A method for evaluating fault sealing

Abstract

The present invention relates to a method for evaluating fault sealing property. The evaluation method comprises the following steps: establishing a fine structural model based on stratigraphic correlation and seismic interpretation results to reproduce the basic properties of the fault; establishing a facies model and a shale content model based on seismic inversion and sedimentary facies research results; establishing a fault reservoir juxtaposition map according to the configuration relationship of the facies model on both sides of the fault; calculating fault parameters based on the fine structural model and the shale content model; and evaluating the fault sealing property based on the fault parameters and the fault reservoir juxtaposition map. The solution provided by the present invention is carried out based on the existing three-dimensional geological model, which not only saves the data preparation time, improves the accuracy of fault sealing evaluation, but also improves the development effect of the oilfield.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas field exploration and development, and particularly relates to a method for evaluating fault sealing property. Background Art

[0002] At present, since the concepts of "fault sealing" and "sealed fault" emerged, the research on fault sealing property has attracted attention. If a fault is sealed, it can act as an occlusion for oil and gas accumulation; if a fault is open, it can serve as a channel for oil and gas migration, and fault-controlled reservoir plays a key role in oil and gas exploration and development. Therefore, it is of great significance to study fault sealing property.

[0003] From the existing methods for studying fault sealing property, there are many methods with different applicable scopes. To improve the success rate of projects and reduce implementation risks, the currently widely recognized methods for studying fault sealing property include quantitative and qualitative methods. Qualitative methods: (1) Fault activity; (2) Basic properties of faults; (3) Geochemistry; (4) Lithology. Quantitative methods: (1) Lithology; (2) Mechanics.

[0004] For example, CN109239778A discloses a quantitative evaluation method for fault lateral sealing property, belonging to the field of oil and gas exploration and development. This method takes into account formation compaction correction and can accurately evaluate the evolution characteristics of fault lateral sealing in multiple periods from the oil and gas accumulation period to the present. The evaluation method includes the following steps: for each time unit from the oil and gas accumulation period to before the present time, the formation of each time unit from the oil and gas accumulation period to before the present time is restored by the decompaction correction method, and the paleo-mudstone smear factor, paleo-mudstone smear potential, and paleo-fault gouge ratio corresponding to different depths of single sand layers at each time unit are calculated respectively; calculate the current mudstone smear factor, current mudstone smear potential, and current fault gouge ratio corresponding to the current time; when the mudstone smear factor, mudstone smear potential, and fault gouge ratio corresponding to the ancient period and the current period all meet the threshold requirements, the fault is laterally sealed; otherwise, the fault is laterally open.

[0005] CN105760668A discloses a method for quantitatively evaluating the lateral sealing property of a fault. Based mainly on the research of the fault sealing mechanism and its influencing factors, the fault-reservoir displacement pressure difference method for quantitatively evaluating the fault sealing property is improved by considering the fault pressure-bearing time, and a geological and mathematical model for quantitatively evaluating the fault sealing property considering time factors is established. By using an algorithm with a given step size and gradually approaching, the burial depth of the surrounding rock formation with the same shale content and diagenetic degree as the target fault rock is determined, and then according to the relationship between the product of the shale content and burial depth of the rock and the displacement pressure established in the study area, the displacement pressure of the target fault rock is quantitatively calculated, and compared with the displacement pressure of the reservoir in the target plate to quantitatively evaluate whether the fault is sealed and the size of the sealing ability. This method has been verified by actual data and compared with the shale content (SGR) method of fault rock and the method for evaluating fault sealing property by the fault-reservoir displacement pressure difference without considering the pressure-bearing time, and it is proved to be feasible.

[0006] However, due to the relatively complex fault sealing mechanism, large spatio-temporal differences in fault sealing property, and many influencing factors, the evaluation process is greatly affected by human factors and the evaluation accuracy is relatively low. Summary of the Invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for evaluating the fault sealing property to solve the problems of great influence of human factors and relatively low evaluation accuracy existing in the prior art during the evaluation process.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for evaluating the fault sealing property, and the evaluation method includes the following steps:

[0010] Based on the stratigraphic correlation and seismic interpretation results, establish a fine structural model to reproduce the basic attributes of the fault;

[0011] Based on the seismic inversion and sedimentary facies research results, establish a facies model and a shale content model;

[0012] Based on the configuration relationship of the facies model on both sides of the fault, establish a fault-reservoir juxtaposition map;

[0013] Based on the fine structural model and the shale content model, calculate the fault parameters;

[0014] Based on the fault parameters and the fault-reservoir juxtaposition map, conduct the evaluation of the fault sealing property.

[0015] The solution provided by the present invention is carried out based on the existing three-dimensional geological model, which not only saves the data preparation time, improves the accuracy of fault sealing evaluation, but also improves the development effect of the oilfield.

[0016] In the present invention, the formation correlation refers to the process of comprehensively analyzing and comparing various geological data such as seismic, drilling, logging, and well logging collected in an exploration or development area, finding strata with equivalent horizons through the comprehensive analysis and comparison of single-well geological profiles, connecting the geological profiles of each well, and overall understanding the distribution and characteristics of sedimentary strata in the vertical and horizontal directions.

[0017] In the present invention, the seismic inversion is a process of imaging (solving) the spatial structure and physical properties of underground rock formations by using surface-observed seismic data and constrained by known geological laws and drilling and logging data. In a broad sense, seismic inversion includes the entire content of seismic data processing and interpretation.

[0018] In the present invention, the research results of sedimentary facies include sedimentary facies maps, specifically, the logging facies models of sedimentary facies determined based on cores, further dividing the sedimentary facies of each formation in a single well, and then drawing the planar distribution map of sedimentary facies based on the planar combination of single-well facies, sedimentary background, and seismic inversion maps.

[0019] As a preferred technical solution of the present invention, the basic attributes include the throw of the fault and the geometric parameters of the fault.

[0020] As a preferred technical solution of the present invention, the throw of the fault is obtained by determining the extension direction and distance of the fault based on seismic interpretation and seismic attributes and performing fine formation correlation under the control of marker beds.

[0021] As a preferred technical solution of the present invention, the geometric parameters of the fault are obtained through the fine structural model.

[0022] As a preferred technical solution of the present invention, the geometric parameters of the fault include the strike, dip, extension distance, fault-developed horizons, and fault intersection relationship of the fault.

[0023] As a preferred technical solution of the present invention, the fine structural model is established based on seismic and formation correlation.

[0024] As a preferred technical solution of the present invention, under the calibration of core analysis data, the reservoir is divided into different sedimentary facies or lithofacies by using well logging curves, the reservoir is classified, and then the relationships between various types of reservoirs and seismic inversion and attributes are analyzed, and established by applying seismic inversion constraints.

[0025] As a preferred technical solution of the present invention, the shale content model is established by discretizing the shale content curve into the facies model, analyzing the distribution of shale content in each facies, and under the constraint of the seismic inversion shale content volume.

[0026] As a preferred technical solution of the present invention, the establishment of the fault reservoir juxtaposition map is based on stratigraphic correlation and facies models, determining the reservoir thickness and distribution in the strata on both sides of the fault, and determining the contact relationship of different facies on the fault plane with the help of the fault throw, and finally produced.

[0027] As a preferred technical solution of the present invention, the fault parameters include fault SGR.

[0028] As a preferred technical solution of the present invention, the evaluation method includes the following steps:

[0029] Based on stratigraphic correlation and seismic interpretation results, establish a fine structural model to reproduce the basic properties of the fault; the basic properties include the fault throw and the geometric parameters of the fault; the fault throw is determined based on seismic interpretation and seismic attributes, determining the extension direction and distance of the fault, and performing fine stratigraphic correlation under the control of marker beds; the geometric parameters of the fault are obtained through the fine structural model; the geometric parameters of the fault include the strike, dip, extension distance, fault development horizons and fault intersection relationships of the fault; the fine structural model is established based on seismic and stratigraphic correlation;

[0030] Based on seismic inversion and sedimentary facies research results, establish a facies model and a shale content model; under the calibration of core analysis data, use well logging curves to divide the reservoir into different sedimentary facies or lithofacies, classify the reservoir, and then analyze the relationship between various types of reservoirs and seismic inversion and attributes, and establish by applying seismic inversion constraints; the shale content model is established by discretizing the shale content curve into the facies model, analyzing the distribution of shale content in each facies and under the constraint of the seismic inversion shale content volume;

[0031] Based on the configuration relationship of the facies model on both sides of the fault, establish a fault reservoir juxtaposition map; the establishment of the fault reservoir juxtaposition map is based on stratigraphic correlation and facies models, determining the reservoir thickness and distribution in the strata on both sides of the fault, and determining the contact relationship of different facies on the fault plane with the help of the fault throw, and finally produced;

[0032] Based on the fine structural model and the shale content model, calculate the fault parameters; the fault parameters include fault SGR;

[0033] Based on the fault parameters and the fault reservoir juxtaposition map, evaluate the fault sealing property.

[0034] In the present invention, the evaluation criteria for fault sealing property are as follows:

[0035] Condition 1, for faults where mudstone is in contact with the reservoir, the fault is sealed due to occlusion, and it is confirmed based on the fault reservoir juxtaposition map;

[0036] Condition 2: For a fault with reservoir docking, if the SGR value of the fault with reservoir docking > the standard value (20%), it is a sealing fault; otherwise, the fault is not sealed.

[0037] If one of the above conditions is met, the fault is determined to be a sealing fault.

[0038] Compared with the existing technical solutions, the present invention has the following beneficial effects:

[0039] Compared with the current fault sealing evaluation method, this method can quickly and accurately quantify and evaluate the sealing property of faults and the sealing pressure of faults in the work area based on the existing 3D geological model, integrating multi-disciplinary data, providing guidance for later development, improving the exploration and development efficiency of oilfields, and having broad application prospects. Description of the Drawings

[0040] Figure 1 is the flow chart of the evaluation method provided in this embodiment;

[0041] Figure 2 is the stratigraphic correlation schematic diagram in Application Example 1 of the present invention;

[0042] Figure 3 is the stratigraphic correlation schematic diagram in Application Example 1 of the present invention;

[0043] Figure 4 Schematic diagram of the 3D fault model (fault medium) in Application Example 1 of the present invention;

[0044] Figure 5 is the schematic diagram of the 3D fault model (fault model) in Application Example 1 of the present invention;

[0045] Figure 6 is the schematic diagram of the phase model obtained in Application Example 1 of the present invention;

[0046] Figure 7 is the schematic diagram of the shale content model obtained in Application Example 1 of the present invention;

[0047] Figure 8 is the fault-reservoir juxtaposition map obtained in Application Example 1 of the present invention;

[0048] Figure 9 is the schematic diagram of the fault SGR content obtained in Application Example 1 of the present invention;

[0049] Figure 10 is the fault sealing evaluation map in Application Example 1 of the present invention;

[0050] Figure 11 is the fault sealing evaluation map in Application Example 1 of the present invention.

[0051] The present invention will be further described in detail below. However, the following examples are merely simple examples of the present invention and do not represent or limit the scope of the claimed protection of the present invention. The scope of protection of the present invention shall be subject to the claims. Detailed implementation manners

[0052] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0053] The evaluation method provided in this embodiment, as Figure 1 shown, specifically includes:

[0054] ① Based on comprehensive formation correlation and seismic interpretation results, establish a fine structural model to accurately reproduce the basic attributes of faults;

[0055] ② Based on seismic inversion and sedimentary facies research results, establish a facies model and a shale content model;

[0056] ③ According to the configuration relationship of the facies model on both sides of the fault, establish a fault reservoir juxtaposition map;

[0057] ④ Based on the structural and shale content models, calculate the fault SGR;

[0058] ⑤ According to the SGR attribute and the fault reservoir juxtaposition map of this fault, evaluate its sealing property.

[0059] The following is a combined actual example:

[0060] Example 1

[0061] This embodiment provides a method for evaluating the sealing property of a fault, which is specifically as follows:

[0062] Step (1): Based on comprehensive formation correlation and seismic interpretation results, establish a fine structural model to accurately reproduce the geometric attributes of the fault.

[0063] Specifically, it includes the following steps:

[0064] 1.1) Under the control of marker beds, carry out formation correlation by combining wells and seismic data.

[0065] The marker beds are the formation segments with significant characteristics on the well logging curves, having particularity and universality characteristics. At the same time, on all formation seismic profiles on the same reflection axis, ensure that the formation division results have the same sedimentation time.

[0066] The combination of wells and seismic data takes advantage of the high vertical resolution of the well logging curves of completed wells. However, the drilled area is only the information of several points relative to the entire oilfield. Seismic data has good traceability in the plane. Combining the high vertical resolution of single wells and the traceability of seismic data in the plane ensures the accuracy and reliability of the formation correlation results.

[0067] Based on seismic interpretation (tracking the dislocation position and depth of the reflection axis on each seismic section), a structural map and seismic attributes are obtained to determine the extension direction and distance of the fault. Under the control of the marker bed, fine stratigraphic correlation is carried out to determine the throw of the fault.

[0068] 1.2) Based on seismic and stratigraphic correlation, a fine structural model of the fault is established.

[0069] Seismic data can well reflect the planar trend of the structure, while well logging stratification data has high resolution in the vertical direction. By combining well and seismic data, a fine structural model of the fault (fault and strata) is established to finely describe the geometric parameters of the fault, such as the strike, dip, extension distance, fault-developed horizons, formation thickness on both sides of the fault, and fault intersection relationship, etc.

[0070] Step (2): Establish a facies model and shale content model based on the results of seismic inversion and sedimentary facies research.

[0071] Specifically, it may include the following steps:

[0072] 2.1) Under the constraints of seismic inversion and sedimentary facies planar distribution map, establish a facies model.

[0073] Under the calibration of core analysis data, use well logging curves to divide the reservoir into different sedimentary facies or lithofacies, classify the reservoir, then analyze the correlation between various types of reservoirs and seismic inversion and attributes, and apply their correlation to establish a facies model under the constraint of seismic inversion.

[0074] 2.2) Under the constraint of the facies model, establish a three-dimensional shale content model.

[0075] Discretize the shale content curve into the facies model, analyze the distribution of shale content and geostatistical distribution parameters layer by layer according to the facies, and adopt the Gaussian algorithm to establish a spatial shale content model under the constraint of the seismic inversion shale content volume.

[0076] Calculate the shale content using the GR curve, and the formula is as follows:

[0077] SH = (GR - GRmin) / (GRmax - GRmin)

[0078] Where: Grmax is the measurement result when the shale content is 100%; GRmin is the well logging reading of pure sandstone rock, representing the measurement result when the shale content is 0; GR is the natural gamma value

[0079] Vsh = (2 2GCUR·SH - 1) / (2 2GCUR - 1)

[0080] Generally, for new formations, GCUR = 3.7, and for old formations, GCUR = 2. A more preferred processing method is to compare the calculated shale content with the actual shale content. If the calculated Vsh is too high, a higher GCUR value should be selected; conversely, a lower GCUR value should be chosen.

[0081] Step (3): Based on the configuration relationship of the facies model on both sides of the fault, establish a fault reservoir juxtaposition map.

[0082] Specifically, it includes the following steps:

[0083] Based on stratigraphic correlation and the facies model, determine the reservoir thickness and distribution in the formations on both sides of the fault. According to the throw of the fault, determine the contact relationship of different facies on the fault plane, and finally produce a fault reservoir juxtaposition map of all faults in three-dimensional space;

[0084] Step (4): Calculate the fault SGR based on the fine structural model and shale content model.

[0085] Specifically, it includes:

[0086] Based on the previously established fine structural model and shale content model, parameters such as the throw of the faults in the work area and the shale content of each formation can be obtained, and the SGR parameter is calculated using the following formula.

[0087] SGR = (∑(Vsh·Δz)) / T·100%

[0088] In the formula: Vsh represents the shale content of the formation, Δz represents the vertical thickness of the formation, and T represents the throw.

[0089] Step (5): Comprehensively evaluate the sealing properties of each fault in the oilfield based on the stratigraphic fault juxtaposition map and SGR attributes.

[0090] First, conduct a comprehensive analysis of the fault reservoir juxtaposition map and SGR parameters: For faults where mudstone and reservoir are in contact, they are blocked and sealed, and the faults are sealing. For faults with reservoir-reservoir contact, it is necessary to further analyze their SGR values and compare them with the standard value (20%). If it is higher than the standard value (20%), it is a sealing fault. This judgment process is carried out sequentially. If the result of one judgment process is that the fault is sealed, then the fault is determined to be sealed.

[0091] Application Example 1

[0092] This application example integrates geological, seismic, and logging results, and uses a three-dimensional geological model to evaluate the sealing properties of faults in an oilfield, which has the advantages of high speed, accuracy, and quantification.

[0093] I. Integrate stratigraphic correlation and seismic interpretation results to establish a fine structural model and accurately reproduce the basic attributes of faults.

[0094] 1. Under the control of the marker bed, well-seismic integration is carried out for stratigraphic correlation.

[0095] Based on seismic interpretation and seismic attributes, determine the extension direction and distance of the fault. Under the control of the marker bed, carry out fine stratigraphic correlation to determine the throw of the fault. The comparison results are shown in Figure 2 and Figure 3 . It can be seen from Figure 2 and Figure 3 that the seismic reflection axis is offset, indicating the development of the fault. According to the marker bed correlation in the logging curves, there is a 90m stratigraphic (blank section) missing in the right well starting from 1908m. Determine the break point depth as 1908m and the throw as 90m.

[0096] 2. Based on the break point information from seismic and stratigraphic correlation, establish the spatial model of the fault. Fine describe the geometric parameters of the fault, such as the strike, dip, extension distance, fault-developed horizons, and fault intersection relationships, etc. See Figure 4 and Figure 5 . It can be seen from Figure 4 and Figure 5 that the strike and dip of the fault can be obtained from the fault interpretation, and the depth of the fault can be obtained from the break points of the stratigraphic correlation.

[0097] II. Establish the facies model and shale content model based on the results of seismic inversion and sedimentary facies research

[0098] 1. Under the constraints of seismic inversion and sedimentary facies map, adopt the principles of statistical geology to establish the facies model.

[0099] According to sedimentary or petrophysical research, divide the reservoir into different sedimentary facies or lithofacies, and then establish the facies model under the selected seismic inversion constraints, as shown in Figure 6 .

[0100] 2. Discretize the shale content curve into the facies model, analyze the distribution of shale content in each facies, and establish the spatial shale content model under the constraints of the seismic inversion shale content volume. See Figure 7 .

[0101] III. According to the configuration relationship of the facies model on both sides of the fault, establish the fault reservoir juxtaposition map.

[0102] According to the different facies on both sides of the fault, set different configuration relationships, analyze their contact relationships, and produce the fault reservoir juxtaposition map on both sides of the fault. See Figure 8 .

[0103] IV. Based on the fine structural model and shale content model, calculate the fault SGR.

[0104] Based on the comprehensive structure and reservoir model, the shale gouge ratio (SGR) parameter is calculated. The calculation results are shown in Figure 9 .

[0105] V. Evaluate the fault sealing property by integrating the fault-reservoir juxtaposition map and SGR attributes.

[0106] First, comprehensively analyze the fault-reservoir juxtaposition map and SGR parameters: For faults where shale is in contact with the reservoir, they are sealing. If there are reservoirs in contact with each other, analyze their SGR values. If the value is higher than the standard value (20%), it is a sealing fault.

[0107] Finally, analyze each fault in the work area one by one to obtain the evaluation results. See Figure 10 、 Figure 11 and Table 1.

[0108] Table 1

[0109]

[0110]

[0111] From the results of the above embodiments and application examples, it can be seen that the solution provided by the present invention is carried out based on the existing three-dimensional geological model, which not only saves the data preparation time, improves the accuracy of fault sealing evaluation, but also improves the development effect of the oilfield.

[0112] It is declared that the present invention uses the above embodiments to illustrate the detailed structural features of the present invention, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent replacement of the components selected by the present invention, the addition of auxiliary components, and the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0113] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0114] In addition, it should be noted that, in the case of no contradiction, the various specific technical features described in the above specific embodiments can be combined in any suitable way. To avoid unnecessary repetition, the present invention does not separately describe various possible combination methods.

[0115] In addition, any combination can be made between different embodiments of the present invention, as long as it does not violate the idea of the present invention, it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for evaluating fault sealing property, characterized in that The evaluation method includes the following steps: Based on stratigraphic correlation and seismic interpretation results, establish a fine structural model to reproduce the basic properties of the fault; Based on seismic inversion and sedimentary facies research results, establish a facies model and a shale content model; Based on the configuration relationship of the facies model on both sides of the fault, establish a fault reservoir juxtaposition map; Based on the fine structural model and the shale content model, calculate the fault parameters; Based on the fault parameters and the fault reservoir juxtaposition map, evaluate the fault sealing property; Among them, the fine structural model is established based on seismic and stratigraphic correlation; the facies model is established by using well logging curves to divide the reservoir into different sedimentary facies or lithofacies, classify the reservoir under the calibration of core analysis data, then analyze the relationship between various types of reservoirs and seismic inversion and attributes, and apply seismic inversion constraints; the shale content model is established by discretizing the shale content curve into the facies model, analyzing the distribution of shale content in each facies and under the constraint of the seismic inversion shale content volume; the establishment of the fault reservoir juxtaposition map is based on stratigraphic correlation and the facies model, determine the reservoir thickness and distribution in the strata on both sides of the fault, and determine the contact relationship of different facies on the fault plane with the help of the fault throw, and finally produce it; the fault parameters include fault SGR.

2. The evaluation method according to claim 1, characterized in that, The basic properties include the fault throw and the geometric parameters of the fault.

3. The evaluation method according to claim 2, characterized in that, The fault throw is obtained by determining the extension direction and distance of the fault based on seismic interpretation and seismic attributes and conducting fine stratigraphic correlation under the control of marker beds.

4. The evaluation method according to claim 2 or 3, characterized in that, The geometric parameters of the fault are obtained through the fine structural model.

5. The evaluation method according to claim 2 or 3, characterized in that The geometric parameters of the fault include the strike, dip, extension distance, fault development horizon and fault intersection relationship of the fault.

6. The evaluation method according to claim 1, wherein The evaluation method includes the following steps: Based on stratigraphic correlation and seismic interpretation results, establish a fine structural model to reproduce the basic properties of the fault; the basic properties include the fault throw and the geometric parameters of the fault; the fault throw is obtained by determining the extension direction and distance of the fault based on seismic interpretation and seismic attributes and conducting fine stratigraphic correlation under the control of marker beds; the geometric parameters of the fault are obtained through the fine structural model; the geometric parameters of the fault include the strike, dip, extension distance, fault development horizon and fault intersection relationship of the fault; the fine structural model is established based on seismic and stratigraphic correlation; Based on seismic inversion and sedimentary facies research results, establish a facies model and a shale content model; the facies model is established by using well logging curves to divide the reservoir into different sedimentary facies or lithofacies, classify the reservoir under the calibration of core analysis data, then analyze the relationship between various types of reservoirs and seismic inversion and attributes, and apply seismic inversion constraints; the shale content model is established by discretizing the shale content curve into the facies model, analyzing the distribution of shale content in each facies and under the constraint of the seismic inversion shale content volume; Based on the configuration relationship of the phase model on both sides of the fault, a fault reservoir juxtaposition map is established; the establishment of the fault reservoir juxtaposition map is determined by stratigraphic correlation and the phase model for the reservoir thickness and distribution in the strata on both sides of the fault, and the contact relationship of different phases on the fault plane is determined with the fault throw, and finally produced; Based on the refined structural model and the shale content model, fault parameters are calculated; the fault parameters include fault SGR; Based on the fault parameters and the fault reservoir juxtaposition map, the fault sealing evaluation is carried out.

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