Quantitative evaluation method and system for geological risk before drilling of shale gas stratum

Abstract

The invention discloses a shale gas stratum pre-drilling geological risk quantitative evaluation method and system, and relates to the technical field of shale gas exploration and development. The method comprises the following specific steps: performing drilling geological risk detection on a pre-selected well site by adopting multiple engineering geophysical prospecting methods to obtain geological abnormal data; interpreting the geological abnormal data to obtain interpreted data; constructing a drilling risk assessment index system according to the interpretation data and the engineering construction data; and performing risk assessment through the drilling risk assessment index system, and determining a risk index. According to the method, the advantages of a geophysical method are combined with the characteristics of engineering geology and hydrogeology, so that geological risk early warning and production guidance are provided for the 1000-meter shallow stratum drilling of shale gas drilling, the risk is quantitatively evaluated by establishing a risk evaluation index system and determining the risk index, the accuracy of evaluating the drilling risk is improved, and the risk assessment efficiency is improved. And a comprehensive and scientific basis is provided for well drilling decision making.

Description

Technical Field

[0001] The present invention relates to the technical field of shale gas exploration and development, and in particular to a method and system for quantitatively assessing geological risks before drilling in shale gas formations. Background Art

[0002] As a clean energy, the large-scale exploration, development and utilization of shale gas is of great significance to the national economy and energy security. During the drilling process of shale gas development, problems such as leakage, water invasion and drill bit drop are frequent in shallow karst and goaf areas, which extend the project cycle, increase costs and increase the risk of environmental impact, seriously restricting the scale and green development of shale gas. Therefore, risk assessment is crucial for decision makers to identify and evaluate drilling risks and take control measures. It also helps to significantly reduce the time cost of unnecessary downtime or downtime during drilling operations, thereby improving the safety, continuity and sustainability of oil and gas production. Therefore, how to conduct efficient and accurate drilling risk assessment of shale gas formations is an urgent problem to be solved by technicians in this field. Summary of the invention

[0003] The purpose of the present invention is to provide a method and system for quantitatively assessing geological risks of shale gas formations before drilling, so as to solve the problems raised in the background technology.

[0004] To achieve the above object, the present invention provides the following solutions: On the one hand, a method for quantitatively assessing geological risks before drilling in shale gas formations is provided, and the specific steps include the following:

[0005] Use a variety of engineering geophysical methods to detect drilling geological risks at pre-selected well locations and obtain geological anomaly data;

[0006] Interpreting the geological anomaly data to obtain interpreted data;

[0007] Constructing a drilling risk assessment index system based on the interpretation data and engineering construction data;

[0008] The risk assessment is performed through the drilling risk assessment index system, and the risk index is determined.

[0009] Preferably, the specific steps of using multiple engineering geophysical exploration methods to conduct drilling geological risk detection on pre-selected well locations are: using high-density electrical methods and seismic wave tomography to detect geological bodies shallower than 100 meters; using transient electromagnetic methods to detect geological bodies of 100-400 meters; and using audio magnetotelluric methods to detect multi-scale depth ranges of geological bodies of 400-1000 meters.

[0010] Preferably, it also includes engineering geological survey and hydrogeological survey of shale gas drilling, analyzing karst development strata, karst pipeline development direction, and coal-bearing strata to provide a scientific basis for survey line layout.

[0011] Preferably, the engineering construction data include: drilling fluid density deviation value, drilling fluid viscosity suitable value, drilling pressure, rotation speed, wellbore structure; the interpretation data include geological structure, broken zone distribution data, goaf data, cave and underground river distribution data, fault and fracture development degree data.

[0012] Preferably, the steps of constructing the drilling risk assessment index system are:

[0013] Using a hierarchical clustering method, the evaluation factors with similar functions in the interpretation data and the engineering construction data are automatically clustered into one category, and the clustering results form a hierarchical relationship with the indicators;

[0014] The analytic hierarchy process is used to calculate the weight values ​​of the evaluation factors in each category, and representative evaluation factors are screened out to construct the drilling risk assessment index system.

[0015] Preferably, clustering the evaluation factors by the hierarchical clustering method comprises the following steps:

[0016] Initialize the clusters, treat each evaluation factor as a separate initial cluster, and calculate the attribute similarity between the initial clusters;

[0017] Merge and update, in the iterative process of hierarchical clustering, two clusters with similarities are selected each time and merged to form a new cluster. In order to merge next time, it is necessary to calculate the similarity between the new cluster and other clusters. The merge-update process is iterated continuously until the clustering state satisfies that all nodes are clustered in one category. Finally, a complete tree structure is formed and the hierarchical clustering is terminated.

[0018] Preferably, the step of calculating the risk index is:

[0019] Each evaluation factor is quantified through the expert scoring method to obtain the quantitative value of the indicator;

[0020] The risk index is calculated using a weighted average method based on the weight values ​​of the evaluation factors and the quantitative values ​​of the indicators.

[0021] Preferably, the method further includes dividing the drilling risk into different levels according to the risk index; and providing different degrees of drilling risk warning according to the risk level.

[0022] On the other hand, a shale gas formation pre-drilling geological risk quantitative assessment system is provided, including a pre-drilling geophysical exploration module, an interpretation module, an assessment system construction module, and a risk assessment module; wherein:

[0023] The pre-drilling geophysical exploration module is used to detect drilling geological risks at pre-selected well locations using a variety of engineering geophysical exploration methods to obtain geological anomaly data;

[0024] The interpretation module is used to interpret the geological anomaly data to obtain interpreted data;

[0025] The evaluation system construction module is used to construct a drilling risk evaluation index system based on the interpretation data and engineering construction data;

[0026] The risk assessment module is used to perform risk assessment through the drilling risk assessment indicator system and determine the risk index.

[0027] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0028] 1. During the drilling process, the risk assessment method can be combined with real-time monitoring data to dynamically assess the drilling risks. Once the risk indicators are found to be beyond the safe range, an early warning can be issued in time, allowing the drilling team to take emergency measures to avoid accidents.

[0029] 2. By establishing a risk assessment indicator system and determining the risk index, the risk can be quantitatively assessed to provide a comprehensive and scientific basis for drilling decisions.

[0030] 3. An exploration method that integrates the use of multiple geophysical methods and combines engineering geological and hydrogeological surveys is adopted, combining the advantages of geophysical methods with the characteristics of engineering geology and hydrogeology, thereby providing geological risk warning and production guidance for drilling in strata shallower than 1,000 meters below the surface during shale gas drilling, and improving the accuracy of drilling risk assessment.

[0031] 4. Use the hierarchical clustering method to automatically cluster the evaluation factors with similar functions into one category. The clustering results form a hierarchical relationship with the indicators, instead of directly selecting the evaluation factors manually, so as to reduce the subjectivity in constructing the drilling risk assessment indicator system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0033] Figure 1 is a flow chart of the method of the present invention;

[0034] Figure 2 It is a schematic diagram of the drilling geological risk detection method of the present invention;

[0035] Figure 3 It is a system structure diagram of the present invention. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] The purpose of the present invention is to provide a method for quantitatively assessing geological risks before drilling in shale gas formations. Figure 1 As shown, the specific steps include the following:

[0038] S1. Use a variety of engineering geophysical methods to detect drilling geological risks at pre-selected well locations and obtain geological anomaly data;

[0039] S2. interpreting the geological anomaly data to obtain interpreted data;

[0040] S3. Construct a drilling risk assessment index system based on interpretation data and engineering construction data;

[0041] S4. Conduct risk assessment through the drilling risk assessment index system and determine the risk index.

[0042] Furthermore, it also includes engineering geological surveys and hydrogeological surveys on shale gas drilling, analyzing karst development strata, karst pipeline development direction, and coal-bearing strata to provide a scientific basis for survey line layout.

[0043] Further, such as Figure 2 As shown, in step S1, the specific steps of using multiple engineering geophysical exploration methods to conduct drilling geological risk detection for pre-selected well locations are: using high-density electrical method and seismic wave tomography method to detect geological bodies shallower than 100 meters; using transient electromagnetic method to detect geological bodies of 100-400 meters; and using audio magnetotelluric method to detect the multi-scale depth range of geological bodies of 400-1000 meters.

[0044] Specifically, according to the strata, structural trends and topography, with the wellhead as the center and a plane range of 300 meters in radius, the geophysical exploration methods and geophysical exploration lines are selected in a targeted manner: transient electromagnetic method and seismic wave tomography are laid out with a grid size of 10 meters × 50 meters horizontally and 10 meters × 100 meters vertically; high-density electrical method and audio-frequency magnetotelluric method are arranged in a "cross" shape; the high-density survey line is 720 meters long with a point spacing of 5 meters, and the audio-frequency magnetotelluric survey line is 1,480 meters long with a point spacing of 40 meters. The electrical distribution characteristics of the shallow strata below 1,000 meters underground are combined with geological results for comprehensive analysis and interpretation, and the risk data of adverse geological anomalies such as karst in the underlying strata of the wellhead are obtained.

[0045] Furthermore, in step S2, interpretation is performed by processing inversion to obtain interpretation data; wherein, the engineering construction data include: drilling fluid density deviation value, drilling fluid viscosity suitable value, drilling pressure, rotation speed, wellbore structure; the interpretation data include geological structure, broken zone distribution data, goaf data, cave and underground river distribution data, fault and fracture development degree data.

[0046] Furthermore, the steps of constructing the drilling risk assessment index system in step S3 are:

[0047] S31. Use the hierarchical clustering method to automatically cluster the evaluation factors with similar functions in the interpretation data and engineering construction data into one category, and the clustering results form a hierarchical relationship with the indicators;

[0048] S32. Use the hierarchical analysis method to calculate the weight value of the evaluation factors in each category, and screen out representative evaluation factors to construct a drilling risk assessment index system.

[0049] In step S31, clustering of evaluation factors by hierarchical clustering method includes the following steps:

[0050] S311, initializing clusters, taking each evaluation factor as a separate initial cluster, and calculating the attribute similarity between the initial clusters;

[0051] S312, merge and update. During the iterative process of hierarchical clustering, two clusters with similarities are selected each time and merged to form a new cluster. For the next merge, the similarity between the new cluster and other clusters needs to be calculated. The merge-update process is iterated continuously until the clustering state satisfies that all nodes are clustered in one category. Finally, a complete tree structure is formed and the hierarchical clustering is terminated.

[0052] Furthermore, in step S32, the specific steps of calculating the weight value using the hierarchical analysis method are as follows:

[0053] S321, constructing a judgment matrix, constructing a judgment matrix A according to the 9-scaling method;

[0054] S322, constructing an antisymmetric matrix B of the judgment matrix A;

[0055] S323, constructing the optimal transfer matrix C of the antisymmetric matrix B;

[0056] S324, constructing a quasi-optimal consistent matrix A* of the judgment matrix A;

[0057] S325, normalize the quasi-optimal consistent matrix A* to obtain a normalized matrix

[0058] S326. Calculate the normalized matrix The sum of each row of elements M i ;

[0059] S327, according to the normalized matrix The sum of each row of elements M i Calculate the weight values ​​of the evaluation factors in each category.

[0060] Furthermore, the step of calculating the risk index in step S4 is:

[0061] S41. Quantify each evaluation factor through expert scoring method to obtain the quantitative value of the indicator;

[0062] S42. Calculate the risk index by weighted average based on the weight values ​​of the evaluation factors and the quantitative values ​​of the indicators.

[0063] Furthermore, it also includes classifying drilling risks into different levels according to the risk index; and issuing different degrees of drilling risk warnings according to the risk level. According to the risk assessment results, formulate targeted risk control measures. For high-risk factors, take emergency measures to deal with them; for medium-risk factors, strengthen monitoring and management; for low-risk factors, keep paying attention and continuously improve them. Regularly update and adjust the risk assessment, and continuously optimize risk control measures as the drilling process progresses and new data is obtained.

[0064] On the other hand, a shale gas formation pre-drilling geological risk quantitative assessment system is provided. Figure 3 As shown, it includes pre-drilling geophysical exploration module, interpretation module, evaluation system construction module and risk assessment module; among them,

[0065] Pre-drilling geophysical exploration module, which is used to detect drilling geological risks at pre-selected well locations using a variety of engineering geophysical exploration methods and obtain geological anomaly data;

[0066] An interpretation module is used to interpret geological anomaly data to obtain interpretation data;

[0067] An assessment system building module is used to build a drilling risk assessment index system based on interpretation data and engineering construction data;

[0068] The risk assessment module is used to conduct risk assessment through the drilling risk assessment indicator system and determine the risk index.

[0069] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A method for quantitatively assessing geological risks before drilling in shale gas formations, characterized in that: The specific steps include the following: Use a variety of engineering geophysical methods to detect drilling geological risks at pre-selected well locations and obtain geological anomaly data; Interpreting the geological anomaly data to obtain interpreted data; Constructing a drilling risk assessment index system based on the interpretation data and engineering construction data; The risk assessment is performed through the drilling risk assessment index system, and the risk index is determined.

2. A method for quantitatively assessing geological risks before drilling in shale gas formations according to claim 1, characterized in that: The specific steps of using multiple engineering geophysical exploration methods to conduct drilling geological risk detection for pre-selected well locations are: using high-density electrical methods and seismic wave tomography to detect geological bodies shallower than 100 meters; using transient electromagnetic methods to detect geological bodies of 100-400 meters; and using audio-frequency magnetotelluric methods to detect multi-scale depth ranges of geological bodies of 400-1000 meters.

3. The method for quantitatively assessing geological risks before drilling in shale gas formations according to claim 1, characterized in that: It also includes engineering geological surveys and hydrogeological surveys of shale gas drilling, analysis of karst development strata, karst pipeline development direction, and coal-bearing strata, to provide a scientific basis for survey line layout.

4. The method for quantitatively assessing geological risks before drilling in shale gas formations according to claim 1, characterized in that: The engineering construction data include: drilling fluid density deviation value, drilling fluid viscosity suitable value, drilling pressure, rotation speed, and wellbore structure; the interpretation data include geological structure, broken zone distribution data, goaf data, cave and underground river distribution data, and fault and fracture development degree data.

5. The method for quantitatively assessing geological risks before drilling in shale gas formations according to claim 1, characterized in that: The steps of constructing the drilling risk assessment index system are as follows: Using a hierarchical clustering method, the evaluation factors with similar functions in the interpretation data and the engineering construction data are automatically clustered into one category, and the clustering results form a hierarchical relationship with the indicators; The analytic hierarchy process is used to calculate the weight values ​​of the evaluation factors in each category, and representative evaluation factors are screened out to construct the drilling risk assessment index system.

6. A method for quantitatively assessing geological risks before drilling in shale gas formations according to claim 5, characterized in that: The clustering of evaluation factors by the hierarchical clustering method includes the following steps: Initialize the clusters, treat each evaluation factor as a separate initial cluster, and calculate the attribute similarity between the initial clusters; Merge and update, in the iterative process of hierarchical clustering, two clusters with similarities are selected each time and merged to form a new cluster. In order to merge next time, it is necessary to calculate the similarity between the new cluster and other clusters. The merge-update process is iterated continuously until the clustering state satisfies that all nodes are clustered in one category. Finally, a complete tree structure is formed and the hierarchical clustering is terminated.

7. A method for quantitatively assessing geological risks before drilling in shale gas formations according to claim 5, characterized in that: The steps for calculating the risk index are: Each evaluation factor is quantified through the expert scoring method to obtain the quantitative value of the indicator; The risk index is calculated using a weighted average method based on the weight values ​​of the evaluation factors and the quantitative values ​​of the indicators.

8. A method for quantitatively assessing geological risks before drilling in shale gas formations according to claim 7, characterized in that: It also includes classifying the drilling risks into different levels according to the risk index; and providing different degrees of drilling risk warning according to the risk levels.

9. A shale gas formation pre-drilling geological risk quantitative assessment system, characterized in that: It includes pre-drilling geophysical exploration module, interpretation module, evaluation system construction module and risk assessment module; among them, The pre-drilling geophysical exploration module is used to detect drilling geological risks at pre-selected well locations using a variety of engineering geophysical exploration methods to obtain geological anomaly data; The interpretation module is used to interpret the geological anomaly data to obtain interpreted data; The evaluation system construction module is used to construct a drilling risk evaluation index system based on the interpretation data and engineering construction data; The risk assessment module is used to perform risk assessment through the drilling risk assessment indicator system and determine the risk index.

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