阅读说明：本技术 盐间地层弹性参数的确定方法、存储介质和计算机设备 (Method for determining elastic parameters of stratum between salts, storage medium and computer equipment ) 是由 章惠 朱博华 陈勇 向雪梅 李洋 董清源 于 2020-06-30 设计创作，主要内容包括：本申请的实施方式提供一种盐间地层弹性参数的确定方法、存储介质和计算机设备。该方法包括：获取测井曲线,解释所述测井曲线得到该盐间地层于目标深度处的矿物组分、孔隙度和总密度；构建分段式盐间岩石物理模型；基于所构建的分段式盐间岩石物理模型,选择相应的弹性模量确定方法；根据盐间地层于目标深度处的矿物组分和孔隙度,利用所选择的弹性模量确定方法确定盐间地层于目标深度处的弹性模量；根据盐间地层于目标深度处的弹性模量和总密度确定用于描述盐间地层于目标深度处的弹性参数。本实施例中的分段式的盐间岩石物理模型,针对不同的岩性地层开展差别化建模,该方法对于横波速度的预测吻合度明显高于常规方法。(Embodiments of the present application provide a method, a storage medium, and a computer device for determining an elastic parameter of an intersalt formation. The method comprises the following steps: obtaining a logging curve, and interpreting the logging curve to obtain mineral components, porosity and total density of the salt stratum at a target depth; constructing a sectional type rock physical model between salts; selecting a corresponding elastic modulus determination method based on the constructed segmented rock physical model between the salts; determining the elastic modulus of the saline-alkali formation at the target depth by using the selected elastic modulus determination method according to the mineral composition and the porosity of the saline-alkali formation at the target depth; an elasticity parameter describing the saline-alkali formation at the target depth is determined from the elastic modulus and the total density of the saline-alkali formation at the target depth. The segmented salt rock physical model in the embodiment carries out differential modeling aiming at different lithologic strata, and the prediction goodness of the method for the transverse wave velocity is obviously higher than that of the conventional method.)

1. A method for determining an elastic parameter of an intersalt formation, comprising the steps of:

acquiring a logging curve of the salt stratum, and interpreting the logging curve to obtain mineral components, porosity and total density of the salt stratum at a target depth, wherein the mineral components comprise clay content and kerogen content;

constructing a sectional type rock physical model between salts;

selecting a corresponding elastic modulus determination method according to the clay content and the kerogen content of the salt stratum at the target depth based on the constructed sectional type salt rock physical model;

determining an elastic modulus of the saline formation at the target depth using the selected elastic modulus determination method based on the mineral composition and porosity of the saline formation at the target depth, wherein the elastic modulus includes a bulk modulus and a shear modulus;

an elasticity parameter describing the saline-alkali formation at the target depth is determined from the elastic modulus and the total density of the saline-alkali formation at the target depth.

2. The method of determining an elastic parameter of an intersalt formation according to claim 1, wherein the segmented intersalt petrophysical model is constructed according to the following steps:

analyzing mineral components of the intersalt formation, mixing brittle minerals to obtain a brittle mixture, and determining the elastic modulus of the brittle mixture based on a VRH average theory;

mixing clay and kerogen in plastic minerals with the brittle mixture according to different volume ratios to obtain different types of intermediate equivalent media;

selecting a corresponding elastic modulus determination method according to the type of the intermediate equivalent medium, and determining the elastic modulus of each type of intermediate equivalent medium according to the contents of clay and kerogen and the elastic modulus of the brittle mixture by using the selected elastic modulus determination method;

adding pore fluid into each type of intermediate equivalent medium to obtain each type of final equivalent medium, and determining the elastic modulus of each type of final equivalent medium based on a differential equivalent medium theory according to the elastic modulus of each type of intermediate equivalent medium, thereby obtaining the segmented salt rock physical model.

3. The method for determining the elastic parameters of the salt-space formation according to claim 2, characterized in that the clay and kerogen in plastic minerals are mixed with the friable mixture according to different volume ratios to obtain different types of intermediate equivalent media, comprising:

when the clay content in the intermediate equivalent medium is less than or equal to a first content threshold value, the type of the obtained intermediate equivalent medium corresponds to a salt rock stratum;

when the clay content in the intermediate equivalent medium is greater than a first content threshold and the kerogen content is less than or equal to a second content threshold, the type of the obtained intermediate equivalent medium corresponds to the lean organic matter mudstone;

when the clay content in the intermediate equivalent medium is greater than a first content threshold and the kerogen content is greater than a second content threshold, the type of intermediate equivalent medium obtained corresponds to an organic-rich shale layer.

4. The method for determining the elastic parameters of the salt formation according to claim 3, wherein the method for determining the elastic modulus is selected according to the type of the intermediate equivalent medium, and the method for determining the elastic modulus of each type of intermediate equivalent medium is determined according to the contents of clay and kerogen and the elastic modulus of the brittle mixture by using the selected method for determining the elastic modulus, and comprises the following steps:

when the type of the obtained intermediate equivalent medium corresponds to the salt rock stratum, determining the elastic modulus of the intermediate equivalent medium based on a differential equivalent medium theory;

when the type of the obtained intermediate equivalent medium corresponds to the lean organic matter shale layer, determining the elastic modulus of the intermediate equivalent medium based on a differential equivalent medium theory;

when the type of the obtained intermediate equivalent medium corresponds to the organic matter-rich shale layer, the elastic modulus of the intermediate equivalent medium is determined based on a self-consistent theory and a differential equivalent medium theory.

5. The method for determining the elastic parameter of the salt-space stratum according to claim 4, wherein the method for determining the elastic modulus is selected according to the clay content and the kerogen content of the salt-space stratum at the target depth based on the constructed segmented salt-space rock physical model, and comprises the following steps:

matching the clay content and the kerogen content of the salt stratum at the target depth with the clay content and the kerogen content of each type of intermediate equivalent medium in the sectional type salt stratum rock physical model, and determining the type of the intermediate equivalent medium corresponding to the salt stratum at the target depth according to the matching result;

and taking the elastic modulus determination method corresponding to the intermediate equivalent medium of the type as the elastic modulus determination method of the salt-space stratum at the target depth.

6. The method for determining an elastic parameter of a salt-space formation according to claim 2, wherein determining the elastic modulus of the brittle mixture based on the VRH average theory comprises:

the elastic modulus of the brittle mixture was calculated using the formula:

wherein M is_VRHDenotes the modulus of elasticity, M, of the brittle mixture_VThe upper limit of the modulus of elasticity of the brittle mixture is expressed,M_Rrepresents the lower limit of the elastic modulus of the brittle mixture,i represents the i-th mineral species,n represents a mineral in the total of N, f_iMi is the elastic modulus of the ith mineral as a percentage of the volume content of the mineral.

7. The method for determining an elastic parameter of a salt formation according to any one of claims 2 to 4, wherein the calculation formula for determining the elastic modulus based on the differential equivalent medium theory is as follows:

K_mix1(0)＝K₁,μ_mix1(0)＝μ₁

wherein, K₁And mu₁The bulk and shear moduli, K, of the background phase mineral, respectively₂And mu₂Respectively the bulk modulus and shear modulus of the added phase mineral, K_mix1(0) And mu_mix1(0) The volume modulus and the shear modulus of the intermediate equivalent medium after 0 iteration are respectively, y is the volume percentage of the added phase mineral, and P and Q are shape factors for controlling the shape of the added phase mineral respectively.

8. The method for determining an elastic parameter of a salt formation according to claim 4, wherein the calculation formula for determining the elastic modulus based on the self-consistent theory is as follows:

wherein f is_jIndicating the j-th phase added phase oreVolume percent of substance, K_jAnd mu_jRespectively representing the bulk modulus and the shear modulus of the j phase added phase mineral, n represents the total n phase added phase minerals,andrespectively representing the bulk and shear moduli of the mixed phase mineral, P^jAnd Q^jRespectively, shape factors for controlling the shape of the j-th phase addition phase mineral.

9. The method of determining an elastic parameter of a salt formation according to claim 1, wherein the elastic parameter comprises at least one of compressional and shear wave velocities.

10. The method of determining an elastic parameter of a salt formation according to claim 9,

when the elastic parameters include longitudinal wave velocity, determining the elastic parameters of the saline formation at the target depth according to the elastic modulus and the total density of the saline formation corresponding to the target depth, including:

calculating the compressional wave velocity of the salt formation at the target depth according to the following formula:

wherein v is_pThe longitudinal wave velocity, K is the bulk modulus obtained through the sectional type rock physical model between the salts, mu is the shear modulus obtained through the sectional type rock physical model between the salts, and rho is the total density of the stratum between the salts corresponding to the target depth;

when the elastic parameters include shear wave velocity, determining the elastic parameters of the saline formation at the target depth according to the elastic modulus and the total density of the saline formation corresponding to the target depth, including:

calculating the shear wave velocity of the salt formation at the target depth according to the following formula:

wherein v is_sFor shear wave velocity, μ is the shear modulus obtained by the segmented intersalt petrophysical model, and ρ is the total density of the intersalt formation corresponding to the target depth.

11. A storage medium storing a computer program which, when executed by a processor, carries out the steps of the method for determining a salt formation elasticity parameter according to any one of claims 1 to 10.

12. A computer device comprising a processor and a storage medium having stored thereon program code which, when executed by the processor, carries out the steps of the method for determining a salt formation elasticity parameter according to any one of claims 1-10.

Technical Field

The invention relates to the technical field of oil and gas geophysical, in particular to a method for determining elastic parameters of a stratum between salts, a storage medium and computer equipment.

Background

In recent years, unconventional oil and gas reservoirs occupy more and more proportion in oil and gas resource exploration, and people gradually turn the eyes from conventional sand shale reservoirs to unconventional fields with wider exploration prospects. The shale gas revolution in north america has achieved revolutionary success. Unconventional exploration in China is still too serious. Salt-intermediate shale oil is a typical unconventional reservoir that develops extensively in the salt lake basin. The exploration and development of the shale oil between the salts is one of the important links of unconventional exploration in China.

Seismic petrophysics plays an important role in geophysical exploration as a bridge between seismic elastic parameters and reservoir physical properties. Seismic exploration can only acquire elastic information (such as velocity and density) of the underground, and when the information is converted into physical property information (such as pore structure, pore form and the like) which is more interesting in petroleum exploration, the intervention of a rock physical model is required.

Rock physics has so far undergone the process of transition from isotropic models to anisotropic models, from semi-empirical formulas to precise parametric models. Through experimental means, the elastic parameter of a certain pure mineral can be measured more accurately. In a practical reservoir, both the mineral and pore fluid content of the reservoir are complex. Equivalent medium model theory is often used when it is desired to predict equivalent elastic parameters for a mixture of various mineral components and different fluid compositions. The method expresses the interrelation among all phases of the mixture in the form of mathematical formulas based on the equivalent model theory, and has higher practicability

The accuracy of the rock physical model directly influences the accuracy of seismic processing and interpretation. Different lithology is due to the fact that differences of mineral components, coupling modes and the like are large, and different models need to be constructed according to characteristics of the lithology. The wide application of petrophysical theory in the field of oil exploration can be roughly summarized into empirical formulas and equivalent theoretical models. The empirical formula theory is generally used to describe a conventional sandstone reservoir, because sandstone usually shows isotropy, and the structural components and pore structures of sandstone are single, so that the variation rule of the elastic parameters of the sandstone reservoir along with the physical parameters is single. Therefore, petrophysicists have empirical formulas for sandstone reservoirs by taking a large number of laboratory measurements and summarizing and analyzing the measurements.

With the gradually strengthened exploration of unconventional reservoirs such as carbonate reservoirs and shale reservoirs, people gradually find that the conventional theoretical model is not enough to accurately describe the properties of the complex reservoir. Thus, as petrophysicists developed petrophysics, they attempted to introduce mathematical models into the model building process in an effort to more finely describe more complex rock structures. Among them, the equivalent medium theory has wider practicability due to the variability and diversity of parameters. The equivalent theory is widely applied to describing sandstone reservoirs (such as an Xu-White model) and carbonate reservoirs (an Xu-Payne model), and achieves better application effect. Modeling of shale model is a research hotspot in recent years, and nowadays, a shale equivalent model applied widely is based on Inclusion Theory (Inclusion Theory). Shale has more complex mineral components and pore morphology, and the inclusion theory (Kuster G T model) considers the internal structural distribution of pores and the interaction between minerals, so that the shale has more obvious advantages in the description of shale. With the intensive research of people, through the intervention of auxiliary means such as core slice scanning and the like, people find that the coupling modes of different minerals are obviously different, so that different equivalent medium theories need to be selected according to different coupling modes. In recent years, a Self-consistent theory (SCA), a Differential equivalent Medium theory (DEM), and the like are widely used in equivalent Medium simulation.

The salt-space stratum is a stratum formed by the mutual layer of a salt rock stratum and a mudstone layer through long water feeding and water withdrawal deposition of a salt lake basin. FIG. 1 is a schematic view of a salt-rock formation consisting of three sets of salt rock and two sets of mudstone formations. The thickness of the salt rock is usually about 10-20 m, the porosity of the salt rock stratum is low, the permeability is poor, and a good pressure plugging effect can be achieved. The intersalt formations, which are typically between 10-40 meters thick, are the primary target formations for continental shale oil. A salt rock layer and a salt interlayer are added to form a set of salt rhythm layer. The target probe usually develops multiple salt prosodic layers simultaneously. The entire formation may contain tens or even hundreds of prosodic layers. In summary, the longitudinal lithology of the salt-salt formation changes dramatically and rapidly.

In most cases, one typically analyzes the entire interval using a fixed petrophysical model, which is applicable to most formations with small longitudinal changes in lithology. But aiming at the stratum between salts, the lithology has large longitudinal change and high change frequency, and the application effect of the conventional method is poor.

Because the salt reservoir has the characteristic of violent longitudinal change of lithology, the rock physical characteristics of the salt reservoir cannot be well described by the conventional sand shale model, carbonate rock and shale model. Therefore, it is highly desirable to construct an inter-salt petrophysical model.

Disclosure of Invention

The invention provides a method for determining elastic parameters of a salt-salt stratum, a storage medium and computer equipment, aiming at solving the problem of accurately determining the elastic parameters under the condition of severe depth change of the salt-salt stratum.

In a first aspect, embodiments of the present application provide a method for determining an elastic parameter of an intersalt formation, comprising the steps of: acquiring a logging curve of the salt stratum, and interpreting the logging curve to obtain mineral components, porosity and total density of the salt stratum at a target depth, wherein the mineral components comprise clay content and kerogen content; constructing a sectional type rock physical model between salts; selecting a corresponding elastic modulus determination method according to the clay content and the kerogen content of the salt stratum at the target depth based on the constructed sectional type salt rock physical model; determining an elastic modulus of the saline formation at the target depth using the selected elastic modulus determination method based on the mineral composition and porosity of the saline formation at the target depth, wherein the elastic modulus includes a bulk modulus and a shear modulus; an elasticity parameter describing the saline-alkali formation at the target depth is determined from the elastic modulus and the total density of the saline-alkali formation at the target depth.

In one embodiment, a segmented salt-salt rock physics model is constructed according to the following steps: analyzing mineral components of the intersalt formation, mixing brittle minerals to obtain a brittle mixture, and determining the elastic modulus of the brittle mixture based on a VRH average theory; mixing clay and kerogen in plastic minerals with the brittle mixture according to different volume ratios to obtain different types of intermediate equivalent media; selecting a corresponding elastic modulus determination method according to the type of the intermediate equivalent medium, and determining the elastic modulus of each type of intermediate equivalent medium according to the contents of clay and kerogen and the elastic modulus of the brittle mixture by using the selected elastic modulus determination method; adding pore fluid into each type of intermediate equivalent medium to obtain each type of final equivalent medium, and determining the elastic modulus of each type of final equivalent medium based on a differential equivalent medium theory according to the elastic modulus of each type of intermediate equivalent medium, thereby obtaining the segmented salt rock physical model.

In one embodiment, clay and kerogen in plastic minerals are mixed with the friable mixture in different volume ratios to obtain different types of intermediate equivalent media, comprising: when the clay content in the intermediate equivalent medium is less than or equal to a first content threshold value, the type of the obtained intermediate equivalent medium corresponds to a salt rock stratum; when the clay content in the intermediate equivalent medium is greater than a first content threshold and the kerogen content is less than or equal to a second content threshold, the type of the obtained intermediate equivalent medium corresponds to the lean organic matter mudstone; when the clay content in the intermediate equivalent medium is greater than a first content threshold and the kerogen content is greater than a second content threshold, the type of intermediate equivalent medium obtained corresponds to an organic-rich shale layer.

In one embodiment, selecting a corresponding elastic modulus determination method according to the type of the intermediate equivalent medium, and determining the elastic modulus of each type of intermediate equivalent medium according to the contents of clay and kerogen and the elastic modulus of the brittle mixture by using the selected elastic modulus determination method, includes: when the type of the obtained intermediate equivalent medium corresponds to the salt rock stratum, determining the elastic modulus of the intermediate equivalent medium based on a differential equivalent medium theory; when the type of the obtained intermediate equivalent medium corresponds to the lean organic matter shale layer, determining the elastic modulus of the intermediate equivalent medium based on a differential equivalent medium theory; when the type of the obtained intermediate equivalent medium corresponds to the organic matter-rich shale layer, the elastic modulus of the intermediate equivalent medium is determined based on a self-consistent theory and a differential equivalent medium theory.

In one embodiment, based on the constructed segmented salt-salt rock physics model, a corresponding elastic modulus determination method is selected according to clay content and kerogen content of the salt-salt formation at a target depth, comprising: matching the clay content and the kerogen content of the salt stratum at the target depth with the clay content and the kerogen content of each type of intermediate equivalent medium in the sectional type salt stratum rock physical model, and determining the type of the intermediate equivalent medium corresponding to the salt stratum at the target depth according to the matching result; and taking the elastic modulus determination method corresponding to the intermediate equivalent medium of the type as the elastic modulus determination method of the salt-space stratum at the target depth.

In one embodiment, determining the elastic modulus of the brittle mixture based on VRH average theory comprises: the elastic modulus of the brittle mixture was calculated using the formula:

wherein M is_VRHDenotes the modulus of elasticity, M, of the brittle mixture_VThe upper limit of the modulus of elasticity of the brittle mixture is expressed,M_Rrepresents the lower limit of the elastic modulus of the brittle mixture,i represents the ith mineral, N represents the total N middle minerals, f_iMi is the elastic modulus of the ith mineral as a percentage of the volume content of the mineral.

In one embodiment, the elastic modulus is determined based on differential equivalent medium theory as follows:

K_mix1(0)＝K₁,μ_mix1(0)＝μ₁

wherein, K₁And mu₁The bulk and shear moduli, K, of the background phase mineral, respectively₂And mu₂Respectively the bulk modulus and shear modulus of the added phase mineral, K_mix1(0) And mu_mix1(0) The volume modulus and the shear modulus of the intermediate equivalent medium after 0 iteration are respectively, y is the volume percentage of the added phase mineral, and P and Q are shape factors for controlling the shape of the added phase mineral respectively.

In one embodiment, the calculation for determining the modulus of elasticity based on self-consistent theory is:

wherein f is_jDenotes the volume percentage of the phase j added to the phase mineral, K_jAnd mu_jRespectively representing the bulk modulus and the shear modulus of the j phase added phase mineral, n represents the total n phase added phase minerals,andrespectively representing the bulk and shear moduli of the mixed phase mineral, P^jAnd Q^jRespectively, shape factors for controlling the shape of the j-th phase addition phase mineral.

In one embodiment, the elastic parameters include at least one of compressional and shear wave velocities.

In one embodiment, when the elastic parameter comprises a compressional wave velocity, determining the elastic parameter of the saline formation at the target depth from an elastic modulus and a total density of the saline formation corresponding to the target depth comprises: calculating the compressional wave velocity of the salt formation at the target depth according to the following formula:

wherein v is_pThe longitudinal wave velocity, K is the bulk modulus obtained through the sectional type rock physical model between the salts, mu is the shear modulus obtained through the sectional type rock physical model between the salts, and rho is the total density of the stratum between the salts corresponding to the target depth;

when the elastic parameters include shear wave velocity, determining the elastic parameters of the saline formation at the target depth according to the elastic modulus and the total density of the saline formation corresponding to the target depth, including: calculating the shear wave velocity of the salt formation at the target depth according to the following formula:

wherein v is_sFor shear wave velocity, μ is the shear modulus obtained by the segmented intersalt petrophysical model, and ρ is the total density of the intersalt formation corresponding to the target depth.

In a second aspect, embodiments of the present application provide a storage medium storing a computer program which, when executed by a processor, performs the steps of the method for determining an elasticity parameter of a salt formation as described above.

In a third aspect, embodiments of the present application provide a computer device comprising a processor and a storage medium having program code stored thereon, which when executed by the processor, implement the steps of the method for determining an elastic parameter of an intersalt formation as described above.

The segmented salt rock physical model constructed by the method overcomes the defect that the traditional rock physical model cannot meet the description of the salt stratum rock physical characteristics, and introduces a segmented modeling idea according to the salt stratum characteristics. And constructing corresponding rock physical models aiming at different lithologic strata, and developing differential modeling. Finally, a segmented salt-salt rock physical model and a longitudinal and transverse wave velocity prediction method are formed for the continental facies salt-salt stratum with violent lithological longitudinal change, and the prediction goodness of fit of the method is obviously higher than that of the conventional method.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention, in which:

FIG. 1 is a schematic illustration of a formation of an intersalt formation;

FIG. 2 is a flow chart of a method for determining a salt interval formation elastic parameter according to an embodiment of the present disclosure;

FIG. 3 is a flow chart of modeling a segmented salt-salt petrophysical model according to an embodiment of the present application;

FIG. 4 is a flow chart of reservoir prediction based on a segmented intersalt petrophysical model according to an embodiment of the present application;

FIG. 5A is a prediction of the compressional and shear wave velocities for a well according to conventional DEM theory;

FIG. 5B is a prediction of the compressional and shear velocity of a well according to one embodiment of the present application;

in fig. 5A and 5B, the black solid line represents the prediction result, and the gray broken line represents the measurement result.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

Example one

FIG. 2 is a flow chart of a method for determining a salt interstratigraphic elasticity parameter according to an embodiment of the present application. As shown in fig. 2, an embodiment of the present application provides a method for determining an elastic parameter of an intersalt formation, which predicts the elastic parameter of the intersalt formation based on a segmented intersalt petrophysical model that is constructed, and may include the following steps:

s100: and acquiring a logging curve of the intersalt stratum, and interpreting the logging curve to obtain the mineral components, the porosity and the total density of the intersalt stratum at a target depth, wherein the mineral components comprise clay content and kerogen content.

S200: and constructing a sectional type rock physical model between the salts.

FIG. 3 is a flow chart of modeling a segmented salt-salt petrophysical model according to an embodiment of the present application. As shown in fig. 3, a segmented salt-salt rock physics model can be constructed according to the following steps:

firstly, analyzing mineral components of the intersalt formation, mixing brittle minerals to obtain a brittle mixture, and determining the elastic modulus of the brittle mixture based on VRH average theory.

Through analyzing the known logging information, the volume components of minerals of the salt-space stratum at different depths can be obtained, so that the main mineral components of the salt-space stratum can be known to comprise quartz, glauberite, salt rock, clay and kerogen. Wherein the clay and the salt rock are main mineral components of the mudstone layer and the salt rock layer respectively. Quartz, glauberite, and salt rock are more brittle than clay and kerogen, and therefore, these three types of brittle minerals can be mixed to obtain a brittle mixture (which may be referred to as an intersalt mixture for intersalt formations).

For the obtained brittle mixture, the elastic modulus of the brittle mixture can be determined based on the VRH (Vogit-Ruess-Hill) average theory, and specifically can be calculated using the following formula:

wherein M is_VRHDenotes the modulus of elasticity, M, of the brittle mixture_VThe upper limit of the modulus of elasticity of the brittle mixture is expressed,M_Rrepresents the lower limit of the elastic modulus of the brittle mixture,i represents the ith mineral, N represents the total N middle minerals, f_iMi is the elastic modulus of the ith mineral as a percentage of the volume content of the mineral. The elastic modulus may include a bulk modulus and a shear modulus, among others.

Secondly, mixing clay and kerogen in the plastic mineral with the brittle mixture according to different volume ratios to obtain different types of intermediate equivalent media, which specifically comprises the following steps:

when the clay content in the intermediate equivalent medium is less than or equal to the first content threshold, the obtained type of the intermediate equivalent medium corresponds to a salt rock formation. When the clay content in the intermediate equivalent medium is greater than a first content threshold and the kerogen content is less than or equal to a second content threshold, the type of intermediate equivalent medium obtained corresponds to an organic lean shale layer. When the clay content in the intermediate equivalent medium is greater than a first content threshold and the kerogen content is greater than a second content threshold, the type of intermediate equivalent medium obtained corresponds to an organic-rich shale layer.

Then, selecting a corresponding elastic modulus determination method according to the type of the intermediate equivalent medium, and determining the elastic modulus of each type of intermediate equivalent medium according to the contents of clay and kerogen and the elastic modulus of the brittle mixture by using the selected elastic modulus determination method, wherein the method specifically comprises the following steps:

when the obtained type of the intermediate equivalent medium corresponds to the salt rock formation, the elastic modulus of the intermediate equivalent medium is determined based on a differential equivalent medium theory. When the obtained type of the intermediate equivalent medium corresponds to the lean organic shale layer, the elastic modulus of the intermediate equivalent medium is determined based on a differential equivalent medium theory. When the type of the obtained intermediate equivalent medium corresponds to the organic matter-rich shale layer, the elastic modulus of the intermediate equivalent medium is determined based on a self-consistent theory and a differential equivalent medium theory.

For example, the first content threshold may be set at 50% and the second content threshold may be set at 3%. Of course, how many the specific first content threshold and the second content threshold are can be set according to needs.

Thus, when the clay content is less than or equal to 50%, the type of intermediate equivalent medium corresponds to a salt rock formation (shown as (r) in fig. 3). At the moment, clay minerals account for a small proportion, clay and kerogen are added into the background phase brittle mixture as addition phases, and the elastic modulus of the intermediate equivalent medium corresponding to the salt rock stratum is determined based on a differential equivalent medium theory.

The basic principle of Differential equivalent Medium theory (DEM) is: equivalent results for biphasic material were simulated by stepwise addition of inclusion phase to the background medium. The differential equivalent medium model first assumes that a certain phase of matter is a background mineral, and takes out a matter with volume DeltaV from the background mineral, and adds another phase of matter (inclusion) with the same volume (DeltaV) to the medium, at which time the equivalent modulus of the resulting mixture will change, replacing the modulus of the original matrix with the new equivalent modulus, and repeating the above process until the volume of the added phase reaches the actual value. When the delta V → 0, the formula for calculating the equivalent elastic modulus of the rock by using the DEM model is as follows:

K_mix1(0)＝K₁,μ_mix1(0)＝μ₁

wherein, K₁And mu₁The bulk and shear moduli, K, of the background phase mineral, respectively₂And mu₂Respectively the bulk modulus and shear modulus of the added phase mineral, K_mix1(0) And mu_mix1(0) The volume modulus and the shear modulus of the intermediate equivalent medium after 0 iteration are respectively, y is the volume percentage of the added phase mineral, and P and Q are shape factors for controlling the shape of the added phase mineral respectively.

When the clay content is more than 50% and the kerogen content is less than 3%, the type of the intermediate equivalent medium corresponds to the lean organic shale layer (as shown in (c) of fig. 3). Among them, kerogen is one of the important mineral components of unconventional reservoirs, and the simulation of kerogen is one of the current hot spots, and its existence makes the self-generation and self-storage of unconventional shale reservoirs possible. Since the elastic modulus of kerogen is much lower than that of other conventional minerals, its effect on the elastic parameters of the rock as a whole is generally strong even if its volume fraction is small. Therefore, the invention makes a targeted consideration on the role of kerogen in modeling.

For the intermediate equivalent medium corresponding to the lean organic mud formation, the elastic modulus thereof was determined based on the DEM theory described above. Because the volume percentage of the kerogen and the brittle mineral is less and the clay mineral accounts for a very high percentage, when the elastic modulus is calculated by utilizing the DEM theory, the clay mineral is used as a background phase mineral, and the brittle mixture and the kerogen are used as addition phase minerals and are sequentially added into the background phase mineral clay.

When the clay content is greater than 50% and the kerogen content is greater than 3%, the type of the intermediate equivalent medium corresponds to an organic-rich shale bed (see (c) in fig. 3). The difficulty in simulating kerogen when it is present in high amounts is that it has very unique physical and elastic properties compared to other mineral components. In particular, kerogen has a very low bulk and shear modulus. While the elastic modulus of quartz, which is also the other major mineral constituent of shale, is relatively high. Thus, kerogen is more like a special "fluid" than a conventional "mineral", so that when a rock skeleton with more kerogen is constructed using conventional mineral equivalence theory, the equivalent result is somewhat different from the true value. Therefore, the invention uses a method of combining a Self-consistent theory (SCA) with a differential equivalent medium theory (SCA + DEM theory) to simulate the influence of kerogen on the elastic modulus so as to better describe the effect generated by the mutual coupling between the kerogen and the clay.

The SCA + DEM theory is formed by combining the SCA theory and the DEM theory. The basic idea of the self-consistent theory is to take each mineral component and pore of a complex medium to be simulated as independent single phases, and place a multi-phase medium in a background medium with adjustable elastic parameters, wherein the background medium is infinite. SCA is an equivalent theory of "symmetry" that treats each mineral constituent as well as the pores in the rock equally. The self-consistent theory of SCA does not choose any of the multiphase materials as the matrix, but rather takes the unknown equivalent medium requiring solution as the matrix, taking into account the interactions between the inclusions by constantly changing the matrix, and thus the method takes into account the interactions between the inclusions. The calculation formula for determining the elastic modulus based on the self-consistent theory is as follows:

wherein f is_jDenotes the volume percentage of the phase j added to the phase mineral, K_jAnd mu_jRespectively representing the bulk modulus and the shear modulus of the j phase added phase mineral, n represents the total n phase added phase minerals,andrespectively representing the bulk and shear moduli of the mixed phase mineral, P^jAnd Q^jRespectively, shape factors for controlling the shape of the j-th phase addition phase mineral.

The SCA theory is widely applied to the construction of complex rock models, and can simultaneously equivalent multiphase minerals, which provides great convenience for the simulation of shale. However, many studies have shown that with the SCA theory equivalent of two-phase materials, the equivalent results with SCA theory coincide with the lower limit of the VRH boundary when the volume content of one of the phases exceeds 60%. At this point, the rock is in a "particle-suspended" state, i.e., the relatively "soft" phase (low bulk modulus phase) of the two phases completely encapsulates the relatively "hard" phase (high bulk modulus phase). At this time, the solid particles are not communicated with each other. Since the SCA theory is a symmetric model, two-phase materials can be well interconnected when the porosity is equal to 40% -60%.

And kerogen and clay generally remain in a coupled, interconnected enriched state, we therefore use the SCA + DEM theory to describe this coupled, interconnected state of kerogen and clay in shale. In practice, because the content of kerogen rarely can reach more than 40%, the description of the mutual coupling and communication state of kerogen and clay needs to be realized by combining the DEM theory. In order to ensure the mutual connectivity of the clay and the kerogen, the clay and the kerogen with the same volume are mixed, the volume content of the clay and the kerogen is 50%, and the elastic modulus after the two-phase substances are mutually fused is determined by utilizing an SCA theory, so that the mutual coupling of the kerogen and the clay is ensured. And then, adjusting the volume content of the kerogen based on the DEM theory to enable the volume ratio of the kerogen to the clay to reach a true value. And finally, taking the mixture of the clay and kerogen as a background phase mineral, adding the brittle mixture into the background phase mineral to obtain an intermediate equivalent medium corresponding to the organic-rich mud rock stratum, and determining the elastic modulus of the intermediate equivalent medium by utilizing the DEM theory.

And finally, adding pore fluid into each type of intermediate equivalent medium to obtain each type of final equivalent medium, and determining the elastic modulus of each type of final equivalent medium based on a differential equivalent medium theory according to the elastic modulus of each type of intermediate equivalent medium, thereby obtaining the segmented salt-rock physical model.

The porosity is generally low in both salt and mudstone formations and does not meet the low frequency assumptions of the Gassmann theory. Based on the DEM theory, the pore fluid can be added into the background phase minerals as an inclusion based on the high-frequency hypothesis, so that the elastic modulus of the final equivalent medium is relatively accurately obtained.

S300: based on the constructed segmented inter-salt rock physical model, selecting a corresponding elastic modulus determination method according to the clay content and the kerogen content of the inter-salt stratum at the target depth, wherein the method comprises the following steps: and matching the clay content and the kerogen content of the salt-space stratum at the target depth with the clay content and the kerogen content of each type of intermediate equivalent medium in the sectional type salt-space rock physical model, determining the type of the intermediate equivalent medium corresponding to the salt-space stratum at the target depth according to the matching result, and using the elastic modulus determination method corresponding to the intermediate equivalent medium of the type as the elastic modulus determination method of the salt-space stratum at the target depth.

For example, if the clay content and the kerogen content of the salt-rich stratum at the target depth are 60% and 5%, the type of the intermediate equivalent medium corresponding to the salt-rich stratum at the target depth is determined to be an organic-rich shale layer, and the elastic modulus of the intermediate equivalent medium is determined based on the VRH average theory, the elastic modulus of the intermediate equivalent medium is determined based on the SCA + DEM theory, and the elastic modulus of the final equivalent medium is determined based on the DEM theory. Therefore, when the type of the intermediate equivalent medium is an organic-rich shale layer, the elastic modulus determination method of the final equivalent medium is used as the elastic modulus determination method of the saline-alkali formation at the target depth.

S400: determining an elastic modulus of the saline formation at the target depth using the selected elastic modulus determination method based on the mineral composition and porosity of the saline formation at the target depth, the elastic modulus including a bulk modulus and a shear modulus.

Specifically, the mineral composition and porosity of the salt-salt formation at the target depth may be input into the segmented salt-salt rock physical model, i.e., the elastic modulus of the salt-salt formation at the target depth may be calculated.

S500: an elasticity parameter describing the saline-alkali formation at the target depth is determined from the elastic modulus and the total density of the saline-alkali formation at the target depth.

The elastic parameters comprise at least one of longitudinal wave velocity and transverse wave velocity, and can also comprise derived elastic parameters such as Young modulus and the like, so that guidance is provided for finely describing the reservoir.

Specifically, when the elastic parameter includes a longitudinal wave velocity, determining the elastic parameter of the saline-alkali formation at the target depth according to the elastic modulus and the total density of the saline-alkali formation corresponding to the target depth, including: calculating the compressional wave velocity of the salt formation at the target depth according to the following formula:

wherein v is_pThe longitudinal wave velocity, K is the bulk modulus obtained through the sectional type rock physical model between the salts, mu is the shear modulus obtained through the sectional type rock physical model between the salts, and rho is the total density of the stratum between the salts corresponding to the target depth;

when the elastic parameters include shear wave velocity, determining the elastic parameters of the saline formation at the target depth according to the elastic modulus and the total density of the saline formation corresponding to the target depth, including: calculating the shear wave velocity of the salt formation at the target depth according to the following formula:

wherein v is_sFor shear wave velocity, μ is the shear modulus obtained by the segmented intersalt petrophysical model, and ρ is the total density of the intersalt formation corresponding to the target depth.

The method for determining the elastic parameters of the salt-bearing stratum provided by the invention is used for constructing a sectional type salt-bearing rock physical model aiming at the salt-bearing stratum with violent longitudinal lithology change and strong interbeddability, and can be used for selecting a proper sub-model for operation aiming at different stratums. The selection process is based on the volume fraction of the key minerals and is driven by data, so that the interference of human factors is reduced. The requirements that the modeling idea of the conventional single model cannot meet are met.

The difference between the salt formation and the mudstone formation is not only the simple difference of the mineral content, but also the difference of the coupling mechanism between the minerals. The method and the device provide corresponding equivalent simulation ideas aiming at different coupling mechanisms, and are beneficial to improvement of prediction precision of different layer sections.

Example two

The present example will use the present method to predict the compressional and shear wave velocities of the intersalt formation. According to the logging curve of a well, the logging of the salt rock stratum shows low GR, high speed, low density and low porosity, and the logging of the salt stratum shows high GR, low speed, medium density and high porosity.

FIG. 4 is a flow chart of reservoir prediction based on a segmented inter-salt petrophysical model according to an embodiment of the present application. And obtaining mineral components, porosity and total density of the saline stratum at the target depth through analyzing logging information, inputting the data into a sectional type saline stratum rock physical model, outputting the volume modulus and shear modulus of the saline stratum at the target depth, and obtaining elastic parameters such as longitudinal and transverse wave speeds, Young modulus and the like for describing the saline stratum by calculation according to the volume modulus and the shear modulus.

FIG. 5A is a prediction of the compressional and shear wave velocities for a well according to conventional DEM theory; FIG. 5B is a prediction of the compressional-compressional velocity of a well according to one embodiment of the present application.

Comparing fig. 5A and 5B, it can be seen that both models can achieve more accurate simulation for the longitudinal wave velocity, and the prediction accuracy is higher. However, for the transverse wave velocity with higher measurement cost and generally less data, the prediction result of the elastic parameter provided by the application is superior to that of the traditional method based on the DEM theory.

Since the model considers the physical characteristics of different stratum types, particularly in two types of stratum segments of a mudstone blocking layer (the position indicated by a black arrow in fig. 5A and 5B) and a salt rock stratum (the position indicated by a white arrow in fig. 5A and 5B), the accuracy of the shear wave velocity prediction is obviously higher than that of the traditional method.

Therefore, the applicability of the segmented salt rock physical model is high, the accuracy of the longitudinal and transverse wave speed and the related elastic parameter obtained through prediction based on the model constructed by the method is obviously higher than that of a conventional method, and the remarkable progress of the method is proved.

EXAMPLE III

An embodiment of the present application provides a storage medium storing a computer program, wherein the computer program, when executed by a processor, performs the steps of the method for determining an elastic parameter of a salt formation as described above.

Example four

Embodiments of the present application provide a computer device comprising a processor and a storage medium having stored thereon program code which, when executed by the processor, carries out the steps of the method for determining an elasticity parameter of an intersalt formation as described above.

Wherein the processor is configured to perform all or a portion of the steps of the method for determining a salt formation elastic parameter of the first embodiment. The storage medium is used to store various types of data, which may include, for example, instructions for any application or method in the computer device, as well as application-related data.

The Processor may be an Application Specific Integrated Circuit (ASIC), a Digital Signal Processor (DSP), a Digital Signal Processing Device (DSPD), a Programmable Logic Device (PLD), a Field Programmable Gate Array (FPGA), a Processor, a microprocessor, or other electronic components, and is configured to perform the method for determining the salt elastic parameter in the first embodiment.

The Memory may be implemented by any type or combination of volatile and non-volatile Memory devices, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read-Only Memory (EPROM), Programmable Read-Only Memory (PROM), Read-Only Memory (ROM), magnetic Memory, flash Memory, magnetic or optical disk, or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by a computer.

It is noted that the terms used herein are merely for describing particular embodiments and are not intended to limit exemplary embodiments according to the present application, and when the terms "include" and/or "comprise" are used in this specification, they specify the presence of features, steps, operations, devices, components, and/or combinations thereof.

It should be understood that the exemplary embodiments herein may be embodied in many different forms and should not be construed as limited to only the embodiments set forth herein. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art, and should not be construed as limiting the present invention.