Optimization method for batch injection parameters of mixed particle size temporary plugging agent and temporary plugging method

Abstract

This invention relates to the field of temporary plugging fracturing construction technology. To address the technical problem of the difficulty in synchronously accumulating mixed particle sizes during transport, it provides a method for optimizing batch injection parameters and a temporary plugging method for mixed particle size plugging agents: optimizing the plugging agent ratio parameters; obtaining the transport time of plugging agents of different particle sizes along the same path; adjusting the batch injection timing of different particle size plugging agents based on the differences in transport time until the clustering effect index c under the batch injection timing meets the requirements; the clustering effect index c = l min / l max , where l min This refers to the distance from the initial position to the nearest particle in the particle cluster after batch injection according to the timing of the batch injection; max This refers to the distance from the initial position to the particle in the particle cluster after batch injection according to the timing of the batch injection. Based on the temporary plugging agent ratio parameters and the batch injection time, temporary plugging agents of different particle sizes are injected in batches sequentially, allowing the temporary plugging agents of different sizes to migrate synchronously to the expected temporary plugging location.

Description

Technical Field

[0001] This invention relates to the field of temporary plugging fracturing construction technology, specifically to a method for optimizing the parameters of batch injection of mixed particle size temporary plugging agent and a temporary plugging method. Background Technology

[0002] Temporary plugging fracturing is beneficial for sealing the flow channels in the main fracture, forcing a rapid increase in the net pressure of the main fracture, thereby inducing the formation and full extension of diverting branch fractures. At the same time, it can further promote the balanced stimulation of multi-perforation clusters. Therefore, temporary plugging fracturing has become the mainstream technology mode for volumetric fracturing in horizontal wells.

[0003] Currently, temporary plugging agents with different particle size combinations are widely used to improve their sealing effect. The principle is that small-particle-size temporary plugging agents fill the pores between large-particle-size temporary plugging agents, thereby reducing the permeability of the temporary plugging agent pile, improving the temporary plugging efficiency, maximizing the pressure rise after temporary plugging, and thus increasing the complexity of the crack.

[0004] However, the above-mentioned design of mixed particle size temporary plugging agents assumes that plugging agents of various particle sizes migrate and accumulate synchronously. In reality, due to the influence of the particle size and density of the temporary plugging agents, different types of temporary plugging agents have different migration speeds in the wellbore and fractures. After long-distance migration through the surface manifold, wellbore, and fractures, significant separation occurs, causing temporary plugging agents of different particle sizes to not accumulate synchronously at the designed temporary plugging location, thus affecting the temporary plugging efficiency, resulting in incomplete intra-fracture temporary plugging and limiting the effectiveness of the intervention.

[0005] Chinese patent (CN110210144A) discloses an optimized design method for promoting uniform fracture propagation in horizontal wells using temporary plugging agents. The method includes the following steps: calculating the particle size and volume range of candidate temporary plugging agents for the applicable target area; establishing a fully fluid-structure coupled hydraulic fracture propagation calculation model; calculating the optimal average particle size required for effective temporary plugging; determining the particle size distribution of the temporary plugging particles based on the optimal average particle size; calculating the required volume of temporary plugging agents for effective temporary plugging; and predicting and evaluating the fracturing effect in the target block after adopting the optimized temporary plugging design. However, this invention does not consider the possibility that temporary plugging agents of different sizes may not accumulate synchronously at the designed temporary plugging location, thus having certain limitations.

[0006] Chinese patent (CN110374569A) discloses a method and system for uniform stimulation of tight reservoirs. The method includes: performing extreme flow-limited fracturing on the reservoir to obtain a perforation stimulation scheme and reservoir fracture data; preparing a temporary plugging agent corresponding to the required fracture size and fracture turning pressure; selecting fractures where the proportion of influent to total fluid volume exceeds a first threshold value as primary plugging fractures based on the reservoir fracture data, and performing primary plugging with a corresponding temporary plugging agent; and generating a reservoir fracturing stimulation scheme based on the reservoir perforation stimulation scheme and the reservoir data after plugging. However, this invention does not consider the possibility that temporary plugging agents of different particle sizes may not accumulate synchronously at the designed plugging location. Summary of the Invention

[0007] The purpose of this invention is to solve the problems existing in the prior art and provide a method for optimizing the batch injection parameters of mixed particle size temporary plugging agents, thereby reducing the separation of temporary plugging agents of different particle sizes during migration and improving the plugging effect of temporary plugging fracturing.

[0008] This invention is achieved through the following technical solution: a method for optimizing batch injection parameters of a mixed particle size temporary plugging agent, comprising the following steps: optimizing the temporary plugging agent ratio parameters; obtaining the migration time of temporary plugging agents of different particle sizes along the same migration path; adjusting the batch injection timing of temporary plugging agents of different particle sizes according to the difference in migration time, until the clustering effect index c under the batch injection timing meets the requirements; wherein the clustering effect index c = 1 min / l max , where l min This refers to the distance from the initial position to the nearest particle in the particle cluster after batch injection according to the timing of the batch injection; max This refers to the distance from the initial position to the particle in the particle cluster after the particles are injected in batches according to the timing of the injection.

[0009] Further steps in optimizing the formulation parameters of the temporary plugging agent include optimizing the mixing ratio of temporary plugging agents with different particle sizes:

[0010] Based on the width of the temporary plug, the initial particle size of the temporary plugging agent is selected according to the bridging theory;

[0011] Based on the initial particle size selection, smaller and larger particle sizes than the initial selection are selected. The mixing ratio of temporary plugging agents with different particle sizes is continuously changed and mixed evenly to prepare rock cores. The permeability of the rock cores is tested, and the minimum permeability is taken as the optimization target. Finally, the optimal mixing ratio of temporary plugging agents with different particle sizes is determined.

[0012] Furthermore, optimizing the formulation parameters of the temporary plugging agent also includes optimizing the parameters of the soluble fiber, including length and concentration:

[0013] The length and concentration of linear fibers were continuously adjusted, and they were mixed evenly with temporary plugging agents of initial particle size, smaller particle size, and larger particle size. The agglomeration effect of each particle size of the temporary plugging agent mixed with linear fibers during the transport process was tested until, under the same soluble fiber parameters, the ratio of the distance from the nearest particle to the initial position to the distance from the farthest particle to the initial position along the flow direction of the three temporary plugging agents was all in the range of 0.9 to 1.0.

[0014] Furthermore, the migration time of temporary plugging agents of different particle sizes along the same path was obtained in the following manner:

[0015] Experiments were conducted to measure the transport time of temporary plugging agents of different particle sizes along the same path. The transport time of temporary plugging agents with smaller particle sizes should be shorter, and the transport time of temporary plugging agents with larger particle sizes should be longer. Furthermore, the time difference between the experimental transport times of temporary plugging agents of different particle sizes should be within 5%. Otherwise, the temporary plugging agent formulation parameters should be readjusted before conducting the experiment, including adjusting the mixing ratio of temporary plugging agents of different particle sizes and / or the soluble fiber parameters.

[0016] Based on the experimental migration time, the migration time of temporary plugging agents of different particle sizes to the same set temporary plugging position in the fracture was simulated under actual well conditions.

[0017] Furthermore, the experimental transport time of temporary plugging agents with different particle sizes is fitted using solid-liquid two-phase flow simulation software, thereby obtaining a particle size-experimental transport time curve with particle size as the abscissa and experimental transport time as the ordinate. Based on the initial particle size selection, the transport time corresponding to different particle sizes is found through the particle size-experimental transport time curve, so as to optimize the particle size combination with a time difference between experimental transport times within 5%.

[0018] Furthermore, the requirement is met when the herding effect index c falls within the range of 0.9 to 1.0.

[0019] Furthermore, the permeability of the core was determined using a gas-based method.

[0020] Furthermore, core samples were first prepared by mixing temporary plugging agents of different particle sizes in a 1:1:1 ratio to test permeability.

[0021] Furthermore, a particle size with a ratio of 3 between the gap width and the average particle size of the temporary plugging agent is selected as the initial particle size of the temporary plugging agent.

[0022] Furthermore, the experimental transport time of temporary plugging agents of different particle sizes along the same path was measured using a ground-based temporary plugging agent simulation device.

[0023] This invention also provides a temporary plugging method, which uses the batch injection parameter optimization method of the mixed particle size temporary plugging agent of this invention to obtain the temporary plugging agent ratio parameters and batch injection time of the mixed particle size temporary plugging agent. According to the temporary plugging agent ratio parameters and batch injection time, temporary plugging agents with larger particle size than the initial selected particle size, temporary plugging agents with the initial selected particle size, and temporary plugging agents with smaller particle size than the initial selected particle size are injected in batches in sequence, so that temporary plugging agents of different particle sizes can be synchronously transported to the expected temporary plugging position.

[0024] Compared with the prior art, the beneficial effects of the present invention include:

[0025] 1. This invention first breaks the unreasonable assumption in the prior art that "the temporary plugging agents of various particle sizes migrate and accumulate synchronously". This invention starts from reality, explores the difference in migration time between temporary plugging agents of different particle sizes, and adjusts the timing of batch injection of temporary plugging agents of different particle sizes so that temporary plugging agents of different particle sizes can migrate synchronously to the expected temporary plugging position.

[0026] 2. The clustering effect index proposed in this invention can effectively quantify the adjustment effect of batch injection timing, ensure that temporary plugging agents of different particle sizes migrate and accumulate synchronously, reduce the separation of temporary plugging agents of different particle sizes during migration, and improve the sealing effect of temporary plugging fracturing.

[0027] 3. By optimizing the parameters of soluble fibers, the agglomeration effect of temporary plugging agents within the same particle size during the migration process can be reduced. Attached Figure Description

[0028] Figure 1 This is a flowchart of the method for optimizing the batch injection parameters of the mixed particle size temporary plugging agent in Example 2. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to the accompanying drawings:

[0030] The basic technical concept of this invention is as follows:

[0031] Batch injection of temporary plugging agent: This method departs from the previous one-time injection approach and instead injects temporary plugging agents of different particle sizes in batches. Batch injection takes into account the different migration velocities of the plugging agents of different particle sizes, with faster-migrating particles injected later and slower-migrating particles injected first. The ultimate goal is for the plugging agents of different particle sizes to migrate synchronously to the intended plugging location.

[0032] Controlling the agglomeration of temporary plugging agents using fiber-reinforced fracturing fluid: Even temporary plugging agents of the same particle size have particle sizes distributed within a certain range, and are not simply uniform particles. Therefore, separation is still possible after long-distance transport. Thus, a method involving linear fiber mixing was designed to ensure the effective agglomeration and transport of each batch of temporary plugging agent.

[0033] Example 1

[0034] A method for optimizing batch injection parameters of a mixed particle size temporary plugging agent includes the following steps: optimizing the temporary plugging agent ratio parameters; obtaining the migration time of temporary plugging agents of different particle sizes along the same migration path; adjusting the batch injection timing of temporary plugging agents of different particle sizes according to the difference in migration time, until the clustering effect index c under the batch injection timing meets the requirements, and the clustering effect index c falling within the range of 0.9 to 1.0 is considered to meet the requirements; the clustering effect index c = 1 min / l max , where l min This refers to the distance from the initial position to the nearest particle in the particle cluster after batch injection according to the timing of the batch injection; max This refers to the distance from the initial position to the particle in the particle cluster after the particles are injected in batches according to the timing of the injection.

[0035] The steps to optimize the formulation parameters of the temporary plugging agent include optimizing the mixing ratio of temporary plugging agents with different particle sizes:

[0036] 1) Based on the gap width at the temporary plug, select the initial particle size of the plugging agent according to the bridging theory; according to the bridging theory, the ratio of gap width to the average particle size of the plugging agent is about 3. On this basis, determine the particle size of the plugging agent.

[0037] 2) Based on the initial particle size selection, select particle sizes smaller than the initial particle size and larger than the initial particle size, continuously change the mixing ratio of temporary plugging agents of different particle sizes and mix them evenly to make a core sample, test the permeability of the core sample, take the minimum permeability as the optimization target, and finally determine the optimal mixing ratio of temporary plugging agents of different particle sizes.

[0038] The initial mixing ratio can be set to 1:1:1, meaning that the permeability change of each particle size plugging agent is measured using conventional gas permeation methods. The ratios of different particle size plugging agents are then varied, and the gas permeability of artificial core samples is tested. The optimal mixing ratio for different particle size plugging agents is determined by minimizing permeability.

[0039] The migration time of temporary plugging agents of different particle sizes along the same path was obtained using the following method:

[0040] 1) The experimental transport time of temporary plugging agents of different particle sizes along the same path was measured using a ground-based temporary plugging agent simulation device. The time difference between the experimental transport times of temporary plugging agents of different particle sizes should be within 5%. Otherwise, the temporary plugging agent ratio parameters should be readjusted before conducting the experiment, including adjusting the mixing ratio of temporary plugging agents of different particle sizes.

[0041] 2) Based on the experimental migration time, simulate the migration time of temporary plugging agents of different particle sizes to the same set temporary plugging position in the fracture under actual well conditions.

[0042] To facilitate the adjustment of the temporary plugging agent formulation parameters, experimental transport times of temporary plugging agents with different particle sizes were fitted using solid-liquid two-phase flow simulation software. This yielded a particle size-experimental transport time curve with particle size as the abscissa and experimental transport time as the ordinate. Based on the initially selected particle size, the transport times corresponding to different particle sizes were identified through the particle size-experimental transport time curve, so as to optimize the particle size combination with a time difference of less than 5% between experimental transport times.

[0043] Example 2

[0044] Building upon Example 1, this example utilizes fiber-reinforced fracturing fluid to control the agglomeration of the temporary plugging agent. Considering that even temporary plugging agents of the same particle size have particle sizes distributed within a certain range, and are not simply uniform particles, separation is still possible after long-distance transport. Therefore, a method involving linear fiber mixing is designed to ensure the effective agglomeration and transport of each batch of temporary plugging agent.

[0045] Specifically, the method for optimizing the batch injection parameters of the mixed particle size temporary plugging agent in this embodiment refers to... Figure 1 As shown, it includes the following steps:

[0046] (1) Optimal particle size of the temporary plugging agent;

[0047] (2) Optimization of the proportion of temporary plugging agents with different particle sizes;

[0048] (3) Parameter optimization of soluble fiber mixing with temporary plugging agent of different particle size;

[0049] (4) The transport time of temporary plugging agents with different particle sizes was measured by indoor experiments;

[0050] (5) Calculate the migration time of temporary plugging agents of different particle sizes under actual well conditions;

[0051] (6) Optimize the timing of injection of temporary plugging agents with different particle sizes.

[0052] In step (1), the current temporary plugging agents mainly include particle sizes of 60-80 mesh, 40-60 mesh, 20-40 mesh, and even 4-16 mesh or other particle sizes. The selection of the temporary plugging agent particle size mainly depends on the width of the crack at the plugging point. According to the bridging theory, the ratio of the crack width to the average particle size of the temporary plugging agent is about 3. Based on this, the particle size of the temporary plugging agent is determined.

[0053] In step (2), based on the particle size of the temporary plugging agent initially selected in step (1), at least smaller and larger particle sizes of temporary plugging agents are selected and mixed together to prepare a core with a certain degree of cementation.

[0054] The initial mixing ratio can be 1:1:1, meaning that the permeability of each particle size (60-80 mesh (small particle size), 40-60 mesh (medium particle size), 20-40 mesh, or even 4-16 mesh (large particle size)) temporary plugging agent is measured using conventional gas permeation methods. The ratio of different particle size temporary plugging agents is then varied, and the gas permeability of artificial core samples is tested. The minimum permeability is taken as the optimization target, and the optimal mixing ratio of different particle size temporary plugging agents is finally determined.

[0055] In step (3), linear fibers of different lengths and concentrations are selected. The length and concentration of the linear fibers are continuously adjusted and mixed evenly with the temporary plugging agent of the initially selected particle size, the temporary plugging agent with a smaller particle size than the initially selected particle size, and the temporary plugging agent with a larger particle size than the initially selected particle size. The agglomeration effect of the temporary plugging agent of each particle size mixed with linear fibers during the transport process is tested until, under the same soluble fiber parameters, the ratio of the distance from the nearest particle to the initial position to the distance from the farthest particle to the initial position of the three temporary plugging agents along the flow direction is all between 0.9 and 1.0.

[0056] Step (4): Based on step (3), using optimized soluble fiber parameters, experimentally test the migration time of temporary plugging agents of different particle sizes from the same initial position to the same fixed position in a ground-based temporary plugging device. The migration time of temporary plugging agents with smaller particle sizes should be shorter, and the migration time of temporary plugging agents with larger particle sizes should be longer. Furthermore, the time difference between experimental migration times of temporary plugging agents of different particle sizes should be within 5%. Otherwise, the temporary plugging agent mixing parameters should be readjusted before conducting the experiment, including adjusting the mixing ratio of temporary plugging agents of different particle sizes and / or the soluble fiber parameters.

[0057] In step (4), the experimental transport time of temporary plugging agents with different particle sizes is fitted by solid-liquid two-phase flow simulation software, thereby obtaining a particle size-experimental transport time curve with particle size as the abscissa and experimental transport time as the ordinate. Based on the initially selected particle size, the particle size is adjusted to be smaller and / or larger than the initially selected particle size according to the particle size-experimental transport time curve, so as to obtain a particle size combination with a time difference between experimental transport times within 5%.

[0058] Step (5) Based on step (4), simulate the time and differences in the arrival time of temporary plugging agents of different particle sizes at a specific temporary plugging location in the fracture under actual well conditions.

[0059] Step (6): Based on step (5), adjust the timing of batch injection of temporary plugging agents of different particle sizes according to the differences in transport time, until the clustering effect index c under the batch injection timing meets the requirements. The clustering effect index c is considered to meet the requirements when it falls within the range of 0.9 to 1.0. Clustering effect index c = l min / l max , where l minThis refers to the distance from the initial position to the nearest particle in the particle cluster after batch injection according to the timing of the batch injection; max This refers to the distance from the initial position to the particle in the particle cluster after the particles are injected in batches according to the timing of the injection.

[0060] A shale gas well in southwestern Sichuan has a vertical depth of 3600m, a measured depth of 5670m, and a horizontal section length of 1500m. The following method was used to optimize the batch injection parameters of the mixed particle size temporary plugging agent:

[0061] (1) The width of the main fracture and secondary fracture was simulated using fracturing software. Based on the bridging principle, the particle size of the temporary plugging agent was optimized to 60-80 mesh (smaller particle size), 40-60 mesh (initial particle size), and 20-40 mesh (larger particle size).

[0062] (2) The proportion of temporary plugging agents with different particle sizes of 60-80 mesh, 40-60 mesh and 20-40 mesh was optimized. The optimized ratio of temporary plugging agents was 5:4:1.

[0063] (3) Based on the results of indoor experiments, the optimal fiber length is 8 mm and the fiber concentration is 0.5%.

[0064] (4) The migration time of temporary plugging agents with different particle sizes was measured using indoor experiments. The model was corrected, and the time difference was within 4%. Based on this, the actual migration time of the 60-80 mesh temporary plugging agent was calculated to be 4.6 min, the 40-60 mesh temporary plugging agent to be 5.1 min, and the 20-40 mesh temporary plugging agent to be 6.2 min. After optimization and adjustment, the design was to first add the 20-40 mesh temporary plugging agent, then add the 40-60 mesh temporary plugging agent after 1 min, and finally add the 60-80 mesh temporary plugging agent after 0.5 min. Under this condition, the agglomeration effect index of the mixed temporary plugging agents with different particle sizes was 0.95.

[0065] The above technical solution is only one embodiment of the present invention. For those skilled in the art, based on the principles disclosed in the present invention, it is easy to make various types of improvements or modifications, and not limited to the technical solutions described in the specific embodiments of the present invention. Therefore, the foregoing description is only a preferred option and is not restrictive.

Claims

1. A method for optimizing the parameters of batch injection of a mixed particle size temporary plugging agent, characterized in that, Includes the following steps: Optimizing the ratio of the temporary plugging agent; obtaining the migration time of temporary plugging agents with different particle sizes migrating the same path; adjusting the batch injection time of temporary plugging agents with different particle sizes according to the migration time difference of temporary plugging agents with different particle sizes until the clump effect index under the batch injection time meets the requirements The clump effect index Wherein, The distance from the particle closest to the initial position to the initial position after batch injection according to the batch injection time; The distance from the particle farthest from the initial position to the initial position after batch injection according to the batch injection time; The steps to optimize the formulation parameters of the temporary plugging agent include optimizing the mixing ratio of temporary plugging agents with different particle sizes: based on the width of the crack at the temporary plugging site, the initial particle size of the temporary plugging agent is selected according to the bridging theory; based on the initial particle size, smaller particle sizes and larger particle sizes than the initial particle size are selected, and the mixing ratio of temporary plugging agents with different particle sizes is continuously changed and mixed evenly to prepare a core sample. The permeability of the core sample is tested, and the minimum permeability is taken as the optimization target. Finally, the optimal mixing ratio of temporary plugging agents with different particle sizes is determined. The migration time of temporary plugging agents of different particle sizes along the same path was obtained as follows: The experimental migration time of temporary plugging agents of different particle sizes along the same path was measured. The migration time of temporary plugging agents with smaller particle sizes was shorter than that of temporary plugging agents with larger particle sizes, and the time difference between the experimental migration times of temporary plugging agents of different particle sizes should be within 5%. Otherwise, the temporary plugging agent ratio parameters should be readjusted before conducting the experiment. Based on the experimental migration time, the migration time of temporary plugging agents of different particle sizes to the same set temporary plugging position in the fracture was simulated under actual well conditions.

2. The method for optimizing the batch injection parameters of the mixed particle size temporary plugging agent according to claim 1, characterized in that, The steps for optimizing the formulation parameters of the temporary plugging agent also include optimizing the parameters of soluble fibers, including length and concentration: The length and concentration of linear fibers were continuously adjusted, and they were mixed evenly with temporary plugging agents of initial particle size, smaller particle size, and larger particle size. The agglomeration effect of each particle size of the temporary plugging agent mixed with linear fibers during the migration process was tested until, under the same soluble fiber parameters, the ratio of the distance from the nearest particle to the initial position to the distance from the farthest particle to the initial position along the flow direction of the three temporary plugging agents was all in the range of 0.9 to 1.

0.

3. The method for optimizing the batch injection parameters of the mixed particle size temporary plugging agent according to claim 2, characterized in that, The experimental transport time of temporary plugging agents with different particle sizes was fitted by solid-liquid two-phase flow simulation software, thereby obtaining a particle size-experimental transport time curve with particle size as the abscissa and experimental transport time as the ordinate. Based on the initial particle size selection, the transport time corresponding to different particle sizes was found through the particle size-experimental transport time curve, so as to optimize the particle size combination with the time difference between experimental transport times within 5%.

4. The method for optimizing the batch injection parameters of the mixed particle size temporary plugging agent according to claim 1, characterized in that, herding effect index The requirement is met when the value falls within the range of 0.9 to 1.

0.

5. The method for optimizing the batch injection parameters of the mixed particle size temporary plugging agent according to claim 1, characterized in that, The permeability of the core was determined using a gas-based method.

6. The method for optimizing the batch injection parameters of the mixed particle size temporary plugging agent according to claim 1, characterized in that, First, core samples were prepared by mixing temporary plugging agents of different particle sizes in a 1:1:1 ratio to test permeability.

7. The method for optimizing the batch injection parameters of the mixed particle size temporary plugging agent according to claim 1, characterized in that, The particle size with a ratio of 3 between the gap width and the temporary plugging agent particle size is selected as the initial particle size of the temporary plugging agent.

8. The method for optimizing the batch injection parameters of the mixed particle size temporary plugging agent according to claim 1, characterized in that, The experimental transport time of temporary plugging agents of different particle sizes along the same path was measured using a ground-based temporary plugging agent simulation device.

9. A temporary blocking method, characterized in that: The mixed particle size temporary plugging agent batch injection parameter optimization method described in any one of claims 1 to 8 is used to obtain the temporary plugging agent ratio parameters and batch injection time of the mixed particle size temporary plugging agent. According to the temporary plugging agent ratio parameters and batch injection time, temporary plugging agents with a larger particle size than the initial selected particle size, temporary plugging agents with the initial selected particle size, and temporary plugging agents with a smaller particle size than the initial selected particle size are injected in batches in sequence, so that temporary plugging agents of different particle sizes can be synchronously transported to the expected temporary plugging position.

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