Method for optimizing perforation avoiding distance of shale oil horizontal well influenced by fault fracture zone

Abstract

In order to solve the problem that in the fracturing process of a complex fault shale oil horizontal well, due to communication between a hydraulic fracture and a fault, fracturing fluid injected into a stratum leaks to the fault, and then formation of a complex fracture network is affected, a perforation ejection avoiding distance optimization model considering the influence of a fault fracture zone is established; the shale oil horizontal well perforation avoiding distance optimization method influenced by the fault crack zone is formed, and the safe distance between the perforation position and the fault can be calculated according to the fracturing site construction parameters. According to the method, the influence of natural fracture parameters and construction parameters on the horizontal well perforation avoiding distance is mainly considered, wherein the natural fracture parameters comprise the natural fracture angle, the natural fracture length, the fracturing fluid viscosity and the construction displacement. The expansion of the hydraulic fracture is influenced by adjusting the parameters, whether the hydraulic fracture is communicated with the fault under the influence of the natural fracture zone is judged, if the hydraulic fracture is just communicated with the fault, the optimal perforation ejection avoiding distance can be determined, and technical support is provided for hydraulic fracturing of a subsequent fault development area.

Description

Technical Field

[0001] The present invention belongs to the technical field of shale oil development, and in particular relates to a method for optimizing the perforation avoidance distance of a shale oil horizontal well affected by a fault fracture zone. Background Art

[0002] Hydraulic fracturing technology mainly involves injecting a large amount of high-pressure fracturing fluid to open the target layer, transform the reservoir, and improve the oil and gas permeability, thereby achieving the purpose of increasing the production of a single well. However, due to the existence of faults, a large amount of fracturing fluid and proppant will penetrate into the fault during the fracturing construction process, which will reduce the utilization rate of fracturing fluid and proppant and increase the cost of transformation. Therefore, if the impact of faults on the fracturing process is not considered, it will inevitably affect the effect of reservoir transformation and the increase in single well production will be limited. However, whether hydraulic fractures can communicate with faults is affected by many factors such as natural fracture parameters, fracturing fluid displacement, and fracturing fluid viscosity. At present, the construction parameters of the fracturing construction site are mostly determined by the experience of the operators, such as perforation position, segment spacing, cluster spacing, construction displacement and other engineering parameters. The process is poorly targeted and affects the transformation effect. For example, if the construction displacement is too large, the hydraulic fracture will cross the natural fracture, which will make the hydraulic fracture extend farther, making it easier for the hydraulic fracture to communicate with the fault, and in severe cases, it may cause a large amount of fracturing fluid and proppant to be lost. Summary of the invention

[0003] An embodiment of the present application provides a method for optimizing the perforation avoidance distance of shale oil horizontal wells taking into account the influence of fault fracture zones. By adjusting natural fracture parameters and construction parameters, the perforation avoidance distance is optimized according to the fracture expansion characteristics to prevent the fracturing fluid from filtering into the fault, thereby affecting the fracture expansion effect.

[0004] The embodiment of the present application provides a method for optimizing the perforation avoidance distance of a shale oil horizontal well affected by a fault fracture zone, comprising:

[0005] S1, establish a fracturing well model: select well type, well layout method, and fracturing type;

[0006] S2, input the required parameters to establish the geological model;

[0007] S3, setting perforating parameters to perform perforating operations;

[0008] S4, slick water and proppant injection construction: adding fracturing fluid and proppant, and setting the corresponding fracturing fluid viscosity, proppant type and mesh size;

[0009] S5, pumping program: designing a pumping program according to the fracturing fluid and proppant added in step S4;

[0010] S6, setting natural fracture parameters;

[0011] S7, when the hydraulic fracture extends toward the fault, the intersection relationship between the hydraulic fracture and the natural fracture is considered;

[0012] S8, with the goal of hydraulic fractures not communicating with faults, set fracturing stages from far to near. If the hydraulic fractures generated by the first stage perforation cluster do not communicate with the faults, repeat the above work and start the second stage perforation until the hydraulic fractures communicate with the faults. The target spacing is the critical distance for optimal perforation avoidance, and the target spacing is the distance between the perforation position and the fault along the well trajectory.

[0013] S9, output the optimization result of the perforation avoidance distance considering the influence of the fault fracture zone.

[0014] Among them, in step S1, the well types include oil wells and gas wells, the well layout methods include horizontal and vertical, and the fracturing types include casing and oil pipe.

[0015] Among them, in step S2, the required parameters include reservoir depth, reservoir pressure, ground stress parameters, porosity parameters, rock tensile strength and friction coefficient.

[0016] In step S3, the perforation parameters include segment length, segment spacing, and perforation diameter.

[0017] Wherein, in step S6, the natural fracture parameters include the natural fracture angle, the natural fracture spacing and the natural fracture length.

[0018] Among them, in step S7, the intersection criterion of hydraulic fractures and natural fractures is as follows:

[0019]

[0020] Where: θθ is the normal stress on the natural fracture surface; x j is the position of the stress concentration point; r is the distance from the hydraulic fracture tip to the stress concentration point; θ j is the extension direction of hydraulic fracture; T0 is the tensile strength of rock.

[0021] In step S8, the first perforation cluster is farthest from the fault.

[0022] Among them, in step S9, the optimization result diagram of the perforation avoidance distance considering the influence of the natural fracture angle, the optimization result diagram of the perforation avoidance distance considering the influence of the natural fracture length, the optimization result diagram of the perforation avoidance distance considering the influence of the fracturing fluid displacement, and the optimization result diagram of the perforation avoidance distance considering the influence of the fracturing fluid viscosity are output.

[0023] The method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones in the embodiment of the present application has the following beneficial effects:

[0024] In view of the fact that during the fracturing process of shale oil horizontal wells with complex faults, the hydraulic fractures are connected with the faults, resulting in the leakage of the fracturing fluid injected into the formation into the faults, which in turn affects the formation of a complex fracture network, this application establishes a perforation avoidance distance optimization model that takes into account the influence of the fault fracture zone, and forms a perforation avoidance distance optimization method that takes into account the influence of the fault fracture zone. The safe distance between the perforation position and the fault can be calculated according to the construction parameters of the fracturing site. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic flow chart of a method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones in an embodiment of the present application;

[0026] Figure 2 This is a technical flow chart of the embodiment of this application;

[0027] Figure 3 This is a schematic diagram of the perforation avoidance distance in this application;

[0028] Figure 4 This is the fault section diagram of this application;

[0029] Figure 5 A two-dimensional map of the fault and fracture zones for this application;

[0030] Figure 6a This is the optimization result diagram of the perforation avoidance distance considering the influence of the natural fracture angle. The natural fracture angle is 45°;

[0031] Figure 6b This is the optimization result diagram of the perforation avoidance distance considering the influence of the natural fracture angle. The natural fracture angle is 75°;

[0032] Figure 7a This is the optimization result diagram of the perforation avoidance distance considering the influence of natural fracture length. The length of natural fracture is 30m.

[0033] Figure 7b This is the optimization result diagram of the perforation avoidance distance considering the influence of natural fracture length. The length of natural fracture is 50m.

[0034] Figure 8a This is the optimization result diagram of the perforation avoidance distance considering the influence of fracturing fluid viscosity. The fracturing fluid viscosity is 1cp;

[0035] Figure 8b This is the optimization result diagram of the perforation avoidance distance considering the influence of fracturing fluid viscosity. The fracturing fluid viscosity is 3cp;

[0036] Figure 9a This is the optimization result diagram of the perforation avoidance distance under the influence of fracturing fluid displacement. The fracturing fluid displacement is 12m 3 / min;

[0037] Figure 9b This is the optimization result diagram of the perforation avoidance distance under the influence of fracturing fluid displacement. The fracturing fluid displacement is 18m 3 / min. DETAILED DESCRIPTION

[0038] The present application is further described below in conjunction with the accompanying drawings and embodiments.

[0039] In the following introduction, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The following introduction provides multiple embodiments of the present invention, and different embodiments can be replaced or combined, so this application can also be considered to include all possible combinations of the same and / or different embodiments recorded. Therefore, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then this application should also be considered to include embodiments containing one or more of all other possible combinations of features A, B, C, and D, even though the embodiment may not be clearly recorded in the following text.

[0040] Embodiment 1

[0041] like Figure 1 As shown, the method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones in the present application includes: S1, establishing a fracturing well model: selecting well type, well layout method, and fracturing type; S2, inputting required parameters to establish a geological model; S3, setting perforation parameters to perform perforation operations; S4, slick water and proppant injection construction: adding fracturing fluid and proppant, and setting the corresponding fracturing fluid viscosity, proppant type and mesh size; S5, pumping program: designing a pumping program according to the fracturing fluid and proppant added in step S4; S6, setting natural fracture parameters ; S7, in the process of hydraulic fractures extending toward the fault direction, the intersection relationship between hydraulic fractures and natural fractures is considered; S8, with the goal of hydraulic fractures not communicating with faults, the fracturing stages are set from far to near. If the hydraulic fractures generated by the first perforation cluster are not communicating with the faults, the above work is repeated and the second perforation is started until the hydraulic fractures communicate with the faults. The target spacing is the critical distance for optimal perforation avoidance, and the target spacing is the distance between the perforation position and the fault along the well trajectory; S9, output the optimization result of the perforation avoidance distance considering the influence of the fault fracture zone.

[0042] The core of this application is to optimize the perforation avoidance distance according to the crack expansion characteristics by adjusting the natural crack parameters and construction parameters to prevent the fracturing fluid from filtering into the fault, thereby affecting the crack expansion effect. Figure 3 As shown in FIG. 1 , when the hydraulic fracture is just connected with the fault, the distance between the perforation position of the hydraulic fracture and the fault along the well trajectory is the perforation avoidance distance.

[0043] Specifically, in step S1, a fracturing well model is established: the well type (oil well, gas well), well layout method (horizontal, vertical), and fracturing type (casing, tubing) are selected. In step S2, a comprehensive geological model is established: reservoir depth, reservoir pressure, geostress parameters, porosity parameters, rock tensile strength, and friction coefficient are input to establish a geological model. In step S3, perforation operation: perforation parameters are set, including segment length, segment spacing, and perforation diameter. In step S4, slick water and proppant injection construction: fracturing fluid and proppant are added, and the corresponding fracturing fluid viscosity, proppant type, and mesh size are set. In step S5, pumping program: the pumping program is designed according to the fracturing fluid and proppant added in step S4. In step S6, natural fracture setting: natural fracture parameters are set, including natural fracture angle, natural fracture spacing, and natural fracture length. In step S7, in the process of hydraulic fractures extending toward the fault direction, the intersection relationship between hydraulic fractures and natural fractures is considered; the intersection criteria for hydraulic fractures and natural fractures are as follows:

[0044]

[0045] Where: θθ is the normal stress on the natural fracture surface, MPa; x j is the position of the stress concentration point, m; r is the distance from the hydraulic fracture tip to the stress concentration point, m; θ j is the extension direction of hydraulic fracture, degrees; T0 is the tensile strength of rock, MPa.

[0046] In step S8, the hydraulic fractures are set from far to near with the goal of not communicating with the fault. If the hydraulic fractures generated by the first perforation cluster (the farthest from the fault) do not communicate with the fault, the above work is repeated and the second perforation is started until the hydraulic fractures communicate with the fault. This spacing (the distance between the perforation position and the fault along the well trajectory) is the critical distance for optimal perforation avoidance.

[0047] In step S9, Figure 1-2 As shown, the calculation process is used to carry out example calculations, and according to the calculation results, the optimization result diagram of the perforation avoidance distance under the influence of the natural fracture angle, the optimization result diagram of the perforation avoidance distance under the influence of the natural fracture length, the optimization result diagram of the perforation avoidance distance under the influence of the fracturing fluid displacement, and the optimization result diagram of the perforation avoidance distance under the influence of the fracturing fluid viscosity are output respectively. In the specific implementation process of this application, the influence of natural fracture parameters and construction parameters on the perforation avoidance distance of horizontal wells is mainly considered, including the natural fracture angle, natural fracture length, fracturing fluid viscosity and construction displacement. By adjusting the above parameters to affect the expansion of hydraulic fractures, and judging whether the hydraulic fractures communicate with the faults under the influence of the natural fracture zone, if the hydraulic fractures just communicate with the faults, the optimal perforation avoidance distance can be determined, providing technical support for subsequent hydraulic fracturing in fault development areas.

[0048] The present invention aims at the problem that during the fracturing process of shale oil horizontal wells with complex faults, the hydraulic fractures are connected with the faults, resulting in the leakage of the fracturing fluid injected into the formation into the faults, which further affects the formation of a complex fracture network. A perforation avoidance distance optimization model considering the influence of the fault fracture zone is established, and a perforation avoidance distance optimization method considering the influence of the fault fracture zone is formed. The safe distance between the perforation position and the fault can be calculated according to the construction parameters of the fracturing site.

[0049] Embodiment 2

[0050] The basic situation of a shale oil horizontal well is that the reservoir is 3500m and the casing is completed. The horizontal section length is 1500m. Figure 4-5 As shown, the horizontal section encounters two faults D1 and D2. The optimal perforation position is determined by using the perforation avoidance distance optimization method provided in the present application.

[0051] Step S1, establishing a fracturing well model: selecting the well type as oil well, horizontal well layout, and casing fracturing;

[0052] Step S2, establishing a comprehensive geological model: inputting reservoir depth, reservoir pressure, geostress parameters, porosity parameters, rock tensile strength and friction coefficient to establish a geological model;

[0053] Step S3, perforation operation: set the perforation cluster to single cluster, segment length to 20m, and perforation diameter to 10.67mm;

[0054] Step S4, fracturing fluid and proppant injection construction: the fracturing fluid is selected from slick water with a viscosity of 1cp and 3cp, and the fracturing fluid displacement is selected from 12 and 18m 3 / min, and the proppant is quartz sand of 70 / 140 and 40 / 70 mesh;

[0055] Step S5, pumping program: designing a pumping program according to the fracturing fluid and proppant added in step S4;

[0056] Step S6, natural fracture setting: setting natural fracture parameters, including natural fracture angle (45°, 75°), natural fracture spacing and natural fracture length (30m, 50m);

[0057] Step S7, when the hydraulic fracture extends toward the fault direction, the intersection relationship between the hydraulic fracture and the natural fracture is considered;

[0058] Step S8, with the goal of preventing the hydraulic fractures from communicating with the faults, set the fracturing stages from far to near. If the hydraulic fractures generated by the first perforation cluster (the farthest from the fault) do not communicate with the faults, repeat the above steps and start the second perforation until the hydraulic fractures communicate with the faults. This distance (the distance between the perforation position and the fault along the well trajectory) is the critical distance for optimal perforation avoidance.

[0059] Step S9: Figure 2 As shown in the figure, the calculation process is used to carry out the example calculation, and the output is as follows: Figure 6a , 6b As shown in Figure 1, the optimization result diagram of the perforation avoidance distance considering the influence of natural fracture angle; Figure 7a-7b As shown in Figure 1, the optimization result diagram of the perforation avoidance distance considering the influence of natural fracture length; Figure 8a-8b As shown in Figure 1, the optimization result of perforation avoidance distance considering the influence of fracturing fluid viscosity is shown in Figure 2. Figure 9a-9b As shown in the figure, the optimization result of perforation avoidance distance considering the influence of fracturing fluid displacement.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones, characterized in that: include: S1, establish a fracturing well model: select well type, well layout method, and fracturing type; S2, input the required parameters to establish the geological model; S3, setting perforating parameters to perform perforating operations; S4, slick water and proppant injection construction: adding fracturing fluid and proppant, and setting the corresponding fracturing fluid viscosity, proppant type and mesh size; S5, pumping program: designing a pumping program according to the fracturing fluid and proppant added in step S4; S6, setting natural fracture parameters; S7, when the hydraulic fracture extends toward the fault, the intersection relationship between the hydraulic fracture and the natural fracture is considered; S8, with the goal of hydraulic fractures not communicating with faults, set fracturing stages from far to near. If the hydraulic fractures generated by the first stage perforation cluster do not communicate with the faults, repeat the above work and start the second stage perforation until the hydraulic fractures communicate with the faults. The target spacing is the critical distance for optimal perforation avoidance, and the target spacing is the distance between the perforation position and the fault along the well trajectory. S9, output the optimization result of the perforation avoidance distance considering the influence of the fault fracture zone.

2. The method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones according to claim 1, characterized in that: In step S1, the well types include oil wells and gas wells, the well layout methods include horizontal and vertical, and the fracturing types include casing and tubing.

3. The method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones according to claim 1 or 2, characterized in that: In step S2, the required parameters include reservoir depth, reservoir pressure, geostress parameters, porosity parameters, rock tensile strength and friction coefficient.

4. The method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones according to claim 1 or 2, characterized in that: In step S3, the perforation parameters include segment length, segment spacing, and perforation diameter.

5. The method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones according to claim 1 or 2, characterized in that: In step S6, the natural fracture parameters include the natural fracture angle, the natural fracture spacing and the natural fracture length.

6. The method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones according to claim 1 or 2, characterized in that: In step S7, the criterion for determining the intersection of hydraulic fractures and natural fractures is as follows: Where: θθ is the normal stress on the natural fracture surface; x j is the position of the stress concentration point; r is the distance from the hydraulic fracture tip to the stress concentration point; θ j is the extension direction of hydraulic fracture; T0 is the tensile strength of rock.

7. The method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones according to claim 1 or 2, characterized in that: In step S8, the first perforation cluster is farthest from the fault.

8. The method for optimizing the perforation avoidance distance of shale oil horizontal wells affected by fault fracture zones according to claim 1 or 2, characterized in that: In step S9, the optimization result diagram of the perforation avoidance distance considering the influence of the natural fracture angle, the optimization result diagram of the perforation avoidance distance considering the influence of the natural fracture length, the optimization result diagram of the perforation avoidance distance considering the influence of the fracturing fluid displacement, and the optimization result diagram of the perforation avoidance distance considering the influence of the fracturing fluid viscosity are output.

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