Quantitative evaluation method for plugging aging of fracture transformation regional mudstone cover layer and application of quantitative evaluation method

Abstract

The invention discloses a quantitative evaluation method for plugging aging of a fracture transformation regional mudstone cover layer and application thereof, and relates to the technical field of oil-gas exploration. The method comprises the steps of firstly obtaining basic geological data; then, diagenesis indexes of the regional mudstone cover layer, the underlying reservoir rock and the fault rock are calculated respectively; respectively determining the formation starting time of the regional mudstone cover layer plugging property and the formation starting time of the fault rock plugging property by comparing the relation curve of the diagenetic index and the time; and finally, passing through two time parameters. And calculating according to a formula to obtain a regional mudstone cover layer plugging time shortening degree index caused by fracture, and realizing quantitative evaluation on the fracture transformation cover layer plugging aging influence. The method is easy and convenient to operate, the evaluation result is accurate and reliable, the effectiveness of the method is proved in the actual application of the Halal basin, and a scientific basis is provided for oil-gas exploration target optimization of the fracture development area of the oil-gas-containing basin.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploration, and particularly relates to a quantitative evaluation method for sealing time of regional mudstone cap rock reformed by faults and application thereof. BACKGROUND

[0002] The regional mudstone cap rock is one of important control factors of oil and gas accumulation, and its sealing performance directly affects the accumulation and preservation of oil and gas. In the oil and gas bearing basin, the fault activity can reform the regional mudstone cap rock, so that the originally complete mudstone cap rock is cut through by the fault to form a channel filled with fault rock. The reforming effect can significantly affect the sealing time of the cap rock, and further control the enrichment degree of oil and gas.

[0003] In the prior art, the evaluation methods for the lateral sealing property of the fault mainly focus on the sealing property evaluation after the formation of the fault rock, and the displacement pressure is used as the main evaluation parameter. However, these methods have the following technical defects: first, a large amount of displacement pressure data needs to be measured, but the fault rock sample is difficult to obtain due to the drilling coring limitation, so that the application of the method is limited; second, the existing method mainly evaluates the sealing property at a certain period after the fault stops activity, and cannot accurately reflect the influence degree of the fault on the sealing time of the regional mudstone cap rock; third, there is no effective method for quantitatively evaluating the degree of shortening of the sealing time of the regional mudstone cap rock caused by the fault, and it is difficult to accurately predict the oil and gas distribution rule.

[0004] Therefore, it is urgent to develop a new quantitative evaluation method, which can accurately evaluate the influence degree of the fault on the sealing time of the regional mudstone cap rock, and provide a scientific basis for oil and gas exploration. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art, and to provide a quantitative evaluation method for sealing time of regional mudstone cap rock reformed by faults and application thereof. The method uses the diagenetic index to replace the displacement pressure for sealing property evaluation, and establishes a quantitative calculation model for the degree of shortening of the sealing time of the regional mudstone cap rock caused by the fault, which can accurately evaluate the influence of the fault on the sealing time of the cap rock, and effectively guide the oil and gas exploration.

[0006] The technical scheme of the present application is as follows: In one aspect, the present application provides a quantitative evaluation method for sealing time of regional mudstone cap rock reformed by faults, comprising the following steps: S1: obtaining the geological data of the research area; S2: calculating the diagenetic index A1 of the regional mudstone cap rock A1=N1R1T, and establishing the relationship between the diagenetic index and the diagenetic time of the regional mudstone cap rock; wherein N1 is the positive pressure generated by the overlying sedimentary rock of the regional mudstone cap rock, MPa; R1 is the argillaceous content of the regional mudstone cap rock; and T is the diagenetic time, Ma; S3: Calculate the diagenetic index A2=N2R2T of the underlying reservoir rock under the regional mudstone cap rock, and establish the relationship between the diagenetic index of the underlying reservoir rock and the diagenetic time; wherein N2 is the positive pressure generated by the overlying sedimentary load (i.e. the positive pressure generated by the regional mudstone cap rock + sedimentary rock), MPa; R2 is the argillaceous content of the underlying reservoir rock; and T is the diagenetic time, Ma; S4: Determine the time T at which the sealing property of the regional mudstone cap rock begins to form according to the time point at which the diagenetic index of the regional mudstone cap rock is equal to that of the underlying reservoir rock c (as shown in FIG. 2); Figure 3 S5: Calculate the diagenetic index A of the fault rock formed by the fracture in the regional mudstone cap rock f =N f R f T, and establish the relationship between the diagenetic index of the fault rock and the diagenetic time; wherein N f is the positive pressure generated by the overlying sedimentary load (i.e. the positive pressure generated by the regional mudstone cap rock + sedimentary rock above the fault rock), MPa; R f is the argillaceous content of the fault rock; and T is the diagenetic time, Ma; S6: Determine the time T at which the sealing property of the fault rock begins to form according to the time point at which the diagenetic index of the fault rock is equal to that of the underlying reservoir rock f (as shown in FIG. 3); Figure 3 S7: Calculate the index a of the degree to which the fracture shortens the sealing time of the regional mudstone cap rock by the formula a= (T c -T f ) / T c ×100%, wherein when a=100%, it indicates that the fault rock does not seal, and the fracture completely destroys the sealing property of the regional mudstone cap rock; and when a<100%, it indicates that the fault rock has a certain sealing ability, and the smaller the a value, the stronger the sealing ability, and the smaller the influence of the fracture on the sealing time of the regional mudstone cap rock, thereby establishing a quantitative evaluation method for the reconstruction of the sealing time of the regional mudstone cap rock by the fracture.

[0007] Preferably, in step S1, the geological data of the research area includes three-dimensional seismic data, drilling data and logging data, and the spatial distribution characteristics of the target fracture, the distribution of the regional mudstone cap rock and the characteristics of the underlying reservoir rock are determined.

[0008] Preferably, in step S2, N1=ρ r1 ×z1, wherein ρ r1 is the average density of the overlying sedimentary rock of the regional mudstone cap rock, g / cm 3 ; and z1 is the burial depth of the regional mudstone cap rock, m.

[0009] Preferably, in step S2, R1= (2 (IGR1×GCUR1) -1) / (2​​GCUR1 -1), I GR1 GCUR1 is an empirical coefficient of the regional shale cap rock, GCUR1 = 2 for old strata, and GCUR1 = 3.7 for new strata.

[0010] Preferably, in step S3, N2 = p r2 x z2, wherein p r2 is the average density of the overlying sedimentary rock of the regional shale cap rock, g / cm 3 ; and z2 is the burial depth of the underlying reservoir rock, m.

[0011] Preferably, in step S3, R2 = (2 (IGR2×GCUR2) -1) / (2 GCUR2 -1), wherein I GR2 is the relative natural gamma value of the underlying reservoir rock; and GCUR2 is an empirical coefficient of the underlying reservoir rock, GCUR2 = 2 for old strata, and GCUR2 = 3.7 for new strata.

[0012] Preferably, in step S5, N f = p r3 x z3 x cos q, wherein p r3 is the average density of the overlying sedimentary rock of the regional shale cap rock, g / cm 3 ; z3 is the burial depth of the fault rock, m; and q is the fault dip angle of the fault rock, °.

[0013] Preferably, in step S5, R f = , wherein H i is the thickness of the i-th layer of rock that is faulted, m; R i is the argillaceous content of the corresponding rock layer; and L is the fault throw, m.

[0014] In another aspect, the present application provides an application of the quantitative evaluation method of the sealing time of the regional shale cap rock that is reformed by faulting, and the method is used for the evaluation of oil and gas exploration targets in a fault development area of an oil and gas basin. The smaller the value of a is, the more favorable it is for the accumulation of oil and gas.

[0015] Compared with the prior art, the present application has the following beneficial effects: 1. The present application innovatively uses a diagenetic index to replace displacement pressure for sealing evaluation, effectively solves the technical problems of difficulty in obtaining fault rock samples and lack of displacement pressure data, and significantly improves the practicability and generalizability of the method.

[0016] 2. The present application establishes a quantitative calculation model for the degree of shortening of the sealing time of the regional shale cap rock by faulting, and for the first time realizes the quantitative characterization of the influence degree of the sealing time of the cap rock reformed by faulting, filling the technical gap in this field.

[0017] 3. The application comprehensively considers the influence of overlying sediment load, shale content and diagenetic time on diagenetic degree, and the evaluation system is more scientific and reasonable, and the evaluation result is more accurate and reliable.

[0018] 4. The method is simple in operation, and the required basic data can be obtained through conventional seismic, drilling and logging data, and has good operability and economy, and is convenient for popularization and application in oil and gas exploration practice. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a flow chart of the quantitative evaluation method of the sealing time of the regional mudstone cap rock of the fault reconstruction area of the application.

[0020] Figure 2 is the oil and gas distribution map of the second member of the South in the F1 fault of the embodiment 1 of the application.

[0021] Figure 3 is a diagram for determining the formation time of the sealing property of the regional mudstone cap rock and the fault rock in it, wherein T0 is the fault stop time.

[0022] Figure 4 is a diagram for determining the sealing position and non-sealing position of the F1 fault in the regional mudstone cap rock of the first member of the Lower in the embodiment 1 of the application.

[0023] Figure 5 is a diagram for determining the formation time of the sealing property of the regional mudstone cap rock of the first member of the Lower and the fault rock of the F1 fault in it in the embodiment 1 of the application.

[0024] Figure 6 is a relationship diagram between the sealing time shortening degree of the regional mudstone cap rock of the first member of the Lower by the F1 fault and the oil and gas enrichment in the embodiment 1 of the application. DETAILED DESCRIPTION

[0025] In order to make the person skilled in the art better understand the technical solutions in the application, the technical solutions of the application will be described clearly and completely in combination with the embodiments of the application.

[0026] Example 1: F1 fault evaluation application in Beier depression of Hailaer basin The F1 fault in the western Huhe Nuoren anticline belt of the Beier depression in the Hailaer basin is selected as the research object, the fault is a north-east trending normal fault, the length is about 13.4km, and extends from the second and third members of Yi to the bedrock Budate group. The target evaluation horizon is the second member of the South reservoir, and the regional mudstone cap rock is developed in the first member of the Lower above it.

[0027] The quantitative evaluation method is as shown in Figure 1 . S1: Collect 3D seismic data and drilling and logging data from 15 exploration wells in the study area to determine the spatial distribution characteristics of the F1 fault at 15 measuring points, such as... Figure 2 As shown.

[0028] S2: Calculate the relationship between the diagenetic index A1 of the regional mudstone cap and the diagenetic time T using the function A1=N1R1T. Calculate the normal pressure N1=ρ generated by the sedimentary rocks overlying the regional mudstone cap in the lower section of the Daxia Formation using well logging data. r1 ×z1;R1=(2 (IGR1×GCUR1) -1) / (2 GCUR1 -1), where I GR1 =(GR-GR min / (GR) max -GR min ), GR is the natural gamma value, GR min The natural gamma value of pure sandstone, GR max The gamma value is the natural value of pure mudstone.

[0029] like Figure 5 As shown, N2, Y1, etc. represent the geological period of the strata, E and N belong to the Tertiary system, and the empirical coefficient GCUR1 is taken as 3.7; the rest belong to the old strata, and the empirical coefficient GCUR1 is taken as 2.

[0030] The calculation results are shown in Table 1.

[0031] Table 1

[0032] Based on the N1 and R1 values, the diagenetic index A1=N1R1T of the regional mudstone cap is derived.

[0033] S3: Calculate the diagenetic index A2=N2R2T of the Nan-2 Member reservoir rocks underlying the regional mudstone caprock. Calculate the normal pressure N2=ρ generated by the regional mudstone caprock and sedimentary rocks in the lower section of the Daxia Formation using well logging data. r2 ×z2;R2=(2 (IGR2×GCUR2) -1) / (2 GCUR2 -1), where I GR2 =(GR-GR min / (GR) max -GR min ), GR is the natural gamma value, GR min The natural gamma value of pure sandstone, GR max The values ​​represent the natural gamma values ​​of pure mudstone. The calculation results are shown in Table 1.

[0034] Based on the N2 and R2 values, the diagenetic index A2=N2R2T is obtained for the rocks underlying the Nan-2 Member reservoir in the regional mudstone caprock.

[0035] S4: Determine the time T when the regional mudstone cap begins to form a sealing effect. c Based on the functions obtained in steps S2 and S3, plot the relationship curves between the regional mudstone caprock diagenesis index and diagenesis time, as well as the relationship curves between the underlying reservoir rock diagenesis index and diagenesis time. The time corresponding to the intersection of the two curves is the time T at which the regional mudstone caprock begins to form a sealing effect. c (like Figure 5 (As shown). Comprehensive calculation results show that, due to fault sealing, measurement points 1-4, 6, and 9-11 do not require quantitative evaluation of sealing time; measurement point 5 represents the late stage of the first stage of deposition, measurement point 7 the late stage, measurement point 8 the middle stage, measurement points 12-13 the early stage, measurement point 14 the middle stage, and measurement point 15 the late stage. The regional mudstone cap sealing formation time T for measurement points 5, 7-8, and 12-15 is also shown. c These are 128.25 Ma, 128.75 Ma, 129 Ma, 126.45 Ma, 126.45 Ma, 126.25 Ma, and 128.25 Ma from now.

[0036] S5: Calculate the diagenetic index A of the fault rocks. f =N f R f T Calculate the normal pressure N generated by the regional mudstone caprock and sedimentary rocks above the fault rock in the lower section of the Daxia section using well logging data. f =ρ r3 ×z3×cosθ;R f = The calculation results are shown in Table 1.

[0037] According to N f R f The value was used to derive the diagenetic index A of the fault rocks. f =N f R f T. A timeline for the formation of the regional mudstone caprock and the sealing rock of the F1 fault within the lower segment of the T-section is shown in the diagram. Figure 5 As shown.

[0038] Depend on Figure 4As can be seen from the data, at measuring points 1-4, 6, and 9-11, the diagenetic index of the fault rocks within the regional mudstone caprock of the F1 fault is lower than that of the reservoir rocks in the South Second Member, indicating that the fault rocks do not provide sealing. The F1 fault reduces the sealing time of the regional mudstone caprock in the Lower Third Member by 100%, so there is no need to study the distribution characteristics of the reduction in sealing time caused by the F1 fault. However, at measuring points 5, 7, 8, and 12-15, the diagenetic index of the fault rocks within the regional mudstone caprock of the Lower Third Member is higher than that of the reservoir rocks in the South Second Member, indicating that the fault rocks provide sealing. Therefore, it is possible to study the distribution characteristics of the reduction in sealing time caused by the F1 fault in the Lower Third Member.

[0039] S6: Determine the time T when the fault rock sealing effect begins to form. f Based on the function obtained in step S5, a curve showing the relationship between the fault rock diagenesis index and diagenesis time is plotted. The time corresponding to the intersection of this curve with the curve showing the relationship between the underlying reservoir rock diagenesis index and diagenesis time plotted in step S4 is the time T at which the fault rock sealing effect begins to form. f (like Figure 5 (As shown). Comprehensive calculations show that monitoring points 1-4, 6, and 9-11 are blocked by faults, so no quantitative evaluation of the blocking time is required; monitoring points 5, 13, and 15 are in the middle Neogene depositional period, monitoring point 7 is in the middle to late Paleogene depositional period, monitoring point 8 is in the middle Qingyuangang depositional period, and monitoring points 12 and 14 are in the middle Quaternary depositional period. The time T at which the fault rock blocking effect began to form for monitoring points 5, 7-8, and 12-15 is also shown. f These are 33.5 Ma, 58 Ma, 80.5 Ma, 1.2 Ma, 33.5 Ma, 1 Ma, and 33.5 Ma from now.

[0040] S7: Calculate the index a of the degree to which the fracture shortens the sealing time of the regional mudstone cap. According to T c T f Through the formula a=(T c -T f ) / T cX100%, and the shortening degree indexes of the regional mudstone caprock sealing time of the 15 measuring points are respectively: the F1 fault makes the shortening degree of the regional mudstone caprock sealing time of the lower part of the first member of the Upper Triassic Xujiahe Formation greater, but less than 100% at the measuring points 5, 7, 8, 12-15, which is favorable for the oil and gas to accumulate and preserve in the reservoir rocks of the second member of the Upper Triassic Xujiahe Formation; the oil and gas drilling obtains oil and gas shows in the second member of the Upper Triassic Xujiahe Formation at the measuring points 7, 8, 12 and 14; the oil and gas drilling does not obtain oil and gas shows in the reservoir rocks of the second member of the Upper Triassic Xujiahe Formation at the measuring points 5, 13 and 15, which is caused by the insufficient oil and gas supply due to the low position of the structure; the F1 fault makes the shortening degree of the regional mudstone caprock sealing time of the lower part of the first member of the Upper Triassic Xujiahe Formation reach 100% at the measuring points 1-4, 6, 9-11, which is not favorable for the oil and gas to accumulate and preserve in the reservoir rocks of the second member of the Upper Triassic Xujiahe Formation, and the oil and gas drilling does not obtain oil and gas shows. This also proves that the distribution research result of the shortening degree of the regional mudstone caprock sealing time of the lower part of the first member of the Upper Triassic Xujiahe Formation caused by the F1 fault is feasible.

[0041] In summary, the actual drilling result verifies the accuracy of the evaluation method of the present application: the oil and gas shows are obtained at the measuring points 7, 8, 12 and 14, while the oil and gas shows are not obtained at the measuring points with the index of 100% (as shown in Figure 6 ), which proves that the quantitative evaluation method of the present application for the fault reformation regional mudstone caprock sealing time is effective and practical.

Claims

1. A quantitative evaluation method for the time limit of sealing of a regional shale cap rock after fracture reconstruction, characterized in that, The method comprises the following steps: S1: obtaining geological data of a study area; S2: calculating a diagenetic index A1=N1R1T of the regional mudstone cap rock, wherein N1 is a positive pressure generated by overlying sedimentary rock of the regional mudstone cap rock, MPa; R1 is a shale content of the regional mudstone cap rock; and T is a diagenetic time, Ma; S3: calculating a diagenetic index A2=N2R2T of rock of a reservoir underlying the regional mudstone cap rock, wherein N2 is a positive pressure generated by overlying sedimentary load, MPa; R2 is a shale content of the rock of the reservoir; and T is the diagenetic time, Ma; S4: According to the time point of the regional mudstone cap rock and the underlying reservoir rock index, the formation of regional mudstone cap rock sealing time T is determined c ; S5: Calculate the diagenetic index A of fault rock formed by fracture in regional mudstone caprock f =N f R f T, wherein N f is the positive pressure generated by overlying sediment load, MPa; R f is the argillaceous content of fault rock; T is the diagenetic time, Ma; S6: According to the time point of the diagenetic index of the fault rock being equal to that of the underlying reservoir rock, determine the time T when the fault rock sealing begins to form f ; S7: Calculate the degree index a of the shortening of the sealing time of regional mudstone cap rock by the formula a= (T c -T f ) / T c x 100%, when a = 100%, it is determined that the fault rock is not sealing; when a < 100%, it is determined that the fault rock has sealing capacity, and the smaller the a value, the stronger the sealing capacity, thereby establishing a quantitative evaluation method for the sealing time of the fault reconstruction regional mudstone cap rock.

2. The method for quantitative evaluation of the time of plugging of the fracture-modified regional shale cap rock according to claim 1, characterized in that, In step S1, the geological data of the study area comprises three-dimensional seismic data, drilling data and logging data.

3. The method for quantitative evaluation of the time of plugging of the fracture-modified regional shale cap rock according to claim 1, characterized in that, In step S2, N1 = p r1 x z1, wherein p r1 is the average density of the overlying sedimentary rock of the regional mudstone cap rock, g / cm 3 ; and z1 is the burial depth of the regional mudstone cap rock, m.

4. The method for quantitative evaluation of the time of plugging of the fracture-modified regional shale cap rock according to claim 1, characterized in that, Step S2, R1= (2 (IGR1×GCUR1) -1) / (2 GCUR1 -1), wherein I GR1 is the relative natural gamma value of the regional mudstone cap rock, and GCUR1 is the empirical coefficient of the regional mudstone cap rock.

5. The method for quantitative evaluation of the time of plugging of the fracture-modified regional shale cap rock according to claim 1, characterized in that, In step S3, N2 = p r2 x z2, where p r2 is the average density of the overlying sedimentary rock of the regional mudstone cap, g / cm 3 ; and z2 is the depth of the underlying reservoir rock, m.

6. The method for quantitative evaluation of the time of plugging of the fracture-modified regional shale cap rock according to claim 1, characterized in that, Step S3, R2= (2 (IGR2×GCUR2) -1) / (2 GCUR2 -1), where I GR2 is the relative natural gamma value of the underlying reservoir rock and GCUR2 is an empirical coefficient of the underlying reservoir rock.

7. The method for quantitative evaluation of the time of plugging of the fracture-modified regional shale cap rock according to claim 1, characterized in that, In step S5, N f = p r3 x z3 x cos θ, where p r3 is the average density of the overlying sedimentary rock above the regional mudstone cap, g / cm 3 ; z3 is the fault rock burial depth, m; and θ is the fault rock fracture dip, °.

8. The method for quantitative evaluation of the time of plugging of the fracture-modified regional shale cap rock according to claim 1, characterized in that, In step S5, R f = where H i is the thickness of the i-th layer of rock being fractured, m; R i is the shale content of the respective rock layer; and L is the fracture spacing, m.

9. The use of the method for quantitative evaluation of the time of plugging of the fracture-modified regional shale cap rock according to any of claims 1 to 8, characterized by the fact that, The method is used for evaluation of an oil and gas exploration target in a fault development area of an oil and gas bearing basin, and the smaller the value of a is, the more favorable for oil and gas accumulation.

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