Method for quantitatively describing fault inversion process based on equilibrium profile

Abstract

The invention discloses a method for quantitatively describing a fault inversion process based on an equilibrium profile. The method comprises the following steps: S1, selecting a geological profile; s2, dividing different inversion stage sequence stratums; s3, geological historical periods of different activity stages of the reverse fault are determined; s4, recovering the evolution history of the reverse fault by using a balance section technology; s5-S7, calculating slip distances of the inversion faults in different stages, and calculating slip rates and inversion strength coefficients in different inversion stages; s8, a trend chart of the equivalent point distance, the total slip distance, the slip rate and the inversion strength coefficient changing along with the geological age is established, the method is suitable for the technical field of basin structure analysis, the equilibrium profile technology is introduced, and the fault inversion process can be recovered more accurately; moreover, the inversion process of the fault can be clearly, accurately and quantitatively represented from the aspects of fault slippage distance, activity intensity and inversion intensity at different stages and the like, and the work of comparison of different inversion structures, basin structure analysis and the like can be conveniently carried out.

Description

Technical Field

[0001] The present invention belongs to the technical field of basin tectonic analysis, and specifically relates to a method for quantitatively describing the fault inversion process based on a balanced section. Background Art

[0002] Inversion structures are superimposed composite structures, which are the vertical superposition of extensional or compressional structures caused by stress changes in the same geological body during different geological history periods (Hou Xubo, 2010). As an important type of structure, inversion structures are widely developed in basins. Among them, inversion faults are a typical manifestation of inversion structures. According to the superposition order of extensional and compressional structures, inversion faults can be divided into positive inversion faults and negative inversion faults. The quantitative description of the fault inversion process has important theoretical value and practical significance for basin evolution, stress field analysis, and oil and gas exploration.

[0003] All along, the research on inversion faults has mainly focused on analyzing the inversion intensity of faults, such as methods like inversion rate, structural elevation, and inversion intensity coefficient (Williams, 1989; Song T, 1997; Hou Xubo, 2010). These methods are mainly used to describe the inversion intensity at the end of the fault inversion, and cannot reflect the intermediate inversion process. Moreover, there are many uncertainties in the parameter values related to the inversion intensity. Therefore, how to accurately and quantitatively describe the fault inversion process is an urgent problem for geological researchers to solve. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and provide a method for quantitatively describing the fault inversion process based on a balanced section.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A method for quantitatively describing the fault inversion process based on a balanced section, comprising the following steps:

[0007] S1: Select a geological section;

[0008] S2: Divide the sequence stratigraphy of different inversion stages;

[0009] S3: Determine the geological history periods of different active stages of the inversion fault;

[0010] S4: Use the balanced section technique to restore the evolution history of the inversion fault;

[0011] S5: According to the fault evolution history restored in step S4, determine the equivalent point distances at different stages, and calculate the slip distances of the inversion fault at different stages based on the equivalent point distances;

[0012] S6: Based on the slip distances determined in S5, calculate the slip rates at different inversion stages;

[0013] S7: Based on the slip distance determined in S5, calculate the inversion intensity coefficients for different inversion stages;

[0014] S8: Establish a trend graph of the equivalent point distance, total slip distance, slip rate, and inversion intensity coefficient varying with geological age.

[0015] Preferably, in the step S1, the geological section is required to be selected perpendicular to the strike of the inversion fault, and the sequence characteristics are obvious, which can clearly reflect the inversion fault structure and sequence characteristics.

[0016] Preferably, in the step S2, the sequence of the inversion fault includes the pre-inversion sequence, the inversion period sequence, and the post-inversion sequence.

[0017] Preferably, in the step S2, the following positive and negative inversion fault sequence characteristics are included:

[0018] ① Pre-inversion sequence: The sequence characteristics and thickness of both sides of the fault are consistent, and the sedimentary filling characteristics are independent of the fault activity;

[0019] ② Inversion period sequence: The lower strata of the hanging wall have typical sedimentary filling characteristics of a fault depression basin, overlapping along the direction away from the fault plane, forming an angular unconformity with the underlying strata; the seismic profile in-phase axis erosion phenomenon on the top of the hanging wall is obvious, and the erosion thickness increases along the direction pointing to the fault plane;

[0020] Post-inversion sequence: The stratigraphic sequence characteristics of the hanging wall and footwall of the fault are nearly the same, showing an angular unconformity contact relationship with the inversion period sequence.

[0021] Preferably, in the step S2, the following negative inversion fault sequence characteristics are included:

[0022] Pre-inversion sequence: Affected by the fault extrusion and erosion, the pre-inversion sequence on the hanging wall of the fault is a wedge-shaped thinning towards the negative inversion fault, and the direction with a larger erosion thickness points to the fault direction;

[0023] Inversion period sequence: The external form is a wedge-shaped thinning towards the direction away from the fault, and the overlapping direction points from the near-fault end to the far-fault end, reflecting the control of the extensional fault on the sedimentary filling process of the inversion period sequence;

[0024] Post-inversion sequence: The thickness of the post-inversion sequence is relatively stable, and it shows an angular unconformity contact relationship with the inversion period sequence.

[0025] Preferably, in the step S3, the inversion stage should correspond to the sequence of the inversion fault, that is, the pre-inversion sequence, the inversion period sequence, and the post-inversion sequence respectively correspond to the pre-inversion, inversion, and post-inversion stages.

[0026] Preferably, in the step S3, before inversion, there is a stage when the fault has not started to move; during inversion, it includes the stages of compression → extension or extension → compression; after inversion, it includes the stage after the fault has stopped moving.

[0027] Preferably, in the step S3, the inversion period needs to be further divided into the extension stage and the compression thrust stage according to the unconformity surface and sequence characteristics.

[0028] Preferably, in the step S4, the balanced section technique in structural geology is used to restore the evolutionary history of fault inversion.

[0029] Preferably, in the step S4, during the restoration of the balanced section, in the extension stage, the newly deposited strata are restored using the vertical shear model, and for the section with the oblique shear mechanism, the oblique shear model is used for restoration; in the compression thrust stage, the triangular shear model is adopted.

[0030] Preferably, in the step S4, it further includes: during the restoration of the balanced section, marking the change in the position of the equivalent points on the hanging wall and footwall of the fault.

[0031] Preferably, in the step S5, the calculation formula for the total slip distance of the normal and reverse faults in the extension stage and the compression thrust stage is as follows:

[0032] Extension stage: De = D0;

[0033] Compression thrust stage: Dc = D0 - De max ;

[0034] Where, D 0 is the distance between the equivalent points on the hanging wall and footwall parallel to the fault plane. When Ep on the hanging wall is below Ep on the footwall, D 0 is a positive value; when Ep on the hanging wall is above Ep on the footwall, D 0 is a negative value. De is the total slip distance in the extension stage, De max is the maximum slip distance at the end of the extension stage, Dc is the slip distance in the compression stage, and Dc max is the maximum slip distance at the end of the compression stage.

[0035] Preferably, in the step S5, the calculation formula for the total slip distance of the negative reverse fault in the extension stage and the compression thrust stage is as follows:

[0036] Compression thrust stage: Dc = D 0 ;

[0037] Extension stage: De = D 0 - Dc max ;

[0038] Where, D 0It is the distance between the equivalent points of the upper and lower plates parallel to the fault plane. When Ep upper is below Ep lower, D 0 is a positive value; when Ep upper is above Ep lower, D 0 is a negative value. De is the total slip distance in the extension stage, and De max is the maximum slip distance at the end of the extension stage. Dc is the slip distance in the compression stage, and Dc max is the maximum slip distance at the end of the compression stage.

[0039] Preferably, in the step S6, the slip rate is the ratio of the slip distance between the upper and lower plates of the fault to the time within a certain geological stage, that is, V = D / t;

[0040] wherein, D is the slip distance of the reverse fault in different activity stages; t is the geological age interval of this activity stage. When the fault is in the tensile extension stage, V is a positive value; when the fault is in the compression thrust stage, V is a negative value.

[0041] Preferably, in the step S7, the reverse intensity coefficient Ci of the positive and reverse fault = |Dc / De max |, and the reverse intensity coefficient of the negative reverse fault is C i = |De / Dc max |;

[0042] Among them, the reverse intensity coefficient is a dimensionless value, and its geological significance is to reflect the reverse degree of the fault. The larger Ci is, the higher the reverse degree. When 0 < Ci < 1, the fault is not completely reversed; when Ci = 1, the fault is exactly completely reversed; when Ci > 1, the fault has been completely reversed, the positive and reverse fault shows a reverse fault, and the negative reverse fault shows a normal fault.

[0043] Preferably, in the step S8, using a rectangular coordinate system, establish a trend diagram of the equivalent point distance, total slip distance, slip rate and reverse intensity coefficient changing with the geological age.

[0044] To sum up, due to the adoption of the above technical solutions, the beneficial effects of the present invention are:

[0045] In the present invention, by introducing the balanced section technology, the reverse process of the fault can be restored more accurately; at the same time, the selection of the equivalent point is relatively easy, and the relevant parameters are easier to obtain and more accurate; moreover, it can clearly, accurately and quantitatively characterize the reverse process of the fault from aspects such as the fault slip distance, the activity intensity and reverse intensity in different stages, which is convenient for the comparison of different reverse structures and the analysis of basin structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is the technical flow chart of the present invention;

[0047] Figure 2is the normal and reverse fault seismic profile in the embodiment of the present invention;

[0048] Figure 3 is the restoration of the normal and reverse fault balanced profile in the embodiment of the present invention;

[0049] Figure 4 is the comprehensive illustration of the fault normal and reverse process in the embodiment of the present invention;

[0050] Figure 5 is the negative reverse fault seismic profile in the embodiment of the present invention;

[0051] Figure 6 is the restoration of the negative reverse fault balanced profile in the embodiment of the present invention;

[0052] Figure 7 is the comprehensive illustration of the fault negative reverse process in the embodiment of the present invention. Specific Embodiment

[0053] The following combines the attached Figure 1-7 , and further describes the specific embodiment of a method for quantitatively describing the fault inversion process based on a balanced profile in the present invention. The method for quantitatively describing the fault inversion process based on a balanced profile in the present invention is not limited to the description of the following embodiments.

[0054] Embodiment 1:

[0055] A method for quantitatively describing the fault inversion process based on a balanced profile, as Figure 1 shown, includes the following steps:

[0056] S1: Select a geological profile;

[0057] S2: Divide the sequence stratigraphy of different inversion stages;

[0058] S3: Determine the geological historical periods of different active stages of the reverse fault;

[0059] S4: Use the balanced profile technique to restore the evolution history of the reverse fault;

[0060] S5: According to the fault evolution history restored in step S4, determine the equivalent point distance in different stages, and calculate the slip distance of the reverse fault in different stages according to the equivalent point distance;

[0061] S6: On the basis of the slip distance determined in S5, calculate the slip rate in different inversion stages;

[0062] S7: On the basis of the slip distance determined in S5, calculate the inversion intensity coefficient in different inversion stages;

[0063] S8: Establish a trend diagram of the equivalent point distance, total slip distance, slip rate and inversion intensity coefficient changing with geological age.

[0064] Example 2:

[0065] A method for quantitatively describing the fault inversion process based on a balanced profile, as Figure 1 shown. The other steps are similar to those in Example 1. Further, in step S1, the profile is required to be a geological profile perpendicular to the strike of the inverted fault, and the sequence characteristics are obvious, which can clearly reflect the inverted fault structure and sequence characteristics.

[0066] Example 3:

[0067] A method for quantitatively describing the fault inversion process based on a balanced profile, as Figure 1 shown. The other steps are similar to those in Example 1. Further, in step S2, the sequence of the inverted fault includes the pre-inversion sequence, the inversion period sequence, and the post-inversion sequence.

[0068] Example 4:

[0069] A method for quantitatively describing the fault inversion process based on a balanced profile, as Figure 1 shown. The other steps are similar to those in Example 1. Further, in step S2, it includes the following positive and negative inverted fault sequence characteristics:

[0070] ① Pre-inversion sequence: The sequence characteristics and thickness of the two fault blocks are consistent, and the sedimentary filling characteristics are independent of fault activity;

[0071] ② Inversion period sequence: The lower strata of the hanging wall have typical sedimentary filling characteristics of a fault depression basin, overlapping along the direction away from the fault plane, forming an angular unconformity with the underlying strata; The seismic profile in-phase axis erosion phenomenon on the top of the hanging wall is obvious, and the erosion thickness increases along the direction pointing to the fault plane;

[0072] Post-inversion sequence: The stratigraphic sequence characteristics of the upper and lower fault blocks are almost the same, showing an angular unconformity contact relationship with the inversion period sequence.

[0073] Further, in step S2, it includes the following negative inverted fault sequence characteristics:

[0074] Pre-inversion sequence: Affected by the fault compression and erosion, the pre-inversion sequence on the hanging wall of the fault is a wedge-shaped thinning towards the negative inverted fault, and the direction with a larger erosion thickness points to the fault direction;

[0075] Inversion period sequence: The external shape is a wedge-shaped thinning towards the direction away from the fault, and the overlapping direction is from the near-fault end to the far-fault end, reflecting the control of the extensional fault on the sedimentary filling process of the inversion period sequence;

[0076] Post-inversion sequence: The thickness of the post-inversion sequence is relatively stable, and it shows an angular unconformity contact relationship with the inversion period sequence.

[0077] Example 5:

[0078] A method for quantitatively describing the fault inversion process based on a balanced profile, as Figure 1 shown. The other steps are similar to those in Embodiment 1. Further, in step S3, the inversion stage should correspond to the sequence of the inversion fault, that is, the pre-inversion sequence, the inversion-period sequence, and the post-inversion sequence respectively correspond to the three stages of pre-inversion, inversion period, and post-inversion.

[0079] Further, in step S3, the pre-inversion includes the stage when the fault has not started to move, the inversion period includes the stage of compression → extension or extension → compression activity, and the post-inversion includes the stage after the fault stops moving.

[0080] Furthermore, in step S3, the inversion period needs to be further divided into a tensile extension stage and a compressive thrust stage according to the unconformity surface and sequence characteristics.

[0081] Embodiment 6:

[0082] A method for quantitatively describing the fault inversion process based on a balanced profile, as Figure 1 shown. The other steps are similar to those in Embodiment 1. Further, in step S4, in order to accurately describe the fault inversion process, the balanced profile technique in structural geology is used to restore the fault inversion evolution history.

[0083] Further, in step S4, during the restoration of the balanced profile, the basic principle of area conservation is generally followed. In the tensile extension stage, the newly deposited strata are restored using the vertical shear model, and the oblique shear mechanism profile is restored using the oblique shear model; in the compressive thrust stage, the triangular shear model is used.

[0084] Furthermore, in step S4, it also includes: in order to facilitate the accurate and quantitative description of the fault inversion process, the equivalent point Ep (The equivalent point) is introduced. The equivalent point refers to the point where the hanging wall and footwall of the fault are at the same position before the fault activity. The equivalent point is generally selected at a certain interface of the pre-fault activity sequence, and this interface is relatively intact during the later extension or compression process. During the restoration of the balanced profile, the position changes of the equivalent points on the hanging wall and footwall of the fault are marked.

[0085] Embodiment 7:

[0086] A method for quantitatively describing the fault inversion process based on a balanced profile, as Figure 1 shown. The other steps are similar to those in Embodiment 1. Further, in step S5, the calculation formulas for the total slip distance of the normal and reverse faults in the tensile extension stage and the compressive thrust stage are as follows:

[0087] Tensile extension stage: De = D0;

[0088] Compressive thrust stage: Dc = D0 - De max ;

[0089] Among them, D 0 is the distance between the equivalent points of the upper and lower plates parallel to the fault plane. When Ep upper is below Ep lower, D 0 is a positive value; when Ep upper is above Ep lower, D 0 is a negative value. De is the total slip distance in the extension stage, and De max is the maximum slip distance at the end of the extension stage. Dc is the slip distance in the compression stage, and Dc max is the maximum slip distance at the end of the compression stage.

[0090] Furthermore, in step S5, the calculation formula for the total slip distance of the negative reverse fault in the tensile extension stage and the compression thrust stage is as follows:

[0091] Compression thrust stage: Dc = D 0 ;

[0092] Tensile extension stage: De = D 0 - Dc max ;

[0093] Among them, D 0 is the distance between the equivalent points of the upper and lower plates parallel to the fault plane. When Ep upper is below Ep lower, D 0 is a positive value; when Ep upper is above Ep lower, D 0 is a negative value. De is the total slip distance in the extension stage, and De max is the maximum slip distance at the end of the extension stage. Dc is the slip distance in the compression stage, and Dc max is the maximum slip distance at the end of the compression stage.

[0094] Example 8:

[0095] A method for quantitatively describing the fault inversion process based on a balanced cross-section, as Figure 1 shown. Other steps are similar to those in Example 1. Furthermore, in step S6, the slip rate is the ratio of the slip distance between the upper and lower plates of the fault to the time within a certain geological stage, that is, V = D / t;

[0096] Among them, D is the slip distance of the reverse fault in different activity stages; t is the geological age interval of this activity stage. When the fault is in the tensile extension stage, V is a positive value; when the fault is in the compression thrust stage, V is a negative value.

[0097] Example 9:

[0098] A method for quantitatively describing the fault inversion process based on a balanced cross-section, as Figure 1 shown. Other steps are similar to those in Example 1. Furthermore, in step S7, the inversion intensity coefficient Ci of the positive and negative reverse fault = |Dc / De max|, and the reverse strength coefficient of the negative reverse fault is C i =|De / Dc max |;

[0099] Among them, the reverse strength coefficient is a dimensionless value, and its geological significance is to reflect the degree of fault reversal. The larger Ci is, the higher the degree of reversal. When 0 < Ci < 1, the fault is not fully reversed; when Ci = 1, the fault is exactly fully reversed; when Ci > 1, the fault has been fully reversed, the positive and negative reverse faults show reverse faults, and the negative reverse faults show normal faults.

[0100] Example 10:

[0101] A method for quantitatively describing the fault reversal process based on a balanced section, as Figure 1 shown. Other steps are similar to those in Example 1. Further, in step S8, a rectangular coordinate system is used to establish a trend diagram of the equivalent point distance, total slip distance, slip rate, and reverse strength coefficient with geological age.

[0102] Example 11:

[0103] A method for quantitatively describing the fault reversal process based on a balanced section. Taking the positive and negative reverse fault F1 in a certain area as an example, as Figures 2-4 shown, it includes the following steps:

[0104] Step 1: Select a seismic section perpendicular to the strike of fault F1 with obvious reverse characteristics.

[0105] Step 2: According to the sequence characteristics of the positive and negative reverse faults, divide the sequence stratigraphy of different reverse stages. The in-phase axes in the middle Paleozoic strata in the hanging wall of the fault are continuous and parallel, and the overall thickness tends to be consistent. It has an angular unconformity contact relationship with the overlying EK + Es 4 strata, which is the pre-reversal sequence. Ek - Ed 1 is the sequence during the reversal period, with typical sedimentary filling characteristics of a fault depression basin. The bottom of Ek overlaps along the direction away from the fault plane, and its sedimentary filling characteristics are obviously controlled by fault F1; the upper Es 3 -Ed has obvious truncation characteristics, and the erosion thickness increases along the direction pointing to the fault plane, which is obviously affected by the late reverse thrust activity of fault F1. N + Q is the post-reversal sequence, with an angular unconformity contact relationship with the underlying strata, and the in-phase axes inside are parallel and continuous, and are stably distributed on both the hanging wall and footwall of the fault, which is the regional depression sedimentation.

[0106] Step 3: According to the sequence division and the development characteristics of the unconformity surface, divide it into pre-reversal (before Ek deposition), reversal period (Ek - Ed deposition period), and post-reversal (after N). Combining the regional geological structure background and stress field analysis, the reversal period can be further divided into a tensile extension stage (Ek - Ed 1 ), and a compressive reverse thrust stage (Ed 2 ).

[0107] Step 4: Convert the selected seismic profile into a geological profile. Use the balanced profile technique to restore the evolution process of fault F1 during the geological history period from Mz to N. Fault F1 is a boundary fault. In the early stage of Ek - Ed, it was in the tensile extension stage and was restored using the vertical shear model; in the late stage of Ed, it was in the compressive thrust stage and was restored using the triangular shear model. In order to more accurately and quantitatively describe the activity characteristics of the fault, according to the sequence division, the fault evolution during the inversion period was further subdivided into EK + Es 4 、Es 3 +Es 2 、Es 1 +Ed 1 、Ed 2 four stages. Select the bottom surface section of the Middle - Paleozoic in the pre - inversion sequence as the equivalent point Ep, which was not eroded during the later evolution process. During the balanced profile restoration process, the equivalent points of the hanging wall and footwall (Ep 上 and Ep 下 ) positions should be clearly marked to facilitate the later calculation of the slip distance, slip rate, and inversion intensity.

[0108] In steps 5 - 7, according to the normal and reverse processes of fault F1 restored by the balanced profile, the distances between equivalent points at different stages, the total slip distance, the slip distance at each stage, the slip rate, and the inversion intensity coefficient are shown in Table 1.

[0109] Table 1 Calculation table of relevant parameters for the normal and reverse processes of the fault

[0110]

[0111] In step 8, establish a curve graph showing the variation of the distance between fault equivalent points, the total slip distance, the slip rate, and the inversion intensity coefficient with geological time, as shown in Figure 4 . Fault F1 started to be active since the Ek period and changed from tensile extension to compressive thrust at the end of Ed 1 , and stopped being active at the end of Ed 2 . The total slip distance of fault F1 in the extension stage was 81.1 km, and the total slip distance in the compressive thrust stage was - 14.4 km. The slip rate of fault F1 was the largest during Es3 + Es2, with a maximum of 4.16 km / Ma. The inversion intensity coefficient of fault F1 at the end of Ed2 was 0.18, and the fault was not completely inverted.

[0112] Example 12:

[0113] A method for quantitatively describing the fault inversion process based on the balanced profile, taking the negative inversion fault F2 in a certain area as an example, as shown in Figures 5-7 , includes the following steps:

[0114] Step 1: Select a seismic profile perpendicular to the strike of fault F2 with obvious inversion features.

[0115] Step 2: Based on the sequence characteristics of negative inversion faults, divide the sequence stratigraphy of different inversion stages. The overall shape of C-P is a wedge thinning towards fault F2, with obvious truncation at the top, and the erosion thickness increases along the direction pointing to the fault plane, which is the pre-inversion sequence. The overall shape of K1-Ed is a wedge thickening along the direction pointing to the fault plane, with onlap at the bottom along the direction away from the fault plane, and the stratigraphic deposition is obviously controlled by the extensional activity of fault F2. Therefore, K1-Ed belongs to the inversion-stage sequence. It should be noted that although the external shape of J is the same as that of the pre-inversion sequence, there is no erosion trace at the top of J, and onlap occurs at the bottom along the direction pointing to the fault. Therefore, J was deposited during the initial stage of the extensional activity of fault F2 and belongs to the extensional-stage sequence. The thickness of the N+Q area is stable, the internal isophase axes are parallel and continuous, and it has an angular unconformity contact relationship with the lower inversion-stage sequence, which is the regional depression sedimentation. Its sedimentary filling characteristics have nothing to do with fault F2 and belong to the post-inversion sequence.

[0116] Step 3: According to the sequence division and the development characteristics of unconformity surfaces, divide it into pre-inversion (T1+2 and before), inversion stage (sedimentary period of T3-Ed), and post-inversion (N+Q). Combining the regional geological tectonic background and stress field analysis, the inversion stage can be further divided into the compressive thrust stage (T3) and the extensional stage (J, K1, Es4-Ed).

[0117] Step 4: Convert the selected seismic profile into a geological profile. Use the balanced profile technique to restore the evolution process of fault F2 during the geological history period from T1+2 to N+Q. Since fault F2 shows different types of faults in different stages, different models should be selected during the restoration process. In the pre-inversion sequence, the bottom surfaces of the Cambrian-Ordovician systems on both the hanging wall and the footwall of fault F2 have not been eroded. Therefore, select the intersection point of the bottom surface of the Cambrian-Ordovician system and the fault plane as the equivalent point. The positions of the equivalent points on both the hanging wall and the footwall at different stages are as Figure 6 shown.

[0118] In steps 5-7, according to the positive and negative inversion process of fault F2 restored by the balanced profile, the distance (D0) between equivalent points at different stages, the total slip distance (De, Dc), the slip distance (D) at each stage, the slip rate (V), and the inversion intensity coefficient (Ci) are shown in Table 2.

[0119] Table 2 Calculation table of parameters related to the negative inversion process of the fault

[0120]

[0121] In step 8, establish a curve graph showing the variation of the distance between fault equivalent points, the total slip distance, the slip rate, and the inversion intensity coefficient with geological time, as Figure 7 shown. Fault F2 since T 3The activity starts at time T 3 At the end of the period, the fault begins to change from compressive thrusting to extensional stretching, and the fault stops activity at the end of Ed. The total slip distance of the fault during the compressive thrusting stage is -10.1 km, and the total slip distance during the extensional stretching stage is 77.3 km. The fault has the maximum slip rate during Es 4 -Ed, with a maximum of 0.83 km / Ma. The inversion intensity coefficient at the end of the Jurassic is 1, and the fault F2 is exactly completely inverted. The fault continues to undergo extensional stretching in the later stage, and the inversion intensity coefficient reaches 7.7 at the end of Ed. The fault F2 is completely inverted from a reverse fault to a normal fault.

[0122] Comparing the inverted faults in Example 11 and Example 12, the inversion period of fault F1 in Example 11 is short, the fault activity intensity is high, and the inversion degree is weak; the inversion period of fault F2 in Example 12 is long, the activity intensity at each stage is low, but the inversion degree is large.

[0123] Comparison with existing methods:

[0124] ① In the quantitative analysis of inverted faults, the inversion rate Rfi (Song T, 1997) and the inversion intensity coefficient Ci (Hou Xubo, 2010) are commonly used quantitative characterization methods. In both of these calculation methods, the tensile and compressive displacement amounts are involved. For inverted faults with syndepositional characteristics, the values of compressive and extensional displacement amounts are relatively clear. However, for the inversion of boundary normal faults similar to those in Example 11, both the upper and lower plate strata have been eroded, and it is difficult to directly obtain the values of compressive and extensional displacement amounts from the current profile, and there is a large uncertainty in the values. In contrast, according to the technical method provided by the present invention, the evolution process of the inverted fault is first restored by using the balanced cross-section technique; on this basis, according to the set equivalent points on the upper and lower plates, the values of displacement amounts or slip distances at different stages can be read more accurately, improving the accuracy of the inversion rate Rfi or the inversion intensity coefficient Ci.

[0125] ② In the comparative analysis of inverted faults, most use the inversion rate or the inversion intensity coefficient for horizontal comparative analysis. However, a single method is difficult to comprehensively and accurately describe the characteristics of inverted faults. Taking positive and reverse faults with the same inversion intensity as an example, the inversion intensity coefficient Ci of inverted fault a a = (-100 m) / (-200 m) = 0.5, and the inversion intensity coefficient Ci of inverted fault b b= (-10 km) / (-20 km) = 0.5. Although the inversion intensities of Fault a and Fault b are the same, their activity intensities and the influence on the basin during the inversion process are quite different. Assuming that the duration of the compressional thrusting stage is 10 Ma, according to the technical method provided by the present invention, the slip distance of Fault a is -0.1 km, and the slip rate Va = (-0.1 km) / 10 Ma = -0.01 km / Ma; the slip distance of Fault b is -10 km, and the slip rate is Vb = (-10 km) / 10 Ma = -1 km / Ma, and |Vb| is much larger than |Va|. That is, Fault a is small in scale and has a small activity intensity during the inversion process, only affecting local minor structures; Fault b is large in scale and has a large activity intensity during the inversion process, playing an important role in the structural pattern of the zone and even the entire basin.

[0126] Compared with the existing methods, the present invention has the following beneficial effects:

[0127] 1. By introducing the balanced cross-section technique, the fault inversion process can be restored more accurately;

[0128] 2. The selection of equivalent points is relatively easy, and the relevant parameters are easier to obtain and more accurate;

[0129] 3. It can clearly, accurately and quantitatively characterize the fault inversion process from aspects such as the fault slip distance, activity intensity in different stages and inversion intensity, facilitating the comparison of different inversion structures and the analysis of basin structures.

[0130] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for quantitatively describing the fault inversion process based on a balanced profile, characterized in that, it includes the following steps: S1: Select a geological profile; S2: Divide the sequence stratigraphy of different inversion stages; S3: Determine the geological historical periods of different active stages of the inversion fault; S4: Use the balanced profile technique to restore the evolution history of the inversion fault; S5: According to the fault evolution history restored in step S4, determine the equivalent point distances of different stages, and calculate the slip distances of the inversion fault in different stages based on the equivalent point distances; S6: Based on the slip distances determined in S5, calculate the slip rates of different inversion stages; S7: Based on the slip distances determined in S5, calculate the inversion intensity coefficients of different inversion stages; S8: Establish a trend diagram of the equivalent point distance, total slip distance, slip rate, and inversion intensity coefficient changing with geological age.

2. The method for quantitatively describing the fault inversion process based on a balanced profile according to claim 1, characterized in that, in step S1, the profile is required to be a geological profile perpendicular to the strike of the inversion fault, and the sequence characteristics are obvious, which can clearly reflect the structural and sequence characteristics of the inversion fault.

3. The method for quantitatively describing the fault inversion process based on a balanced profile according to claim 1, characterized in that, in step S2, the sequence of the inversion fault includes the pre-inversion sequence, the inversion period sequence, and the post-inversion sequence.

4. The method for quantitatively describing the fault inversion process based on a balanced profile according to claim 3, characterized in that, in step S2, it includes the following positive and negative inversion fault sequence characteristics: ① Pre-inversion sequence: The sequence characteristics and thickness of the two fault blocks are consistent, and the sedimentary filling characteristics are independent of fault activity; ② Inversion period sequence: The lower strata of the hanging wall have typical sedimentary filling characteristics of a fault depression basin, overlapping along the direction away from the fault plane, and forming an angular unconformity with the underlying strata; The seismic profile in-phase axis erosion phenomenon at the top of the hanging wall is obvious, and the erosion thickness increases along the direction pointing to the fault plane; Post-inversion sequence: The stratigraphic sequence characteristics of the upper and lower fault blocks are almost the same, showing an angular unconformity contact relationship with the inversion period sequence.

5. The method for quantitatively describing the fault inversion process based on a balanced profile according to claim 3, characterized in that, in step S2, it includes the following negative inversion fault sequence characteristics: Pre-inversion sequence: Affected by the fault extrusion and erosion, the pre-inversion sequence on the hanging wall of the fault is a wedge-shaped thinning towards the negative inversion fault, and the direction with a larger erosion thickness points to the fault direction; Inversion period sequence: The external shape is a wedge-shaped thinning towards the direction away from the fault, and the overlapping direction points from the near-fault end to the far-fault end, reflecting the control of the extensional fault on the sedimentary filling process of the inversion period sequence; Post-inversion sequence: The thickness of the post-inversion sequence is relatively stable, and it shows an angular unconformity contact relationship with the inversion period sequence.

6. The method for quantitatively describing the fault inversion process based on a balanced profile according to claim 1, characterized in that, in step S3, the inversion stage should correspond to the sequence of the inversion fault, that is, the pre-inversion sequence, the inversion period sequence, and the post-inversion sequence respectively correspond to the pre-inversion, inversion period, and post-inversion stages.

7. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 6, characterized in that, in step S3, before inversion, it includes the stage when the fault has not started to move; during inversion, it includes the stages of compression → extension or extension → compression; after inversion, it includes the stage after the fault has stopped moving.

8. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 6, characterized in that, in step S3, during inversion, it needs to be further divided into a tensile extension stage and a compressive thrust stage according to the unconformity surface and sequence characteristics.

9. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 1, characterized in that, in step S4, the balanced profile technique in structural geology is used to restore the fault inversion evolution history.

10. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 9, characterized in that, in step S4, during the restoration of the balanced profile, in the tensile extension stage, the newly deposited strata are restored using the vertical shear model, and the profile with the oblique shear mechanism is restored using the oblique shear model; in the compressive thrust stage, the triangular shear model is used.

11. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 1, characterized in that, in step S4, it further includes: during the restoration of the balanced profile, marking the change in the position of the equivalent points on the hanging wall and footwall of the fault.

12. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 1, characterized in that, in step S5, the calculation formula for the total slip distance of the normal and reverse faults in the tensile extension stage and the compressive thrust stage is as follows: Tensile extension stage: De = D0; Compression thrust stage: Dc = D0 - De max ; Among them, D 0 is the distance between the equivalent points of the upper and lower plates parallel to the fault plane. When Ep upper is below Ep lower, D 0 is positive; when Ep upper is above Ep lower, D 0 is negative. De is the total slip distance in the extension stage, and De max is the maximum slip distance at the end of the extension stage. Dc is the slip distance in the compression stage, and Dc max is the maximum slip distance at the end of the compression stage.

13. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 1, characterized in that, in step S5, the calculation formula for the total slip distance of the negative reverse faults in the tensile extension stage and the compressive thrust stage is as follows: Compressive thrust stage: Dc = D 0 ; Tensile stretching stage: De = D 0 -Dc max ; Among them, D 0 is the distance between the equivalent points of the upper and lower plates parallel to the fault plane. When Ep_up is below Ep_down, D 0 is positive; when Ep_up is above Ep_down, D 0 is negative. De is the total slip distance in the extension stage, and De max is the maximum slip distance at the end of the extension stage. Dc is the slip distance in the compression stage, and Dc max is the maximum slip distance at the end of the compression stage.

14. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 1, characterized in that, in step S6, the slip rate is the ratio of the slip distance between the hanging wall and footwall of the fault to the time within a certain geological stage, that is, V = D / t; wherein, D is the slip distance of the reverse fault in different activity stages; t is the geological time interval of this activity stage. When the fault is in the tensile extension stage, V is a positive value; when the fault is in the compressive thrust stage, V is a negative value.

15. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 1, characterized in that: In the step S7, the reverse strength coefficient Ci of the normal-reverse fault is Ci = |Dc / De max |, and the reverse strength coefficient of the negative reverse fault is C i = |De / Dc max |; wherein, the inversion intensity coefficient is a dimensionless value, and its geological significance is to reflect the degree of fault inversion. The larger Ci is, the higher the degree of inversion. When 0 < Ci < 1, the fault is not fully inverted; when Ci = 1, the fault is exactly fully inverted; when Ci > 1, the fault has been fully inverted, the normal and reverse faults show reverse faults, and the negative reverse faults show normal faults.

16. A method for quantitatively describing the fault inversion process based on a balanced profile as described in claim 1, characterized in that: In the step S8, a rectangular coordinate system is used to establish a trend chart of the equivalent point distance, total slip distance, slip rate, and reverse strength coefficient varying with geological age.

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