A method for quantitatively determining the fault evolution time by combining geometry and chronology

Abstract

The present invention relates to the field of oil and gas exploration, and specifically relates to a method for quantitatively determining the evolution time of faults by combining geometry and chronology, comprising the following steps: Step 1, dividing the tectonic system; Step 2, qualitatively judging the fault activity evolution process by using geometric methods, and the geometric methods include acoustic emission analysis method, fault activity rate method, balanced profile method and / or iterative backstripping fault offset method; Step 3, based on the judgment results obtained in Step 2, analyzing the fault evolution process by using chronology methods, and the chronology methods include carbon and oxygen isotope method and / or inclusion thermometry analysis method. The method provided by the present invention combines the determination of chronology on the basis of qualitatively determining the fault evolution stages. Compared with the prior art solutions, the present invention can perform spatio-temporal matching of the critical moments of the fault activity time and other hydrocarbon accumulation geological conditions, thereby improving the accuracy of determining the fault evolution time.

Description

Technical Field

[0001] The present invention relates to the field of oil and gas exploration, and in particular to a method for quantitatively determining the evolution time of faults by combining geometry and chronology. Background Art

[0002] At present, the research on the evolution time of faults mainly focuses on the qualitative determination of fault stages, etc. According to paleostress and geometric characteristics, and by using balanced section means, the determination accuracy of the fault formation stage is relatively fuzzy and the time span is relatively large, which is equivalent to only qualitative determination.

[0003] For the quantitative analysis of the fault activity time in the prior art, at present, it is mainly determined by using tests such as acoustic emission. The principle is that brittle materials have memory of the load they have experienced. That is, when rocks are under compressive stress, when the stress on the rocks is greater than the maximum pre-existing stress, obvious acoustic emission signals will appear. By using this characteristic of rocks, in the laboratory, through uniaxial compression tests on rock specimens, and simultaneously measuring the acoustic emission signals generated by the specimens during compression, different levels of stress components are determined according to several mutation points of the acoustic emission signals, so as to analyze how many times the rocks have cracked or the cracks have propagated during compression. This method can accurately determine the time of the last activity of the fault, but cannot determine the stages and activity times of multi-stage active faults. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for quantitatively determining the evolution time of faults by combining geometry and chronology, which can determine the stages and activity times of multi-stage active faults, has higher determination accuracy, and can be regarded as realizing quantitative evaluation, aiming at the problems existing in the prior art.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for quantitatively determining the evolution time of faults by combining geometry and chronology, comprising the following steps:

[0007] Step 1, dividing the tectonic system;

[0008] Step 2, qualitatively judging the evolution process of fault activity by using geometric methods, and the geometric methods include acoustic emission analysis method, fault activity rate method, balanced section method and / or iterative backstripping fault displacement method;

[0009] Step 3, based on the judgment result obtained in Step 2, quantitatively analyzing the evolution process of the fault by using chronology methods, and the chronology methods include carbon-oxygen isotope method and / or inclusion thermometry analysis method.

[0010] As an optional solution of the present invention, in Step 2, the following steps are included:

[0011] Analyze the number of times of tectonic stress through acoustic emission analysis method;

[0012] Determine the geological period of fault activity through the fault activity rate method;

[0013] Iteratively strip back each stratum to analyze the intensity of fault activity in each geological period;

[0014] Perform balanced cross-section restoration on the tectonic deformation, and verify the rationality of the analysis results of the tectonic deformation patterns in different periods of the study area carried out by the foregoing several geometric methods under the macroscopic geological background.

[0015] As an optional solution of the present invention, in the second step, the iterative backstripping fault offset method includes the following steps:

[0016] Obtain the static fault offset parameters;

[0017] Based on the fault graphic curves generated by two adjacent sets of strata, classify the superposition relationship of the fault offsets of two adjacent sets of strata in the single-peak state;

[0018] Based on the classification results, calculate the offset generated by the previous sedimentary period on the previous sedimentary layer in two adjacent sedimentary strata;

[0019] Calculate the offsets generated by each sedimentary period on the corresponding sedimentary layer in sequence according to the order from the later to the earlier sedimentary period.

[0020] As an optional solution of the present invention, it further includes the following steps:

[0021] Calculate the plastic deformation adjustment amount of the stratum.

[0022] As an optional solution of the present invention, the calculation method of the plastic deformation adjustment amount is:

[0023] △K = max(f X1n ) - g X1K

[0024] Wherein, △K is the total value of the accumulated plastic deformation adjustment amount of the plastic stratum K;

[0025] max(f X1n ) is the maximum offset of the brittle stratum;

[0026] g X1K is the offset of the plastic stratum K.

[0027] As an optional solution of the present invention, the superposition relationship of the single-peak curves of the fault offsets of two adjacent sets of strata includes the following types:

[0028] A. The fault pattern curve generated in the previous sedimentation period includes the fault pattern curve generated in the subsequent sedimentation period;

[0029] B. The fault pattern curve generated in the previous sedimentation period intersects with the fault pattern curve generated in the subsequent sedimentation period;

[0030] C. The fault pattern curve generated in the subsequent sedimentation period includes the fault pattern curve generated in the previous sedimentation period.

[0031] As an alternative solution of the present invention, when the superposition relationship of the fault throw between two adjacent strata is of type A, the throw function generated on the previous sedimentary layer in the previous sedimentation period is:

[0032] f′ X2 =f X2 -f X1

[0033] Wherein, f X2 is the fault pattern curve function generated in the previous sedimentation period;

[0034] f X1 is the fault pattern curve function generated in the subsequent sedimentation period;

[0035] f' X2 is the throw function generated on the previous sedimentary layer in the previous sedimentation period;

[0036] As an alternative solution of the present invention, when the superposition relationship of the fault throw between two adjacent strata is of type C, if the attitude of the fault throw changes after the subsequent sedimentation period, the throw function generated on the previous sedimentary layer in the previous sedimentation period is:

[0037]

[0038] If there is a plastic deformation amount in the subsequent sedimentary layer, the throw function generated on the previous sedimentary layer in the previous sedimentation period is:

[0039] f′ X2 =f X2 -f X1 -ΔK X1

[0040] Wherein, f X2 is the fault pattern curve function generated in the previous sedimentation period;

[0041] f X1 is the fault pattern curve function generated in the subsequent sedimentation period;

[0042] α is the dip angle of the fault formed in the previous sedimentation period;

[0043] β is the dip angle of the fault formed in the subsequent sedimentation period;

[0044] Δk X1 It is the total value of the adjusted amount of plastic deformation accumulated during the subsequent deposition period.

[0045] As an alternative embodiment of the present invention, when the fault pattern curves generated during the previous deposition period intersect with the fault pattern curves generated during the subsequent deposition period, the superposition relationship of the fault offsets of two adjacent strata includes the following types:

[0046] B1. The fault pattern curve generated during the previous period is similar to the fault pattern curve generated during the subsequent deposition period;

[0047] B2. The peak value of the fault pattern curve generated during the subsequent deposition period is close to the peak value of the fault pattern curve generated during the previous period, and the peak value of the fault pattern curve generated during the previous period is greater than the peak value of the fault pattern curve generated during the subsequent deposition period;

[0048] B3. The peak position of the pattern generated during the subsequent deposition period is close to the peak value of the fault pattern curve generated during the previous period, and the peak value of the fault pattern curve generated during the previous period is less than the peak value of the fault pattern curve generated during the subsequent deposition period;

[0049] B4. The peak value of the fault pattern curve generated during the subsequent deposition period is far from the peak value of the fault pattern curve generated during the previous period, and the peak value of the fault pattern curve generated during the previous period is greater than the peak value of the fault pattern curve generated during the subsequent deposition period;

[0050] B5. The peak value of the fault pattern curve generated during the subsequent deposition period is far from the peak value of the fault pattern curve generated during the previous period, and the peak value of the fault pattern curve generated during the previous period is less than the peak value of the fault pattern curve generated during the subsequent deposition period.

[0051] As an alternative embodiment of the present invention, when the superposition relationship of the fault offsets of two adjacent strata is of type B1, the offset function generated by the previous deposition period on the previous deposition layer is:

[0052] f′ X2 = f X2 - f X1'

[0053] When the superposition relationship of the fault offsets of two adjacent strata is of type B2, the offset function generated by the previous deposition period on the previous deposition layer is:

[0054]

[0055] When the superposition relationship of the fault offsets of two adjacent strata is of type B3, the offset function generated by the previous deposition period on the previous deposition layer is:

[0056]

[0057] When the superposition relationship of the fault throw between two adjacent strata is of B4 type, the fault throw function generated on the previous sedimentary layer in the previous sedimentary period is:

[0058]

[0059] When the superposition relationship of the fault throw between two adjacent strata is of B5 type and the attitude of the fault plane remains unchanged, the fault throw function generated on the previous sedimentary layer in the previous sedimentary period is:

[0060]

[0061] When the superposition relationship of the fault throw between two adjacent strata is of B5 type and the attitude of the fault plane changes, the fault throw function generated on the previous sedimentary layer in the previous sedimentary period is:

[0062]

[0063] Among them, f' X2 is the fault throw function generated on the previous sedimentary layer in the previous sedimentary period;

[0064] f X2 is the fault graphic curve function generated in the previous sedimentary period;

[0065] f X1 is the fault graphic curve function generated in the later sedimentary period;

[0066] f X1' is the new graphic curve obtained by translating the peak value of the fault graphic curve generated in the later sedimentary period until it is close to the peak value of the fault graphic curve generated in the previous sedimentary period when the peak value of the fault graphic curve generated in the later sedimentary period is far from the peak value of the fault graphic curve generated in the previous sedimentary period;

[0067] α is the dip angle of the fault formed in the previous sedimentary period;

[0068] β is the dip angle of the fault formed in the later sedimentary period;

[0069] Δk is the plastic deformation adjustment amount that occurs in the previous sedimentary layer during the later sedimentary period.

[0070] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are:

[0071] The method for quantitatively determining the fault evolution time by combining geometry and chronology provided by the present invention combines the determination of chronology on the basis of the qualitative determination of the fault evolution stages. Compared with the technical solution in the prior art that only uses geometry for fault evolution analysis, the present invention can perform spatio-temporal matching of the fault activity time and other hydrocarbon accumulation geological conditions at critical moments, thereby improving the accuracy of the determination of the fault evolution time and can be regarded as achieving quantitative evaluation. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a schematic flowchart of the method for quantitatively determining the fault evolution time by combining geometry and chronology provided by the present invention.

[0073] Figure 2 During the process of iterative backstripping of the fault displacement, it is the fault graphic curve of two adjacent strata when the superposition relationship of the fault displacements of two adjacent strata is of type A.

[0074] Figure 3 During the process of iterative backstripping of the fault displacement, it is the fault graphic curve of two adjacent strata when the superposition relationship of the fault displacements of two adjacent strata is of type B.

[0075] Figure 4 During the process of iterative backstripping of the fault displacement, it is the fault graphic curve of two adjacent strata when the superposition relationship of the fault displacements of two adjacent strata is of type B1.

[0076] Figure 5 During the process of iterative backstripping of the fault displacement, it is the fault graphic curve of two adjacent strata when the superposition relationship of the fault displacements of two adjacent strata is of type B2.

[0077] Figure 6 During the process of iterative backstripping of the fault displacement, it is the fault graphic curve of two adjacent strata when the superposition relationship of the fault displacements of two adjacent strata is of type B3.

[0078] Figure 7 During the process of iterative backstripping of the fault displacement, it is the fault graphic curve of two adjacent strata when the superposition relationship of the fault displacements of two adjacent strata is of type B4.

[0079] Figure 8 During the process of iterative backstripping of the fault displacement, it is the fault graphic curve of two adjacent strata when the superposition relationship of the fault displacements of two adjacent strata is of type B5.

[0080] Figure 9 During the process of iterative backstripping of the fault displacement, it is the fault graphic curve of two adjacent strata when the superposition relationship of the fault displacements of two adjacent strata is of type C.

[0081] Figure 10During the process of iterative backstripping fault offset, when the superposition relationship of the fault offsets of two adjacent strata is of type D, the fault graphic curves of two adjacent strata.

[0082] Figure 11 It is a schematic diagram of the paleo-throw and activity speed of the fault.

[0083] Figure 12-1 is a schematic diagram of the fault profile morphology pattern in a certain Area A.

[0084] Figure 12-2 is a schematic diagram of the fault profile morphology pattern in a certain Area B. Detailed implementation manners

[0085] The present invention will be described in detail below with reference to the accompanying drawings.

[0086] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0087] Embodiment

[0088] Please refer to Figure 1 , the present invention provides a method for determining the fault evolution time by combining geometry and chronology for the top beam, which includes the following steps:

[0089] Step 1: Divide the tectonic system;

[0090] Specifically, according to the type and mechanical origin of the structural plane, taking those with common combined morphological characteristics and unified stress characteristics as the benchmark, the tectonic system is divided.

[0091] The tectonic system has various types and manifestations. Each type of tectonic system has a certain morphology and characteristics, has a certain directionality or azimuth, and reflects the mode of tectonic movement and the characteristics of the stress field.

[0092] Step 2: Qualitatively judge the fault activity evolution process by using geometric methods, and the geometric methods include acoustic emission analysis method, fault activity rate method, balanced profile method and / or iterative backstripping fault offset method;

[0093] Combined with the characteristics of regional tectonic evolution, based on the combination patterns, activity characteristics of fault structures in different periods, as well as their influence and role on other tectonic deformations, the three-dimensional geometric characteristics of faults are described in terms of plane and longitudinal directions to clarify their activity patterns and combination characteristics. On this basis, the tectonic deformation characteristics related to faults are analyzed. One is that the fault is the dominant deformation element, and folds are associated with the main deformation faults, affected by the fault attitude. The formation mechanism of folds is mostly related to the propagation, turning, etc. of the fault; the second is that the fold is the dominant deformation element, and the fault is formed by the further development of the fold. Its developed position is mostly at the turning end of the fold, and the generation of the fold has no relation with the development of faults in this area.

[0094] Specifically, in step two, combined with the characteristics of macroscopic tectonic evolution, acoustic emission analysis method, fault activity rate method, balanced profile method and iterative backstripping fault offset method can be used to qualitatively analyze the fault evolution stage.

[0095] Furthermore:

[0096] The acoustic emission analysis method is as follows: When rocks are under compressive stress, when the stress on the rocks is greater than the maximum pre-existing stress, obvious acoustic emission signals will appear. Utilizing this property of rocks, in the laboratory, through uniaxial compression tests on rock specimens, and simultaneously measuring the acoustic emission signals generated by the specimens during compression, different levels of stress components are determined based on several mutation points of the acoustic emission signals, so as to analyze how many times the rocks have cracked or the cracks have propagated during compression.

[0097] Please refer to Figure 11 , the fault activity rate method is as follows: The principle of fault activity rate is based on the fact that fault activity causes differences in the sedimentary thickness of the strata on the hanging wall and footwall of the observed fault. However, under the action of multi-stage and multi-directional stresses, the fault cannot be in a certain stable posture (such as strike-slip), and it will undergo non-coaxial rotation, gradation, etc., which can also cause changes in the thickness of the hanging wall and footwall of the fault, thereby affecting the change in the observed fault offset.

[0098] Please refer to Figure 12-1 and 12-2 , in order to comprehensively reflect the intensity of the fault activity period, first, a suitable horizon and a suitable section need to be found for analysis to comprehensively reflect the activity characteristics of the fault. The superposition analysis of the fault shows that the fault should have the following two characteristics: ① It has a good reflection of the vertical fault offset horizon, which for faults with different attitudes is the horizon close to the lower inflection point; ② It is close to the initial growth point of the fault, such as the detachment surface, decollement surface.

[0099] During the research, first, a tangent is made along the projection of the fault curve. The tangent at the peak position of the curve is the position where the influence of multiple-stage fault activities is most comprehensively manifested. Then, analyze the development of secondary faults in this section, and remove the multiple influences of secondary faults at this point to obtain the activity rate curve that can best reflect the activity stages of the main fault. Summarize this analysis process into four steps: ① Analyze the attitude of the fault surface as a whole and select an appropriate horizon; ② Find the points with large deformations on the projection curve of the fault throw through multiple tangents; ③ Analyze secondary faults in combination with the section and remove the influence of this fault on the fault throw of the main fault; ④ Use the fault throw method to analyze the development period of the fault at this location.

[0100] The balanced cross-section method is as follows: Based on the principle of material balance, reverse the tectonic deformation and gradually restore the tectonic deformation patterns in different periods. The balanced cross-section restoration process mainly includes: ① Determine the stratigraphic and tectonic interpretation schemes; ② Remove faults and folds according to the balance principle; ③ If the balance is not satisfied, modify the interpretation scheme again; ④ Backstrip layer by layer and repeat the above steps for each layer until it is correctly restored. Attention should be paid to the geological tectonic background conditions during the balanced cross-section restoration. On the basis of the research of the acoustic emission and activity rate methods, the tectonic evolution characteristics of the fault depicted by the balanced cross-section method can be further constrained.

[0101] The iterative backstripping throw method is to backstrip the end throws of each fault in each sedimentary period layer by layer. Specifically, the iterative backstripping throw method includes obtaining static fault throw parameters;

[0102] Please refer to Figures 2 - 10 . Specifically, according to the seismic interpretation scheme, obtain fault throw parameters through multiple tangents, where the spatial distribution of the faults that control the tangent coverage range is recorded, the intersection points of the faults and horizons are recorded, and the data with obvious errors are excluded.

[0103] For the same sedimentary layer, judge whether the fault graphic curve is a single-peak curve or a multi-peak curve; for a multi-peak curve, segment the multi-peak curve and divide the multi-peak curve into single-peak curves;

[0104] When segmenting the multi-peak curve into single-peak curves, use the inflection point of the throw change as the segmentation benchmark for segmentation.

[0105] Calculate the plastic deformation adjustment amount;

[0106] Specifically, for two adjacent strata, due to the differences in the physical properties of rocks, there are three relationships. One is a homogeneous medium stratum; the second is that the plasticity of the upper stratum is less than that of the lower stratum, that is, the upper stratum is a brittle stratum and the lower stratum is a plastic stratum; the third is that the plasticity of the upper stratum is greater than that of the lower stratum, that is, the upper stratum is a plastic stratum and the lower stratum is a brittle stratum.

[0107] The lower stratum is the stratum formed in the previous sedimentary period, and the upper stratum is the stratum formed in the later sedimentary period.

[0108] For a homogeneous medium formation, the deformations of the upper and lower formations are uniform, and the plastic deformation amount will not affect the relative positions between the two formations. Therefore, there is no need to consider the plastic deformation adjustment amount;

[0109] For a brittle formation in the upper layer and a plastic formation in the lower layer, the plastic deformation adjustment amount needs to be considered;

[0110] For a plastic formation in the upper layer and a brittle formation in the lower layer, the plastic adjustment of the upper formation is converted into the deformation or folding of the rock. Therefore, there is no need to consider the plastic deformation adjustment amount either.

[0111] Under the action of tectonic stress, not all faults in the plastic formation will immediately undergo obvious slip along the fault plane; under the action of the normal pressure on the fault plane, a frictional force parallel to the fault plane is generated. The magnitude of the frictional force is affected by the physical properties of the rock and the contact relationship between the two sides of the fault; therefore, under the action of external forces, the first to deform are the plastic deformation amounts of the two sides of the fault in the rock layer; the occurrence of its deformation amount needs to meet the requirement of the difference in fault throw between the upper and lower deformation layers under the adjustment of the first-stage stress to achieve energy balance; then, for a fault that has experienced multiple sedimentary periods, the difference between the maximum fault throw of the brittle formation observed in a certain section and the fault throws of each plastic formation is the total value △K of the plastic deformation adjustment amount generated by the fault action from the geological history time to the present.

[0112] For the X1 sedimentary period, assuming f X1n is the fault throw of the brittle formation, then there exists a plastic formation K such that the total value △K of the accumulated plastic deformation adjustment amount of K during the X1 sedimentary period is f X1n the difference between the maximum fault throw of the brittle formation and the fault throw of the plastic formation K. Its mathematical relationship is:

[0113] △K = max(f X1n ) - g X1K

[0114] where △K is the total value of the accumulated plastic deformation adjustment amount of the plastic formation K during the X1 sedimentary period;

[0115] max(f X1n ) is the maximum fault throw of the brittle formation;

[0116] g X1K is the fault throw of the plastic formation K.

[0117] According to the chronological order of the sedimentary periods, based on the obtained f X1n , g X1K , the plastic deformation adjustment amount △k formed separately in each sedimentary period can be calculated.

[0118] For example, for faults with distribution survey line numbers of 50, 100, 150, and 200 respectively, the fault throw f of each layer X11 ={30 / 50, 80 / 100, 100 / 150, 10 / 200}, f X12 ={20 / 50, 90 / 100, 120 / 150, 15 / 200}, g X13 ={5 / 50, 20 / 100, 20 / 150, 10 / 200};

[0119] Select the maximum value for each number in the fault throw sets of the two brittle strata, and get max(f X1n )={30 / 50, 90 / 100, 120 / 150, 15 / 200};

[0120] Then △K = max(f X1n ) - g X1K ={25 / 50, 70 / 100, 100 / 150, 5 / 200}.

[0121] Based on the fault graphic curves generated by adjacent two sets of strata, classify the superposition relationship of the single-peak curves of the fault throws of adjacent two sets of strata, and based on the classification results, calculate the fault throw generated by the previous sedimentary period on the previous sedimentary layer in adjacent two sets of sedimentary strata;

[0122] Let the previous sedimentary period be X2, the fault graphic curve generated in the X2 period be f X2 , the latter sedimentary period be X1, the fault graphic curve generated in the X1 period be f X1 , then there are four cases for the positional relationship between f X2 and f X1 :

[0123] A. The curve of f X2 contains the curve of f X1 ;

[0124] At this time, the fault continues to thrust along the fault that occurred during the X2 sedimentation period during the X1 sedimentation period, and continues to expand along the fault strike on the plane. During the X1 sedimentation, the generated fault throw is f X1 , and its influence on the X2 sedimentation period is also f X1 . Then, after eliminating the influence during the X1 sedimentation, the fault throw function generated during the X2 period itself is:

[0125] f' X2 = f X2 - f X1

[0126] B. The curve of f X2 intersects with the curve of f X1 ;

[0127] At f X2 When the curve of X1 intersects with the curve of f X2 the situation becomes more complex due to re-thrusting at different parts such as oblique reverse thrust and strike-slip of the fault. According to the intersection relationship between the curve of f X1 and the curve image of f

[0128] B1. f X2 is similar to f X1 :

[0129] This similarity means that: translate the graphic curve of f X1 until the peak of f X1 overlaps with the peak of f X2 The new curve obtained by moving is f X1′ At this time, the translated graphic curve of f X1′ coincides or basically coincides with the graphic curve of f X2 In this case, it is considered that after the X1 deposition period, an oblique reverse thrust fault with a certain amount of smoothness occurred, and the one-time reverse thrust caused this overlapping relationship. Then, after eliminating the influence during the X1 deposition, the fault displacement function generated during the X2 period itself is:

[0130] f′ X2 = f X2 - f X1′

[0131] B2. f X1 The peak position of the f X2 graphic is close to the peak position of the f X1 graphic, and the peak of the f X2 graphic is less than the peak of the f

[0132] This closeness means that: the distance between the peak position of the f X1 graphic and the peak position of the f X2 graphic accounts for less than 15% of the total length of the two fault lines. Further, it accounts for less than 10% of the total length of the two fault lines. At this time, it is considered that the oblique reverse thrust fault occurred after the X1 deposition period, but since the oblique stress gradually weakens along the lower oblique side of the main peak when tearing, the fracture did not extend downward. Then, after eliminating the influence during the X1 deposition, the fault displacement function generated during the X2 period itself is:

[0133]

[0134] B3. f X1 The peak position of the f X2 graphic is close to the peak position of the f X1 graphic peak position, and the peak of the f X2The peak of the graph;

[0135] This proximity means that: f X1 The peak position of the graph and f X2 The distance between the peak of the graph and the peak of f is less than 15% of the total length of the two fault lines. Further, it is less than 10% of the total length of the two fault lines. At this time, it is considered that due to the oblique thrust of the oblique thrust fault after the X1 sedimentation period, but due to the plastic adjustment of the X2 sedimentary layer, there is a plastic adjustment amount for the thrust fault. Therefore, after eliminating the influence during X1 sedimentation, the throw function generated by the X2 period itself is:

[0136]

[0137] In the formula, Δk is the plastic deformation adjustment amount that occurs in the X2 sedimentary layer during the X1 sedimentation period.

[0138] B4.f X1 The peak position of the graph is far from f X2 The peak position of the graph, and f X1 The peak of the graph is less than f X2 The peak of the graph;

[0139] This distance means that: f X1 The peak position of the graph and f X2 The distance between the peak of the graph and the peak of f is far enough that X1 The relative relationship between the graph and f X2 The graph cannot be determined to be in proximity. At this time, it is considered that due to the oblique thrust of the oblique thrust fault after the X1 sedimentation period and a large strike-slip amount, but when the oblique stress tears, it gradually weakens obliquely downward along the main peak and the fracture does not extend downward. Therefore, first translate f X1 , so that f X1 The peak of is close to the peak of f X2 The peak of the graph, and the translated curve is f X1′ . Therefore, after eliminating the influence during X1 sedimentation, the throw function generated by the X2 period itself is:

[0140]

[0141] B5.f X1 The peak position of the graph is far from the peak position of f X2 The graph, and f X1 The peak of the graph is greater than the peak of f X2 The peak of the graph;

[0142] At this time, it is considered that there is a large amount of oblique thrust strike-slip after the X1 sedimentation, and there is an influence of the plasticity of the X2 sedimentary layer, and there may also be an influence of the fault plane attitude. Therefore, first translate fX1 , make the peak of f X1 approach the peak of f X2 graph, and the translated curve is f X1′ .

[0143] If there is no influence of the fault plane attitude, after eliminating the influence during X1 deposition, the throw function generated by X2 itself is:

[0144]

[0145] If there is an influence of the fault plane attitude, after eliminating the influence during X1 deposition, the throw function generated by X2 itself is:

[0146]

[0147] Among them, α is the dip angle of the fault formed during X2 deposition;

[0148] β is the dip angle of the fault formed during X1 deposition;

[0149] Δk is the plastic deformation adjustment amount that occurs in the X2 sedimentary layer during X1 deposition.

[0150] C. The curve of f X1 contains the curve of f X2 ;

[0151] At this time, it is considered that there is a possibility of a change in the throw attitude of the fault after X1 deposition, or there is a plastic deformation amount in X2; for the change in the fault plane dip angle, during the movement of the fault, the horizontal throw at the X1 deposition level is converted into a vertical throw; and the vertical throw on the X2 sedimentary layer also changes to a horizontal throw, so the vertical throw state under the same state conditions is restored. Therefore:

[0152]

[0153] If there is a plastic deformation adjustment amount, then:

[0154]

[0155] Among them, α is the dip angle of the fault formed during X2 deposition;

[0156] β is the dip angle of the fault formed during X1 deposition;

[0157] Δk is the plastic deformation adjustment amount that occurs in the X2 sedimentary layer during X1 deposition.

[0158] D. The f X1 graph and the f X2 graph neither intersect nor have an inclusion relationship;

[0159] At this time, it is considered that the interpretation of two faults or one fault is incorrect, and the fault interpretation scheme needs to be modified again.

[0160] Repeat the above steps in the order from the later sedimentary period to the earlier one, and calculate the throw generated in each sedimentary period on the corresponding sedimentary layer layer by layer in turn.

[0161] For the throw on the latest sedimentary layer in geological time, it can be directly read through reading without calculation.

[0162] Step 3: Based on the judgment result obtained in Step 2, analyze the fault evolution process by using chronological methods, and the chronological methods include carbon and oxygen isotope method and / or inclusion thermometry analysis method.

[0163] Among them, the carbon and oxygen isotope analysis method is as follows: Due to the differences in the physical and chemical environments of fluids in different periods, the carbon and oxygen isotope analysis data of fracture fillings in different stages are different. Therefore, the fault activities, filling stages and times can be discriminated according to the carbon and oxygen isotope characteristics of the fillings.

[0164] The beneficial effects of the method for quantitatively determining the fault evolution time by combining geometry and chronology provided by the embodiments of the present invention are as follows:

[0165] 1. On the basis of the qualitative determination of the fault evolution stages, the chronological determination is combined. Compared with the technical solution that only uses geometry to analyze the fault evolution in the prior art, the present invention can perform spatio-temporal matching of the key moments of the fault activity time and other hydrocarbon accumulation geological conditions, thereby improving the accuracy of determining the fault evolution time;

[0166] 2. Based on the fault graphic curves generated by two adjacent sets of strata, the superposition relationship between two adjacent sets of strata is classified in detail. On this basis, the throw is calculated layer by layer, and the entire cross-section of the strata is considered as a whole, which is beneficial to the quantitative analysis of the development of the fault; the plastic deformation adjustment amount is introduced, and the influence of the plasticity of the strata itself on the fault evolution characteristics is considered.

[0167] Taking a certain fault system in western Sichuan as an example, the method for quantitatively determining the fault evolution time by combining geometry and chronology provided by the present invention will be introduced in more detail.

[0168] Perform Step 1: Divide the tectonic system.

[0169] There are two peak points in the upper shallow layer of the fault system described by the geometric characteristics of the fault system, which are located on two survey lines of M1 - M2 - M3 respectively, and are the results of multiple thrusts in different parts. Among them, M1, M2, and M3 are the codes of three different regions respectively. The analysis of the deformation mode shows that there are two directions of thrust: one is from M3 in the north gradually transitioning to M1 in the south; the other is the thrust from the M2 region to the north, with the characteristics of strike - slip thrust.

[0170] Proceed to Step 2. Use geometric methods to qualitatively judge the evolution process of fault activity. The geometric methods include acoustic emission analysis method, fault activity rate method, balanced cross - section method, and / or iterative back - stripping fault offset method;

[0171] Specifically, determine the stages of tectonic stress through the acoustic emission method. The tested acoustic emission curves generally have 4 - level Kaiser effect points, confirming that at least 4 stages of tectonic stress have been experienced.

[0172] Analyze the activity rates of the faults and their secondary faults at the two peak points through the fault activity rate method. The results show that in the entire geological history period, the fault activity in the M1 region is relatively weak. There are three stages of activity in the M2 region, which are after 212 Ma (million years), 215 Ma, and 131 Ma respectively. There are three stages of activity in the M3 region, which are after 212 Ma, 215 Ma, and 131 Ma respectively. From the lateral comparison of the fault activity rates, in the early stage of 212 Ma, M3 is stronger than M2 and M1 regions, showing the characteristic of activity from north to south; while after 131 Ma in the late stage, M2 region is stronger than M3 and M1, showing the characteristic of activity from south to north. At the same time, the NNE - trending F3 fault starts to move after 131 Ma, and the NE - trending F2 also starts to move after 131 Ma.

[0173] Conduct the fault offset iterative back - stripping analysis method. The results show that the fault starts to move in the early Indosinian period, but the development of the fault is relatively limited. At one of the survey lines, the fault offset is about 200 m. In the early and middle Yanshan period, the fault is relatively quiet and basically inactive. After the late Yanshan period, the fault offset expands comprehensively in the shallow, middle, and deep layers to the current range. From the middle Himalayan period to the present, the activity of the fault in another area continues to strengthen.

[0174] The balanced cross-section method is used to verify the rationality of the determination of the aforementioned fault activity periods from a macroscopic perspective. The analysis of three different parts by the balanced cross-section method reveals that: Before the Cretaceous sedimentation, the structure in Area M1 was not well-developed and was in an overall flat state. During the Indosinian and early to middle Yanshanian periods, the tectonic activity in Area M1 was relatively calm. However, after the late Yanshanian period, with the intense occurrence of basin compression and deformation, folding deformation and fault development occurred in Area M1. In the early Indosinian period, affected by tectonic movements, folding deformation occurred in Area M2 and faults began to develop, forming a slight uplift. During the early to middle Yanshanian periods, the tectonic activity in Area M2 was relatively calm. However, after the late Yanshanian period, with the intense occurrence of basin compression and deformation, strong folding deformation occurred in Area M2 and faults and their derivative faults developed. In the Indosinian period, faults began to develop in Area M3. During the early to middle Yanshanian periods, Area M3 was a region with relatively calm tectonic activity. However, after the late Yanshanian period, with the intense occurrence of basin compression and deformation, strong folding deformation occurred in Area M3 and fault growth took place.

[0175] Analysis of the folding deformation layers shows that the folds associated with the faults are single deformation layers in Area M1 and gradually transition to multiple deformation layers in Area M3. Analyzing the deformation layer parameters, it can be seen that deformation in Area M1 only started after the late Yanshanian period, while Area M3 experienced multiple deformations after the middle Indosinian period, late Indosinian period, and late Yanshanian period. Area M2 is between the two.

[0176] Constrained by seismic data and affected by tectonic erosion, the data after 131 Ma (after the late Yanshanian period) cannot be finely divided. However, within a sedimentary time period, there cannot be two different directions of stress. The only stress that conforms to the activity from south to north at 131 Ma, forming faults with a strike-slip feature of NNE - NS, is the eastward extrusion stress of the Tibetan Plateau in the mid - late Himalayan period. And the only stress that conforms to the generation of NE - trending structures and faults and activity from north to south after 131 Ma is the passive thrust stress of the Longmenshan to the east in the late Yanshanian - early Himalayan period.

[0177] Combined with the study of the regional tectonic evolution history, it shows that: In the early and middle Indosinian periods, affected by the Anxian movement, major changes occurred in the sedimentation and tectonic pattern of the basin. A regional unconformity contact formed between the Xujiahe Formation Member 3 and Member 4, marking the end of the history of the passive continental margin basin in western Sichuan. The Yangtze Plate and the Qiangtang Block further collided, causing intense deformation in the Longmenshan and overall uplift of the western Sichuan depression. Affected by the tectonic movements in the early Indosinian period, folding deformation occurred in Areas M3 and M2, forming a slight uplift, while Area M1, being far from the orogenic belt, was relatively calm and the fault system began to develop in a NE - trending direction in Areas M3 and M2.

[0178] In the late Indosinian epoch, affected by the Longmenshan thrust nappe, folding deformation occurred in areas M2 and M3, and faults developed in an inherited manner. In the early to middle Yanshanian epoch, the central and northern parts of western Sichuan were in a post-orogenic tectonic extension stagnation period. The Lower Cretaceous in western Sichuan suffered severe erosion, and in some areas, it was even completely eroded. The subsidence center of the basin migrated to the middle and southern sections of the Longmenshan Mountains. The fault-fold belt in front of the Longmenshan Mountains had been in a continuous sedimentation area, with relatively calm tectonic activities. At this time, each structure in the area inherited its original characteristics, and the fault system no longer developed and grew. In the late Yanshanian - early Himalayan epoch, throughout the fault-fold belt in front of the Longmenshan Mountains, along with the strong occurrence of basin compression deformation, the Longmenshan Mountains strongly uplifted and folded, faults and their derivative faults developed, structures M1, M2, and M3 inherited and developed, faults further developed and extended southward. At this time, the fault and structure trends were still mainly NE. In the middle to late Himalayan epoch, with the strong uplift of the Qinghai-Tibet Plateau, squeezing eastward, right-lateral strike-slip compression and thrusting occurred, and the originally formed folds in areas M1, M2, and M3 were transformed and deformed. Affected by the boundary conditions of the orogenic belt, it was most obvious in area M2. The fault underwent right-lateral strike-slip at this location, developed and connected from south to north, and transformed the original fault morphology.

[0179] The above-mentioned geometric methods such as the acoustic emission method, improved fault activity rate method, balanced profile method, and iterative backstripping fault offset method were used to analyze the evolution of each fault and tectonic system, dynamically reproducing the evolution process of each fault system. However, these methods can only qualitatively determine the evolution process of fault activities, and there are multiple solutions for judging the activities of faults at a certain stage. On this basis, if chronological analysis methods are used to constrain the fault evolution process and conduct fine evolution analysis on different parts of the main faults, the spatio-temporal evolution characteristics of faults can be further quantitatively determined.

[0180] Perform Step 3: Based on the judgment results obtained in Step 2, use chronological methods to analyze the fault evolution process.

[0181] Specifically, according to the carbon and oxygen isotope analysis of the calcite in the associated fractures filled in faults with different strikes in different horizons in the study area, and combined with the thermal history and burial history of the study area, it can be seen that for the Lower Xujiahe Formation (Member 2 - Member 3 of the Xujiahe Formation), the carbon and oxygen isotope values of the fracture fillings show a negative correlation and are mainly distributed in four regions, indicating that the fractures were mainly formed by four phases of tectonic movements: In the late Indosinian epoch, the fracture fillings had relatively high oxygen isotope values (δ 18 O > -12‰). At this time, the maturity of the source rocks in Member 2 and Member 3 of the Xujiahe Formation was relatively low (Ro < 0.8%), and the organic matter in the source rocks underwent thermal decarboxylation and released some organically derived carbon dioxide, resulting in relatively low carbon isotope values of the carbonate cements formed (δ 13 C < -8‰); In the early to middle Yanshanian epoch, with the increase in burial depth and temperature, the oxygen isotope values of the fracture fillings decreased (-15‰ < δ 18O < -12‰). At this time, the maturities of the second - stage and third - stage source rocks are relatively high. Affected by the high - temperature fluid containing inorganic - origin carbon dioxide, the carbon isotope value of carbonate cements increases. In the late Yanshanian period, the burial depth further increases and the temperature further rises, and the oxygen isotope value of fracture - filling materials further decreases (δ 18 O < -15‰); In the Himalayan period, with tectonic uplift, the formation temperature decreases, and the oxygen isotope value of fracture - filling materials increases (-15‰ < δ 18 O < -12‰). At the same time, the north - south faults have a relatively long continuous activity time, and the activity time is from the late Indosinian to the Himalayan period; while the north - east - south - west faults have an activity time from the early - middle Yanshanian to the Himalayan period.

[0182] For the Xushang Formation (the fourth - fifth members of the Xujiahe Formation), the carbon and oxygen isotope values of fracture - filling materials are mainly distributed in three regions, indicating that the fractures are mainly formed by three - stage tectonic movements: In the middle Yanshanian period, with the increase of burial depth and temperature, the oxygen isotope value of fracture - filling materials decreases (δ 18 O > -15‰). At the same time, affected by the medium - high - temperature fluid containing organic - origin CO₂, the carbon isotope value of carbonate cements is relatively negative (δ 13 C < -2‰); In the late Yanshanian period, the burial depth further increases and the temperature further rises, and the oxygen isotope value of fracture - filling materials further decreases (δ 18 O < -15‰); In the Himalayan period, with tectonic uplift, the formation temperature decreases. Affected by the medium - low - temperature fluid containing inorganic - origin CO₂, the carbon and oxygen isotope values of fracture - filling materials increase (δ 18 O > 0‰, δ 18 O > -15‰). According to the results, it can be concluded that the north - south faults have a long continuous activity time, and the activity time is from the middle Yanshanian to the Himalayan period; while the north - east - south - west faults have an activity time from the middle Yanshanian to the late Yanshanian, and in some areas (such as the Majing area), they can continue to be active until the Himalayan period.

[0183] For the Jurassic, the carbon and oxygen isotope values of fracture - filling materials are also mainly distributed in three regions, indicating that the fractures are mainly formed by three - stage tectonic movements: In the middle Yanshanian period, with the increase of burial depth and temperature, affected by the medium - high - temperature fluid containing organic - origin CO₂, the carbon and oxygen isotope values of fracture - filling materials are relatively low (δ 13 C < -7‰, δ 18 O < -15‰); In the late Yanshanian period, the burial depth further increases and the temperature further rises, and the oxygen isotope value of fracture - filling materials further decreases (δ 18 O < -17‰); In the Himalayan period, with tectonic uplift, the formation temperature decreases. Affected by the medium - low - temperature fluid containing inorganic - origin CO₂, the carbon and oxygen isotope values of fracture - filling materials increase (δ 13 C > -5‰, δ 18O > -15‰). It can be seen from the results that the north-south fault has a long continuous activity time, which is from the middle and late Yanshanian to the Himalayan period, while the activity time of the northeast-southwest fault is the Himalayan period.

[0184] In addition, according to the statistics of the homogenization temperature of the inclusions (quartz) in the fractures of the Shaximiao Formation in Well 21 in Area M1, the main peak value of the homogenization temperature of the inclusions is between 100 and 110 °C. Combining the analysis of the thermal history and burial history, it is analyzed that the fault was active during the late K2 - early E1 (late Yanshanian - early Himalayan).

[0185] Generally speaking, the north-south fault has a long continuous activity time, which is from the late Indosinian, middle Yanshanian to the Himalayan period; while the activity time of the northeast-southwest fault is from the early and middle Yanshanian to the Himalayan period.

[0186] The above description is only the preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for quantitatively determining the formation time of a fault by combining geometry and chronology, characterized in that, It includes the following steps: Step 1: Divide the tectonic system; Step 2: Qualitatively judge the evolution process of fault activity by using geometric methods, and the geometric methods include acoustic emission analysis method, fault activity rate method, balanced profile method and / or iterative backstripping fault offset method; Step 3: Based on the judgment results obtained in Step 2, analyze the fault evolution process by using chronology methods to obtain the fault evolution time, and the chronology methods include carbon-oxygen isotope method and / or inclusion thermometry analysis method; In Step 2, it includes the following steps: Analyze how many times of tectonic stresses have passed through the acoustic emission analysis method; Determine the geological period of fault activity through the fault activity rate method; Iteratively backstrip each stratum and analyze the intensity of fault activity in each geological period; Restore the balanced profile of the tectonic deformation, and verify whether the analysis results of the acoustic emission analysis method, the fault activity rate method and the iterative backstripping fault offset method for the tectonic deformation in different periods are reasonable under the geological background; In Step 2, the iterative backstripping fault offset method includes the following steps: Obtain static fault offset parameters; Classify the superposition relationship of the fault offsets of adjacent two sets of strata in the single-peak state based on the fault graphic curves generated by adjacent two sets of strata; Based on the classification results, calculate the fault offset generated by the previous sedimentary period on the previous sedimentary layer in adjacent two sets of sedimentary strata; Calculate the fault offsets generated by each sedimentary period on the corresponding sedimentary layer in turn in the order from the later to the earlier sedimentary period; Calculate the plastic deformation adjustment amount of the strata; The calculation method of the plastic deformation adjustment amount is: △K = max( f X1n ) - g X1K Wherein, △K is the total value of the accumulated plastic deformation adjustment amount of the plastic stratum K; max( f X1n ) is the maximum fault throw of the brittle formation; g X1K is the throw of the plastic formation K; The superposition relationships of the fault offset single-peak curves of adjacent two sets of strata include the following types: A. The fault graphic curve generated by the previous sedimentary period includes the fault graphic curve generated by the later sedimentary period; B. The fault graphic curve generated by the previous sedimentary period intersects with the fault graphic curve generated by the later sedimentary period; C. The fault graphic curve generated by the later sedimentary period includes the fault graphic curve generated by the previous sedimentary period; When the superposition relationship of the fault offsets of adjacent two sets of strata is of type A, the fault offset function generated by the previous sedimentary period on the previous sedimentary layer is: Among them, is the fault graphic curve function generated in the previous deposition period; is the fault graphic curve function generated in the subsequent deposition period; is a function of the throw generated on the advancing sedimentary layer during the previous sedimentation period; When the superposition relationship of the fault offsets of adjacent two sets of strata is of type C, if the fault offset attitude changes after the later sedimentary period, the fault offset function generated by the previous sedimentary period on the previous sedimentary layer is: If there is a plastic deformation amount in the later sedimentary layer, the fault offset function generated by the previous sedimentary period on the previous sedimentary layer is: Among them, is the fault graphic curve function generated in the previous deposition period; is the fault graphic curve function generated in the subsequent deposition period; is the dip angle of the fault formed in the previous sedimentation period; is the dip angle of the fault formed in the subsequent sedimentary period; For the subsequent deposition period, the total value of the accumulated plastic deformation adjustment amount; When the fault graphic curve generated by the previous sedimentary period intersects with the fault graphic curve generated by the later sedimentary period, the superposition relationships of the fault offsets of adjacent two sets of strata include the following types: B1. The fault graphic curve generated by the previous period is similar to the fault graphic curve generated by the later sedimentary period; B2. The peak value of the fault graphic curve generated by the later sedimentary period is close to the peak value of the fault graphic curve generated by the previous period, and the peak value of the fault graphic curve generated by the previous period is greater than the peak value of the fault graphic curve generated by the later sedimentary time; B3. The peak position of the pattern generated in the later sedimentation period is close to the peak of the fault pattern curve generated in the previous period, and the peak of the fault pattern curve generated in the previous period is smaller than the peak of the fault pattern curve generated in the later sedimentation period; B4. The peak of the fault pattern curve generated in the later sedimentation period is far from the peak of the fault pattern curve generated in the previous period, and the peak of the fault pattern curve generated in the previous period is greater than the peak of the fault pattern curve generated in the later sedimentation period; B5. The peak of the fault pattern curve generated in the later sedimentation period is far from the peak of the fault pattern curve generated in the previous period, and the peak of the fault pattern curve generated in the previous period is smaller than the peak of the fault pattern curve generated in the later sedimentation period; When the superposition relationship of the fault throw between two adjacent strata is of type B1, the throw function generated in the previous sedimentation period on the previous sedimentary layer is: When the superposition relationship of the fault throw between two adjacent strata is of type B2, the throw function generated in the previous sedimentation period on the previous sedimentary layer is: When the superposition relationship of the fault throw between two adjacent strata is of type B3, the throw function generated in the previous sedimentation period on the previous sedimentary layer is: When the superposition relationship of the fault throw between two adjacent strata is of type B4, the throw function generated in the previous sedimentation period on the previous sedimentary layer is: When the superposition relationship of the fault throw between two adjacent strata is of type B5 and the attitude of the fault plane remains unchanged, the throw function generated in the previous sedimentation period on the previous sedimentary layer is: When the superposition relationship of the fault throw between two adjacent strata is of type B5 and the attitude of the fault plane changes, the throw function generated in the previous sedimentation period on the previous sedimentary layer is: wherein, is the throw function generated on the previous sedimentary layer during the previous sedimentary period; is the fault graphic curve function generated in the previous deposition period; is the fault graphic curve function generated in the subsequent deposition period; When the peak of the fault pattern curve generated in the latter deposition period is far from the peak of the fault pattern curve generated in the former deposition period, translate the peak of the fault pattern curve generated in the latter deposition period until it approaches the peak of the fault pattern curve generated in the former deposition period, and obtain a new pattern curve; is the dip angle of the fault formed in the previous deposition period; is the dip angle of the fault formed in the subsequent sedimentary period; It is the adjustment amount of plastic deformation that occurs in the previous deposition layer during the subsequent deposition period.

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