Method and system for improving accuracy of post-stack wave impedance inversion result

Abstract

The invention provides a method and system for improving the accuracy of a post-stack wave impedance inversion result, and the method comprises the steps: obtaining logging information of a research work area, and building a low-frequency model based on channel integration speed inversion; applying the low-frequency model to post-stack deterministic inversion to obtain a post-stack longitudinal wave impedance inversion result under the constraint of the low-frequency model based on channel integral velocity inversion; according to the method, a low-frequency model which can be suitable for carbonate fractured-vuggy reservoirs, under-salt dolomite reservoirs and other types with high heterogeneity is obtained based on trace integral velocity inversion, and the problem that in practical application, a conventional stratum control well data interpolation low-frequency model is inconsistent with a real stratum in spatial change characteristics is solved; when the method is applied to post-stack wave impedance inversion, an inversion result with richer detail features and higher interpretability can be obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of seismic reservoir prediction and relates to a method and a system for improving the accuracy of post-stack wave impedance inversion results. Background Art

[0002] Wave impedance inversion in seismic reservoir prediction technology is a special seismic processing and interpretation technology that uses seismic data observed on the surface to solve under the constraints of known geological knowledge, drilling and logging data to obtain the wave impedance of the formation. Wave impedance inversion is usually divided into two categories: pre-stack inversion and post-stack inversion. The inversion method based on the convolution model theory organically combines seismic and logging, which can make up for the shortcomings of the band limitation of seismic data and obtain high-resolution inversion results. It is also one of the most commonly used inversion methods in reservoir prediction. The main role of the low-frequency model is to supplement the missing low-frequency information of the seismic data and reduce the multi-solution of the inversion. However, the establishment of the low-frequency model needs to be as close to the actual formation conditions as possible. An incorrect low-frequency model will cause the inversion results to deviate seriously from the true solution. Therefore, how to establish a more accurate low-frequency model has become a key issue. Conventionally, the low-frequency model in the inversion is established by the logging data interpolation and extrapolation method based on the constraints of the seismic interpretation horizon. The applicable conditions of this method are that the stratum changes are relatively stable and have good lateral continuity, and the following conditions must also be met: ① The seismic horizons and faults can be interpreted and meet the requirements of three-dimensional modeling; ② The research area requires logging information of the wells that have been drilled, and the wells that have been drilled are evenly distributed in the research area and have certain quantity requirements; ③ The strata in the research area have layered distribution characteristics and have spatial proximity similarity. However, there are various problems in actual exploration. For example, many exploration research areas have no information on wells that have been drilled, or the reservoir types are carbonate fracture-cavity type, subsalt dolomite and other highly heterogeneous targets that cannot meet the characteristics of layered distribution. Therefore, the use of interpolation and extrapolation methods similar to horizon control to establish low-frequency models will definitely not obtain a relatively accurate initial model, thereby affecting the accuracy of the final inversion results.

[0003] The theoretical background of the seismic trace convolution model and the trace integration algorithm can be briefly explained as follows: The reflection coefficient is defined as the ratio of the reflected wave amplitude to the incident wave amplitude, and the calculation formula is ρ is the rock density, α is the P-wave velocity, and I is the P-wave impedance (the product of velocity and density). The subscripts represent the numbers of the upper and lower layers of the reflection interface. From the calculation formula, we can see that the reflection coefficient can be regarded as the ratio of the wave impedance change to the average value of twice the wave impedance. Usually, the change in formation density is smaller than the change in velocity. Therefore, if the density is assumed to be a constant, the reflection coefficient equation can be further simplified to Where i is the sampling number. Therefore, the reflection coefficient can be obtained by taking the derivative of the acoustic logging curve, and the reflection coefficient sequence can be expressed as function R(t) On the other hand, the inverse process of obtaining the synthetic acoustic logging curve from the reflection coefficient to the layer velocity requires integration, which is the theoretical basis of the Dow integral algorithm. The Dow integral calculation formula, which is widely used, is: Here I0 represents the initial background impedance value. Usually R(t) is calculated directly using the seismic trace control value range. The trace integral inversion method is simple and direct and does not rely on logging data. It is often used in the early stages of exploration. Its results directly reflect the velocity changes of the rock formations. However, due to the inherent bandwidth limitations of earthquakes, the resolution is low, and the absolute wave impedance or absolute velocity of the formation cannot be obtained. Moreover, the initial background impedance is usually difficult to accurately give. In addition, the overall calculation result is relatively rough when the seismic trace control value range is directly used as the reflection coefficient and then integrated to obtain the exponential power.

[0004] Although the industrial application of post-stack inversion is relatively mature, how to solve the problem of inaccurate low-frequency model establishment has always been a key factor restricting the accuracy of post-stack inversion, especially the establishment of low-frequency models for reservoirs with strong heterogeneity. This is also a key issue that the industry has been committed to solving. Summary of the invention

[0005] In order to solve the problem in the prior art that the establishment of low-frequency models in post-stack wave impedance inversion is inaccurate and thus affects the quality of inversion results, the present invention provides a method and system for improving the accuracy of post-stack wave impedance inversion results, which mainly involves the establishment of low-frequency models in post-stack inversion, forming a low-frequency model that can be applied to carbonate fracture-vuggy reservoirs, Cambrian sub-salt dolomite reservoirs and other types of reservoirs with strong heterogeneity, and solves the difficult problem of inconsistency between the low-frequency model of conventional stratum-controlled well data interpolation and the spatial variation characteristics of the real formation in practical applications.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for improving the accuracy of post-stack impedance inversion results, the specific steps are:

[0007] S1 obtains the well logging data of the study area and establishes a low-frequency model based on trace integral velocity inversion to obtain the longitudinal wave impedance volume P of the entire work area. imp (t);

[0008] S2 applies the low-frequency model to post-stack deterministic inversion to obtain post-stack P-wave impedance inversion results under the constraints of the low-frequency model based on trace-integrated velocity inversion;

[0009] In S1, the trace-integrated velocity inversion is used to characterize the absolute value of the P-wave velocity of the formation in the study area.

[0010] Furthermore, in S1, establishing a low-frequency model based on track-integrated velocity inversion has the following steps:

[0011] S1.1 Establish the trace-integrated velocity inversion, and obtain the P-wave velocity body V(t) of the entire study area based on the trace-integrated velocity inversion;

[0012] S1.2 Time-depth calibration is performed on the wells that have been drilled in the study area, and the P-wave velocity body V(t) of the entire study area is combined to extract the P-wave velocity pseudo-well curve υ(t) along the well trajectory;

[0013] S1.3 Obtain the well logging curves of the wells drilled in the study area and obtain the longitudinal wave impedance curve p imp (t);

[0014] S1.4 Perform curve fitting to establish the drilled P-wave velocity pseudo-well curve υ(t) and P-wave impedance curve p imp (t), denoted as p imp =f(υ);

[0015] S1.5 Substitute the longitudinal wave velocity volume V(t) of the entire study area into the relationship p imp =f(υ), the longitudinal wave impedance of the entire work area is obtained imp (t), that is, the low-frequency model based on trace-integrated velocity inversion is obtained.

[0016] Furthermore, the specific formula of the P-wave velocity body V(t) in the entire study area is obtained based on the trace integrated velocity inversion as follows:

[0017]

[0018] Among them, V0(t) is the seismic velocity field, Rc(t) is the seismic trace controlled to the reflection coefficient value range, and K0 is the velocity fusion proportional factor.

[0019] Furthermore, the calculation formula of the seismic trace Rc(t) controlled within the reflection coefficient range is as follows:

[0020]

[0021] Where S(t) is the seismic trace and m is the reflection coefficient control factor.

[0022] Furthermore, the numerical variation range ΔV of the longitudinal wave velocity V in the logging curve is obtained, and the velocity fusion proportional factor K0 of the work area is determined according to the numerical variation range ΔV.

[0023] Furthermore, the speed fusion proportional factor K0 calculation formula is as follows:

[0024] max|ΔV|≤K0.

[0025] Furthermore, the range of the longitudinal wave impedance P of the formation in the study area is obtained [P min ,P max], the variation range of the reflection coefficient of the research area is determined according to the value range of the formation longitudinal wave impedance P, that is, the reflection coefficient control factor m is obtained.

[0026] Furthermore, the calculation formula of the reflection coefficient control factor m is as follows:

[0027]

[0028] The present invention also provides a system for improving the accuracy of post-stack wave impedance inversion results by using the above method, comprising:

[0029] The low-frequency model building module is used to obtain the logging data of the research area and build a low-frequency model based on the track integral velocity inversion to obtain the longitudinal wave impedance volume P of the entire work area. imp (t);

[0030] The post-stack deterministic inversion module is used to apply the low-frequency model to the post-stack deterministic inversion to obtain the post-stack P-wave impedance inversion result under the constraint of the low-frequency model based on the trace-integrated velocity inversion.

[0031] Furthermore, the low-frequency model building module includes:

[0032] The trace-integrated velocity inversion establishment module is used to establish the trace-integrated velocity inversion and obtain the P-wave velocity volume of the entire study area based on the trace-integrated velocity inversion;

[0033] The pseudo-well curve acquisition module is used to calibrate the time and depth of the wells drilled in the study area, and extract the P-wave velocity pseudo-well curve υ(t) along the well trajectory in combination with the P-wave velocity body V(t) of the entire study area;

[0034] The longitudinal wave impedance curve acquisition module is used to obtain the well logging curves of the wells drilled in the research area and obtain the longitudinal wave impedance curve p imp (t);

[0035] Curve fitting module, used for curve fitting, to establish the drilled P-wave velocity pseudo-well curve υ(t) and P-wave impedance curve p imp (t), denoted as p imp =f(υ);

[0036] The longitudinal wave impedance calculation module is used to substitute the longitudinal wave velocity body V(t) of the entire study area into the relationship p imp =f(υ), the longitudinal wave impedance of the entire work area is obtained imp (t).

[0037] Compared with the prior art, the present invention has at least the following beneficial effects:

[0038] The present invention proposes a method for improving the accuracy of post-stack wave impedance inversion results, and establishes a low-frequency model for trace-integrated velocity inversion considering seismic disturbance. Compared with the original layered interpolation initial model, the model is more consistent with the spatial variation characteristics of seismic data, and can be applied to the establishment of low-frequency models of carbonate fracture-vuggy reservoirs, dolomite reservoirs and other types with strong heterogeneity. The model can also be used as a low-frequency model for exploration areas with few wells or even no wells, and seismic inversion based on the low-frequency model is carried out. For the establishment of low-frequency models that do not conform to layered medium interpolation, the method is an innovative volume-constrained spatial modeling method, which can effectively solve the problem of inconsistent spatial variation characteristics of interpolation of layer-controlled well data. Compared with the inversion results of conventional low-frequency model establishment methods, the post-stack deterministic inversion results constrained by the low-frequency model of the present invention can better conform to geological laws and understandings, and the inversion results have richer detailed features and stronger interpretability.

[0039] The trace-integrated velocity inversion of the present invention can effectively solve the problem of mismatch between the actual seismic trace amplitude and the reflection system order of magnitude existing in the conventional trace-integrated theory by optimizing and controlling the numerical range of the seismic trace amplitude. At the same time, the seismic velocity is proportionally integrated with the traditional trace-integrated inversion result, and the seismic velocity field is combined as a large background trend, thereby obtaining a physically meaningful trace-integrated velocity inversion result, which is used to characterize the absolute value of the longitudinal wave velocity of the formation in the study area instead of the relative change value. This can effectively solve the problem of large difference in the value range of the inversion result caused by the difference in the amplitude values ​​of different working areas or new and old seismic data in the practical application of the traditional trace-integrated inversion.

[0040] The velocity volume V(t) of the work area obtained by the trace-integrated velocity inversion of the present invention can be directly used as a velocity inversion result in reservoir prediction research. It can also be used as a low-frequency model for exploration areas with few wells or even no wells to carry out model-based seismic inversion. It can be regarded as a data-driven volume-constrained space modeling method, which can effectively solve the problem of inconsistent spatial variation characteristics of layer-controlled well interpolation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a comparison diagram of the same arbitrary line section in a dolomite reservoir research area.

[0042] Figure 2 For this research area and Figure 1 Comparison of spectrum analysis corresponding to the same section.

[0043] Figure 3 This is a comparison chart of the logging curves of three drilled wells in the study area and the seismic velocity and trace integrated velocity inversion results.

[0044] Figure 4The plan views of the average longitudinal wave impedance of the target layer of the conventional low-frequency model and the low-frequency model based on the trace integral velocity inversion method, wherein (a) is the low-frequency model established by the conventional layer-controlled well interpolation method, and (b) is the low-frequency model established by the method proposed in the present invention.

[0045] Figure 5 This is the result section of post-stack P-wave impedance inversion constrained by the low-frequency model established using the conventional layer-controlled well interpolation method.

[0046] Figure 6 This is a profile of the post-stack longitudinal wave impedance inversion results using the low-frequency model constraints of the present invention.

[0047] Figure 7 The plan views of the average longitudinal wave impedance of the target layer from the post-stack longitudinal wave impedance inversion results constrained by the conventional low-frequency model and the low-frequency model of the present invention: (a) conventional method (b) method of the present invention. DETAILED DESCRIPTION

[0048] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0049] The present invention proposes a method for improving the accuracy of post-stack wave impedance inversion results, and the specific steps are:

[0050] 1. Obtain well logging data in the study area;

[0051] 2. Establish a low-frequency model based on trace integral velocity inversion to obtain the longitudinal wave impedance body P of the entire work area imp (t);

[0052] 2.1 Determine the calculation formula of the trace integral velocity inversion and obtain the P-wave velocity volume V(t) of the entire study area as follows:

[0053] 2.1.1 The present invention controls the relative velocity change degree by a certain proportional factor on the conventional trace integral inversion result, The difficult-to-determine I0 parameter term and the exponential power of e are improved and rewritten into a new calculation formula to characterize the velocity change difference. The velocity fusion proportional factor K0 is introduced to control the numerical range of the velocity disturbance change to make it consistent with the logging data of the actual study area. Then the seismic velocity field is fused as the background trend to obtain the physically meaningful trace integral velocity inversion result, which characterizes the absolute value of the P-wave velocity of the formation in the study area, rather than the relative change value. The specific calculation formula is:

[0054]

[0055] Among them, V0(t) is the seismic velocity field, Rc(t) is the seismic trace controlled to the range of the reflection coefficient value, and the velocity fusion proportional factor K0 that controls the degree of change needs to be selected according to the actual drilling situation in the study area. When there is no well, it can also be selected according to the drilling situation in the neighboring area.

[0056] 2.1.2 Determination of seismic trace Rc(t) within the range of reflection coefficient

[0057] In order to solve the problem that the magnitude of the reflection coefficient in the actual seismic trace amplitude does not match that in the conventional trace integration theory, and the result of the direct integration calculation using the seismic trace is rough, the present invention proposes a reflection coefficient control factor m to characterize the variation range of the reflection coefficient in the research area, and matches the numerical range of the seismic trace to the numerical range of the reflection coefficient. Compared with directly integrating with the seismic trace, this invention has a clear physical meaning, specifically:

[0058]

[0059] Where S(t) is the seismic trace, m is the reflection coefficient control factor, and the reflection coefficient control factor m can be calculated based on the formation wave impedance range in the study area or the drilled well information.

[0060] 2.2 Curve fitting, establishing the corresponding relationship between the P-wave velocity pseudo-well curve and the P-wave impedance curve

[0061] 2.2.1 After time-depth calibration of the selected wells in the work area, the P-wave velocity body V(t) of the entire study area obtained by the above calculation is extracted along the well trajectory to obtain the P-wave velocity pseudo-well curve υ(t);

[0062] 2.2.2 The longitudinal wave impedance curve p is calculated from the well logging curves of the wells selected in the work area. imp (t);

[0063] 2.2.3 The longitudinal wave impedance curve p imp The intersection diagram analysis and multivariate fitting of the P-wave velocity pseudo-well curve υ(t) and the P-wave velocity pseudo-well curve υ(t) are performed to establish the P-wave velocity pseudo-well curve υ(t) fitting calculation P-wave impedance curve p imp (t), denoted as p imp =f(υ), thus establishing the relationship between the P-wave impedance and the P-wave velocity in the drilled area;

[0064] 2.3 Calculate the longitudinal wave impedance P of the entire work area imp (t), obtain the low-frequency model based on trace-integrated velocity inversion;

[0065] Get the P-wave velocity volume V(t) of the entire study area obtained in step 2.1, and combine it with the fitting relationship p obtained in step 2.2 imp=f(υ) for longitudinal wave impedance P imp The calculation of (t) is extended from the drilled area to the undrilled area, thus obtaining the longitudinal wave impedance body P of the entire work area. imp (t), and obtain the low-frequency model based on trace-integrated velocity inversion.

[0066] 3. The above low-frequency model is used for post-stack deterministic inversion;

[0067] Then the longitudinal wave impedance P of the entire work area obtained in step 2.3 is imp (t) It is used as the initial model in the standard process of post-stack deterministic inversion to replace the low-frequency model of conventional layer-controlled well interpolation (such as post-stack constrained sparse pulse inversion CSSI), and the post-stack P-wave impedance inversion results under the constraints of the low-frequency model based on trace-integrated velocity inversion can be obtained.

[0068] Preferably, in step 2.1.1, the well logging data of the research area are collected and sorted, the numerical variation range ΔV of the longitudinal wave velocity v in the well logging curve is obtained, and the velocity fusion proportional factor K0 of the work area is determined according to the numerical variation range ΔV, as follows:

[0069] max|ΔV|≤K0;

[0070] Preferably, in step 2.1.2, the range of the longitudinal wave impedance P of the formation in the study area is obtained [P min ,P max ], according to the range of the formation longitudinal wave impedance P, the variation range of the reflection coefficient in the research area is determined, that is, the reflection coefficient control factor m is obtained, specifically:

[0071]

[0072] Preferably, if the study area belongs to an exploration area without drilling data: in steps 2.1.1 and 2.1.2, the velocity fusion proportional factor K0 and the reflection coefficient control factor m can be selected by referring to the drilling information of the adjacent area; step 2.1.1 only needs to scale the longitudinal wave velocity body V(t) to the value range of the longitudinal wave impedance.

[0073] The present invention also provides a system for improving the accuracy of post-stack wave impedance inversion results by using the above method, comprising:

[0074] The low-frequency model building module is used to obtain the logging data of the research area and build a low-frequency model based on the track integral velocity inversion to obtain the longitudinal wave impedance volume P of the entire work area. imp (t);

[0075] The post-stack deterministic inversion module is used to apply the low-frequency model to the post-stack deterministic inversion to obtain the post-stack P-wave impedance inversion result under the constraint of the low-frequency model based on the trace-integrated velocity inversion.

[0076] Furthermore, the low-frequency model building module includes:

[0077] The trace-integrated velocity inversion establishment module is used to establish the trace-integrated velocity inversion and obtain the P-wave velocity volume of the entire study area based on the trace-integrated velocity inversion;

[0078] The pseudo-well curve acquisition module is used to calibrate the time and depth of the wells drilled in the study area, and extract the P-wave velocity pseudo-well curve υ(t) along the well trajectory in combination with the P-wave velocity body V(t) of the entire study area;

[0079] The longitudinal wave impedance curve acquisition module is used to obtain the well logging curves of the wells drilled in the research area and obtain the longitudinal wave impedance curve p imp (t);

[0080] Curve fitting module, used for curve fitting, to establish the drilled P-wave velocity pseudo-well curve υ(t) and P-wave impedance curve p imp (t), denoted as p imp =f(υ);

[0081] The longitudinal wave impedance calculation module is used to substitute the longitudinal wave velocity body V(t) of the entire study area into the relationship p imp =f(υ), the longitudinal wave impedance of the entire work area is obtained imp (t).

[0082] Example

[0083] The actual seismic data of a dolomite work area were used for post-stack wave impedance inversion. Firstly, the logging data of three drilled wells (including one sidetracked well) in the work area were collected and sorted out, and the velocity fusion proportional factor K0=600 and the reflection coefficient control factor m=0.25 of the work area were obtained.

[0084] The post-stack pure wave time domain seismic data and the time domain seismic velocity volume of the study area are sorted into a completely matched three-dimensional data volume (same data range and sampling points). The calculation formula of step 4 of the present invention is used to calculate the seismic data and the corresponding velocity volume one by one to obtain the longitudinal wave velocity volume of the entire study area. The profile display is shown in the attached figure. Figure 1 (c).

[0085] After the time-depth calibration of the drilled wells in the work area, the P-wave velocity pseudo-well curve obtained in step 4 is extracted along the well trajectory. The P-wave impedance curve calculated from the logging curves of the three drilled wells and the extracted pseudo-well curve are analyzed by intersection diagram. The depth range selection needs to include the target layer and multivariate fitting is performed to obtain the relationship:

[0086] p imp =f(υ)=-757757+566.523×υ-0.13636×υ 2 +1.0807×10 -5 ×v 3 .

[0087] By using this relationship to calculate the P-wave velocity body calculated for the entire work area, the P-wave impedance body of the entire work area can be obtained, which is the low-frequency model based on trace-integrated velocity inversion;

[0088] The average longitudinal wave impedance along the target layer can be obtained as shown in the following figure. Figure 4 (b) is the plane diagram of the average longitudinal wave impedance of the target layer of the low-frequency model based on the trace-integrated velocity inversion method, which can be used to control the reliability of the initial low-frequency model establishment.

[0089] The obtained low-frequency model based on trace-integrated velocity inversion is then used in the standard process of post-stack deterministic inversion to replace the low-frequency model of conventional layer-controlled well interpolation (the Jason post-stack constrained sparse pulse inversion CSSI used in this embodiment is quite mature in the industry, so the detailed steps and processes are not expanded here), and the post-stack P-wave impedance inversion result under the constraint of the low-frequency model based on trace-integrated velocity inversion can be obtained. The cross-section and plane display are shown in the attached Figure 6 With attached Figure 7 (b).

[0090] Figure 1 This is a comparison diagram of the same arbitrary line profile in a dolomite reservoir research area. The target layer is between the two interpreted horizon curves at 3800ms shown in the figure, where (a) is the post-stack time domain seismic data, (b) is the corresponding seismic velocity field, and (c) is the trace-integrated velocity inversion result calculated by the present invention. The trace-integrated velocity inversion method proposed in the present invention can fuse the relative change of velocity as a disturbance with the seismic velocity. By comparison, it can be seen that it has good consistency with the seismic data and has richer detailed information.

[0091] Figure 2 For this research area and Figure 1 Comparison of spectrum analysis corresponding to the same section, where (a) is the spectrum of post-stack time-domain seismic data, (b) is the spectrum of the corresponding seismic velocity field, and (c) is the spectrum of the trace-integrated velocity inversion result calculated by the present invention. The trace-integrated velocity inversion result of the present invention improves the high-frequency information based on the frequency band of the seismic velocity field, and can better supplement the low-frequency loss of the original seismic data.

[0092] Figure 3This is a comparison chart of the logging curves of three wells drilled in the research area with the seismic velocity and trace integrated velocity inversion results. The curve with the highest frequency is the P-wave velocity curve calculated by the well logging acoustic time difference, the flattest curve is the seismic velocity, and the curve with a certain amount of disturbance is the P-wave velocity calculated by the trace integrated velocity inversion. It can be seen that the P-wave velocity results of the trace integrated inversion are highly consistent with the well logging P-wave velocity, the frequency band is widened, and the detailed features are richer.

[0093] Figure 4 The plane diagrams of the average longitudinal wave impedance of the target layer of the conventional low-frequency model and the low-frequency model based on the trace integral velocity inversion method, where (a) is the low-frequency model established by the conventional layer-controlled well interpolation method, and (b) is the low-frequency model established by the method proposed in the present invention. Compared with the low-frequency model established by the conventional method, the wave impedance plane law of the target layer of the low-frequency model established by the method of the present invention is more consistent with the geological understanding of the work area and the drilling results.

[0094] Figure 5 This is a section of the post-stack P-wave impedance inversion results constrained by a low-frequency model established using the conventional layer-controlled well interpolation method. The target layer is between the two interpreted stratigraphic curves at approximately 3820ms and 3840ms on the left. The wave impedance of the dolomite reservoir exhibits a relatively high-resistance characteristic. It can be seen from the figure that only the high part near the drilled well on the left is developed in the target layer, while the drilled well on the right and other low parts are not developed. This is seriously inconsistent with the drilled well information on the right (both wells encountered dolomite reservoirs). In addition, the dolomite reservoir in this work area belongs to the development law of structure + lithology closure, and some development still exists in the low part of the structure. It can be seen that the post-stack inversion results constrained by the conventional low-frequency model cannot meet the needs of practical applications.

[0095] Figure 6 This is the result profile of the post-stack longitudinal wave impedance inversion using the low-frequency model constraint of the present invention. Figure 5 It can be clearly found that the prediction results of dolomite reservoirs within the target layer are highly consistent with the drilling results and geological knowledge of the work area, and can effectively solve the modeling problem of reservoirs with strong heterogeneity.

[0096] Figure 7 The following are the average P-wave impedance plane diagrams of the target layer of the post-stack P-wave impedance inversion results constrained by the conventional low-frequency model and the low-frequency model of the present invention: (a) conventional method (b) the method of the present invention. The comparison shows that the plane law of the final inversion result constrained by the low-frequency model of the present invention is more consistent with the geological knowledge of the work area and the drilling results, with richer detailed features and stronger interpretability.

Claims

1. A method for improving the accuracy of post-stack impedance inversion results, characterized in that: The specific steps are: S1 obtains the well logging data of the study area and establishes a low-frequency model based on trace integral velocity inversion to obtain the longitudinal wave impedance volume P of the entire work area. imp (t); S2 applies the low-frequency model to post-stack deterministic inversion to obtain post-stack P-wave impedance inversion results under the constraints of the low-frequency model based on trace-integrated velocity inversion; In S1, the trace-integrated velocity inversion is used to characterize the absolute value of the P-wave velocity of the formation in the study area.

2. A method for improving the accuracy of post-stack impedance inversion results according to claim 1, characterized in that: In S1, the establishment of a low-frequency model based on trace-integrated velocity inversion has the following steps: S1.1 Establish the trace-integrated velocity inversion, and obtain the P-wave velocity body V(t) of the entire study area based on the trace-integrated velocity inversion; S1.2 Time-depth calibration is performed on the wells that have been drilled in the study area, and the P-wave velocity body V(t) of the entire study area is combined to extract the P-wave velocity pseudo-well curve υ(t) along the well trajectory; S1.3 Obtain the well logging curves of the wells drilled in the study area and obtain the longitudinal wave impedance curve p imp (t); S1.4 Perform curve fitting to establish the drilled P-wave velocity pseudo-well curve υ(t) and P-wave impedance curve p imp (t), denoted as p imp =f(υ); S1.5 Substitute the longitudinal wave velocity volume V(t) of the entire study area into the relationship p imp =f(υ), the longitudinal wave impedance of the entire work area is obtained imp (t), that is, the low-frequency model based on trace-integrated velocity inversion is obtained.

3. A method for improving the accuracy of post-stack impedance inversion results according to claim 2, characterized in that: The specific formula for obtaining the P-wave velocity body V(t) in the entire study area based on the trace integral velocity inversion is as follows: V(t)=V0(t)+K0[2∫0 t Rc(t)dt] Among them, V0(t) is the seismic velocity field, Rc(t) is the seismic trace controlled to the reflection coefficient value range, and K0 is the velocity fusion proportional factor.

4. A method for improving the accuracy of post-stack impedance inversion results according to claim 3, characterized in that: The calculation formula of seismic trace Rc(t) controlled within the reflection coefficient range is as follows: Where S(t) is the seismic trace and m is the reflection coefficient control factor.

5. The method for improving the accuracy of post-stack impedance inversion results according to claim 3, characterized in that: The numerical variation range ΔV of the longitudinal wave velocity V in the logging curve is obtained, and the velocity fusion proportional factor K0 of the work area is determined according to the numerical variation range ΔV.

6. A method for improving the accuracy of post-stack impedance inversion results according to claim 5, characterized in that: The calculation formula of speed fusion proportional factor K0 is as follows: max|ΔV|≤K0.

7. The method for improving the accuracy of post-stack impedance inversion results according to claim 3, characterized in that: Obtain the range of the longitudinal wave impedance P of the formation in the study area [P min ,,P max ,], according to the value range of the formation longitudinal wave impedance P, the variation range of the reflection coefficient in the study area is determined, that is, the reflection coefficient control factor m is obtained.

8. A method for improving the accuracy of post-stack impedance inversion results according to claim 7, characterized in that: The calculation formula of reflection coefficient control factor m is as follows:

9. A system for improving the accuracy of post-stack wave impedance inversion results using the method of any one of claims 1 to 8, characterized in that: include: The low-frequency model building module is used to obtain the logging data of the research area and build a low-frequency model based on the track integral velocity inversion to obtain the longitudinal wave impedance volume P of the entire work area. imp (t); The post-stack deterministic inversion module is used to apply the low-frequency model to the post-stack deterministic inversion to obtain the post-stack P-wave impedance inversion result under the constraint of the low-frequency model based on the trace-integrated velocity inversion.

10. A system for improving the accuracy of post-stack wave impedance inversion results according to claim 9, characterized in that: The low-frequency model building module includes: The trace-integrated velocity inversion establishment module is used to establish the trace-integrated velocity inversion and obtain the P-wave velocity volume of the entire study area based on the trace-integrated velocity inversion; The pseudo-well curve acquisition module is used to calibrate the time and depth of the wells drilled in the study area, and extract the P-wave velocity pseudo-well curve υ(t) along the well trajectory in combination with the P-wave velocity body V(t) of the entire study area; The longitudinal wave impedance curve acquisition module is used to obtain the well logging curves of the wells in the research area and obtain the longitudinal wave impedance curve p imp (t); Curve fitting module, used for curve fitting, to establish the wellbore P-wave velocity pseudo-well curve υ(t) and P-wave impedance curve p imp (t), denoted as p imp =f(υ); The longitudinal wave impedance calculation module is used to substitute the longitudinal wave velocity body V(t) of the entire study area into the relationship p imp =f(υ), the longitudinal wave impedance of the entire work area is obtained imp (t).

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