Method for estimating relative structure extrusion stress based on mudstone sound wave time difference inflection point

Abstract

The invention discloses a method for estimating relative structure extrusion stress based on mudstone interval transit time inflection points, and relates to the field of oil exploration. The method for estimating the relative tectonic extrusion stress based on the mudstone interval transit time inflection point comprises the following steps of screening out pure mudstone section interval transit time logging data, making a mudstone interval transit time curve, determining the mudstone interval transit time inflection point burial depth of a standard well, determining the mudstone interval transit time inflection point burial depth of an evaluation well, and calculating the relative tectonic extrusion stress. According to the method for estimating the relative structure extrusion stress based on the mudstone sound wave time difference inflection point, the magnitude of the relative structure extrusion stress of different well point areas is estimated through the inflection point difference of the mudstone sound wave time difference from elastic compaction to inelastic compaction, and the method has the advantages that parameters are easy to obtain, calculation is simple, and results are effective and reliable; the problems that the credibility of the tectonic extrusion stress value simulated by a conventional method is not high and the method can only be used for evaluating the relative magnitude of the tectonic extrusion stress are solved.

Description

Technical Field

[0001] This application relates to the field of petroleum exploration, and more specifically, to a method for estimating relative tectonic compressive stress based on the inflection point of sonic transit time in mudstone. Background Technology

[0002] Tectonic compressive stress is a crucial factor in evaluating formation deformation, predicting fractures, designing engineering fracturing schemes, and analyzing the causes of abnormal high pressure in compressional basins. While laboratory methods such as acoustic emission and quartz lattice dislocation methods can reconstruct the magnitude of tectonic compressive stress relatively well, the reliability of their experimental results is often low, and their high testing costs limit their application in regional stress assessments.

[0003] Currently, the main method for estimating regional tectonic compressive stress is the finite element method. This method can estimate the magnitude of tectonic compressive stress, but due to the lack of constraints, the simulated tectonic compressive stress values ​​are not very reliable and are only used to evaluate the relative magnitude of tectonic compressive stress. Summary of the Invention

[0004] The purpose of this application is to provide a method for estimating relative tectonic compressive stress based on the inflection point of sonic transit time in mudstone. By utilizing the difference in the inflection point of sonic transit time from elastic compaction to inelastic compaction in mudstone, the relative tectonic compressive stress in different well point areas can be estimated. This method has the advantages of readily available parameters, simple calculation, and effective and reliable results.

[0005] This application is implemented as follows: This application provides a method for estimating relative tectonic compression stress based on the inflection point of sonic transit time in mudstone, including the following steps: Step 1: Select sonic transit time logging data for pure mudstone sections; Step 2: Create a sonic transit time curve for mudstone; Step 3: Determine the burial depth of the inflection point of the sonic transit time in mudstone in the standard well; Step 4: Determine the depth of the inflection point of the sonic transit time in the mudstone of the appraisal well; Step 5: Calculate the relative structural compressive stress.

[0006] In some alternative implementations, when screening sonic transit time logging data for pure mudstone sections, the sonic transit time logging data for mudstone sections of each well is screened based on the lithology data of each well, and the sonic transit time logging data for mudstone sections is retained.

[0007] In some alternative implementations, when constructing the sonic transit time curve for mudstone, the sonic transit time logging data of mudstone is plotted against the mudstone depth to create a depth-sonic transit time cross-plot, where the vertical axis represents depth in meters (m), and the horizontal axis represents sonic transit time values ​​on a logarithmic scale in μs·m. -1Or μs·ft -1 .

[0008] In some alternative implementations, when determining the inflection point depth of the mudstone sonic transit time of a standard well, wells in areas without structural compression stress or with weak structural compression stress are used as standard wells, and the depth of the mudstone sonic transit time inflection point of the standard well is regarded as the depth where the structural compression stress is zero.

[0009] In some alternative implementations, when determining the depth of the inflection point of the sonic transit time in the mudstone of the appraisal well, drilling is carried out in the tectonic compression development zone to determine the inflection point of the sonic transit time in the mudstone.

[0010] In some alternative implementations, the structural compression development zone includes a thrust fracture zone and a fold development zone.

[0011] In some alternative implementations, when calculating the relative tectonic squeezing stress, the burial depth of the sonic transit time in the appraisal well and the burial depth of the sonic transit time in the standard well are substituted into the following formula to calculate the tectonic squeezing stress σ. X =(Hh)ρg;where, σ X The relative structural compression stress is represented by H, which is the burial depth of the sonic transit time inflection point of mudstone in the standard well, h is the burial depth of the sonic transit time inflection point of mudstone in the appraisal well, ρ is the average density of the formation, and g is the gravitational acceleration.

[0012] The beneficial effects of this application are as follows: The method for estimating relative tectonic compressive stress based on the inflection point of sonic transit time in mudstone provided by this application includes the following steps: screening sonic transit time logging data of pure mudstone sections, generating sonic transit time curves for mudstone, determining the burial depth of the inflection point of sonic transit time in mudstone in standard wells, determining the burial depth of the inflection point of sonic transit time in appraisal wells, and calculating the relative tectonic compressive stress. The method for estimating relative tectonic compressive stress based on the inflection point of sonic transit time in mudstone provided by this application estimates the magnitude of relative tectonic compressive stress in different well point areas by utilizing the difference in the inflection point of sonic transit time from elastic compaction to inelastic compaction in mudstone. It has the advantages of readily available parameters, simple calculation, and effective and reliable results, solving the problems of low reliability of tectonic compressive stress values ​​simulated by conventional methods and their limitation to evaluating only the relative magnitude of tectonic compressive stress. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0014] Figure 1A flowchart illustrating the method for estimating relative tectonic compression stress based on the inflection point of acoustic transit time in mudstone, provided in an embodiment of this application; Figure 2 The inflection point diagram is shown in the method for estimating relative tectonic compression stress based on the inflection point of sonic transit time of mudstone provided in the embodiments of this application. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0016] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0017] The following describes in further detail the features and performance of the method for estimating relative tectonic compressive stress based on the inflection point of sonic transit time in mudstone, with reference to embodiments.

[0018] like Figure 1 As shown in the figure, this embodiment provides a method for estimating relative tectonic compression stress based on the inflection point of sonic transit time in mudstone, including the following steps: Step 1: Screening out sonic transit time logging data for pure mudstone sections; Taking the Kuqa Depression in the northern Tarim Basin as the study area, logging data and lithological data of each well were obtained, including wells such as Sha 45, Sha 49, Sha 54, Sha 57, Kela 1, Kela 2, Kela 3, Dina 201, and Yinan 2; the depth data of the mudstone section of each well were read, and the sonic transit time data in the logging data of each well were retained according to the depth of the mudstone section, thereby screening out the sonic transit time data of the mudstone section.

[0019] Step 2: Construct sonic transit time curves for mudstone. Compile the sonic transit time logging data of mudstone from each well in the study area with the mudstone depth into a depth-sonic transit time cross-plot in an Excel spreadsheet. The vertical axis represents depth (a linear axis, in meters), and the horizontal axis represents sonic transit time (a logarithmic axis, in μs·m). -1 .

[0020] Step 3: Determine the inflection point depth of the sonic transit time in mudstone in the standard well. In the Yakela-Luntai area of ​​the Kuqa Depression, where tectonic compression is very weak, wells Sha 45, Sha 54, Yaha 401, and Yangta 6 were selected. The inflection point depth of the sonic transit time in mudstone was determined to be 4000m, which is the inflection point depth H of the standard well. In areas without tectonic compression stress or with weak tectonic compression stress, the overlying pressure is the maximum principal stress. The porosity of mudstone will decrease regularly with the increase of overlying pressure. After the mudstone reaches a depth approximating its skeleton velocity, the rock transitions from elastic compaction to inelastic compaction, and its sonic transit time curve will gradually become a straight segment. This is the inflection point of the sonic transit time in mudstone. Wells in areas without tectonic compression stress or with weak tectonic compression stress are selected as standard wells, and the depth of their sonic transit time inflection point is regarded as the inflection point depth H where the tectonic compression stress is zero.

[0021] Step 4: Determine the burial depth of the sonic transit time inflection point in the appraisal well. A series of thrust and padlock structures have developed in the Kelasu structural belt, resulting in strong tectonic compression. Wells with good sonic transit time curves are selected: Kela 2, Kela 203, Kela 204, Kela 3, Dabei 1, Keshen 7, Dongqiu 6, Dongqiu 8, Yinan 2, Yinan 5, and Dina 22 and Ku 1. The sonic transit time inflection point is determined, which is the burial depth h of the sonic transit time inflection point in the appraisal well. Figure 2 As shown. In areas with well-developed tectonic compression, such as thrust faults and folds, mudstone is subjected to tectonic compression in addition to the compaction of the overlying strata. This combined effect of overlying strata pressure and tectonic compression results in complete compaction of the mudstone (leading to a mudstone sonic transit time inflection point). Therefore, the burial depth of the mudstone sonic transit time inflection point in appraisal wells in tectonic compression zones is less than that in standard wells. In this case, the tectonic compression stress of each well can be quantitatively estimated using the burial depth of the mudstone sonic transit time inflection point. Combined with the regional tectonic background of the study area, the mudstone sonic transit time curves of each well in the study area are observed to determine its mudstone sonic transit time inflection point h.

[0022] Step 5: Calculate the relative tectonic compressive stress. Given that H is 4000m, the sonic transit time inflection point h of wells Kela 1, Kela 2, Kela 3, Yinan 2, and Dina 201 is 2500m, and the sonic transit time inflection point h of well Ku 1 is 3300m. In the Kuqa Depression, take ρ as 2.35g / cm³. 3 g is 9.8 m / s 2 Substitute the above data into the calculation formula σ X = (Hh)ρg, the structural relative structural compression stress of each well area is calculated as shown in Table 1 below.

[0023] Table 1. Relative tectonic compressive stress in each well area

[0024] The method for estimating relative tectonic compressive stress based on the inflection point of sonic transit time in mudstone provided in this application estimates the magnitude of relative tectonic compressive stress in different well point areas by utilizing the difference in the inflection point of sonic transit time from elastic compaction to inelastic compaction in mudstone. It has the advantages of readily available parameters, simple calculation, and effective and reliable results. It solves the problems that the tectonic compressive stress values ​​simulated by conventional methods have low reliability and can only be used to evaluate the relative magnitude of tectonic compressive stress. It can effectively guide the implementation of the overall deployment plan and well location deployment for oil and gas exploration and development, and improve exploration and development efficiency.

[0025] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for estimating relative tectonic compressive stress based on the inflection point of acoustic transit time in mudstone, characterized in that, Includes the following steps: Step 1: Select sonic transit time logging data for pure mudstone sections; Step 2: Create a sonic transit time curve for mudstone; Step 3: Determine the burial depth of the inflection point of the sonic transit time in mudstone in the standard well; Step 4: Determine the depth of the inflection point of the sonic transit time in the mudstone of the appraisal well; Step 5: Calculate the relative structural compressive stress.

2. The method for estimating relative tectonic compressive stress based on the inflection point of acoustic transit time in mudstone according to claim 1, characterized in that, When selecting sonic transit time logging data for pure mudstone sections, the sonic transit time logging data for each well is selected based on the lithology data of each well, and the sonic transit time logging data for mudstone sections is retained.

3. The method for estimating relative tectonic compressive stress based on the inflection point of acoustic transit time in mudstone according to claim 1, characterized in that, When constructing the sonic transit time curve for mudstone, the sonic transit time logging data of mudstone is plotted against the mudstone depth to create a depth-sonic transit time cross plot. The vertical axis represents depth in meters (m), and the horizontal axis represents sonic transit time values ​​on a logarithmic scale in μs·m. -1 Or μs·ft -1 .

4. The method for estimating relative tectonic compressive stress based on the inflection point of acoustic transit time in mudstone according to claim 1, characterized in that, When determining the inflection point depth of the mudstone sonic transit time of a standard well, wells in areas without structural compression stress or with weak structural compression stress are used as standard wells, and the depth of the mudstone sonic transit time in a standard well is regarded as the depth where the structural compression stress is zero.

5. The method for estimating relative tectonic compressive stress based on the inflection point of acoustic transit time in mudstone according to claim 1, characterized in that, When determining the depth of the inflection point of the sonic transit time in mudstone in an appraisal well, drilling should be carried out in a tectonic compression development zone to determine the inflection point of the sonic transit time in mudstone.

6. The method for estimating relative tectonic compressive stress based on the inflection point of acoustic transit time in mudstone according to claim 5, characterized in that, The structural compression development zone includes a thrust fracture zone and a fold development zone.

7. The method for estimating relative tectonic compressive stress based on the inflection point of acoustic transit time in mudstone according to claim 1, characterized in that, When calculating the relative tectonic compression stress, the burial depth of the sonic transit time indices of mudstone in the appraisal well and the standard well is substituted into the following formula to calculate the tectonic compression stress σ. X =(Hh)ρg;where, σ X The relative structural compression stress is represented by H, which is the burial depth of the sonic transit time inflection point of mudstone in the standard well, h is the burial depth of the sonic transit time inflection point of mudstone in the appraisal well, ρ is the average density of the formation, and g is the gravitational acceleration.

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