Method and system for evaluating tight reservoir dessert based on fault segmentation characteristics

Abstract

The invention provides a method and system for evaluating tight reservoir sweet spots based on fault segment characteristics, and the method comprises the steps: determining the ground stress field characteristics of a to-be-detected region in a critical period according to geological data, determining the segment characteristics of a target fault based on the ground stress field characteristics, and correspondingly dividing segmented faults and connecting bands; analyzing stress states of different parts of the fault in combination with a crustal stress field state in a critical period, and dividing fault types by considering openness; calculating the area of the connecting band, and further determining comprehensive evaluation parameters of the connecting band based on the area; and according to the fault type and the comprehensive evaluation parameters of the connecting band, evaluating crack-related sweet spots at different positions of the target fault. By the adoption of the method, the problems that the prior art is limited by seismic data and geological analysis result quality and operation is complex can be solved, the sectionality of the current continuous fault is determined based on the fracture sectionalized growth process, tight reservoir dessert distribution at different positions of the fault is evaluated, and reliable reference support is provided for exploiting and well releasing.

Description

Technical Field

[0001] The present invention relates to the technical field of reservoir sweet spot analysis and evaluation, and particularly to a method and system for evaluating the sweet spots of tight reservoirs based on fault segmentation characteristics. Background Art

[0002] The oil and gas saturation of tight reservoirs is generally low, and after experiencing complex geological processes, the oil and gas heterogeneity is extremely strong. Existing conventional geological analysis methods are difficult to predict the distribution of tight reservoir sweet spots at a smaller scale. Currently, there are mainly three types of methods for determining tight reservoir sweet spots. One is the seismic prediction method, that is, a method of directly predicting the sweet spot distribution by continuously improving seismic technology; the second is the geological prediction method, mainly to clarify the main controlling factors based on geological research, and combine the mapping and overlay of the main controlling factors to find more favorable sweet spots; the third is the comprehensive method, that is, a method of comprehensively analyzing and predicting the sweet spot distribution by combining geological understanding and seismic prediction.

[0003] However, the seismic prediction method is controlled by the quality of seismic data, and with the gradually emerging characteristics of "small, micro, thin, and scattered" in exploration and development targets, the multi-solution of seismic prediction results is rapidly increasing, and the reliability of analysis results is insufficient; the geological prediction method depends on the understanding of the main controlling factors of high-yield enrichment and the predictability of different factors themselves. Although it has strong compatibility, it is also restricted by the interaction of multiple factors, and it is difficult to improve certainty and accuracy; the existing comprehensive method belongs to the simple fusion application of the seismic prediction method and the geological prediction method. To a certain extent, it extracts the advantages of the above two methods to reduce uncertainty and improve the accuracy of sweet spot prediction, but it inevitably inherits the limitations of the two methods themselves. Restricted by the two methods, the operation is complex and the accuracy of the analysis results is limited, and it cannot well meet the requirements of development well placement engineering.

[0004] The information disclosed in the background art section of the present invention is only intended to deepen the understanding of the general background art of the present invention, and should not be regarded as an admission or any form of suggestion that this information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0005] To solve the above problems, the present invention provides a method for evaluating the sweet spots of tight reservoirs based on fault segmentation characteristics. The method determines the segmentation characteristics of the target fault based on the characteristics of the in-situ stress field, and correspondingly divides the segmented faults and the connection zones; then combines the stress state analysis of different parts of the fault with the in-situ stress field state during the key period, and considers the opening property to divide the fault types; according to the fault types and the comprehensive evaluation parameters calculated, evaluate the fracture-related sweet spots at different positions of the target fault. By using this method, it is possible to overcome the problems of being limited by the quality of seismic data, geological analysis results, and complex operation in the prior art, determine the segmentation of the current continuous fault based on the process of fracture segmentation growth, and evaluate the distribution of tight reservoir sweet spots at different positions of the fault. Preferably, in one embodiment, the method includes:

[0006] Steps of in - situ stress analysis: Determine the characteristics of the in - situ stress field during the key period of the area to be measured according to geological data;

[0007] Steps of segment feature analysis: Based on the distribution of the fault zone, determine the segment features of the target fault according to the characteristics of the in - situ stress field;

[0008] Steps of fault division: Based on the segment features, correspondingly divide the segment faults and the connecting zones, and then analyze the stress states of different parts of the fault in combination with the in - situ stress field state during the key period, and consider the opening property to divide the fault types;

[0009] Steps of calculating evaluation parameters: Calculate the area of the connecting zone, and then determine the comprehensive evaluation parameters of the connecting zone based on it;

[0010] Steps of sweet spot evaluation: Evaluate the fracture - related sweet spots at different positions of the target fault according to the fault type and the comprehensive evaluation parameters of the connecting zone.

[0011] Furthermore, in one embodiment, in the steps of in - situ stress analysis, set the period before large - scale hydrocarbon injection as the key geological period, and determine the stress field action characteristics in the area where the fault is located during the period before large - scale hydrocarbon injection as the characteristics of the in - situ stress field of the target fault during the key period.

[0012] Optionally, in one embodiment, in the steps of segment feature analysis, determine the main trend of the fault zone of the target fault as the main strike, identify the fault segments consistent with the parallel line direction, identify the local fault turning points with a set - requirement included angle with the strike of the fault zone, and associate the relative movement relationship between the two fault blocks to form the segment features of the target fault.

[0013] In a preferred embodiment, in the steps of fault division, the process of dividing the segment faults and the connecting zones based on the segment features includes:

[0014] Make parallel lines according to the main strike of the target fault, match the parallel lines with the fault, the fault segments consistent with the parallel line direction are one - segment faults, and the local fault turning points with a set - requirement included angle with the strike of the fault zone are the connecting zones between the segment faults.

[0015] Furthermore, in one embodiment, in the steps of fault division, according to the stress states of different parts during the fault growth process, further consider the opening property to divide different parts of the target fault into three fault types in units of segment faults and connecting zones, including tensile segments, strike - slip segments and compressive segments, where the tensile segments have the strongest fracture opening property, followed by the strike - slip segments, and the compressive segments have the weakest fracture opening property.

[0016] In an alternative embodiment, in the evaluation parameter calculation step, the distance of the connection belt along the strike of the fracture zone is the length, and the distance of the connection belt perpendicular to the strike of the fracture zone is the width. The different connection belt widths and lengths are determined respectively, and the area of the connection belt and the quantitative evaluation parameter of the connection belt opening property are calculated according to the length and width, and then the comprehensive evaluation parameter is determined based on the two.

[0017] Further, in one embodiment, the comprehensive evaluation parameter of the connection belt is determined by the following calculation:

[0018] Mi = Si * Kii = 1, 2, …, m

[0019] In the formula, Mi represents the comprehensive evaluation parameter of the i-th connection belt, Si represents the area of the i-th connection belt, Ki represents the quantitative evaluation parameter of the opening property of the i-th connection belt, and m represents the number of connection belts participating in the calculation.

[0020] In an alternative embodiment, the sweet spot evaluation step: perform a first-level evaluation and ranking on the relevant sweet spots of the fault according to the fault type; for the relevant sweet spots containing multiple connection belts within each type, perform a second-level evaluation and ranking in descending order of the comprehensive evaluation parameter.

[0021] Based on other aspects of the method described in any one or more of the above embodiments, the present invention further provides a storage medium, on which program code for implementing the method described in any one or more of the above embodiments is stored.

[0022] Based on the application aspect of the method described in any one or more of the above embodiments, the present invention further provides a system for evaluating sweet spots of tight reservoirs based on fault segmentation characteristics, and the system executes the method described in any one or more of the above embodiments.

[0023] Compared with the closest prior art, the present invention also has the following beneficial effects:

[0024] A method and system for evaluating sweet spots of tight reservoirs based on fault segmentation characteristics provided by the present invention. The method determines the segmentation characteristics of the target fault based on the key period in-situ stress field characteristics, and correspondingly divides the segmented faults and connection belts; further analyzes the stress state of different parts of the fault in combination with the key period in-situ stress field state, and considers the opening property to divide the fault types; calculates the area and comprehensive evaluation parameter of the connection belt; and evaluates the fracture-related sweet spots at different positions of the target fault according to the fault type and the comprehensive evaluation parameter of the connection belt. Using this method, it is possible to effectively avoid the influence of the multi-solution of seismic prediction and the ambiguity of geological prediction on the sweet spot analysis results, accurately predict the fault-related sweet spots of tight reservoirs through concise geological analysis means and quantitative calculations, effectively evaluate the development of sweet spots of tight reservoirs at different positions of the fault, improve the sweet spot prediction accuracy of tight reservoirs, and provide important reference guidance for well placement in development.

[0025] Other features and advantages of the present invention will be described in the following specification. Moreover, some of them will become apparent from the specification or be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the structures specifically pointed out in the specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0027] Figure 1 is a schematic flow chart of a method for evaluating sweet spots of tight reservoirs based on fault segmentation features provided by an embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of the shape, strike, and relative movement directions of the two fault blocks of the F1 fault during the key period in the method for evaluating sweet spots of tight reservoirs based on fault segmentation features provided by an embodiment of the present invention;

[0029] Figure 3 is a schematic diagram for comparing the differential stress conditions of faults in different strike directions in the method for evaluating sweet spots of tight reservoirs based on fault segmentation features provided by an embodiment of the present invention;

[0030] Figure 4 is a schematic diagram of the segmentation features of the F1 fault in the method for evaluating sweet spots of tight reservoirs based on fault segmentation features provided by an embodiment of the present invention;

[0031] Figure 5 is a schematic diagram of the segmented growth characteristics of the F1 fault and the stress states at different positions in the method for evaluating sweet spots of tight reservoirs based on fault segmentation features provided by an embodiment of the present invention;

[0032] Figure 6 is an example diagram of the drilling and production capacity characteristics distribution of the F1 fault in the method for evaluating sweet spots of tight reservoirs based on fault segmentation features provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following will describe in detail the embodiments of the present invention in conjunction with the drawings and embodiments. Through this, those skilled in the art of the present invention can fully understand how to apply technical means to solve technical problems and achieve the process of technical effects, and implement the present invention according to the above implementation process. It should be noted that as long as there is no conflict, the various embodiments in the present invention and the various features of each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.

[0034] Although the flowchart describes the operations as sequential processes, many of the operations can be implemented in parallel, concurrently, or simultaneously. The order of the operations can be rearranged. The process can be terminated when its operations are completed, but it can also have additional steps not included in the figures. The process can correspond to a method, function, procedure, subroutine, subprogram, and so on.

[0035] Computer devices include user devices and network devices. Among them, user devices or clients include, but are not limited to, computers, smartphones, PDAs (Personal Digital Assistants), etc.; network devices include, but are not limited to, a single network server, a server group composed of multiple network servers, or a cloud composed of a large number of computers or network servers based on cloud computing. Computer devices can run independently to implement the present invention, or can be connected to a network and implement the present invention through interactive operations with other computer devices in the network. The network where the computer device is located includes, but is not limited to, the Internet, wide area network, metropolitan area network, local area network, VPN network, etc.

[0036] Here, terms such as "first", "second", etc. may be used to describe various units, but these units should not be limited by these terms. These terms are only used to distinguish one unit from another. The term "and / or" used here includes any and all combinations of one or more of the listed related items. When a unit is referred to as being "connected" or "coupled" to another unit, it can be directly connected or coupled to the other unit, or there can be an intermediate unit.

[0037] The terms used here are only for describing specific embodiments and are not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "a", "an" used here are also intended to include the plural. It should also be understood that the terms "comprises" and / or "comprising" used here specify the presence of the stated features, integers, steps, operations, units, and / or components, and do not preclude the presence or addition of one or more other features, integers, steps, operations, units, components, and / or their combinations.

[0038] The oil and gas saturation in tight reservoirs is generally low, and after experiencing complex geological processes, the oil and gas heterogeneity is extremely strong. Existing conventional geological analysis methods are difficult to predict the distribution of sweet spots in tight reservoirs at a smaller scale. However, with the increasing attention to unconventional oil and gas at home and abroad, the impact of how to accurately predict the sweet spots in tight reservoirs using geological analysis means in addition to seismic technology has become more and more prominent. Determining the distribution of sweet spots in tight reservoirs has important reference value for well placement in later development.

[0039] At present, there are mainly three types of methods for determining the sweet spots of tight reservoirs. One is the seismic prediction method, that is, a method of directly predicting the distribution of sweet spots by continuously improving seismic technology; the second is the geological prediction method, which mainly identifies the main controlling factors based on geological research, and combines mapping and overlaying of the main controlling factors to find more favorable sweet spots; the third is the comprehensive method, that is, a method of comprehensively analyzing and predicting the distribution of sweet spots by combining geological understanding and seismic prediction.

[0040] However, there are some problems when applying the above existing methods. Among them, the seismic prediction method is controlled by the quality of seismic data, and with the characteristics of "small, micro, thin, and scattered" gradually emerging in exploration and development targets, the multi-solution of seismic prediction results is rapidly increasing, and the reliability of analysis results is insufficient;

[0041] The geological prediction method depends on the understanding of the main controlling factors of high-yield enrichment and the predictability of different factors themselves. Although it has strong compatibility, it is also restricted by the interaction of multiple factors, and it is difficult to improve certainty and accuracy;

[0042] The existing comprehensive method belongs to the simple fusion application of the seismic prediction method and the geological prediction method. To a certain extent, it extracts the advantages of the above two methods to reduce uncertainty and improve the accuracy of sweet spot prediction. However, it inevitably inherits the limitations of the two methods themselves. Restricted by the two methods, the operation is complex and the accuracy of the analysis results is limited, and it cannot well meet the requirements of development well placement engineering.

[0043] The researchers of the present invention considered that, with the gradual understanding of the important role of fractures in the sweet spots of tight reservoirs in the law of high-yield enrichment, a technology for relatively accurately predicting the fault-related sweet spots of tight reservoirs by using the development characteristics of fractures can be explored based on this. Based on the process of segmented growth of fractures, determine the segmentation of the currently continuous same fault, and further combine the tectonic geological background to evaluate the sweet spots of tight reservoirs at different positions on the same fault, so as to achieve the goal of relatively accurately predicting the sweet spots of tight reservoirs by using geological analysis means, which has important reference value for development well placement.

[0044] To solve the above problems, the present invention provides a method and system for evaluating the sweet spots of tight reservoirs based on fault segmentation characteristics. The method adopts the following technical ideas:

[0045] ① Investigate the regional geological data to clarify the characteristics of the in-situ stress field during the key period;

[0046] ② Select the target fault and determine the strike of the target fault, and combine the regional stress field during the key period to clarify the relative movement relationship between the two fault blocks

[0047] ③ According to the relationship between the fault and the fault zone, the segmented characteristics of the fault are determined on the target fault and named F1-1, F1-2...F1-N respectively; the connecting zones between the segmented faults are determined and named A1, A2, A3...An respectively;

[0048] ④ Determine the stress or movement state of different parts of the fault based on the relationship between the fault morphology and the fault zone trend;

[0049] ⑤ Calculate the quantitative evaluation parameters of the connection zone, determine the length of the connection zone along the fault zone and the width perpendicular to the fault zone, calculate the area S of the connection zone, calculate the quantitative evaluation parameter K of the opening of the connection zone, and then determine the comprehensive evaluation parameter M, M1 = S1*K1...Mn = Sn*Kn;

[0050] ⑥ According to the stress state at different positions and the comprehensive evaluation parameters of the connection zone, the crack-related sweet spots at different positions of the fault are sorted.

[0051] Next, the detailed process of the method of the embodiment of the present invention is described in detail based on the accompanying drawings. The steps shown in the flowchart of the accompanying drawings can be executed in a computer system including a set of computer executable instructions. Although the logical order of each step is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0052] Embodiment 1

[0053] Figure 1 A schematic diagram of a process for evaluating a sweet spot in a tight reservoir based on fault segmentation characteristics provided by the first embodiment of the present invention is shown, referring to Figure 1 It can be seen that the method includes the following steps.

[0054] Geostress analysis step S1: determining the geostress field characteristics of the key period of the area to be tested based on geological data;

[0055] Segment feature analysis step S2: determining the segment features of the target fault based on the distribution of the fault zone and the characteristics of the in-situ stress field;

[0056] Fault division step S3: dividing the segmented faults and connecting zones based on the segmented characteristics, and then analyzing the stress state of different parts of the fault in combination with the state of the ground stress field during the critical period, and dividing the fault types considering the openness;

[0057] Evaluation parameter calculation step S4: calculating the area of the connection belt, and then determining the comprehensive evaluation parameter of the connection belt based on the area of the connection belt;

[0058] Sweet spot evaluation step S5: According to the fault type and the comprehensive evaluation parameters of the connection zone, the fracture-related sweet spots at different positions of the target fault are evaluated.

[0059] In the above embodiments of the present invention, the relationship between fracture segmented growth and the development of fault-related sweet spots in tight reservoirs is established. Based on fracture segmented growth, the fault-related sweet spots of tight reservoirs at different positions of the target fault are predicted. Based on the process of fracture segmented growth, it is clarified that the currently continuous same fault has segmented characteristics. Further, combined with the tectonic geological background, the stress and fracture characteristics at different positions on the same fault or fault zone are determined, and then the development of fault-related sweet spots in tight reservoirs along the fault is evaluated. The operation is concise, and it overcomes the multi-solution problem of seismic prediction technology and the ambiguity of geological analysis methods. It can accurately evaluate the development of fault-related sweet spots in tight reservoirs at different positions of the fault, effectively improve the prediction accuracy of sweet spots in tight reservoirs, and relatively accurately predict the distribution of sweet spots in tight reservoirs within the fault zone through geological analysis means, providing a reliable reference for well placement in development.

[0060] Preferably, in one embodiment, in the in-situ stress analysis step S1, it is determined that the period before large-scale hydrocarbon charging is the key geological period. Through regional geological investigation, the stress field action characteristics in the area where the fault is located before large-scale hydrocarbon charging are determined as the in-situ stress field characteristics of the target fault during the key period.

[0061] Taking the F1 fault in the northeast of a certain oilfield as an example, the fault cuts through the main oil-producing layer. The fault is interpreted as slightly curved through fine seismic information. According to the fracture growth theory, the fault has obvious segmented characteristics, such as Figure 2 shown.

[0062] Execute the in-situ stress analysis step, investigate the regional geological data, and determine that the late Jurassic period before large-scale hydrocarbon charging is the key geological period. The area where the fault is located was mainly affected by the left-lateral compressive stress field during the late Jurassic period.

[0063] Furthermore, execute the segmented characteristic analysis step S2, and determine the segmented characteristics of the target fault based on the fracture zone distribution according to the in-situ stress field characteristics;

[0064] Select the target fault and determine the strike of the target fault. Combine the regional stress field during the key period to clarify the relative movement relationship between the two fault blocks. In an optional embodiment, in the segmented characteristic analysis step, determine the main strike of the fracture zone of the target fault, identify the fault segments consistent with the parallel line direction, identify the local fault bends presenting a set angle with the strike of the fracture zone, and associate the relative movement relationship between the two fault blocks to form the segmented characteristics of the target fault.

[0065] For example, first determine the strike of the fracture zone to which the target fault belongs. The local fault bend presents a certain angle with the strike of the fracture zone, which is caused by the segmented growth of the fault. The two fault blocks are in a left-lateral or right-lateral relationship.

[0066] Next, perform the fault division step S3. First, divide the segmented faults and connection zones based on the segmented features, and then analyze the stress states of different parts of the faults in combination with the stress field state during the key period, and consider the opening property to divide the fault types.

[0067] Preferably, in one embodiment, in the fault division step S3, the process of dividing the segmented faults and connection zones based on the segmented features includes:

[0068] Draw parallel lines along the main trend of the target fault, match the parallel lines with the fault. The fault segments with the same direction as the parallel lines are segmented faults, and the local fault turning points with a set angle with the fault zone trend are the connection zones between the segmented faults. In practical applications, according to the relationship between the fault and the fault zone trend, each segmented fault and connection zone of the fault can be determined on the target fault and named respectively; each different segmented fault is determined and named as F1-1, F1-2... F1-N; the connection zones between the segmented faults are determined and named as A1, A2, A3... An respectively.

[0069] For example, draw parallel lines along the main trend of the target fault in the north-northeast direction, match the parallel lines with the fault. Those with the same direction as the parallel lines are segmented faults, and the non-parallel parts are the connection zones between the faults. According to this method, the segmented faults F1-1, F1-2,..., F1-N are determined respectively, where N represents the number of segmented faults; and the connection zones A1, A2,..., An are determined, where n represents the number of connection zones; among them, A1 is located between F1-1 and F1-2, and A2 is located between F1-2 and F1-3.

[0070] According to the fracture segmentation growth theory, F1-1, F1-2, F1-3 parallel to the fault zone trend are the core parts of the fault, which are formed prior to the connection zones. Under the further action of the stress field, the fracture continues to grow and connects the originally three smaller faults through the connection zones to merge into a larger fault. Combining the stress field state of the key period in the region, the stress or movement states of different parts during the fault growth process can be determined, and the connection zones with different opening properties can be further divided. The differential stress division of the fault in different directions is as Figure 3 shown.

[0071] Therefore, in one embodiment, the fault division step S3 further includes:

[0072] Analyze the stress states of different parts of the fault in combination with the stress field state during the key period,

[0073] According to the stress states of different parts during the fault growth process, considering the opening property, different parts of the target fault are divided into three fault types in units of segmented faults and connection zones, including tensile segments, strike-slip segments, and compressive segments;

[0074] Among them, the tensile segment has the strongest crack opening, followed by the strike-slip segment, and the compressive segment has the weakest crack opening.

[0075] Taking the F1 fault located in the northeast of a certain oilfield as an example, it is determined that F1 is the target fault. It is determined that the strike of the fault zone to which the F1 fault belongs is NEE, and there is a certain angle between the local fault bend and the strike of the fault zone, which is caused by the segmented growth of the fault (for details, see Figure 2 ); The two plates of the fault are in a left-lateral relationship, that is, the upper plate in the north of the F1 fault moves relatively to the left, and the lower plate in the south of the F1 fault moves relatively to the right.

[0076] Parallel lines are drawn according to the main strike of the F1 fault, which is NEE. The parallel lines are matched with the fault. The part that is consistent with the direction of the parallel lines is one segment, and the non-parallel part is the connection zone between the faults. According to this method, the segmented faults F1-1, F1-2, and F1-3 are determined respectively; and the connection zones A1 and A2 are determined; where A1 is located between F1-1 and F1-2, and A2 is located between F1-2 and F1-3, as Figure 4 shown.

[0077] Among them, according to the theory of fault segmented growth, F1-1, F1-2, and F1-3 parallel to the strike of the fault zone are the core parts of the fault. Combining the state of the in-situ stress field in the key period area, the stress or movement state of different parts during the fault growth process can be determined; among them, the F1-1, F1-2, and F1-3 faults are divided into strike-slip segments. Further combining the slight changes in the fault morphology and the main strike, it is considered that F1-1 is a strike-slip and partial compression characteristic segment, and F1-3 is a strike-slip and partial tensile segment; the A1 connection zone under the action of tensile stress is divided into a tensile segment, and the connection zone A2 under the state of compressive stress is divided into a compressive segment, as Figure 5 shown.

[0078] Furthermore, by evaluating the operation steps of parameter S4, the area of the connection zone is calculated, and then the comprehensive evaluation parameter of the connection zone is determined based on it;

[0079] In an optional embodiment, in the evaluation parameter operation step S4, for the connection zone, the distance along the strike of the fault zone is used as the length, and the distance perpendicular to the strike of the fault zone is used as the width. The widths and lengths of different connection zones are determined respectively. The area of the connection zone and the quantitative evaluation parameter of the crack opening of the connection zone are calculated according to the length and width, and then the comprehensive evaluation parameter is determined based on the two.

[0080] In an optional embodiment, the comprehensive evaluation parameter of the connection zone is calculated according to the following formula:

[0081] Mi = Si * Ki i = 1, 2, …, m

[0082] Wherein, Mi represents the comprehensive evaluation parameter of the i-th connecting zone, Si represents the area of the i-th connecting zone, Ki represents the quantitative evaluation parameter of the openness of the i-th connecting zone, and m represents the number of connecting zones participating in the operation.

[0083] For example, to calculate the quantitative evaluation parameter of the connecting zone, respectively determine the lengths B1, B2, B3... Bm of the connecting zone along the strike of the fault zone and the widths C1, C2, C3... Cm perpendicular to the strike of the fault zone;

[0084] Calculate the areas S1, S2,..., Sn of the connecting zones, where S1 = B1 * C1,..., Sn = Bm * Cm;

[0085] Calculate the quantitative evaluation parameter K of the openness of the connecting zone, K1 = C1 / B1... Km = Cm / Bm;

[0086] Furthermore, determine the comprehensive evaluation parameter M, M1 = S1 * K1... Mm = Sm * Km.

[0087] In practical applications, within the range of each connecting zone, calculate the length and width of the connecting zone. The length is the distance between two segmented faults along the strike direction of the fault zone where the F1 fault is located. For example, B1 is the distance between the boundaries of F1-1 and F1-2; the width is the distance between two segmented faults perpendicular to the strike direction of the F1 fault. For example, C1 is the distance between the boundaries of F1-1 and F1-2. Calculate the area S of each connecting zone respectively, where S1 = B1 * C1, S2 = B2 * C2, the quantitative parameter of openness K, K1 = C1 / B1, K2 = C2 / B2. Note here that when under extrusion pressure, the openness evaluation is negative. The comprehensive evaluation parameter M, M1 = S1 * K1, M2 = S2 * K2; the higher the comprehensive evaluation parameter, the more favorable the connecting zone.

[0088] Taking the F1 fault in the northeast of a certain oilfield as an example, within the range of the connecting zone, calculate the length and width of the connecting zone. The length is the distance between two segmented faults along the strike direction of the fault zone where the F1 fault is located. For example, B1 is the distance between the boundaries of F1-1 and F1-2; the width is the distance between two segmented faults perpendicular to the strike direction of the F1 fault. For example, C1 is the distance between the boundaries of F1-1 and F1-2. Calculate the area S of each connecting zone respectively, where S1 = B1 * C1, S2 = B2 * C2, the quantitative parameter of openness K, K1 = C1 / B1, K2 = C2 / B2. Note here that when under extrusion pressure, the openness evaluation is negative. The comprehensive evaluation parameter M, M1 = S1 * K1, M2 = S2 * K2; the higher the comprehensive evaluation parameter, the more favorable the connecting zone. The specific evaluation for the F1 fault is shown in Table 1.

[0089] Table 1 Statistical Characteristics Table of Quantitative Evaluation Parameters of Connecting Zones

[0090]

[0091] Further, perform the sweet spot evaluation step S5. According to the fault type and the comprehensive evaluation parameters of the connection zone, evaluate the fracture-related sweet spots at different positions of the target fault.

[0092] Since the sweet spots in tight reservoirs are strongly affected by fractures, the different positions of the fault can be evaluated according to the fracture opening characteristics during the key geological periods. First, rank the positions with the strongest opening and large tensile forces at the top, rank the positions in the strike-slip state with balanced forces in the middle, and rank the positions with weaker opening and extrusion forces at the bottom.

[0093] Based on the qualitative ranking, there may be cases where some connection zones have similar stress states. Combining the quantitative comprehensive evaluation of the connection zones can further refine the ranking.

[0094] Therefore, in an optional embodiment, in the sweet spot evaluation step S5, perform the first-level evaluation and ranking of the relevant sweet spots of the fault according to the fault type; for the relevant sweet spots of multiple connection zones included in each type, perform the second-level evaluation and ranking from large to small using the comprehensive evaluation parameters.

[0095] For the F1 fault, the A1 position is affected by tensile force, with the strongest fracture opening, ranking first. The F1-3 position affected by the strike-slip and tensile component ranks second. The strike-slip tensile segment F1-3 ranks third. The strike-slip and extrusion segment F1-1 ranks fourth. The A2 position affected by extrusion force ranks fifth. Since the scale of the F1 fault is limited and there are fewer fault segments and connection zones, the method proposed in this patent can be applied to more complex fault-related sweet spot analysis, accurately predicting the relative advantages and disadvantages of fault-related sweet spots at different positions of the same fault, and laying a foundation for finding the optimal sweet spots in tight reservoirs.

[0096] It should be noted that the evaluation results of this method are in good agreement with the oil well production results. There is no well control in the F1-1 and A1 sections in the western part of the F1 fault. The cumulative oil production of Well No. 6 located in the F1-3 section ranked second reached 21240 m 3 , and the cumulative oil production of Well No. 3 located in the F1-2 section ranked third reached 13998 m 3 , while there are two wells, Well No. 3 and Well No. 4, in the extrusion segment ranked fifth, with an average cumulative oil production of only 4513 m 3 , further proving the effectiveness of this method. For details, see Figure 6 and the information in Table 2 below.

[0097] Table 2 Statistical Table of Comprehensive Evaluation and Oil Well Productivity of F1 Fault in a Certain Oilfield

[0098]

[0099] The embodiment of the present invention provides a method for predicting fault-related sweet spots in tight reservoirs based on fracture segmentation growth, which overcomes the multi-solution problem of seismic prediction technology and the ambiguity of geological analysis methods. It has important practical significance for improving development effects and realizing the effective development of tight oil from the aspects of development well layout. Therefore, this method has broad application prospects.

[0100] In the embodiment of the present invention, the relationship between fracture segmentation growth and the development of fault-related sweet spots in tight reservoirs is established. Based on fracture segmentation growth, the tight reservoir sweet spots related to the same fault or fault zone are predicted, getting rid of the dependence on seismic prediction technology and geological analysis methods, accurately evaluating the development of tight reservoir sweet spots at different positions of the same fault, and improving the prediction accuracy of sweet spots in tight reservoirs.

[0101] For the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0102] It should be noted that in other embodiments of the present invention, the method can also obtain a new method for evaluating tight reservoir sweet spots based on fault segmentation characteristics by combining one or several of the above embodiments to realize the distribution prediction and development analysis of tight reservoir-related sweet spots.

[0103] It should be noted that based on the method in any one or more of the above embodiments of the present invention, the present invention also provides a storage medium on which program codes for implementing the method described in any one or more of the above embodiments are stored. When the codes are executed by an operating system, the method for evaluating tight reservoir sweet spots based on fault segmentation characteristics as described above can be realized.

[0104] Embodiment 2:

[0105] In the above embodiments disclosed by the present invention, the method is described in detail. The method of the present invention can be implemented by various forms of devices or systems. Therefore, based on other aspects of the method in any one or more of the above embodiments, the present invention also provides a system for evaluating tight reservoir sweet spots based on fault segmentation characteristics, which is used to execute the method for evaluating tight reservoir sweet spots based on fault segmentation characteristics described in any one or more of the above embodiments. Specific embodiments are given below for detailed description.

[0106] Specifically, the system for evaluating tight reservoir sweet spots based on fault segmentation characteristics provided in the embodiment of the present invention includes:

[0107] The in-situ stress analysis module is configured to determine the characteristics of the in-situ stress field during the key period of the area to be measured according to geological data;

[0108] The segmentation feature analysis module is configured to determine the segmentation features of the target fault based on the fracture zone distribution according to the characteristics of the in-situ stress field;

[0109] The fault division module is configured to correspondingly divide the segmented faults and connection zones based on the segmentation features, and then analyze the stress states of different parts of the fault in combination with the in-situ stress field state during the key period, and consider the opening property to divide the types of connection zones;

[0110] The evaluation parameter calculation module is configured to calculate the area of the connection zone, and then determine the comprehensive evaluation parameter of the connection zone based on it;

[0111] The sweet spot evaluation module is configured to evaluate the fracture-related sweet spots at different positions of the target fault according to the connection zone type and the comprehensive evaluation parameter of the connection zone.

[0112] Furthermore, in one embodiment, the in-situ stress analysis module sets the period before large-scale hydrocarbon charging as the key geological period, and determines the stress field action characteristics in the area where the fault is located during the period before large-scale hydrocarbon charging as the characteristics of the in-situ stress field during the key period of the target fault.

[0113] Optionally, in one embodiment, the segmentation feature analysis module is configured to determine the main direction of the fracture zone of the target fault as the main trend, identify the fault segments consistent with the parallel line direction, identify the local fault turning points presenting a set required angle with the fracture zone trend, and associate the relative movement relationship between the two fault blocks to form the segmentation features of the target fault.

[0114] In a preferred embodiment, the fault division module divides the segmented faults and connection zones based on the segmentation features according to the following operations:

[0115] Make parallel lines according to the main trend of the target fault, match the parallel lines with the fault, the fault segments consistent with the parallel line direction are one segmented fault, and the local fault turning points presenting a set required angle with the fracture zone trend are the connection zones between the segmented faults.

[0116] Furthermore, in one embodiment, the fault division module is configured to further divide different parts of the target fault into three fault types, including tensile segments, strike-slip segments and compressive segments, in units of segmented faults and connection zones according to the stress states of different parts during the fault growth process, considering the opening property, where the tensile segments have the strongest fracture opening property, followed by the strike-slip segments, and the compressive segments have the weakest fracture opening property.

[0117] In an alternative embodiment, the evaluation parameter calculation module determines different connection belt widths and lengths with the distance along the fracture zone of the connection belt as the length and the distance perpendicular to the fracture zone of the connection belt as the width, calculates the area of the connection belt and the quantitative evaluation parameter of the connection belt opening based on the length and width, and then determines the comprehensive evaluation parameter based on the two.

[0118] Further, in one embodiment, the evaluation parameter calculation module calculates and determines the comprehensive evaluation parameter of the connection belt according to the following formula:

[0119] Mi = Si * Kii = 1, 2, …, m

[0120] In the formula, Mi represents the comprehensive evaluation parameter of the i-th connection belt, Si represents the area of the i-th connection belt, Ki represents the quantitative evaluation parameter of the opening of the i-th connection belt, and m represents the number of connection belts participating in the operation.

[0121] In an alternative embodiment, the sweet spot evaluation module is configured to perform a first-level evaluation and sorting on the relevant sweet spots of the fault according to the fault type; for the relevant sweet spots containing multiple connection belts within each type, perform a second-level evaluation and sorting in descending order of the comprehensive evaluation parameter.

[0122] In the system for evaluating sweet spots of tight reservoirs based on fault segmentation characteristics provided by the embodiments of the present invention, each module or unit structure can operate independently or in combination according to actual geological analysis requirements and parameter calculation requirements to achieve corresponding technical effects.

[0123] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments and do not mean limitation.

[0124] The phrase "one embodiment" mentioned in the specification means that the specific features, structures or features described in connection with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrase "one embodiment" appearing throughout the specification does not necessarily refer to the same embodiment.

[0125] Although the disclosed embodiments of the present invention are as above, the content described above is only an embodiment adopted for the convenience of understanding the present invention and is not used to limit the present invention. Any person skilled in the technical field to which the present invention pertains can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A method for evaluating sweet spots of tight reservoirs based on fault segmentation characteristics, characterized in that The method includes the following steps: In-situ stress analysis step: determining the characteristics of the in-situ stress field during the key period of the area to be measured according to geological data; Segmental characteristic analysis step: determining the segmental characteristics of the target fault based on the fracture zone distribution according to the in-situ stress field characteristics; Fault division step: correspondingly dividing the segmented faults and connecting zones based on the segmental characteristics, and then analyzing the stress states of different parts of the fault in combination with the in-situ stress field state during the key period, and considering the openness to divide the fault types; Evaluation parameter calculation step: calculating the area of the connecting zone, and then determining the comprehensive evaluation parameter of the connecting zone based on it; Sweet spot evaluation step: evaluating the fracture-related sweet spots at different positions of the target fault according to the fault type and the comprehensive evaluation parameter of the connecting zone; 2. The method according to claim 1, wherein In the in-situ stress analysis step, the period before large-scale hydrocarbon charging is set as the key geological period, and the stress field action characteristics in the area where the fault is located during the period before large-scale hydrocarbon charging are determined as the in-situ stress field characteristics of the target fault during the key period; 3. The method according to claim 1, wherein In the segmental characteristic analysis step, the direction of the fracture zone of the target fault is determined as the main trend, the fault segments consistent with the parallel line direction are identified, the local fault turning points with a set included angle with the fracture zone trend are identified, and the relative movement relationship between the two fault blocks is associated to form the segmental characteristics of the target fault; 4. The method according to claim 1, wherein In the fault division step, the process of dividing the segmented faults and connecting zones based on the segmental characteristics includes: Making parallel lines according to the main trend of the target fault, matching the parallel lines with the fault, the fault segments consistent with the parallel line direction are one segmented fault, and the local fault turning points with a set included angle with the fracture zone trend are the connecting zones between the segmented faults; 5. The method according to claim 1 or 4, characterized in that, In the fault division step, according to the stress states of different parts during the fault growth process, further considering the openness, different parts of the target fault are divided into three fault types in units of segmented faults and connecting zones, including tensile segments, strike-slip segments and compressive segments, where the tensile segments have the strongest fracture openness, followed by the strike-slip segments, and the compressive segments have the weakest fracture openness; 6. The method according to claim 1, characterized in that In the evaluation parameter calculation step, the distance of the connecting zone along the fracture zone trend is the length, and the distance perpendicular to the fracture zone trend of the connecting zone is the width. The widths and lengths of different connecting zones are respectively determined, and the area of the connecting zone and the quantitative evaluation parameter of the connecting zone openness are calculated according to the length and width, and then the comprehensive evaluation parameter is determined based on the two; 7. The method according to claim 1, characterized in that, The comprehensive evaluation parameter of the connecting zone is calculated according to the following formula: Mi = Si * Ki, i = 1, 2,..., m In the formula, Mi represents the comprehensive evaluation parameter of the i-th connecting zone, Si represents the area of the i-th connecting zone, Ki represents the quantitative evaluation parameter of the openness of the i-th connecting zone, and m represents the number of connecting zones participating in the calculation; 8. The method according to claim 1, wherein Sweet spot evaluation step: performing the first-level evaluation and ranking on the relevant sweet spots of the fault according to the fault type; for the relevant sweet spots containing multiple connecting zones within each type, performing the second-level evaluation and ranking in descending order of the comprehensive evaluation parameter; 9. A storage medium, characterized in that, The program code for implementing the method described in any one of claims 1 to 8 is stored on the storage medium; 10. A system for evaluating sweet spots of tight reservoirs based on fault segmentation characteristics, characterized in that The system executes the method described in any one of claims 1 to 8.

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