An elastic parameter calculation method suitable for offshore complex lithologic formation of Paleogene system

Abstract

The application relates to a kind of elastic parameter calculation methods suitable for offshore complex lithology formation of Paleogene system, comprising the following steps: wellbore collapse single well environment correction and logging curve pretreatment of multi-well consistency are carried out to abnormal elastic parameter curve, to obtain pretreated logging curve; rock volume model is solved, to obtain lithology, physical property information such as formation mineral component, porosity; the volume modulus of rock matrix of multi-mineral mixture and the shear modulus of rock matrix are calculated using Hill average method; the equivalent volume modulus and shear modulus of multi-mineral mixture matrix containing unconnected pore are calculated through model; the equivalent elastic modulus of rock skeleton containing complex pore structure is calculated through SCA self-consistent model; the equivalent elastic modulus calculation model of saturated rock is established, and the equivalent elastic modulus of Paleogene system complex lithology saturated rock is calculated.The application improves the calculation precision of equivalent elastic parameter of Paleogene system complex lithology saturated rock.

Description

Technical Field

[0001] This invention relates to the field of reservoir geophysical exploration technology, specifically to a method for calculating elastic parameters applicable to complex lithological strata of Paleogene marine formations. Background Technology

[0002] As my country's offshore oil and gas exploration deepens, the focus of exploration is gradually shifting from shallow conventional oil and gas reservoirs to medium-deep complex oil and gas reservoirs. Recent exploration practices have shown that medium-deep reservoirs are important strata for discovering large and medium-sized oil and gas fields and have become one of the important growth points for future reserves.

[0003] However, offshore oil and gas exploration is characterized by high risk, high investment, and high technology, especially in the mid-to-deep Paleogene strata, where there are often problems such as limited drilling and insufficient prior knowledge. Seismic rock physics is a primary technical means of constructing quantitative relationships between reservoir physical conditions and rock elastic properties. Based on seismic rock physics modeling technology, theoretical basis and data support can be provided for pre-stack reservoir prediction and fluid identification. Looking at the existing Paleogene well drilling information, insufficient offshore logging curves, particularly the lack of shear wave data, and poor measurement quality are among the key issues restricting the prediction of mid-to-deep Paleogene reservoirs.

[0004] The Paleogene strata at sea are mineralized diverse, primarily composed of quartz and clay, but also including unique lithologies such as limestone, dolomite, calcareous mudstone, argillaceous dolomite, and andesitic sandstone and conglomerate. Thick mudstone layers are heavy with calcareous material and have complex internal structures. Current research on petrophysical modeling of sandstone and mudstone reservoirs mainly involves constructing equivalent elastic medium models based on the Xu-White model. However, for complex Paleogene strata, the traditional Xu-White model assumes that the rock mineral composition consists only of quartz and clay, while Paleogene rocks have a complex mineral composition, containing not only quartz and clay but also calcareous, dolomitic, and andesitic minerals. Secondly, the traditional Xu-White model assumes that the pore shape is equivalent and invariant, while Paleogene pore and fracture structures are complex and change with depth. Therefore, calculating the elastic parameters of complex Paleogene reservoirs based on conventional sandstone and mudstone petrophysical models introduces errors.

[0005] Therefore, there is an urgent need for a method to calculate elastic parameters applicable to complex lithological strata of Paleogene marine formations. Summary of the Invention

[0006] The purpose of this invention is to provide a method for calculating elastic parameters of complex Paleogene lithological strata at sea, in order to solve the problem of inaccurate elastic parameters of complex Paleogene reservoirs in the aforementioned background art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for calculating elastic parameters applicable to complex Paleogene lithological strata at sea, comprising the following steps:

[0009] For abnormal elastic parameter curves, well logging curve preprocessing is performed to correct the single-well environment of wellbore collapse and to ensure consistency across multiple wells, resulting in preprocessed well logging curves.

[0010] Based on geological logging data and core analysis of formation mineral types, a rock volume model is established using preprocessed logging curves as constraints. The rock volume model is then solved to obtain formation mineral composition and volume content.

[0011] Based on the formation mineral composition and volume content obtained from the rock volume model, the bulk modulus and shear modulus of the rock matrix of the multi-mineral mixture were calculated using the Hill averaging method.

[0012] Substituting the bulk modulus and shear modulus of the obtained multi-mineral mixture rock matrix into Kuster- The model was used to calculate the equivalent bulk modulus and shear modulus of a multi-mineral mixture matrix containing unconnected pores.

[0013] A fast simulated annealing optimization algorithm is introduced to invert the pore structure parameters of sandstone and special lithology. With the measured P-wave velocity as a constraint, the objective function is obtained. Based on the optimization of the objective function, the formation pore structure parameters are quantitatively characterized, thereby obtaining the input parameters of the optimized SCA self-compatible model. The equivalent elastic modulus of the rock skeleton with complex pore structure is calculated through the SCA self-compatible model.

[0014] A model for calculating the equivalent elastic modulus of saturated rocks was established using the equivalent elastic modulus of a rock skeleton with complex pore structures. The equivalent elastic modulus of saturated rocks with complex Paleogene lithology was calculated to complete the calculation of elastic parameters of complex Paleogene lithological strata at sea.

[0015] The aforementioned method for calculating elastic parameters applicable to complex Paleogene lithological formations at sea, preferably, includes the following steps in the step "well logging curve preprocessing for wellbore collapse environmental correction in response to elastic parameter curve anomalies":

[0016] Select curves that are less affected by the wellbore environment and establish a linear relationship between abnormal and normal curves;

[0017] The linear relationship between the abnormal curve and the normal curve is used to correct the wellbore collapse of the abnormal segments of the sonic transit time curve and the density curve, so that the sonic transit time curve and the density curve return to the vicinity of the baseline.

[0018] The linear relationship between the abnormal curve and the normal curve is as follows:

[0019]

[0020]

[0021] in,

[0022] GR is the gamma curve;

[0023] RT is the deep resistivity;

[0024] CNL stands for neutron porosity;

[0025] DT edit The acoustic transit time after wellbore collapse correction;

[0026] DEN edit The acoustic density after wellbore collapse correction;

[0027] m i n i p i q i C i are the fitting coefficients, where i = 1, 2.

[0028] The aforementioned method for calculating elastic parameters applicable to complex Paleogene lithological formations at sea, preferably, includes the following steps in the step of "preprocessing logging curves for multi-well consistency in response to elastic parameter curve anomalies":

[0029] Identify marker layers and standard wells;

[0030] Based on the criterion of consistent histogram probability distribution shape of the marker layer, the value range and probability type of other wells are adjusted according to the standard well to make the interval and shape of the probability distribution of each well consistent and to remove systematic errors.

[0031] The aforementioned method for calculating elastic parameters in complex Paleogene lithological strata at sea, preferably, includes a rock volume model specifically comprising:

[0032] ρ=ρ qua V qua +ρ clay V clay +ρ spec V spec .+..+ρ f V f

[0033] GR = GR qua V qua +GR clay V clay +.GR spec V spec +..+GR f Vf ...

[0035] 1 = V1 + V2 + V3 + ... + V m (3)

[0036] in,

[0037] V i Let i represent the volume fractions of different mineral components, i = 1, 2, 3...m;

[0038] qua is a quartz mineral;

[0039] clay is a clay mineral;

[0040] spec refers to special lithological minerals;

[0041] f represents the pore fluid;

[0042] ρ represents density;

[0043] V represents volume.

[0044] The method for calculating elastic parameters applicable to complex Paleogene lithological strata at sea, preferably, includes the following steps in the step of "calculating the bulk modulus and shear modulus of the rock matrix of a multi-mineral mixture using the Hill averaging method based on the mineral composition and volume content obtained from the rock volume model":

[0045] Based on geological logging data and lithological and physical property information of complex Paleogene lithological strata, the stratigraphic mineral types are determined, and the volume fraction of multiple minerals in the Paleogene strata is determined by rock volume model.

[0046] When the mineral composition and volume content are determined, the elastic modulus of the matrix is ​​distributed between the upper limit of Voigt and the lower limit of Reuss. The volume modulus and shear modulus of the multi-mineral mixture are calculated using the Hill averaging method.

[0047] The Hill averaging method is calculated using formulas (4), (5), and (6);

[0048]

[0049]

[0050]

[0051] in,

[0052] M V Voigt represents the upper limit of the effective elastic modulus of the rock mixture;

[0053] MR The Reuss lower limit represents the effective elastic modulus of a rock mixture;

[0054] f i This represents the volume fraction of the i-th medium (the i-th component of the rock);

[0055] M i Represents the elastic modulus of the i-th medium;

[0056] M VRH Hill average represents elastic parameters such as bulk modulus and shear modulus.

[0057] The aforementioned method for calculating elastic parameters applicable to complex Paleogene lithological strata at sea, preferably, involves the Kuster- The model is as follows:

[0058]

[0059]

[0060]

[0061] in,

[0062] Indicates the effective bulk modulus;

[0063] Indicates the effective shear modulus;

[0064] K m Indicates the bulk modulus of the rock matrix;

[0065] μ m Indicates the shear modulus of the rock matrix;

[0066] K i Indicates the bulk modulus of a porous filler;

[0067] μ i Indicates the shear modulus of the pore-filled material;

[0068] Q mi P mi It is a geometric factor related to pore shape, representing the influence of pore filling material on matrix rock;

[0069] x i This refers to the volume fraction of the interstitial material.

[0070] ζ m The factor characterizing the elastic properties of the matrix is ​​expressed as (9).

[0071] The aforementioned method for calculating elastic parameters applicable to complex Paleogene lithological strata at sea, preferably, includes the objective function as follows:

[0072]

[0073] in,

[0074] α sand These are the pore structure parameters of sandstone;

[0075] α spec Pore ​​structure parameters for special lithologies;

[0076] For the actual measured longitudinal wave velocity;

[0077] Calculate the P-wave velocity for the model;

[0078] K is the bulk modulus of each mineral;

[0079] U represents the shear modulus of each mineral;

[0080] F represents the volume fraction of each mineral;

[0081] φ represents the rock porosity;

[0082] ρ is the density;

[0083] S w Water saturation;

[0084] f is the model for calculating the longitudinal wave velocity.

[0085] The aforementioned method for calculating elastic parameters applicable to complex Paleogene lithological strata at sea, preferably, includes the following SCA self-compatible model:

[0086]

[0087]

[0088] in,

[0089] K i Let be the bulk modulus of the i-th type of pore filler;

[0090] μ i Let i be the shear modulus of the i-th type of pore filler;

[0091] The equivalent bulk modulus of rocks containing pore-filling materials;

[0092] The equivalent shear modulus of rock containing pore-filled materials;

[0093] fi This represents the volume fraction of the interstitial material.

[0094] P *i Q *i The shape expression of the contained object is given by formulas (12) and (13):

[0095]

[0096]

[0097] Among them, tensor T ijij T iijj It is related to the elastic modulus and porosity of the background medium.

[0098] The method for calculating elastic parameters applicable to complex Paleogene lithological strata at sea, preferably, includes a specific model for calculating the equivalent elastic modulus of saturated rocks:

[0099]

[0100]

[0101]

[0102] in,

[0103] K i Let i be the bulk modulus of the rock when it is saturated with fluid i.

[0104] μ i Let i be the shear modulus of the rock when it is saturated with fluid i.

[0105] M i Let i be the longitudinal wave modulus when the rock is saturated with fluid i.

[0106] M is the equivalent longitudinal wave modulus of the rock;

[0107] μ is the equivalent shear modulus of the rock;

[0108] μ d The shear modulus of the rock skeleton;

[0109] K d The bulk modulus of the rock skeleton;

[0110] K m Indicates the bulk modulus of the rock matrix;

[0111] K fl-i Let be the bulk modulus of fluid i;

[0112] S o Oil saturation;

[0113] S g Gas saturation;

[0114] S w Water saturation;

[0115] M o The longitudinal wave modulus when the rock is saturated with oil;

[0116] M g The longitudinal wave modulus of a rock saturated with gas;

[0117] M w The longitudinal wave modulus of a rock saturated with water;

[0118] φ represents the porosity of the rock.

[0119] Secondly, the present invention provides a system for calculating elastic parameters of complex Paleogene lithological strata at sea, comprising:

[0120] The first processing unit is used to perform wellbore collapse single-well environmental correction and multi-well consistency logging curve preprocessing for elastic parameter curve anomalies, and to obtain the preprocessed logging curve.

[0121] The second processing unit is used to establish a rock volume model based on geological logging data and core analysis of formation mineral types, using pre-processed logging curves as constraints, solving the rock volume model, and obtaining formation mineral composition and volume content.

[0122] The third processing unit is used to calculate the bulk modulus and shear modulus of the rock matrix of the multi-mineral mixture based on the formation mineral composition and volume content obtained from the rock volume model, using the Hill averaging method.

[0123] The fourth processing unit is used to substitute the bulk modulus and shear modulus of the obtained multi-mineral mixture rock matrix into Kuster- The model was used to calculate the equivalent bulk modulus and shear modulus of a multi-mineral mixture matrix containing unconnected pores.

[0124] The fifth processing unit is used to introduce a fast simulated annealing optimization algorithm to invert sandstone pore and special lithology pore structure parameters. With the measured P-wave velocity as a constraint, the objective function is obtained. Based on the objective function, the formation pore structure parameters are quantitatively characterized by optimization, thereby obtaining the input parameters of the optimized SCA self-compatible model. The equivalent elastic modulus of the rock skeleton with complex pore structure is calculated through the SCA self-compatible model.

[0125] The sixth processing unit is used to establish a calculation model for the equivalent elastic modulus of saturated rocks and to calculate the equivalent elastic modulus of Paleogene complex lithology saturated rocks.

[0126] Thirdly, the present invention provides a computer storage medium storing a computer program thereon, wherein when the computer program is executed by a processor, it implements the steps of a method for calculating elastic parameters applicable to complex lithological strata of Paleogene at sea.

[0127] Fourthly, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of a method for calculating elastic parameters applicable to complex marine Paleogene lithological strata.

[0128] The present invention has the following advantages due to the adoption of the above technical solutions:

[0129] Based on the characteristics of the varied lithology and complex pore structure of Paleogene strata at sea, this invention takes into account the complex structures such as sandstone pores, special lithology pores and non-connected pores, as well as the uneven distribution of fluids. Based on the adaptive algorithm for complex pore structure, it realizes the quantitative characterization of pore structure parameters and improves the calculation accuracy of equivalent elastic parameters of Paleogene complex lithological saturated rocks. Attached Figure Description

[0130] Figure 1 This is a flowchart illustrating the process for calculating elastic parameters in complex Paleogene lithological strata at sea, as described in this embodiment.

[0131] Figure 2 The optimal stratigraphic evaluation curve for the Paleogene strata in the coastal waters of China, oriented towards the seismic surface of well A.

[0132] Figure 3 shows the distribution histograms of the calculated pore structure parameters for the two types of structures. Figure 3a This is a distribution diagram of P-wave and S-wave parameters in sandstone pores. Figure 3a This is a distribution diagram of P-wave and S-wave parameters in the pores of special lithologies;

[0133] Figure 4 shows the P-wave and S-wave velocities of well A calculated based on the conventional Xu-White model, where... Figure 4a To compare the measured and predicted P-wave velocities, Figure 4b Comparison of measured and predicted shear wave velocities;

[0134] Figure 5 shows the P-wave and S-wave velocities of well A calculated using the elastic parameter calculation method for complex Paleogene lithology in marine formations according to the present invention. Figure 5a To compare the measured and predicted P-wave velocities, Figure 5b The measured curves and predicted curves of shear wave velocity are compared. Detailed Implementation

[0135] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0136] This invention provides a method for calculating elastic parameters in complex Paleogene lithological formations at sea, comprising the following steps: preprocessing logging curves for single-well environmental correction and multi-well consistency to address anomalies in elastic parameter curves, obtaining preprocessed logging curves; establishing a rock volume model based on geological logging data and core analysis of formation mineral types, using the preprocessed logging curves as constraints, solving the rock volume model, and obtaining lithological and physical property information such as formation mineral composition and porosity; calculating the bulk modulus and shear modulus of the multi-mineral mixture matrix using the Hill averaging method based on the formation mineral composition and volume content obtained from the rock volume model; and substituting the obtained bulk modulus and shear modulus of the multi-mineral mixture matrix into the Kuster-... The model calculates the equivalent bulk modulus and shear modulus of a multi-mineral mixture matrix containing unconnected pores. A fast simulated annealing optimization algorithm is introduced to invert the pore structure parameters of sandstone and special lithologies. Using measured P-wave velocity as a constraint, an objective function is obtained. Based on the optimization of the objective function, the pore structure parameters of the formation are quantitatively characterized, thus obtaining the input parameters of the optimized SCA self-compatible model. The equivalent elastic modulus of the rock skeleton containing complex pore structures is calculated using the SCA self-compatible model. A model for calculating the equivalent elastic modulus of saturated rocks with complex Paleogene lithology is established to calculate the equivalent elastic modulus of saturated rocks.

[0137] Based on the characteristics of the varied lithology and complex pore structure of Paleogene strata at sea, this invention takes into account the complex structures such as sandstone pores, special lithology pores and non-connected pores, as well as the uneven distribution of fluids. Based on the adaptive algorithm for complex pore structure, it realizes the quantitative characterization of pore structure parameters and improves the calculation accuracy of equivalent elastic parameters of Paleogene complex lithological saturated rocks.

[0138] Example 1

[0139] like Figure 1 As shown, the method for calculating elastic parameters of complex Paleogene lithological strata at sea provided by this invention includes the following specific steps:

[0140] S1: For abnormal elastic parameter curves, perform wellbore collapse single-well environmental correction and multi-well consistency logging curve preprocessing to obtain preprocessed logging curves.

[0141] S11: The specific method for logging curve preprocessing for single-well environmental correction in response to elastic parameter curve anomalies is as follows:

[0142] S111: Based on the degree to which the caliper curve deviates from the drill bit diameter, and using the intersection analysis of the acoustic and density curves, the abnormal value regions of the acoustic transit time curve and density curve affected by the caliper collapse are located.

[0143] S112: Select curves less affected by the wellbore environment, such as GR, deep resistivity, and neutron porosity, and statistically fit the region with good wellbore diameter near the abnormal section to establish a linear relationship between the abnormal curve and the normal curve:

[0144] DT edit =m1GR+n1log(RT)+p1CNL+C1 (1)

[0145] DEN edit = m2GR + n2log(RT) + p2CNL + q2DT edit +C2 (2)

[0146] in,

[0147] GR is the gamma curve;

[0148] RT is the deep resistivity;

[0149] CNL stands for neutron porosity;

[0150] DT edit The acoustic transit time after wellbore collapse correction;

[0151] DEN edit The acoustic density after wellbore collapse correction;

[0152] m i n i p i q i C i represents the fitting coefficient.

[0153] S113: Based on the linear relationship between the abnormal curve and the normal curve, wellbore collapse correction is performed on the abnormal sections of the sonic transit time curve and density curve. Specifically, the P-wave transit time curve is corrected using GR, deep resistivity, and neutron porosity, and the density curve is corrected using the accurately corrected P-wave transit time, GR, deep resistivity, and neutron porosity curves, so that the curves return to near the baseline.

[0154] S12: The specific method for preprocessing logging curves to ensure consistency across multiple wells in response to anomalies in elastic parameter curves is as follows:

[0155] S121: Identify marker layers and standard wells;

[0156] Using the stable strata distributed throughout the region as marker layers, the probability distribution of all well marker layer segments was statistically analyzed using histograms;

[0157] Wells with good borehole environment, complete logging curves, and complete well stratification are used as standard wells;

[0158] S122: Based on the criterion of consistent probability distribution shape of marker layer histogram, the value range and probability type of other wells are adjusted according to the standard well to make the interval and shape of probability distribution of each well consistent, and to remove the influence of systematic errors such as differences in logging instruments and mud performance between different series.

[0159] S2: Based on geological logging data and core analysis of formation mineral types, a rock volume model is established using preprocessed logging curves as constraints. The rock volume model is then solved to obtain lithological and physical property information such as formation mineral composition and porosity.

[0160] Step S2 specifically includes the following steps:

[0161] S21: By using neutron-density and acoustic-density intersection, neutron, density, and acoustic values ​​of dry clay skeleton points are extracted using a triangular plot. Based on geological logging data and core analysis of formation mineral types, and using pre-processed logging curves as constraints, a rock volume model is established.

[0162] ρ=ρ qua V qua +ρ clay V clay +ρ spec V spec .+..+ρ f V f

[0163] GR = GR qua V qua +GR clay V clay +.GR spec V spec +..+GR f V f ...

[0165] 1 = V1 + V2 + V3 + ... + V m (3)

[0166] in,

[0167] V i This represents the volume fraction of different mineral components;

[0168] qua is a quartz mineral;

[0169] clay is a clay mineral;

[0170] spec refers to special lithological minerals;

[0171] f represents the pore fluid;

[0172] ρ represents density.

[0173] S22: The least squares method is used to solve the rock volume model, interpret the contents of various minerals such as quartz, clay, calcite, dolomite, and feldspar, and obtain lithological and physical property information such as stratigraphic mineral composition and porosity.

[0174] S3: Based on the formation mineral composition and volume content obtained from the rock volume model, the bulk modulus and shear modulus of the rock matrix of the multi-mineral mixture are calculated using the Hill averaging method.

[0175] Step S3 specifically includes the following steps:

[0176] S31: Based on geological logging data and lithological and physical property information of complex Paleogene lithological strata, the stratigraphic mineral types are determined. The volume fraction of multiple minerals within the Paleogene strata is determined using a rock volume model. These multiple minerals include quartz, clay, calcite, dolomite, and feldspar, etc. The volume fraction is the volume content of each rock mineral component obtained from the rock volume model, i.e., the percentage of each rock mineral component in the total rock volume. Once the mineral components and volume contents are determined, and the elastic modulus of the matrix is ​​distributed between the upper Voigt limit and the lower Reuss limit, the volume modulus and shear modulus of the multi-mineral mixture are calculated using the Hill averaging method.

[0177] The Hill averaging method is calculated using formulas (4), (5), and (6):

[0178]

[0179]

[0180]

[0181] in,

[0182] M V Voigt represents the upper limit of the effective elastic modulus of the rock mixture;

[0183] M R The Reuss lower limit represents the effective elastic modulus of a rock mixture;

[0184] f i This represents the volume fraction of the i-th medium (the i-th component of the rock);

[0185] M i Represents the elastic modulus of the i-th medium;

[0186] M VRH Hill average represents elastic parameters such as bulk modulus and shear modulus.

[0187] S4: Substitute the bulk modulus and shear modulus of the obtained multi-mineral mixture rock matrix into Kuster- The model is used to calculate the equivalent bulk modulus and shear modulus of a multi-mineral mixture matrix containing unconnected pores.

[0188] Step S4 specifically includes the following steps:

[0189] S41: A comprehensive analysis of Paleogene rocks, utilizing core, cuttings, logging, and geological data, reveals micropore types. The mid-to-deep Paleogene strata, influenced by compaction, are relatively dense. Intense diagenesis leads to an increase in non-connected pores, resulting in a higher total porosity φ. T With effective porosity φ effe and non-connected pores φ clay The relationship is:

[0190] φ T =φ effe +φ clay (18)

[0191] S42: Treating unconnected pores as part of the matrix background, using Kuster- The model incorporates mudstone minerals and solves for the equivalent bulk modulus and shear modulus of a multi-mineral mixture matrix containing unconnected pores.

[0192] Among them, the Kuster- The model is specifically represented by formulas (7), (8), and (9):

[0193]

[0194]

[0195]

[0196] in,

[0197] Indicates the effective bulk modulus;

[0198] Indicates the effective shear modulus;

[0199] K m Indicates the bulk modulus of the rock matrix;

[0200] μ m Indicates the shear modulus of the rock matrix;

[0201] K i Indicates the bulk modulus of a porous filler;

[0202] μ i Indicates the shear modulus of the pore-filled material;

[0203] Q mi P mi It is a geometric factor related to pore shape, representing the influence of pore filling material on matrix rock;

[0204] x i This refers to the volume fraction of the interstitial material.

[0205] ζ m This is a factor characterizing the elastic properties of the matrix.

[0206] S5: A fast simulated annealing optimization algorithm is introduced to invert the pore structure parameters of sandstone and special lithology. The objective function is obtained by using the measured P-wave velocity as a constraint. The formation pore structure parameters are quantitatively characterized by the optimization solution based on the objective function, thereby obtaining the input parameters of the optimized SCA self-compatible model. The equivalent elastic modulus of the rock skeleton with complex pore structure is calculated through the SCA self-compatible model.

[0207] Step S5 is described in detail below:

[0208] S51: Based on the microscopic pore structure type observed in core thin sections, the effective pore space φ in complex Paleogene lithological strata is determined. effe Divided into sandstone pore φ sand and special lithological pore φ spec The relationship is expressed as:

[0209] φ effe =φ sand +φ spec (19)

[0210] S52: The content of two types of porosity is calculated using the content of quartz minerals and Paleogene special lithological minerals (i.e., complex types of minerals other than quartz and clay) as weights:

[0211] φ spec =φ effe ×V spec / (V spec +V qua (20)

[0212] φ qua =φ effe ×V qua / (V spec +Vqua ) (twenty one)

[0213] S53: Based on the SCA self-compatibility model, the above two types of pores are added to the background matrix containing bound water pores to form a drying skeleton:

[0214]

[0215]

[0216] in,

[0217] K i Let be the bulk modulus of the i-th type of pore filler;

[0218] μ i Let i be the shear modulus of the i-th type of pore filler;

[0219] The equivalent bulk modulus of rocks containing pore-filling materials;

[0220] The equivalent shear modulus of rock containing pore-filled materials;

[0221] f i Volume fraction of pore filler.

[0222] P *i Q *i The shape expression of the contained object is given by formulas (12) and (13):

[0223]

[0224]

[0225] Among them, tensor T ijij T iijj It is related to the elastic modulus and porosity of the background medium.

[0226] S54: Given the measured P-wave velocity as a constraint, with initial model parameters and objective function:

[0227]

[0228] in,

[0229] α san d These are the pore structure parameters of sandstone;

[0230] α spec Pore ​​structure parameters for special lithologies;

[0231] For the actual measured longitudinal wave velocity;

[0232] Calculate the P-wave velocity for the model;

[0233] K is the bulk modulus of each mineral;

[0234] U represents the shear modulus of each mineral;

[0235] F represents the volume fraction of each mineral;

[0236] φ represents the rock porosity;

[0237] ρ is the density;

[0238] S w This represents the water saturation level.

[0239] S55: A fast simulated annealing optimization algorithm is introduced to minimize the objective function, and the pore structure parameters of sandstone and special lithology are solved by inversion. This process is a nonlinear multivariate function problem. The optimization direction is established by using the information of the objective function itself, and two types of pore structure parameters that can accurately characterize the changes with the burial depth of the strata are obtained. This enables the model to accurately describe the pore structure characteristics of Paleogene strata rocks, and then optimizes the inclusion structure parameters of the SCA self-compatible model. The equivalent elastic modulus of the rock skeleton containing complex pore structures is calculated through the SCA self-compatible model.

[0240] S6: Establish a calculation model for the equivalent elastic modulus of saturated rocks using the equivalent elastic modulus of the rock skeleton with complex pore structure, and calculate the equivalent elastic modulus of saturated rocks with complex Paleogene lithology to complete the calculation of elastic parameters of complex Paleogene lithological strata at sea.

[0241] When the optimal formation evaluation result in S2 contains special lithologies such as feldspar, calcite, and limestone, the elastic properties of the pore-filling components in each phase differ, resulting in varying pore pressures induced by each phase. This makes it difficult for the pore pressure to reach equilibrium throughout the pore space, leading to patch saturation. Therefore, a patch saturation model is used to add fluid. Step S6 is described in detail below:

[0242] S61: Assume the rock fluid state is a mixture of oil, gas, and water, with saturations of S0, S1, S2, S3, S4, S5, S66, S7, S8, S9, S10o S g and S w The equivalent elastic modulus of the rock is the equivalent average of the rock's elastic modulus when each phase of the fluid is distributed in a "patch" pattern. A calculation model for the equivalent elastic modulus of saturated rock is established as follows:

[0243]

[0244]

[0245]

[0246] In the formula,

[0247] K i Let i be the bulk modulus of the rock when it is saturated with fluid i.

[0248] μ i Let i be the shear modulus of the rock when it is saturated with fluid i.

[0249] M i Let i be the longitudinal wave modulus when the rock is saturated with fluid i.

[0250] M is the equivalent longitudinal wave modulus of the rock;

[0251] μ is the equivalent shear modulus of the rock;

[0252] μ d The shear modulus of the rock skeleton;

[0253] K d The bulk modulus of the rock skeleton;

[0254] K m Indicates the bulk modulus of the rock matrix;

[0255] K fl-i Let be the bulk modulus of fluid i;

[0256] S o Oil saturation;

[0257] S g Gas saturation;

[0258] S w Water saturation;

[0259] M o The longitudinal wave modulus when the rock is saturated with oil;

[0260] M g The longitudinal wave modulus of a rock saturated with gas;

[0261] M w The longitudinal wave modulus of a rock saturated with water;

[0262] φ represents the porosity of the rock.

[0263] Example 2

[0264] The technical effectiveness of the method of the present invention will be tested using actual data below:

[0265] Figure 2The optimal stratigraphic evaluation curves for the Paleogene strata in the coastal waters of China, oriented towards the seismic surface of Well A, are used to interpret the mineral content and porosity curves of quartz, clay, calcite, and limestone, as well as the water saturation curves. Figure 3a This is a distribution diagram of P-wave and S-wave parameters in sandstone pores. Figure 3b This is a distribution map of P-wave and S-wave parameters in the pores of special lithologies. Figure 3a and Figure 3b The distribution and proportion of two types of pores in the Paleogene strata were quantitatively described: the aspect ratio of sandstone pores was less than 0.4, the pore types in special lithological minerals were abundant, and the aspect ratio of special lithological pores was widely distributed, among which fracture-type pores with an aspect ratio of less than 0.12 were the most common.

[0266] Figure 4 shows the P-wave and S-wave velocities of well A calculated based on the conventional Xu-White model, where... Figure 4a To compare the measured and predicted P-wave velocities, Figure 4b Comparison of measured and predicted shear wave velocities;

[0267] Figure 5 shows the P-wave and S-wave velocities of well A calculated using the elastic parameter calculation method for complex Paleogene lithology in marine formations according to the present invention. Figure 5a To compare the measured and predicted P-wave velocities, Figure 5b Comparison of measured and predicted shear wave velocities;

[0268] go through Figure 4a , 4b , Figure 5a , Figure 5b The comparison of the results shows that the predicted P-wave and S-wave velocities of this method have better consistency with the measured curves and higher accuracy, thus verifying the applicability of the model in the calculation of elastic parameters of complex Paleogene strata.

[0269] Example 3

[0270] The above-described embodiment 1 provides a system for calculating elastic parameters of complex Paleogene lithological strata at sea. Correspondingly, this embodiment provides a system for calculating elastic parameters of complex Paleogene lithological strata at sea. The system provided in this embodiment can implement the triangular method for calculating elastic parameters of complex Paleogene lithological strata at sea described in embodiment 1. This method can be implemented through software, hardware, or a combination of both. For example, the method may include integrated or separate functional modules or units to execute the corresponding steps in the methods of embodiment 1. Since the system for calculating elastic parameters of complex Paleogene lithological strata at sea described in this embodiment is basically similar to the method embodiment, the description process in this embodiment is relatively simple. Relevant details can be found in the description of embodiment 1. The system for calculating elastic parameters of complex Paleogene lithological strata at sea described in this embodiment is merely illustrative.

[0271] This embodiment provides a system for calculating elastic parameters in complex Paleogene lithological strata at sea. The system includes:

[0272] The first processing unit is used to perform wellbore collapse single-well environmental correction and multi-well consistency logging curve preprocessing for elastic parameter curve anomalies, and to obtain the preprocessed logging curve.

[0273] The second processing unit is used to establish a rock volume model based on geological logging data and core analysis of stratigraphic mineral types, using pre-processed logging curves as constraints, solving the rock volume model, and obtaining lithological and physical property information of complex Paleogene lithological strata.

[0274] The third processing unit is used to calculate the bulk modulus and shear modulus of the rock matrix of the multi-mineral mixture based on the mineral composition and volume content obtained from the rock volume model and the Hill averaging method.

[0275] The fourth processing unit is used to substitute the bulk modulus and shear modulus of the obtained multi-mineral mixture rock matrix into Kuster- The model was used to calculate the equivalent bulk modulus and shear modulus of a multi-mineral mixture matrix containing unconnected pores.

[0276] The fifth processing unit is used to introduce a fast simulated annealing optimization algorithm to invert sandstone pore and special lithology pore structure parameters. With the measured P-wave velocity as a constraint, the objective function is obtained. Based on the objective function, the formation pore structure parameters are quantitatively characterized by optimization, thereby obtaining the input parameters of the optimized SCA self-compatible model. The equivalent elastic modulus of the rock skeleton with complex pore structure is calculated through the SCA self-compatible model.

[0277] The sixth processing unit is used to establish a calculation model for the equivalent elastic modulus of saturated rocks and to calculate the equivalent elastic modulus of Paleogene complex lithology saturated rocks.

[0278] Example 4

[0279] Thirdly, the present invention provides a computer storage medium storing a computer program thereon, wherein when the computer program is executed by a processor, it implements the steps of a method for calculating elastic parameters applicable to complex lithological strata of Paleogene at sea.

[0280] Example 5

[0281] Fourthly, a computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the steps of a method for calculating elastic parameters applicable to complex marine Paleogene lithological strata.

[0282] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating elastic parameters applicable to complex lithological strata of Paleogene strata at sea, characterized in that, Includes the following steps: For abnormal elastic parameter curves, well logging curve preprocessing is performed to correct the single-well environment of wellbore collapse and to ensure consistency across multiple wells, resulting in preprocessed well logging curves. Based on geological logging data and core analysis of formation mineral types, a rock volume model was established and solved using preprocessed logging curves as constraints to obtain formation mineral composition and volume content. Based on the formation mineral composition and volume content obtained from the rock volume model, the bulk modulus and shear modulus of the rock matrix of the multi-mineral mixture were calculated using the Hill averaging method. Substitute the bulk modulus and shear modulus of the obtained multi-mineral mixture into the Kuster-Toksöz model to calculate the equivalent bulk modulus and shear modulus of the multi-mineral mixture matrix containing unconnected pores. A fast simulated annealing optimization algorithm is introduced to invert the pore structure parameters of sandstone and special lithology. With the measured P-wave velocity as a constraint, the objective function is obtained. Based on the optimization of the objective function, the formation pore structure parameters are quantitatively characterized, thereby obtaining the input parameters of the optimized SCA self-compatible model. The equivalent elastic modulus of the rock skeleton with complex pore structure is calculated through the SCA self-compatible model. A calculation model for the equivalent elastic modulus of saturated rocks was established using the equivalent elastic modulus of the rock skeleton with complex pore structure. The equivalent elastic modulus of saturated rocks with complex Paleogene lithology was calculated to complete the calculation of elastic parameters of complex Paleogene lithological strata at sea. The step "Well logging curve preprocessing for wellbore collapse single-well environmental correction in response to elastic parameter curve anomalies" specifically includes the following steps: Select curves that are less affected by the wellbore environment and establish a linear relationship between abnormal and normal curves; The linear relationship between the abnormal curve and the normal curve is used to correct the wellbore collapse of the abnormal segments of the sonic transit time curve and the density curve, so that the sonic transit time curve and the density curve return to the vicinity of the baseline. The linear relationship between the abnormal curve and the normal curve is as follows: (1) (2) in, GR is the gamma curve; RT is the deep resistivity; CNL stands for neutron porosity; The acoustic transit time after wellbore collapse correction; The acoustic density after wellbore collapse correction; , , , , are the fitting coefficients, where i = 1, 2; The step "calculating the bulk modulus and shear modulus of the rock matrix of the multi-mineral mixture based on the mineral composition and volume content obtained from the rock volume model and using the Hill averaging method" specifically includes the following steps: Based on geological logging data and lithological and physical property information of complex Paleogene lithological strata, the stratigraphic mineral types are determined, and the volume fraction of multiple minerals in the Paleogene strata is determined by rock volume model. When the mineral composition and volume content are determined, the elastic modulus of the matrix is ​​distributed between the upper limit of Voigt and the lower limit of Reuss. The volume modulus and shear modulus of the multi-mineral mixture are calculated using the Hill averaging method. The Hill averaging method is calculated using formulas (4), (5) and (6); (4) (5) (6) in, Voigt represents the upper limit of the effective elastic modulus of the rock mixture; The Reuss lower limit represents the effective elastic modulus of a rock mixture; This represents the volume fraction of the i-th medium, which is the i-th component of the rock. Represents the elastic modulus of the i-th medium; Hill average values ​​representing bulk modulus, shear modulus, and elastic parameters; The Kuster-Toksöz model is specifically as follows: （7） （8） （9） in, Indicates the effective bulk modulus; Indicates the effective shear modulus; Indicates the bulk modulus of the rock matrix; Indicates the shear modulus of the rock matrix; Indicates the bulk modulus of a porous filler; Indicates the shear modulus of the pore-filled material; , It is a geometric factor related to pore shape, representing the influence of pore filling material on matrix rock; x i This refers to the volume fraction of the interstitial material. A factor characterizing the elastic properties of the matrix; The objective function is specifically: （14） in, These are the pore structure parameters of sandstone; Pore ​​structure parameters for special lithologies; For the actual measured longitudinal wave velocity; Calculate the P-wave velocity for the model; K is the bulk modulus of each mineral; U represents the shear modulus of each mineral; F represents the volume fraction of each mineral; Rock porosity; Density; Water saturation; f A model for calculating P-wave velocity; The specific calculation model for the equivalent elastic modulus of saturated rock is as follows: (15) (16) (17) in, Rocks saturated with fluid The bulk modulus at that time; Rocks saturated with fluid Shear modulus at time; Rocks saturated with fluid Longitudinal wave modulus at time; The equivalent longitudinal wave modulus of the rock; The equivalent shear modulus of the rock; The shear modulus of the rock skeleton; The bulk modulus of the rock skeleton; Let be the bulk modulus of fluid i; Oil saturation; Gas saturation; The longitudinal wave modulus when the rock is saturated with oil; The longitudinal wave modulus of a rock saturated with gas; This is the longitudinal wave modulus when the rock is saturated with water.

2. The method for calculating elastic parameters of complex Paleogene lithological strata at sea according to claim 1, characterized in that, The step "preprocessing of logging curves for multi-well consistency in response to elastic parameter curve anomalies" specifically includes the following steps: Identify marker layers and standard wells; Based on the criterion of consistent histogram probability distribution shape of the marker layer, the value range and probability type of other wells that need to be adjusted for consistency are adjusted according to the standard well, so that the interval and shape of the probability distribution of each well are consistent and systematic errors are eliminated.

3. The method for calculating elastic parameters of complex lithological strata in marine Paleogene formations according to claim 2, characterized in that, The rock volume model is specifically as follows: (3) in, Let i represent the volume fraction of different mineral components, i = 1, 2, 3...m; qua It is a quartz mineral; clay It is a clay mineral; spec It is a special type of lithological mineral; f It is a pore fluid; Represents density; V represents volume.

4. The method for calculating elastic parameters of complex lithological strata in marine Paleogene formations according to claim 3, characterized in that, The SCA self-compatible model is specifically as follows: （10） （11） in, Let be the bulk modulus of the i-th type of pore filler; Let i be the shear modulus of the i-th type of pore filler; The equivalent bulk modulus of rocks containing pore-filling materials; The equivalent shear modulus of rock containing pore-filled materials; f i The volume fraction of the interstitial material; , The shape expressions for the included objects are specifically formulas (12) and (13): （12） （13） Among them, tensor , It is related to the elastic modulus and porosity of the background medium.

5. A system for calculating elastic parameters of complex lithological strata in marine Paleogene formations, characterized in that, include: The first processing unit is used to perform wellbore collapse single-well environmental correction and multi-well consistency logging curve preprocessing for elastic parameter curve anomalies, and to obtain the preprocessed logging curves. The second processing unit is used to establish a rock volume model based on geological logging data and core analysis of formation mineral types, using pre-processed logging curves as constraints, solving the rock volume model, and obtaining formation mineral composition and volume content. The third processing unit is used to calculate the bulk modulus and shear modulus of the rock matrix of the multi-mineral mixture based on the formation mineral composition and volume content obtained from the rock volume model, using the Hill averaging method. The fourth processing unit is used to substitute the bulk modulus and shear modulus of the obtained multi-mineral mixture rock matrix into the Kuster-Toksöz model to calculate the equivalent bulk modulus and shear modulus of the multi-mineral mixture matrix containing unconnected pores. The fifth processing unit is used to introduce a fast simulated annealing optimization algorithm to invert sandstone pore and special lithology pore structure parameters. With the measured P-wave velocity as a constraint, the objective function is obtained. Based on the objective function, the formation pore structure parameters are quantitatively characterized by optimization, thereby obtaining the input parameters of the optimized SCA self-compatible model. The equivalent elastic modulus of the rock skeleton with complex pore structure is calculated through the SCA self-compatible model. The sixth processing unit is used to establish a calculation model for the equivalent elastic modulus of saturated rocks and to calculate the equivalent elastic modulus of Paleogene complex lithology saturated rocks.

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