Quantitative evaluation method for three-dimensional shale smear effect of listric composite faults

Abstract

The present application relates to a kind of quantitative evaluation method of tendency composite fault mudstone daub effect, which can accurately calculate and determine the sealing capacity of different fault dip tendency, stratigraphic dip tendency lower fault, realize the prediction and evaluation of oil and gas migration direction.This method is used in the strike-slip fault zone of Zhunzhong area and western depression area in Junggar Basin, the scale thrust fault of the middle section of the southern margin of Junggar Basin and the normal fault oil and gas fine exploration research in Xianhe area of Jiyang depression in Bohai Bay Basin, successfully predicted multiple fault-controlled oil and gas enrichment favorable zones, increased the drilling success rate by 30%, fully proved from the practice level that the technology is suitable for the fault sealing evaluation in China east and west, plays an important role in the prediction of fault-controlled oil and gas reservoir and fault migration path.

Description

Technical Field

[0001] This invention relates to the field of oil and gas exploration technology, and more specifically, to a quantitative evaluation method for the effect of three-dimensional mudstone smearing on composite faults. Background Technology

[0002] Faults are a crucial structural type in oil and gas basins. Their formation and evolution not only control the basin's structure and evolution but also the formation and development of traps, directly or indirectly influencing the development characteristics of source rocks and reservoirs, and controlling the migration, accumulation, and distribution of oil and gas reservoirs. The control of faults on oil and gas accumulation is mainly manifested in their control over the migration, accumulation, and distribution of oil and gas. The opening and closing properties of faults play a significant role in the migration, accumulation, destruction, and reaccumulation of oil and gas reservoirs. Dip-composite faults emphasize the combined relationship between the fault and the stratigraphic dip, and can be divided into: parallel faults and reverse faults. Parallel faults are those whose dip direction is the same as or similar to that of the stratigraphic dip; reverse faults are those whose dip direction is opposite to that of the stratigraphic dip. Dip-composite faults are abundant in oil and gas basins in both eastern and western my country and have a significant controlling effect on oil and gas accumulation, but their sealing evaluation methods require further research.

[0003] Fault sealing has long been an important research topic both domestically and internationally. In the early stages of fault sealing research, the existence of a sealing layer within the fault zone structure was primarily demonstrated through field profiles. Subsequent studies summarized five fault sealing mechanisms based on lithological differences, formation methods, and formation conditions: 1) mudstone smear sealing; 2) butt joint sealing; 3) fracturing sealing; 4) diagenetic sealing; and 5) layered / platy silicate sealing. Current research on fault sealing primarily focuses on quantitatively studying the correlation between various fault properties or geostress and the formation of sealing layers within the fault zone. Quantifying fault sealing facilitates comparative analysis.

[0004] Because faults have been found to have a dual nature in actual oil exploration research—serving as both channels for oil and gas migration and controlling oil and gas reservoirs by blocking their transport—determining the role of faults in the formation of oil and gas reservoirs is crucial for accurate drilling and oil finding, and for reducing development costs. Fault sealing is often the most direct evidence for this assessment. Therefore, numerous research methods for fault sealing have emerged in recent years. For example, Allan proposed a sandstone-mudstone junction model for two fault blocks in 1989. This model uses known logging lithological information to construct different lithological junction combinations under different fault displacements, selecting the optimal junction combination and predicting strong sealing areas within the three-dimensional fault space. Yielding proposed the SGR (Shale Gouge Ratio) parameter in 1997, quantifying the percentage content of mudstone sealing layers within the fault zone, thus moving fault sealing from qualitative analysis to quantitative evaluation. Lü Yanfang, Fu Guang, and others proposed the cross-sectional normal pressure method, which uses the pressure exerted on the fault surface to quantitatively evaluate whether a fault is open or closed. Based on the vertical normal stress of the fault section, Tian Hui further considered the influence of mudstone and sandstone content on the degree of internal fracturing within the fault zone. He used the fault sealing index method to evaluate whether the fault zone had formed cohesive fracturing, meeting the conditions for sealing oil and gas. Other methods utilize reservoir geochemistry to analyze the geochemical parameters of oil-bearing layers near the fault sides to determine whether the fault has been connected from the reservoir formation period to the present, and whether the fault can seal the lateral migration of oil and gas. Some methods also use sonic transit time to determine the magnitude of the displacement pressure of the target strata, thereby analyzing and determining the fault's vertical sealing capacity. Of course, the above-mentioned fault sealing evaluation methods currently have certain limitations, and there are instances where theoretically evaluated favorable zones do not correspond to actual exploration.

[0005] With the deepening of geological exploration and research, Sylvester proposed the concept of strike-slip faults in 1988: a type of fault with a nearly vertical cross-section where rock blocks on one side move horizontally relative to those on the other side, which is significantly different from normal and reverse faults. Yielding's 1997 proposal of the SGR (Shale Gouge Ratio) mudstone smearing coefficient is mainly applicable to the slip model of faults on the vertical cross-section of normal and reverse faults. However, strike-slip faults can be tensional-torsional or compressional-torsional, with both vertical slip and horizontal displacement. The two-dimensional calculation model of the SGR mudstone smearing coefficient is clearly unsuitable for the three-dimensional spatial displacement of strike-slip faults. Therefore, Wu Kongyou et al. (2010) proposed the SSGR (Shale Gouge Ratio) for quantitative evaluation of the mudstone smearing effect of tensional-torsional faults. This method requires observing the striations on the fractured borehole core to obtain the three-dimensional slip direction of the strike-slip fault. However, in practice, it is impossible to guarantee that all fractures will be drilled through to a well, and near-vertical strike-slip fractures are generally impossible to drill through to extract core samples from the fracture zone. Therefore, it is impossible to accurately conduct a systematic evaluation of the fracture sealing of all fractures in the study area, and this method has significant problems with insufficient applicability.

[0006] In reality, deep underground faults are often not purely normal or reverse faults, involving only vertical slippage, but also horizontal displacement. They could also be strike-slip faults with the main displacement occurring horizontally. Therefore, previous assessments of fault sealing, lacking reasonable methods, have resulted in discrepancies between the assessment results and actual exploration findings.

[0007] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0008] This invention provides a quantitative evaluation method for the three-dimensional mudstone smearing effect of inclined composite faults, in order to solve the technical problem of insufficient applicability of existing technologies. It can accurately calculate and determine the sealing capacity of faults under different fault dip angles and strata dip angles, and realize the prediction and evaluation of oil and gas migration direction.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A quantitative evaluation method for the effect of three-dimensional mudstone smearing on composite faults, the method comprising the following steps:

[0011] Step 1: Correct the seismic profile using well logging curves and lithological data to determine the horizon and fault location of the dip-bending composite fault, and to determine whether the dip-bending composite fault is a reverse fault or a forward fault; measure the fault strike and dip on the structural plan; select a marker bedding layer as the equivalent layer on the profile, measure the vertical distance between the fault points of the marker bedding layer, perform time-depth conversion, and obtain the vertical apparent fault displacement H. 视 And the fracture dip angle δ;

[0012] Step 2: Project the lithological data onto the seismic profile. Based on the phase axis of the seismic profile, predict the lithology of the two sides of the fault and draw the lithological profile to obtain lithological data of different layers on the two sides of the fault. Measure the vertical thickness h of each mudstone layer in the hanging wall and footwall along the fault surface. i ;

[0013] Step 3: First, construct a time-depth conversion model for the study area using the drilling record time-depth relationship; second, interpret the typical strata in the required study strata using two-dimensional grid lines; then, through the time-depth conversion model, convert the time domain strata into the depth domain and assign them contour lines to obtain a stratum depth contour map. The stratum dip can be easily obtained using the stratum depth contour lines. Then, calculate the ratio of the elevation difference between adjacent contour lines to the plane distance between adjacent contour lines, and combine the arctangent function of the triangle to obtain the true dip angle α of the strata.

[0014] Step 4: Based on the azimuth angle between the strata dip and the fault strike, obtain the acute angle β between the strata dip and the fault strike;

[0015] Step 5: Based on the type of the dip-oriented composite fault determined in Step 1, determine the vertical thickness h. i Vertical sight distance H 视 Substituting the fault dip angle δ, the true dip angle α, and the acute angle β between the stratum dip and the fault strike into the corresponding formula below, the three-dimensional mudstone smearing coefficient TSGR is calculated:

[0016]

[0017] The quantitative evaluation method for the three-dimensional mudstone smearing effect of the dip-composite faults described above determines the type of dip-composite faults as follows: if the dip direction of the fault is consistent with the dip direction of the strata, it is a dip-fault; otherwise, it is a reverse fault.

[0018] The technical solution of this invention has the following technical advantages over the prior art: ① This method considers the influence of multiple fault-related geometric properties under composite trends, such as fault dip angle, fault dip direction, true dip angle of the formation, and formation dip direction, on the evaluation value of fault mudstone smearing, making the evaluation results more accurate and the effect of predicting whether oil and gas will accumulate more significantly; ② This method considers the characteristics of three-dimensional spatial movement of faults and establishes four models: forward tension-torsion model, forward compression-torsion model, reverse tension-torsion model, and reverse compression-torsion model (see...). Figure 8 This method encompasses most fault-stratum contact situations deep underground, possessing strong universality; ③ This method is derived through geometric algebra, without subjective formula creation, theoretically proving the feasibility of the three-dimensional mudstone smearing effect evaluation method for inclined composite faults; ④ This method has been used in the fine exploration study of strike-slip fault zones in the central and western Junggar Basin, large-scale thrust faults in the central section of the southern margin of the Junggar Basin, and normal fault oil and gas in the Xianhe area of ​​the Jiyang Depression in the Bohai Bay Basin. It has successfully predicted multiple fault-controlled oil and gas enrichment zones, increasing drilling success rate by 30%. From a practical perspective, it fully demonstrates that this technology is applicable to the evaluation of fault sealing in eastern and western China, playing an important role in predicting fault-controlled oil and gas reservoirs and fault migration pathways. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a diagram showing the relationship between the actual fault displacement and the apparent fault displacement in the vertical direction.

[0021] Figure 2 This is a contour map of the depth domain of the stratigraphic layers.

[0022] Figure 3 This is a schematic diagram showing the strike and dip angle of stratigraphic faults.

[0023] Figure 4 This is a schematic diagram of the apparent dip angle of a stratigraphic fault surface.

[0024] Figure 5 This is a diagram of the actual slip pattern during fracture.

[0025] Figure 6 This is a schematic diagram showing the direction and length of fault activity in the mudstone layer.

[0026] Figure 7 This is a planar stratigraphic diagram.

[0027] Figure 8The diagram shows the modalities of transverse compression-torsion and tension-torsion faults and reverse compression-torsion and tension-torsion faults.

[0028] Figure 9 This is a schematic diagram illustrating the principle of three-dimensional mudstone smearing along and in the opposite direction of faults. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0031] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0032] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0033] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0034] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0035] This invention mainly utilizes the mudstone smearing sealing mechanism: due to the strong plastic flow capacity of mudstone layers in deep underground, during fracture activity, influenced by the frictional traction of the fault surface or fracture zone, the mudstone layers on both sides of the fracture will smear onto the fault surface or inject into the fracture zone, forming a mudstone sealing layer. This increases the breakthrough pressure required for oil and gas to pass through the fracture zone, thus blocking the lateral migration of oil and gas. The mud content in the fracture zone is calculated using the thickness of the mudstone layers on both sides of the fracture. Drawing on the idea of ​​three-dimensional mudstone smearing proposed by Wu Kongyou et al. (2010), a general strike-slip fracture model is first established (i.e., generalized fault dip, fault dip angle, fault slip direction, stratum dip, and fault dip angle), making the model more complex and closer to the actual underground situation. Secondly, using geometric algebra, the geometric properties of fractures and strata—which are not on the same plane in three-dimensional space—such as fracture dip and dip direction, fracture slip direction, and stratum dip and dip, are transformed into a single two-dimensional plane—the fracture surface (obtaining the mudstone length and fracture slip distance in the fracture slip direction on the fracture surface). Finally, the dip-composite mudstone smearing parameters are calculated using the two-dimensional fracture mudstone smearing coefficient method proposed by Yielding in 1997. This method is an innovative improvement on the old method, achieving the organic combination of complex three-dimensional spatial geometric properties and converting them into two parameters on a two-dimensional plane (i.e., mudstone length in the fracture slip direction and fracture slip distance). It not only considers multiple factors, making the method highly accurate in closure assessment, but also eliminates the influence of the fracture slip direction (i.e., core striations through the fracture) on the two-dimensional plane parameters during the transformation of three-dimensional geometric properties into a two-dimensional plane. This makes the required geometric properties easy to obtain accurately.

[0036] A quantitative evaluation method for the effect of three-dimensional mudstone smearing on composite faults:

[0037] Step 1: The data used includes high-precision 3D seismic data volumes, 2D seismic profiles, well logging curves, lithology, and planar stratigraphic maps. In Petrel software, the seismic profiles are corrected using well logging curves and lithological data to determine the stratigraphic horizons and fault locations, and to identify the type of dip-dipping composite faults, whether they are reverse or parallel faults (see...). Figure 8 If the dip direction of the fault is the same as the dip direction of the strata, it is a perpendicular fault; otherwise, it is a reverse fault. The strike of the fault is measured on a structural plan (see...). Figure 7 On the cross-section, a marker layer is selected as the equivalent layer. The distance between the breakpoints of the marker layer is measured, and time-depth conversion is performed to obtain the vertical apparent displacement H. 视 and fracture dip angle δ (see Figure 9 ).

[0038] Step 2: After detailed interpretation of the seismic profile, project the logging lithology data onto the seismic profile in CorelDRAW software. Based on the phase axis of the seismic profile, predict the lithology of the two sides of the fault and draw the lithology profile to obtain lithology data of different layers on the two sides of the fault. Measure the vertical thickness h of each mudstone layer in the hanging wall and footwall along the fault surface. i (See Figure 9 ).

[0039] Step 3: In Petrel software, firstly, a time-depth conversion model for the study area is constructed using the drilling record's time-depth relationship. Secondly, a two-dimensional grid line interpretation is performed on typical strata within the required study area. Then, using the time-depth conversion model, the time-domain strata are transformed into the depth domain and assigned contour lines, resulting in a stratum depth contour map (see...). Figure 2 The basic method for calculating the dip angle and dip direction of strata using stratum elevation lines is as follows: the downward direction of the vertical stratum contour lines is the dip direction of the strata. The true dip angle α is obtained by combining the elevation difference between adjacent contour lines and the plane distance between them with the arcsine function of a triangle.

[0040] Step 4: Based on the relationship between the dip direction of the strata and the strike direction of the fault, the acute angle β between the dip direction of the strata and the strike direction of the fault can be obtained.

[0041] Step 5: Based on the type of composite fault determined in Step 1, substitute the aforementioned vertical thickness of the strata (hi), apparent vertical displacement (Happarent), fault dip angle (δ), true dip angle (α), and acute angle β between the strata dip and fault strike into the corresponding formula below to calculate the three-dimensional mudstone smearing coefficient:

[0042]

[0043] h i :i: thickness of rock stratum unit (m); δ: fracture dip angle; H 视 : Vertical apparent fault displacement (m); α: True dip angle of the strata (°); β: Acute angle between the dip of the strata and the strike of the fault (°).

[0044] Figure 9 In the middle, H 真 True vertical displacement of the fracture (m);

[0045] θ: The lateral angle (°) of the fracture sliding direction;

[0046] γ': Apparent dip angle (°) on the stratigraphic section;

[0047] Blue infill layer: mudstone layer; yellow infill layer: sandstone layer.

[0048] The TSGR coefficient is an accurate and effective measure for assessing the sealing of dip-bound composite fractures in clastic sequence strata, playing an important role in the prediction of oil reservoir reserves. All necessary measurements can be obtained from seismic and well logging data, eliminating the need for experimental measurements. This ensures accuracy while also being economical and convenient.

[0049] Feasibility explanation and detailed derivation process of the steps:

[0050] (1) Based on the literature review and the summary of previous understanding of the regional geological background of the study area, and based on the seismic data, the combination of structural patterns of the faults in the profile and plane was clarified, and the tension-torsion composite faults were identified.

[0051] (2) Based on the detailed interpretation of the seismic profile and combined with logging and survey data, the location of the fault development, the corresponding layers on both sides of the fault, the location of the fault points, and the fault strike information are determined. The distance between the fault points is measured on the seismic profile, and the vertical apparent fault displacement H is obtained through time-depth conversion. 视 and fracture dip angle δ (see Figure 1 The fracture strike was determined by planar visualization using geological interpretation software such as Petrel.

[0052] Figure 1 Chinese: H 视 : Apparent fault displacement on the vertical profile (the sum of the actual fault displacement and the distance caused by misjudgment due to stratigraphic dip);

[0053] H 真 The actual fracture displacement on the vertical cross-section;

[0054] δ: fracture dip angle;

[0055] θ: The lateral angle of the fracture sliding direction;

[0056] γ': Apparent dip angle of strata on the cross section.

[0057] (3) Project the logging lithology data onto the seismic profile to obtain lithology data of different layers on the two sides of the fault.

[0058] (4) Using geological interpretation software such as Petrel, the stratigraphic identification of the required study interval is depicted as a two-dimensional grid. Based on the time-depth relationship of the well logging records in the study area, the two-dimensional time-domain grid is transformed into the depth domain, and then a bedding contour map is constructed (see...). Figure 2 The precise dip and true dip angle of the strata can be obtained from the contour lines in the figure.

[0059] (5) From steps 2 and 4, the dip direction and true dip angle of the strata and the strike of the fault are obtained. The apparent dip angles on the strike and dip directions of the fault can be obtained using the formula for apparent dip angle of the strata (see...). Figure 3 ):

[0060] tanγ=tanαcosβ (1)

[0061] tanχ=tanαsinβ (2)

[0062] Combining equations (1) and (2), we get:

[0063] tanχ=tanγtanβ (3)

[0064]

[0065] Figure 3 In the middle: h: vertical thickness of the strata;

[0066] α: True dip angle of the strata;

[0067] β: The acute angle between the dip direction of the strata and the strike direction of the fault;

[0068] γ: Apparent dip angle in the direction of the strike of the stratigraphic fault;

[0069] χ: Apparent dip angle along the direction of the stratigraphic fault;

[0070] δ: Fault dip angle;

[0071] θ: Lateral angle of the fracture sliding direction.

[0072] (6) Based on the fracture dip angle and the apparent dip angle of the stratigraphic fracture dip direction obtained in steps 2 and 5, the apparent dip angle γ' of the stratigraphic fracture on the fault surface can be obtained through simple geometric principles (see...). Figure 1 , Figure 4 It was identified as a dip fault.

[0073] Figure 6 In the middle: h: vertical thickness of the strata;

[0074] δ: Fault dip angle;

[0075] χ: Dip angle of the strata along the direction of the fault dip;

[0076] θ: The lateral angle of the fracture sliding direction;

[0077] γ': Apparent dip angle on a stratigraphic section;

[0078] γ: Apparent dip angle of the strata along the fault strike direction.

[0079] First, the vertical thickness of the mudstone layer is converted into the thickness of the mudstone layer on the cross section using geometric algebraic methods. The specific implementation steps are as follows:

[0080] L IJ =L IL +L LJ (5)

[0081]

[0082] Let L LM If x, then L KM =L KL +x

[0083]

[0084] L KM =L KL +x (8)

[0085] L KM tanχ=xtanδ (9)

[0086] Combining (3), (7), (8), and (9), we get:

[0087]

[0088]

[0089] Combining (5), (6), (10), and (11), we get:

[0090]

[0091] This allows us to obtain the thickness of the strata on the fault surface, and then calculate the apparent dip angle of the strata on the fault surface.

[0092] Based on the fundamental property of parallelograms: opposite sides are parallel and equal, we can obtain:

[0093]

[0094] Because right triangle JIN (see Figure 4 According to the geometric laws of right triangles, we get:

[0095] L IJ =L IN tanγ' (14)

[0096] Combining (12), (13), and (14), we get:

[0097]

[0098] This yields the apparent dip angle γ' of the stratigraphic section.

[0099] (7) Due to the actual underground geological conditions, strata often have a certain dip angle. Therefore, the location of the fault points shown on the seismic profile often has a deviation caused by the dip of the strata. What is observed is the vertical apparent fault displacement (see Figure 1 , Figure 5Based on the apparent dip angle of the stratigraphic section obtained from the above steps, the actual fracture slip distance L can be obtained. 滑 The specific steps are as follows:

[0100] Figure 5 Chinese: H 真 : The actual vertical displacement of the fracture;

[0101] H 视 The vertical displacement of the fracture is considered.

[0102] δ: Fault dip angle;

[0103] θ: The lateral angle of the fracture sliding direction;

[0104] γ': Apparent dip angle on a stratigraphic cross section.

[0105]

[0106] H 视 =H 垂 +L PQ tanγsinδ (17)

[0107] H 垂 =L PQ tanθsinδ (18)

[0108] Combining (16), (17), and (18), we can obtain:

[0109]

[0110] (8) The horizontal length of the mudstone layer in the direction of the fault strike can be obtained by using the apparent dip angle in the direction of the fault strike and the vertical thickness of the mudstone layer:

[0111]

[0112] (9) Based on the apparent dip angle of the cross section and the horizontal length of the mudstone layer along the fracture strike direction obtained in steps 6 and 8, the length L of the mudstone layer along the fracture activity direction can be obtained through simple geometric algebra principles. TV (See Figure 6 The specific steps are as follows:

[0113] Figure 6 In the middle: θ: the lateral angle of the fracture sliding direction;

[0114] γ': Apparent tilt angle on the cross-section.

[0115] Based on the property of parallelograms: opposite sides are parallel and equal, we can obtain:

[0116]

[0117] Let LTU If y, then L US =L TS -y

[0118]

[0119] L US tanγ'=ytanθ (22)

[0120] By combining (21) and (22), we can obtain:

[0121]

[0122] Therefore L 泥1 The solution can then be obtained as follows:

[0123]

[0124] (10) Based on the actual slip distance of the fracture obtained in steps 7 and 9 and the length along the slip direction of the fracture, the three-dimensional mudstone smearing coefficient TSGR (Three-dimensional Shale Gouge Ratio) of the tension-torsional fracture can be calculated. The specific calculation steps are as follows:

[0125]

[0126] By combining (2), (15), (19), (24), and (25), we can obtain:

[0127]

[0128] h i : Vertical thickness of mudstone; δ: Fault dip angle; H 视 : Vertical apparent fault displacement; α: True dip angle of the strata; β: Acute angle between the fault strike and the strata dip.

[0129] The above process ultimately yields the simplest expression for TSGR. This formula is applicable not only to parallel extensional faults but also, through geometric algebraic methods, to parallel compressive faults. Substituting the required physical quantities from this expression into the calculation yields the accurate three-dimensional parallel fault mudstone smear coefficient.

[0130] Using the above method, a reverse fracture model is established. Figure 9 By performing geometric and algebraic derivation, the three-dimensional mudstone smearing coefficient (TSGR) of the reverse fault can also be obtained:

[0131]

[0132] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A quantitative evaluation method for the effect of three-dimensional mudstone smearing on composite faults, characterized in that, The method includes the following steps: Step 1: Correct the seismic profile using well logging curves and lithological data to determine the horizon and fault location of the dip-bending composite fault, and to determine whether the dip-bending composite fault is a reverse fault or a forward fault; measure the fault strike and dip on the structural plan; select a marker bedding layer as the equivalent layer on the profile, measure the vertical distance between the fault points of the marker bedding layer, perform time-depth conversion, and obtain the vertical apparent fault displacement H. 视 And the fracture dip angle δ; Step 2: Project the lithological data onto the seismic profile. Based on the phase axis of the seismic profile, predict the lithology of the two sides of the fault and draw the lithological profile to obtain lithological data of different layers on the two sides of the fault. Measure the vertical thickness h of each mudstone layer in the hanging wall and footwall along the fault surface. i ; Step 3: First, construct a time-depth conversion model for the study area using the drilling record time-depth relationship; second, interpret the typical strata in the required study strata using two-dimensional grid lines; then, through the time-depth conversion model, convert the time domain strata into the depth domain and assign them contour lines to obtain a stratum depth contour map. The stratum dip can be easily obtained using the stratum depth contour lines. Then, calculate the ratio of the elevation difference between adjacent contour lines to the plane distance between adjacent contour lines, and combine the arctangent function of the triangle to obtain the true dip angle α of the strata. Step 4: Based on the azimuth angle between the strata dip and the fault strike, obtain the acute angle β between the strata dip and the fault strike; Step 5: Based on the type of the dip-oriented composite fault determined in Step 1, determine the vertical thickness h. i Vertical sight distance H 视 Substituting the fault dip angle δ, the true dip angle α, and the acute angle β between the stratum dip and the fault strike into the corresponding formula below, the three-dimensional mudstone smearing coefficient TSGR is calculated:

2. The quantitative evaluation method for the three-dimensional mudstone smearing effect of inclined composite faults according to claim 1, characterized in that, The method for determining the type of a dip-bearing composite fault is as follows: if the dip direction of the fault is the same as the dip direction of the strata, it is a dip-bearing fault; otherwise, it is a reverse fault.

Images