Faulted sand body connectivity evaluation method based on seismic data

Abstract

The application provides a fault two-plate sand body connectivity evaluation method based on seismic data, comprising the following steps: step 1, carrying out structural interpretation of a fault plane based on three-dimensional seismic data to form a fault plane planar structure map; step 2, using three-dimensional seismic data to perform layer flattening with the fault plane as a target layer, and establishing a layer flattening seismic data body; step 3, using the layer flattening seismic data body to extract attributes of the upper and lower plates of the fault respectively, and calculating a difference ratio A of the attributes on both sides of the fault; step 4, using the A value of a known open fault to determine the A value range of the sand body connectivity of the two plates of the fault, and defining the A value range as a threshold B, and determining the sand body connectivity of the two plates of the whole fault according to the B and the attribute graph A. The method is based on three-dimensional seismic data, fully utilizes logging data and is relatively simple to apply. The fault two-plate sand body layering connectivity can be effectively carried out in a three-dimensional seismic data coverage area, and a new method is provided for evaluating the feasibility of layering water injection between fault block reservoirs.

Description

Technical Field

[0001] This invention relates to the field of oilfield exploration and development technology, and in particular to a method for evaluating the connectivity of sand bodies on both sides of a fault based on seismic data. Background Technology

[0002] The eastern exploration area of ​​Shengli Oilfield features a wide variety of fault-block reservoirs across multiple strata, including shallow and red beds. Wells deployed near fault boundaries in these reservoirs often suffer from poor water injection effectiveness due to the small swept area after injection within the same fault block. However, for sand bodies with staggered connections between the two sides of a fault, this problem of small swept area can be solved by staggered water injection between the fault blocks, thereby improving the recovery rate of the fault-block reservoir. Evaluating the connectivity of staggered sand bodies between the two sides of a fault is crucial for determining the appropriate water injection strategy. Currently, commonly used evaluation methods primarily rely on qualitative analysis of lithological connections; however, lithological connection methods are difficult to quantify and have low precision, failing to meet the requirements for precise water injection in development.

[0003] With the widespread application of 3D seismic data and various data derived from its processing, fault imaging has become increasingly accurate. Conducting connectivity evaluations of the ground-bound sand bodies between the two fault blocks is of great significance for water injection in the development of fault-block cross-sections.

[0004] Chinese patent application CN201710376308.X discloses a method and apparatus for evaluating sand body connectivity. The method includes: establishing transversely connected sand body samples, longitudinally connected sand body samples, and internally connected sand body samples within a work area, and dividing each type of sand body sample into training samples and test samples; training the training samples of each type of sand body sample using a preset machine learning algorithm to establish a corresponding sand body connectivity prediction model; optimizing the corresponding sand body connectivity prediction model based on the test samples of each type of sand body sample to ensure that the prediction results of the corresponding sand body connectivity prediction model meet preset conditions; and evaluating the sand body connectivity of the sand body data corresponding to the sand body to be identified within the work area based on the optimized sand body connectivity prediction model to obtain the evaluation results. This application embodiment can improve the accuracy and efficiency of sand body connectivity evaluation.

[0005] Chinese patent application CN201611217596.6 discloses a method and apparatus for evaluating reservoir connectivity between injection wells and production wells. The method includes: obtaining designated reservoirs of the injection wells as designated reservoirs in a first designated reservoir set; selecting designated reservoirs connected to the production wells from the first designated reservoir set as designated reservoirs in a second designated reservoir set; obtaining designated reservoirs of the production wells as designated reservoirs in a third designated reservoir set; selecting designated reservoirs connected to the injection wells from the third designated reservoir set as designated reservoirs in a fourth designated reservoir set; and evaluating the connectivity of designated reservoirs between the injection wells and production wells based on the thickness values ​​of each designated reservoir in the first designated reservoir set, the thickness and permeability values ​​of each designated reservoir in the second designated reservoir set, the thickness values ​​of each designated reservoir in the third designated reservoir set, and the thickness and permeability values ​​of each designated reservoir in the fourth designated reservoir set.

[0006] Chinese patent application CN201510309557.8 discloses a method for identifying superimposed sand bodies using seismic forward modeling, belonging to the field of oilfield reservoir prediction technology. This invention first obtains the spectral range and dominant frequency of seismic data from the exploration area, as well as the rock physical parameters of the sand bodies. Then, based on the rock physical parameters of the sand bodies, it establishes geological forward modeling models for different superimposed sand body structures. Seismic forward modeling simulations are performed on different geological forward modeling models using the obtained spectral range and dominant frequency. Finally, the seismic forward modeling simulation results are compared with actual seismic reflections to determine the forward modeling result that can completely separate the waveforms of the superimposed sand bodies. The superimposed sand bodies are then identified based on this simulation result. This application uses seismic forward modeling technology to simulate the seismic reflection characteristics of different superimposed sand body structures, compares and analyzes them with actual seismic reflection profiles, identifies superimposed sand bodies, and confirms the connectivity of sand bodies, providing a basis for the overall evaluation and deployment of exploration and development.

[0007] The existing technologies described above are significantly different from the present invention and have failed to solve the technical problem we want to address. Therefore, we have invented a new method for evaluating the connectivity of sand bodies on both sides of a fault based on seismic data. Summary of the Invention

[0008] The purpose of this invention is to provide a seismic data-based method for evaluating the connectivity of sand bodies on both sides of a fault, which is simple to apply, establishes a layer-flattened seismic data volume along the fault plane based on the interpretation of the fault plane structure, and uses the layer-flattened seismic data volume to evaluate the connectivity of sand bodies on both sides of the fault.

[0009] The objective of this invention can be achieved through the following technical measures: a method for evaluating the connectivity of sand bodies on both sides of a fault based on seismic data, comprising:

[0010] Step 1: Based on 3D seismic data, perform structural interpretation of fault planes to generate fault plane structural maps;

[0011] Step 2: Using 3D seismic data, perform layer flattening with fault planes as the target layers, and establish a seismic data volume along the layer flattening.

[0012] Step 3: Extract attributes from the strata on the hanging wall and footwall of the fault using the layer-flattened seismic data volume, and calculate the attribute difference ratio A between the two sides of the fault.

[0013] Step 4: Use the known A value of the fault to determine the range of A values ​​for the connectivity of the sand bodies on both sides of the fault, and define it as threshold B. Based on B and attribute map A, determine the connectivity of the sand bodies on both sides of the fault.

[0014] The objective of this invention can also be achieved through the following technical measures:

[0015] In step 1, the three-dimensional seismic data, velocity data, and well data of the study area are comprehensively analyzed. Based on the three-dimensional seismic data, the structural interpretation of the fault plane is performed, and the fault plane structural map is obtained.

[0016] In step 2, three-dimensional seismic data is first used to flatten the fault layers explained in step 1 as the target layers. Then, a virtual flattened seismic data volume is established along the layer, and the virtual volume is converted into an actual flattened seismic data volume.

[0017] In step 2, the 0-hour plane in the flattened seismic data volume is the fault plane interpreted in the original seismic data volume.

[0018] In step 2, when establishing the virtual flattened seismic data volume, the values ​​of the upper and lower time windows must meet the time window requirements for subsequent layer attribute extraction.

[0019] In step 2, the hanging wall time at the fault plane of the seismic data volume is negative, and the absolute value increases with distance from the fault plane; while the hanging wall time at the corresponding fault plane is positive, and the value increases with distance from the fault plane.

[0020] In step 3, after setting the time window for the strata on the hanging wall and footwall of the fault using the ZZ attribute extraction method on the flattened seismic data, the attributes of the fault plane on the hanging wall and footwall are extracted, and the attribute interpolation ratio A on both sides of the fault plane is calculated.

[0021] In step 3, the formula for calculating the interpolation ratio A of the attributes on both sides of the fault is: A = A1 / (A1-A2), where A1 is the amplitude value of the strata on the hanging wall of the fault and A2 is the amplitude value of the strata on the footwall of the fault.

[0022] In step 4, the attribute difference ratio A at the fault where the two sand bodies are connected is analyzed, and a quantitative relationship between the attribute difference ratio and the sand body cross-layer connectivity is established. The range B of the fault attribute difference ratio A at the sand body connection when water injection at the cross-layer of the two faults is effective is clarified. Based on B, the attribute A of the entire fault is evaluated, and the connectivity of the two cross-layered sand bodies in the fault space is clarified.

[0023] This invention presents a method for evaluating the connectivity of sand bodies on both sides of a fault based on seismic data. After meticulously determining the fault morphology, a layer-flattened seismic data volume is established with the fault plane as the target layer. Using the ZZ attribute extraction method, upper and lower time windows are set on this volume, and attributes are extracted from the strata on both sides of the fault. The attribute difference ratio of the strata on both sides of the fault is then calculated. Simultaneously, based on the known attribute difference ratios corresponding to the fault at the point of cross-connection between sand bodies on both sides of the fault, a quantitative relationship between the attribute difference ratio and the cross-connection of sand bodies is established, clarifying the characterization threshold for cross-connection of sand bodies on both sides of the fault based on the attribute difference ratio. This method is based on 3D seismic data and makes full use of well logging data, making it relatively simple to apply. It can effectively assess the cross-connection of sand bodies on both sides of a fault in areas covered by 3D seismic data, providing a new method for evaluating the feasibility of cross-connection water injection between fault-block reservoirs. Attached Figure Description

[0024] Figure 1 This is a flowchart of a specific embodiment of a method for evaluating the connectivity of sand bodies on two sides of a fault based on seismic data, according to the present invention.

[0025] Figure 2 This is a longitudinal seismic profile of a plane where the original seismic data volume is interrupted, according to a specific embodiment of the present invention.

[0026] Figure 3 This is a planar structural diagram of the fracture surface in a specific embodiment of the present invention;

[0027] Figure 4 This is a seismic profile of the original seismic body along the fault plane in a specific embodiment of the present invention;

[0028] Figure 5 This is a schematic diagram of a flattened seismic data volume along a fault plane in a specific embodiment of the present invention;

[0029] Figure 6 This is a schematic diagram of a longitudinal seismic profile of a flattened seismic data volume along a fault plane in a specific embodiment of the present invention.

[0030] Figure 7 This is a root mean square amplitude attribute map of the disk on the cross-section in a specific embodiment of the present invention;

[0031] Figure 8This is a root mean square amplitude property diagram of the lower plate of the fracture surface in a specific embodiment of the present invention;

[0032] Figure 9 This is a graph showing the ratio of the root mean square amplitude attribute difference between the two disks at the fracture surface in a specific embodiment of the present invention.

[0033] Figure 10 In one specific embodiment of the present invention, a scatter plot is used to determine the connectivity attribute values ​​of the sand bodies on both sides of a fault and the height of the connected sand bodies. Detailed Implementation

[0034] To make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings.

[0035] The present invention provides a method for evaluating the connectivity of sand bodies on both sides of a fault based on seismic data. This method includes: interpreting the fault plane structure using 3D seismic data to create a fault plane structural map; performing layer flattening using the fault plane as the target layer based on the 3D seismic data and establishing a layer flattened seismic data volume; extracting attributes from the strata of the hanging wall and footwall of the fault using the layer flattened seismic data volume, with the attributes of the strata on the hanging wall designated as A1 and the attributes of the strata on the footwall designated as A2; calculating the attribute difference ratio A = (A1-A2) / A1 at the point of cross-connection of sand bodies on both sides of the fault, and defining the range of the attribute difference ratio when the sand bodies on both sides of the fault are cross-connected, which is set as a threshold B. Based on B and the attribute map A, the connectivity of the sand bodies on both sides of the fault is finally determined.

[0036] The following are several specific embodiments of the application of the present invention.

[0037] Example 1

[0038] In a specific embodiment 1 of the present invention, the method for evaluating the connectivity of sand bodies on both sides of a fault based on seismic data includes the following steps:

[0039] In step 1, the three-dimensional seismic data, velocity data, and well data of the study area are comprehensively analyzed. Based on the three-dimensional seismic data, the structural interpretation of the fault plane is performed, and the planar structural map of the fault plane is obtained.

[0040] In step 2, the interpolated layers of the fault plane are used as the target layers for layer flattening based on the 3D seismic data. Then, a virtual flattened seismic data volume along the fault plane is established by taking appropriate time windows above and below the target layer. Finally, the virtual volume is converted into an actual flattened seismic data volume.

[0041] In step 3, after setting the time window for the hanging wall and footwall strata of the fault using the ZZ attribute extraction method on the flattened seismic data, the attributes of the fault plane of the hanging wall and footwall are extracted, and the attribute interpolation ratio A on both sides of the fault plane is calculated, A = A1 / (A1-A2), where A1 is the amplitude value of the hanging wall strata and A2 is the amplitude value of the footwall strata.

[0042] In step 4, the attribute difference ratio A at the fault where the two sand bodies are connected is analyzed, and a quantitative relationship between the attribute difference ratio and the sand body cross-layer connectivity is established. The range B of the fault attribute difference ratio A at the sand body connection when water injection at the cross-layer of the two faults is effective is clarified. Based on B, the attribute A of the entire fault is evaluated, and the connectivity of the two cross-layered sand bodies in the fault space is clarified.

[0043] Example 2

[0044] In a specific embodiment 2 of the present invention, such as Figure 1 As shown, Figure 1 This is a flowchart of a method for evaluating the connectivity of sand bodies on two sides of a fault based on seismic data, according to the present invention.

[0045] In step 101, a comprehensive analysis of the 3D seismic data, velocity data, and well data of the study area is performed, and the structural interpretation of fault planes is conducted based on the 3D seismic data (e.g., Figure 2 ), to obtain the planar structural diagram of the fault plane (e.g. Figure 3 ). Figure 3 Using 3D seismic data, a detailed structural interpretation of the target fault is performed to generate a fault plane structural map. The process proceeds to step 102;

[0046] In step 102, layer flattening is performed using 3D seismic data with fault planes as the target layers, and a layer-flattened seismic data volume is established (e.g., ...). Figure 4 Then, appropriate time windows are selected above and below the target layer to create a virtual flattened seismic data volume along the fault plane, and then this virtual volume is converted into an actual flattened seismic data volume (e.g., Figure 5 , Figure 6 ), Figure 6 In the diagram, H represents the fault plane interpreted from the original seismic data volume. The workflow proceeds to step 103;

[0047] In step 103, attributes are extracted from the strata of the hanging wall and footwall of the fault using the layer-flattened seismic data volume, and the attribute difference ratio A on both sides of the fault is calculated, A = A1 / (A1-A2), where A1 is the attribute value of the strata on the hanging wall and A2 is the attribute value of the strata on the footwall (e.g., ...). Figure 7 , Figure 8 , Figure 9 ), Figure 7 In the middle, the time window range is -30 at the top and 0 at the bottom; Figure 8 In the middle, the time window range is 0 at the top and 30 at the bottom. The process proceeds to step 104;

[0048] In step 104, the property difference ratio A at the fault where the two sandstone blocks are connected is analyzed, and a quantitative relationship between the property difference ratio and the sandstone block cross-layer connectivity is established. The range B of the fault property difference ratio A at the sandstone block connectivity when water injection at the cross-layer connection between the two fault blocks is effective is clarified. Figure 10 Based on B, the entire fault attribute A is evaluated to clarify the connectivity of the two staggered sand bodies in the fault space.

[0049] Example 3

[0050] In a specific embodiment 3 of this invention, the method for evaluating the connectivity of sand bodies on both sides of a fault based on seismic data, after accurately determining the structural morphology of the fault plane, establishes a layer-flattened seismic data volume with the fault plane as the target layer. On the layer-flattened seismic data volume, after setting the upper and lower time windows using the ZZ attribute extraction method, attributes are extracted from the strata on both sides of the fault, and the attribute difference ratio of the strata on both sides of the fault is calculated. Simultaneously, based on the known attribute difference ratio of the fault corresponding to the cross-connection of sand bodies on both sides of the fault, a quantitative relationship between the attribute difference ratio and the cross-connection of sand bodies is established, clarifying the characterization threshold for cross-connection of sand bodies on both sides of the fault based on the attribute difference ratio. This method is based on 3D seismic data and makes full use of well logging and other data, and is relatively simple to apply. In areas covered by 3D seismic data, the cross-layer connectivity of sand bodies on both sides of a fault can be effectively investigated, providing a new method for evaluating the feasibility of cross-layer water injection between fault-block reservoirs. This method has broad application value in developing cross-layer water injection between fault-block reservoirs in the Sha-2 Member, Sha-4 Lower Member, and Kongdian Formation of the Jiyang Depression.

[0051] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0052] Except for the technical features described in the specification, all other technologies are known to those skilled in the art.

Claims

1. A method for evaluating faulted two-plate sand body connectivity based on seismic data, characterized in that, This method for evaluating the connectivity of sand bodies on both sides of a fault based on seismic data includes: Step 1: Based on 3D seismic data, perform structural interpretation of fault planes to generate fault plane structural maps; Step 2: Using 3D seismic data, perform layer flattening with fault planes as the target layers, and establish a seismic data volume along the layer flattening. Step 3: Extract attributes from the strata on the hanging wall and footwall of the fault using the layer-flattened seismic data volume, and calculate the attribute difference ratio A between the two sides of the fault. Step 4: Use the known A value of the fault to determine the range of A values ​​for the connectivity of the sand bodies on both sides of the fault, and define it as threshold B. Based on B and attribute map A, determine the connectivity of the sand bodies on both sides of the fault. In step 2, firstly, using 3D seismic data, the fault horizon explained in step 1 is used as the target layer for layer flattening. Then, a virtual flattened seismic data volume is established along the layer, and then the virtual volume is converted into an actual flattened seismic data volume. In step 2, the 0-hour plane in the flattened seismic data volume is the fault plane interpreted in the original seismic data volume; In step 2, when establishing the virtual flattened seismic data volume, the values ​​of the upper and lower time windows must meet the time window requirements for subsequent layer attribute extraction. In step 2, the hanging wall time at the fault plane of the seismic data volume is negative, and the absolute value increases with distance from the fault plane; while the hanging wall time at the corresponding fault plane is positive, and the value increases with distance from the fault plane. In step 3, after setting the time window for the strata on the hanging wall and footwall of the fault using the ZZ attribute extraction method on the flattened seismic data, the attributes of the fault plane on the hanging wall and footwall are extracted, and the attribute interpolation ratio A on both sides of the fault plane is calculated. In step 3, the formula for calculating the interpolation ratio A of the attributes on both sides of the fault is: A = A1 / (A1-A2), where A1 is the amplitude value of the strata on the hanging wall of the fault and A2 is the amplitude value of the strata on the footwall of the fault. In step 4, the attribute difference ratio A at the fault where the two sand bodies are connected is analyzed, and a quantitative relationship between the attribute difference ratio and the sand body cross-layer connectivity is established. The range B of the fault attribute difference ratio A at the sand body connection when water injection at the cross-layer of the two faults is effective is clarified. Based on B, the attribute A of the entire fault is evaluated, and the connectivity of the two cross-layered sand bodies in the fault space is clarified.

2. The method for evaluating faulted two-plate sandbody connectivity based on seismic data according to claim 1, characterized in that, In step 1, the three-dimensional seismic data, velocity data, and well data of the study area are comprehensively analyzed. Based on the three-dimensional seismic data, the structural interpretation of the fault plane is performed, and the fault plane structural map is obtained.

3. The method for evaluating faulted two-plate sandbody connectivity based on seismic data according to claim 1, characterized in that, In step 2, three-dimensional seismic data is first used to flatten the fault layers explained in step 1 as the target layers. Then, a virtual flattened seismic data volume is established along the layer, and the virtual volume is converted into an actual flattened seismic data volume.

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