break, and there is obvious relative movement along the fracture surface. In oil and gas exploration and development, it may be an oil and gas migration channel or a local high-permeability channel in a tight-ultra-tight reservoir, which is of great significance for avoiding exploration and development risks and discovering economic production capacity.

[0003] Using logging technology to directly discover and identify reverse faults is not only helpful for geological research, but also may be an important means to directly find economic sweet spots in tight and ultra-tight reservoirs and avoid investment risks. Traditional logging methods rely on imaging logging or formation dip logging to identify reverse faults. By identifying formation dislocations and abnormal changes in formation dip in imaging logging, reverse faults are judged. This method can only identify and discover reverse faults in a few key wells in the oil field. Due to the exploration and development costs of tight reservoirs, most production wells can only measure the conventional nine logging curves. For oil and gas-bearing areas with frequent reverse faults, reverse faults are easily missed, affecting geological research and timely discovery of economic production capacity.

[0004] Therefore, the present invention provides a method and device for identifying reverse faults using conventional logging curves. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a method for identifying reverse faults using conventional well logging curves, the method comprising the following steps:

[0006] Step 1: Study the known reverse faults in the target area and mark the known reverse faults on nine conventional logging curves;

[0007] Step 2: Based on the formation principle and pattern diagram of reverse faults, combined with the known reverse fault identification and the genetic characteristics of reverse faults, summarize the material characteristics of reverse faults;

[0008] Step 3: Based on the analysis results of step 1 and step 2, determine the corresponding relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve;

[0009] Step 4: Use the corresponding relationship to guide the identification of reverse faults in the target area.

[0010] According to one embodiment of the present invention, the step 1 specifically includes the following steps:

[0011] When identifying reverse faults in a target area, the known reverse faults in the target area are determined through a reverse fault evidence chain.

[0012] According to one embodiment of the present invention, the reverse fault evidence chain includes but is not limited to: the reverse fault depth position determined by seismic interpretation, the formation repetition position identified by logging, and the formation dislocation depth position identified by imaging logging.

[0013] According to an embodiment of the present invention, the step 2 specifically includes the following steps:

[0014] According to the formation principle and pattern diagram of reverse faults, combined with the reverse fault material characteristics of the field outcrops of the target area or the reservoir research in the target area, the structural characteristics of the upper and lower walls of the reverse faults and the characteristics of the cross-section fillings are obtained from the perspective of the principle and the reverse fault structure of the target area.

[0015] According to an embodiment of the present invention, the step 2 specifically includes the following steps:

[0016] According to the reverse fault pattern diagram and the reservoir material analysis in the target area, it can be known that the upper wall of the reverse fault rubs against the lower wall during the thrust process, resulting in an abnormal response in the acoustic time difference. The thickness of the abnormal response is related to the crushing thickness of the upper wall.

[0017] The footwall of the reverse fault is squeezed and pushed by the hanging wall, and the degree of rock compaction increases. In the vicinity of the cross section of the footwall, the increased compaction intensity causes a low sound wave phenomenon caused by local compaction below the cross section. This phenomenon is completely opposite to the sound wave anomaly of the hanging wall.

[0018] At the fracture surface, due to the formation of reverse faults, materials with different rock types from the target area will be filled in, resulting in local mutations in natural gamma.

[0019] According to an embodiment of the present invention, the step three specifically includes the following steps:

[0020] The material-specific relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve is found on the nine conventional logging curves that have been calibrated for the known reverse fault.

[0021] According to an embodiment of the present invention, the step three specifically includes the following steps:

[0022] The corresponding relationship between the material structure characteristics of the upper and lower walls of the known reverse fault and the well logging response structure characteristics of the acoustic wave time difference and natural gamma is established.

[0023] According to an embodiment of the present invention, the step 4 specifically includes the following steps:

[0024] Find the depth position of the natural gamma ray mutation on nine conventional logging curves;

[0025] If the acoustic wave time difference is seen to increase in width above the depth position, and the acoustic wave time difference is seen to decrease and is lower than the adjacent reservoir below the depth position, it is determined to be a reverse fault.

[0026] According to another aspect of the present invention, a storage medium is provided, which contains a series of instructions for executing the method steps as described in any one of the above.

[0027] According to another aspect of the present invention, there is also provided a device for identifying reverse faults using conventional well logging curves, wherein reverse faults are identified by using any of the above methods, and the device comprises:

[0028] A research module, which is used to study known reverse faults in the target area and mark the known reverse faults on nine conventional logging curves;

[0029] A summary module is used to summarize the material characteristics of the reverse fault based on the formation principle and pattern diagram of the reverse fault, combined with the known reverse fault identification and the genesis characteristics of the reverse fault;

[0030] A relationship module, which is used to determine the corresponding relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve based on the analysis results of the research module and the summary module;

[0031] A guidance module is used to guide the identification of reverse faults in the target area through the corresponding relationship.

[0032] The method and device for distinguishing reverse faults by conventional logging curves provided by the present invention can be applied to reverse fault-prone areas in tight and ultra-tight reservoirs. The use of nine conventional logging curves to directly identify reverse faults is an important means for discovering oil and gas and determining the economic sweet spots in such reservoirs, and can provide an accurate basis for improving the effects of oil and gas exploration and development and reducing investment risks. The principle of the present invention is easy to understand, low in cost, easy to implement, wide in coverage, and highly operational.

[0033] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0035] Figure 1A flow chart showing a method for identifying reverse faults using conventional well logging curves according to an embodiment of the present invention is shown;

[0036] Figure 2 A cross-well seismic profile of a well in southwest Sichuan according to an embodiment of the present invention is shown;

[0037] Figure 3 A reverse fault imaging identification diagram of a well in southwest Sichuan according to an embodiment of the present invention is shown;

[0038] Figure 4 A reverse fault genesis analysis pattern diagram according to an embodiment of the present invention is shown;

[0039] Figure 5 A conventional well logging curve identification and calibration diagram of a reverse fault according to an embodiment of the present invention is shown;

[0040] Figure 6 A conventional well logging curve identification diagram of a reverse fault in a well according to an embodiment of the present invention is shown; and

[0041] Figure 7 A structural block diagram of a device for identifying reverse faults using conventional well logging curves according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0043] Reverse faults are key factors in fluid migration and local seepage. According to the literature in my country, there is still a lack of technical methods to accurately identify reverse faults using the conventional nine-logging curve system. Although it is possible to calibrate reverse faults in the conventional nine-logging curves based on a few seismic interpretations combined with logging data, it is difficult to calibrate seismic and logging using the conventional nine-logging curves to identify reverse faults. The reason is the lack of logging identification basis.

[0044] The purpose of the present invention is to directly identify reverse faults in the high-incidence areas of tight and ultra-tight reservoirs using nine conventional logging curves, which is an important means of discovering oil and gas and determining the economic sweet spots in such reservoirs, thereby improving the effects of oil and gas exploration and development and reducing investment risks.

[0045] Figure 1 A flow chart of a method for identifying reverse faults using conventional well logging curves according to an embodiment of the present invention is shown.

[0046] like Figure 1 As shown, in step S101, known reverse faults in the target area are studied and marked on nine conventional logging curves.

[0047] In one embodiment, in step S101, when reverse faults in the target area are identified, known reverse faults in the target area are determined through a reverse fault evidence chain. Specifically, the reverse fault evidence chain includes but is not limited to: reverse fault depth positions determined by seismic interpretation, formation repetition positions identified by logging, and formation dislocation depth positions identified by imaging logging.

[0048] Specifically, in step S101, the known reverse faults in the target area are determined and calibrated. The reverse fault evidence chain is formed through the research results such as the reverse fault depth position determined by seismic interpretation, the formation repetition position identified by logging, and the formation fault depth identified by imaging logging, and the above results are calibrated on the conventional nine logging curves.

[0049] like Figure 1 As shown, in step S102, based on the formation principle and pattern diagram of reverse faults, the material characteristics of reverse faults are summarized in combination with known reverse fault identification and the genesis characteristics of reverse faults.

[0050] In one embodiment, in step S102, based on the reverse fault formation principle and pattern diagram, combined with the reverse fault material characteristics confirmed by field outcrops of the target area or reservoir research in the target area, the structural characteristics of the upper and lower walls of the reverse fault and the characteristics of the section filling are obtained from the perspective of the principle and the reverse fault structure of the target area.

[0051] Furthermore, according to the reverse fault pattern diagram combined with the reservoir material analysis in the target area, it can be known that the upper wall of the reverse fault rubs against the lower wall during the thrust process, resulting in an abnormal response in the acoustic time difference, and the thickness of the abnormal response is related to the crushing thickness of the upper wall.

[0052] Furthermore, the footwall of the reverse fault is squeezed and pushed over by the upper wall, and the degree of rock compaction increases. In the vicinity of the section in the footwall, due to the increased compaction intensity, a low sound wave phenomenon caused by local compaction occurs below the section. This phenomenon is completely opposite to the sound wave anomaly in the upper wall.

[0053] Furthermore, at the fracture surface, due to the formation of reverse faults, materials with rock types different from those in the target area will be filled, resulting in local mutations in natural gamma.

[0054] like Figure 1 As shown, in step S103, based on the analysis results of steps 101 and 102, the corresponding relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve is determined.

[0055] In one embodiment, in step S103, the material-specific relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve is found on the conventional nine logging curves of the calibrated known reverse faults. Further, the corresponding relationship between the material structure characteristics of the upper and lower walls of the known reverse fault and the logging response structure characteristics of the acoustic wave time difference and natural gamma is established.

[0056] Specifically, in step S103, the identification and determination of the exclusive relationship between the genesis mechanism of the reverse fault and the response of the logging curve are studied. According to the analysis results of step S101 and step S102, further research is conducted at the reverse fault depth of the conventional nine logging curves to find the material exclusive relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve. Through the above in-depth analysis, it is studied and deduced whether the identified special logging response characteristic structure is related to the genesis of the reverse fault.

[0057] like Figure 1 As shown, in step S104, the identification of reverse faults in the target area is guided by the corresponding relationship.

[0058] In one embodiment, in step S104, the depth position of the natural gamma ray mutation is searched on the nine conventional logging curves; if the acoustic wave time difference is seen to increase above the depth position, and the acoustic wave time difference is seen to decrease and is lower than the adjacent reservoir below the depth position, it is determined to be a reverse fault.

[0059] In one embodiment, based on the correlation results between the special logging responses of the nine conventional logging curves and the genetic mechanism and genetic structure of the reverse faults, the nine conventional logging curves can be used to carry out extensive reverse fault identification in the study area.

[0060] Specifically, reverse faults are directly identified based on the conventional nine logging curves in step S104. The correlation between the special logging response of the conventional nine logging curves and the genetic mechanism and genetic structure of reverse faults in this area is clarified, and a technical method for identifying reverse faults using the conventional nine logging curves is formed, and this method is used to guide the identification and systematic research of reverse faults in the study area.

[0061] The present invention also provides a storage medium comprising a series of instructions for executing the method steps as described in any one of the above.

[0062] In summary, using known reverse faults to calibrate the specific positions of the nine conventional logging curves, based on the difference in the formation mechanism of the upper and lower plates of the reverse faults and the logging response characteristics of the section filling materials, finding the corresponding response characteristics of the above principles in the nine conventional logging curves (clarifying the exclusive relationship between the logging characteristics and the geological causes of the reverse faults) is undoubtedly a new way to directly use the nine conventional logging curves to identify and discover reverse faults from a completely new perspective, which has practical significance for broadening the identification of reverse faults by logging curves.

[0063] Figure 2 This is a seismic profile of a well in southwest Sichuan. In the seismic profile, a clear fault can be seen below 5,100 meters, which is the seismic identification basis for the development of faults in the Xujiahe Formation in the well.

[0064] Figure 3 According to the imaging interpretation results of the well, an obvious fault was found between 5124 and 5125 meters. Continuous sedimentary strata can be seen below the fault surface; various gravels related to the fault can be seen above the fault surface. The imaging logging interpretation provides clear fault features, which clearly proves Figure 2 Determination of faults based on medium-sized seismic profiles.

[0065] according to Figure 4 The reverse fault pattern diagram shown in the figure, combined with the analysis of reservoir materials in the study area, shows that the upper plate of the reverse fault rubs against the lower plate during the thrust process, which is prone to local crushing. This local crushing can easily cause an abnormal response in the acoustic time difference, and the thickness of this abnormal response (or abnormal change zone) will be related to the thickness of the crushing of the upper plate of the fault; the lower plate of the fault is squeezed and pushed by the upper plate, and the degree of rock compaction will increase. At the section near the lower plate, due to the increase in compaction intensity, there will be a low acoustic wave phenomenon caused by local compaction below the section, which is completely opposite to the acoustic wave anomaly of the upper plate; at the section, the Xujiahe Formation in western Sichuan is mainly composed of dense clastic rocks, so it is often filled with sand and mud materials. If both sides of the section are sandstone reservoirs, the presence of mud will cause a local increase in natural gamma.

[0066] According to the reverse fault genesis model and the reservoir material characteristics in the study area, a unique relationship between the geological genesis mechanism of reverse faults in the study area and the response of well logging curves was constructed. Based on this unique relationship, reverse faults can be directly identified by only nine conventional well logging curves.

[0067] Figure 5 In order to drill the second section of the stratum in a well in southwest Sichuan, Figure 5 There is a thin interface between two sand layers between 5124 and 5125 meters. The natural gamma value of this interface is slightly higher than that of sandstone and much lower than that of mudstone. It is obvious that it can constitute a genetic explanation relationship with the mixed accumulation of various materials. The well logging above this thin interface shows that the three sections of black shale formations are repeated in many places, which further proves that a reverse fault was encountered at this location.

[0068] In the sandstone above the section, the acoustic time difference is significantly increased and has a certain thickness, which can be explained by the acoustic time difference of stratum crushing (stratum crushing causes the acoustic time difference to attenuate, resulting in an increase in the time difference); the acoustic time difference below the thin layer interface is significantly lower than that of the adjacent sandstone reservoir, which can be explained by the compression and thrust of the upper plate under the fault footwall and the increase in rock compaction strength. It can be seen that the abnormal change structure of the acoustic time difference here is consistent with the cause of the reverse fault and can be explained by the cause. Therefore, it can be confirmed that the structural characteristics of the acoustic time difference and natural gamma logging response at this location are exclusive to the reverse fault and are consistent with the cause of the reverse fault.

[0069] Figure 6 The various genetic characteristics of the medium reverse fault also have structural corresponding characteristics in the conventional nine logging curves. First, the natural gamma at 4764 meters increases slightly, which may be related to the mud filling at the section; above this depth, the acoustic time difference value increases widely, which may be related to the acoustic time difference characteristics of the formation breakage; below this depth, the acoustic time difference decreases and is lower than the adjacent sandstone reservoir.

[0070] The special changes in the above logging curves are all related to the structural characteristics of the reverse fault. Obviously, the well encountered a reverse fault. The early gas logging of this section of the formation showed poor results, and the logging did not interpret the gas layer. Although the early test production was not high, the cumulative gas production has reached tens of millions of cubic meters. It can be seen that if such gas-bearing reverse faults are missed, it is easy to cause errors in logging interpretation and affect the timely discovery of gas layers.

[0071] In practical applications, the present invention has a good application effect in the Xujiahe Formation in the western Sichuan region of the Sichuan Basin, and has achieved direct identification of reverse faults using nine conventional logging curves.

[0072] Figure 7 The structure block diagram of the device for identifying reverse faults using conventional well logging curves according to one embodiment of the present invention is shown. Figure 7 As shown, the device 700 for identifying reverse faults using conventional logging curves performs reverse fault identification using any of the methods described above. The device 700 for identifying reverse faults using conventional logging curves comprises: a research module 701, a summary module 702, a relationship module 703 and a guidance module 704.

[0073] The research module 701 is used to study the known reverse faults in the target area and mark the known reverse faults on nine conventional logging curves.

[0074] The summary module 702 is used to summarize the material characteristics of the reverse fault based on the formation principle and pattern diagram of the reverse fault, combined with the known reverse fault identification and the genesis characteristics of the reverse fault.

[0075] The relationship module 703 is used to determine the corresponding relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve based on the analysis results of the research module and the summary module.

[0076] The guidance module 704 is used to guide the identification of reverse faults in the target area through the corresponding relationship.

[0077] In summary, the method and device for identifying reverse faults using conventional logging curves provided by the present invention can be applied to reverse fault-prone areas in tight and ultra-tight reservoirs. Directly identifying reverse faults using nine conventional logging curves is an important means for discovering oil and gas and determining the economic sweet spots in such reservoirs, and can provide an accurate basis for improving the effects of oil and gas exploration and development and reducing investment risks. The principle of the present invention is easy to understand, low in cost, easy to implement, has a wide coverage, and is highly operational.

[0078] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should be extended to equivalent substitutions of these features understood by ordinary technicians in the relevant field. It should also be understood that the terms used herein are only used for the purpose of describing specific embodiments and are not meant to be limiting.

[0079] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0080] Although the embodiments disclosed in the present invention are as above, the contents described are only embodiments adopted for facilitating the understanding of the present invention and are not intended to limit the present invention. Any technician in the technical field to which the present invention belongs can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present invention, but the patent protection scope of the present invention shall still be subject to the scope defined in the attached claims.

Claims

1. A method for identifying reverse faults using conventional well logging curves, characterized in that: The method comprises the following steps: Step 1: Study the known reverse faults in the target area and mark the known reverse faults on nine conventional logging curves; Step 2: Based on the formation principle and pattern diagram of reverse faults, combined with the known reverse fault identification and the genetic characteristics of reverse faults, summarize the material characteristics of reverse faults; The step 2 specifically includes the following steps: according to the reverse fault formation principle and the model diagram, combined with the reverse fault material characteristics of the field outcrop of the target area or the target area reservoir research, from the perspective of the reverse fault formation principle and the reverse fault structure of the target area, obtain the structural characteristics of the upper wall and the lower wall of the reverse fault and the characteristics of the cross-section filling material; Step 3: Based on the analysis results of step 1 and step 2, determine the corresponding relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve; The step three specifically includes the following steps: establishing a corresponding relationship between the material structure characteristics of the upper and lower walls of the known reverse fault and the well logging response structure characteristics of the acoustic wave time difference and natural gamma; Step 4: guiding the identification of reverse faults in the target area through the corresponding relationship; The step four specifically includes the following steps: searching for the depth position of the natural gamma ray mutation on the nine conventional logging curves; if the acoustic wave time difference increases above the depth position, and the acoustic wave time difference decreases below the depth position and is lower than the adjacent reservoir, it is determined to be a reverse fault.

2. The method for identifying reverse faults using conventional well logging curves as claimed in claim 1, characterized in that: The step 1 specifically includes the following steps: When identifying reverse faults in a target area, the known reverse faults in the target area are determined through a reverse fault evidence chain.

3. The method for identifying reverse faults using conventional well logging curves as claimed in claim 2, characterized in that: The reverse fault evidence chain includes: the reverse fault depth position determined by seismic interpretation, the formation repetition position identified by logging, and the formation dislocation depth position identified by imaging logging.

4. The method for identifying reverse faults using conventional well logging curves according to claim 1, characterized in that: The step 2 specifically includes the following steps: According to the reverse fault pattern diagram and the reservoir material analysis in the target area, it can be known that the upper wall of the reverse fault rubs against the lower wall during the thrust process, resulting in an abnormal response in the acoustic time difference. The thickness of the abnormal response is related to the crushing thickness of the upper wall. The footwall of the reverse fault is squeezed and pushed by the hanging wall, and the degree of rock compaction increases. In the vicinity of the cross section of the footwall, the increased compaction intensity causes a low sound wave phenomenon caused by local compaction below the cross section. This phenomenon is completely opposite to the sound wave anomaly of the hanging wall. At the fracture surface, due to the formation of reverse faults, materials with different rock types from the target area will be filled in, resulting in local mutations in natural gamma.

5. The method for identifying reverse faults using conventional well logging curves as claimed in claim 1, characterized in that: The step three specifically includes the following steps: The material-specific relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve is found on the nine conventional logging curves that have been calibrated for the known reverse fault.

6. A storage medium, characterized in that: It contains a series of instructions for executing the method steps as claimed in any one of claims 1-5.

7. A device for identifying reverse faults using conventional well logging curves, characterized in that: Reverse fault identification is performed by the method according to any one of claims 1 to 5, wherein the device comprises: A research module, which is used to study known reverse faults in the target area and mark the known reverse faults on nine conventional logging curves; A summary module is used to summarize the material characteristics of the reverse fault based on the formation principle and pattern diagram of the reverse fault, combined with the known reverse fault identification and the genesis characteristics of the reverse fault; A relationship module, which is used to determine the corresponding relationship between the material structure of the upper and lower walls of the reverse fault and the response mechanism of the logging curve based on the analysis results of the research module and the summary module; A guidance module is used to guide the identification of reverse faults in the target area through the corresponding relationship.

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