A method for quantitatively evaluating fault sealing of clastic rock and application thereof

Abstract

The application provides a clastic rock fault sealing dynamic quantitative evaluation method and application, and relates to the oil and gas exploration technical field.The clastic rock fault sealing dynamic quantitative evaluation method comprises the following steps: 1, low-amplitude fault-controlled trap element research, calculating trap oil and gas filling degree; 2, quantitative evaluation parameter, qualitatively judging whether the fault is sealed or not; 3, simulating sand and mud butt joint relation of each point on the section, and calculating sand and mud ratio and section SGR.Based on single-well lithology data and fault throw of the trap-controlling fault in the Kuqa piedmont zone, the fault sealing property of the Sha 49 well area is dynamically evaluated, simple operation of the sealing quantitative evaluation method is realized, and further method support is provided for the clastic rock trap sealing property in the fault-controlled low-amplitude field.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration technology, specifically to a dynamic quantitative evaluation method and application for the sealing capacity of clastic rock faults. Background Technology

[0002] The Kuqa piedmont region is primarily supplied with hydrocarbons by Jurassic coal-bearing source rocks, supplemented by Triassic strata. Early major faults directly connect source and reservoir, with "T-shaped" transport being the dominant mode. Tightly superimposed high-steep thrust structures control the overall distribution of oil and gas, while local structures control reservoir formation. This presents a complex challenge in processing seismic data both at the surface and underground, making it difficult to identify oil and gas traps and determine reservoir locations.

[0003] Fault sealing is a key factor in the conduction and accumulation of hydrocarbons in low-amplitude structural traps in the Kuqa piedmont region. Significant differences in fault displacement along the Yanan Fault Zone result in variations in lateral sealing across different segments. Unexplored fault-controlled low-amplitude traps in the Kuqa piedmont region generally have an area of ​​<1 km². 2 The sand body thickness is 10-20m, and the fault displacement is <20m. The smaller the fault displacement, the greater the possibility of sand-sand connection between the upper and lower plates of the fault, and the greater the risk of hydrocarbon accumulation in the trap. Therefore, precise assessment of fault sealing performance is required. It is urgent to adopt a research method combining geology and geophysics, and qualitative and quantitative approaches. This involves integrating data from actual drilling lithology, seismic data, and well logging, combined with lithological contrast analysis of the two plates of the controlling fault and parameters such as the sand-mud ratio, to evaluate the fault sealing performance of the Qiuli structural zone. Furthermore, the research results should be applied to the evaluation of low-amplitude trap hydrocarbon potential in the entire Kuqa piedmont zone.

[0004] The existing methods for quantitatively evaluating fault sealing performance are as follows:

[0005] When oil and gas encounter fault planes during migration, there are two main scenarios for continued migration: one is to cross the fault plane and migrate from one side of the fault to the other side, and the other is to migrate along the fault plane to different strata; the former is called lateral migration, and the latter is called vertical migration.

[0006] Currently, the main qualitative evaluation methods include: 1) cross-sectional analysis method, also known as Allan diagram method; 2) comprehensive geological analysis method, mainly the fault-shifted strata sand-soil ratio method to evaluate lateral sealing; 3) nonlinear mapping analysis method to study the sealing of faults in the region; and 4) logical information method to comprehensively judge the sealing of faults.

[0007] The main semi-quantitative-quantitative evaluation methods include: 1) SSF mudstone smearing index method and fault gouge ratio (SGR), which is the ratio of the cumulative thickness of mudstone layer sliding through a certain point on the fault to the fault displacement; 2) sandstone-mudstone docking probability simulation analysis method; 3) cross-sectional pressure method, which can be determined by the pressure formula in physics. Under hydrostatic pressure conditions, the pressure difference (AFPD) on both sides of the fault is essentially the buoyancy pressure on the largest hydrocarbon column in the fault trap.

[0008] Statistics show that the cross-sectional SGR value has an exponential relationship with the pressure difference across the fault:

[0009] Although researchers in this field have established models and evaluation criteria for different factors and aspects affecting fault sealing, some methods have strict usage requirements and conditions, thus having limitations; others are too mathematically rigorous, making practical application difficult and impractical. Comprehensive geological analysis methods, logical information methods, or nonlinear mapping analysis methods, regardless of the scale and characteristics of fault development, all provide an absolute judgment of "sealed" or "unsealed," ignoring the differences in sealing capacity in three-dimensional space caused by various geological factors.

[0010] In summary, due to the unique characteristics of the geological features of the Kuqa piedmont zone, the differences between the geological features and those of the examples described above, and the varying levels of exploration data, it is necessary to optimize and improve the research and analysis methods during the study of fault closure. Summary of the Invention

[0011] To address the aforementioned problems, this invention provides a dynamic quantitative evaluation method for the sealing capacity of clastic rock faults. Based on a clear understanding of the principles of fault sealing capacity quantitative evaluation, the calculation process of dynamic quantitative evaluation is simplified, resulting in an evaluation chart that is easy to operate and yields accurate conclusions. This provides a calculation method for oil and gas migration in low-amplitude fault-controlled traps.

[0012] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0013] On the one hand, the present invention provides a dynamic quantitative evaluation method for the sealing performance of clastic rock faults, comprising the following steps:

[0014] 1) Study on low-amplitude control trap elements and calculation of trap oil and gas filling degree;

[0015] 2) Quantify evaluation parameters and qualitatively determine whether the fault is closed;

[0016] 3) Simulate the sand-mud connection relationship at each point on the cross-section, and calculate the sand-mud ratio and cross-sectional SGR;

[0017] 4) Based on the actual drilling verification of the trap, the low amplitude structural trap controlled by the fault is quantitatively evaluated according to the sand breakage difference, sand-mud ratio and effective sealing zone threshold of cross-section SGR.

[0018] Preferably, in step 1), the element is selected from at least one of the height of the oil and gas column within the trap and the oil and gas-bearing area.

[0019] Preferably, in step 1), the elements include the height of the oil and gas column within the trap and the oil and gas-bearing area.

[0020] Preferably, in step 1), the calculation of the trap's oil and gas filling degree specifically involves: first, statistically analyzing the height of the oil and gas column and the oil and gas-bearing area within the trap; then, compiling a map of the trap's oil and gas-bearing area; and finally, calculating the trap's oil and gas filling degree in conjunction with the actual production of the well area.

[0021] Preferably, in step 2), the evaluation parameter is the discontinuity statistics.

[0022] Preferably, in step 2), the qualitative determination of whether the fault is closed specifically involves: dividing the length of the control ring fracture into 40 parts, calculating the fracture distance of the control ring fracture according to this interval, and comparing it with the thickness of the closed sand layer to qualitatively determine whether the fault is closed.

[0023] More preferably, if the fault distance is greater than or equal to the sand layer thickness, it is determined that the oil and gas can be effectively blocked; if the fault distance is less than the sand layer thickness, it is determined that the oil and gas is randomly blocked.

[0024] Preferably, in step 3), the sand-mud ratio is the ratio of the sandstone thickness to the mudstone thickness of the reservoir within a certain fault distance.

[0025] Preferably, in step 3), the cross section SGR is the ratio of the cumulative thickness of the mudstone layer that slides across a certain point on the fault to the fault displacement.

[0026] Preferably, in step 4), the fault-sand difference is the difference between the thickness of the fault and the sandstone reservoir.

[0027] Furthermore, this invention provides the application of the above-described dynamic quantitative evaluation method for the sealing performance of clastic rock faults in the dynamic quantitative evaluation of fault sealing performance.

[0028] Preferably, the fault is a clastic rock fault.

[0029] Furthermore, this invention provides the application of the above-described dynamic quantitative evaluation method for the sealing performance of clastic rock faults in the construction of a dynamic quantitative evaluation model for fault sealing performance.

[0030] Preferably, the fault is a clastic rock fault.

[0031] Furthermore, this invention provides the application of the above-described dynamic quantitative evaluation method for the sealing performance of clastic rock faults in establishing a dynamic quantitative evaluation system for fault sealing performance.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention addresses the problems of overly mathematical and practically difficult quantitative evaluation methods for the sealing performance of clastic rock faults, as well as inaccurate evaluations due to insufficient dynamic evaluation. It proposes a dynamic quantitative evaluation method for the sealing performance of clastic rock faults. Based on single-well lithological data and fault displacement of the controlling zone in the Kuqa foreland belt, this invention dynamically evaluates the fault sealing performance of the Sha 49 well area, simplifying the operation of the quantitative evaluation method and further providing methodological support for the sealing performance of clastic rock traps in low-amplitude fault-controlled areas. Attached Figure Description

[0034] Figure 1 Statistical diagram of fault displacement in the control zone of the Sha 49 well area.

[0035] Figure 2 The chart shows the fault displacement and sand-mud ratio of the control zone in the Sha 49 well area, where ①, ②, ③, and ④ correspond to... Figure 1 The positions of ①, ②, ③, and ④ in the middle.

[0036] Figure 3 The diagram shows the SGR of the cross section of well Sha 4901, where a is the simulated SGR of well Sha 4901 under different fault displacements; b is the relationship between the simulated SGR of well Sha 4901 and depth under different fault displacements.

[0037] Figure 4 Evaluation diagram of the sealing performance of well Sha 4901. Detailed Implementation

[0038] To make the technical means, creative features, achieved objectives, and effects of this invention readily understandable, the invention is further illustrated below with specific embodiments. However, these embodiments are merely preferred embodiments and not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments described herein without creative effort are all within the scope of protection of this invention. It is worth noting that the raw materials used in this invention are all common commercially available products, and their sources are not specifically limited. The technical and scientific terms used in the embodiments have the meanings commonly understood by those skilled in the art to which this invention pertains.

[0039] Example 1

[0040] Dynamic quantitative evaluation of fault sealing performance in the Sha 49 well area

[0041] 1) Study on low-amplitude fault-controlled trap elements and calculation of trap oil and gas filling degree.

[0042] Sha 49 Well Area:

[0043] Located on the northern block of the eastern segment of the Yanan Fault, extending in a NE direction, the gas column heights of the three gas layers are 13.2m, 20.0m, and 46.5m from top to bottom, respectively, with oil and gas layer thicknesses of 2.5m, 8.5m, and 10.0m. It belongs to a layered condensate gas reservoir with edge water, controlled by a fault-antic structural trap (e.g., Figure 1 (As shown).

[0044] Based on the cumulative production data of the lower gas layer in Well E3s of Sha 49, the oil and gas-bearing area of ​​the Sha 49 well area is estimated to be 0.096 km². 2 The trap's oil and gas saturation is 26%, and the discrepancy between the output and the trap's resource volume is due to fault plugging. A segment of the controlling fault may be in an ineffective plugging state.

[0045] 2) Quantitative evaluation parameters to qualitatively determine whether the fault is sealed: Statistics on fault displacement in the control zone of Sha 49 well area (top surface of lower gas layer T2 in E3s). 3-1 The results are 3m-30m, and the fault displacement of the three traps west of Sha 4901 is 20-36m. Figure 2 The portion of the fault displacement greater than the sand thickness can be qualitatively judged as having good sealing performance. The sand thickness in the Sha 49 well area is 12m, and the portion of the fault displacement greater than 12m has good sealing performance. The sand thickness of the three traps west of Sha 4901 is 13m, and the portion of the fault displacement greater than 13m has good sealing performance.

[0046] 3) The sand-mud connection relationship at each point on the cross-section was precisely simulated, and the calculated sand-mud ratio was 0.56-3.2. The sand-mud ratio of well Sha 49 was 0.58. Figure 2 The sand-sludge ratio of the three traps west of Sha 4901 is <0.8. Simulated cross-sectional SGR of Sha 4901 well at different fault displacements ranges from 5% to 67%. Below 4910m, the cross-sectional SGR is generally <40%, while when the fault displacement is >30m, the cross-sectional SGR is generally >40%. Figure 3 In the three closed sections west of Sha 4901, the SGR (Self-Growth Rate) is generally >40%. Figure 4 ).

[0047] 4) Based on the actual drilling verification of the trap, a quantitative evaluation of the low-amplitude structural trap controlled by the fault is conducted according to the sand breakage difference, sand-sludge ratio, and effective sealing zone threshold of the cross-sectional SGR:

[0048] Based on the spatial distribution and fault displacement of the traps, the Sha-49 well area is divided into western, central, and eastern sections. The sand-to-soil ratio of the fault-triggered formation is less than 0.8. The controlling faults in the Sha-49 well area exhibit a characteristic of decreasing sand-to-soil ratio with increasing fault displacement: the western section has a sand-to-soil ratio >0.8, the central section <0.8, and the eastern section >0.8. The central section shows the best sealing performance at the sand-to-soil junction. In the western section of the Sha-4901 well area, the fault displacement is >30 m, and the cross-sectional SGR is generally >40%, placing it within the effective sealing zone. In the eastern section of the Sha-4901 well area, the fault displacement is <30 m, and the cross-sectional SGR below 4910 m is generally <40%, placing it within the ineffective sealing zone. Based on the verification of the evaluation results by actual drilling, the three traps west of Sha-4901 were evaluated and predicted. Their fault displacements are all greater than the sand thickness, and the sand-to-soil ratio and cross-sectional SGR are within the effective sealing zone threshold, placing them within the effective sealing zone. Figure 4 ).

[0049] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A dynamic quantitative evaluation method for the sealing performance of clastic rock faults, characterized in that, Includes the following steps: 1) Study on low-amplitude control trap elements and calculation of trap oil and gas filling degree; 2) Quantify evaluation parameters and qualitatively determine whether the fault is closed; 3) Simulate the sand-mud connection relationship at each point on the cross-section, and calculate the sand-mud ratio and cross-sectional SGR; 4) Based on the actual drilling verification of the trap, the low amplitude structural trap controlled by the fault is quantitatively evaluated according to the sand breakage difference, sand-mud ratio and effective sealing zone threshold of cross-section SGR.

2. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 1, characterized in that, In step 1), the element is selected from at least one of the height of the oil and gas column within the trap and the oil and gas-bearing area.

3. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 2, characterized in that, In step 1), the elements include the height of the oil and gas column within the trap and the oil and gas-bearing area.

4. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 1, characterized in that, In step 1), the calculation of the trap's oil and gas filling degree specifically involves: first, calculating the height of the oil and gas column and the oil and gas-bearing area within the trap; then, compiling a map of the trap's oil and gas-bearing area; and finally, calculating the trap's oil and gas filling degree in conjunction with the actual production of the well area.

5. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 1, characterized in that, In step 2), the evaluation parameter is the discontinuity statistics.

6. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 1, characterized in that, In step 2), the specific method for qualitatively determining whether the fault is closed is as follows: the length of the control ring fracture is divided into 40 parts, the fracture distance of the control ring fracture is calculated according to this interval, and compared with the thickness of the trapped sand layer to qualitatively determine whether the fault is closed.

7. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 6, characterized in that, If the fault distance is greater than or equal to the thickness of the sand layer, it is determined that the oil and gas can be effectively blocked.

8. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 6, characterized in that, If the fault distance is less than the sand layer thickness, it is determined that the oil and gas are randomly blocked.

9. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 1, characterized in that, In step 3), the sand-mud ratio is the ratio of the thickness of sandstone to mudstone on the reservoir side within a certain fault distance.

10. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 1, characterized in that, In step 3), the cross section SGR is the ratio of the cumulative thickness of the mudstone layer that slides through a certain point on the fault to the fault displacement.

11. The dynamic quantitative evaluation method for the sealing performance of clastic rock faults according to claim 1, characterized in that, In step 4), the fault-sand difference is the difference between the thickness of the fault and the thickness of the sandstone reservoir.

12. The application of the dynamic quantitative evaluation method for fault sealing performance of clastic rock as described in any one of claims 1-11 in the dynamic quantitative evaluation of fault sealing performance.

13. The application according to claim 12, characterized in that, The fault is a clastic rock fault.

14. The application of the dynamic quantitative evaluation method for fault sealing performance of clastic rock as described in any one of claims 1-11 in the construction of a dynamic quantitative evaluation model for fault sealing performance.

15. The application according to claim 14, characterized in that, The fault is a clastic rock fault.

16. The application of the dynamic quantitative evaluation method for fault sealing performance of clastic rock as described in any one of claims 1-11 in the establishment of a dynamic quantitative evaluation system for fault sealing performance.

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