Temporary plugging agent strength evaluation device

Abstract

The invention relates to a device for evaluating the strength of a temporary plugging agent. The device comprises a piston container, a high-pressure pipe, a parallel-bar pump, a rock core holder, a steel crack rock core model, a steel rock core and a waste liquid recovery storage tank, a plug of the piston container is connected with the parallel-bar pump, a lower port of the piston container is connected with the valve mechanism, and the tail end of the valve mechanism is connected with a high-pressure pipe inlet. A pressure sensor is arranged at the inlet end of the high-pressure pipe, and the tail end of the high-pressure pipe is connected with the core holder; a steel fractured rock core model and a steel rock core are arranged in the rock core holder, the outlet end of the steel fractured rock core model is connected with the steel rock core, and the tail end of the steel rock core is connected with the waste liquid recovery storage tank; a displacement experiment is carried out through the temporary plugging agent strength evaluation device, the plugging condition of the temporary plugging agent in a crack is simulated, the pressure change condition after the temporary plugging agent enters the crack is monitored, and the temporary plugging performance of the temporary plugging agent is accurately simulated and evaluated. The temporary plugging agent with poor effect can be prevented from being used, and the cost and time of oilfield development are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield fracturing, and in particular to a device for studying strength evaluation of temporary plugging agents. Background Art

[0002] With the continuous growth of energy demand, some oilfield blocks in my country have entered the middle and late stages of development. Most of the wells that were fractured in the early stage have gradually failed due to long-term production and later operations, and the distribution of remaining oil has become more dispersed and complex. Among the oil reservoirs that have been put into development, a considerable number are low-permeability reservoirs with huge development potential. However, low-permeability reservoirs have the characteristics of poor reservoir properties, low permeability, and insufficient natural energy. To achieve economical and efficient exploitation, the reservoir must be transformed. In the conventional hydraulic fracturing process, the ability of simple fractures to transform the reservoir is limited, resulting in insufficient utilization within the layer. The fracturing transformation measures have great limitations, which makes the development of low-permeability reservoirs face many difficulties.

[0003] In order to solve these problems in the development of low-permeability reservoirs, more and more researchers have begun to pay attention to the temporary plugging and diversion fracturing technology. This technology requires the addition of temporary plugging agents during repeated fracturing, and uses the temporary plugging effect of temporary plugging agents to increase the wellbore pressure, divert the fracturing fluid into the unused area, and promote the opening and extension of secondary fractures, thereby greatly increasing the complexity of fractures, thereby obtaining a larger reservoir transformation volume, better communicating oil and gas reservoirs, tapping the remaining oil-rich areas, and improving oil and gas recovery.

[0004] Temporary plugging is an effective way to increase the complexity of fractures. At present, a large number of temporary plugging agents have been applied on site, but there is still no unified understanding in indoor evaluation. The performance of temporary plugging agents is the key to determining the success of diversion fracturing technology, and the formation of effective plugging is the basis of diversion fracturing. After the fracturing work is completed, whether the temporary plugging agent can be completely unblocked without residue and the formation permeability can be restored is also an important factor affecting whether a structured interconnected fracture network can be formed in the end. The key to the success of this technology lies in the plugging performance of the temporary plugging agent, that is, it must be able to effectively plug old cracks, ensure that high pressure can be formed during construction, and realize the diversion of cracks. Therefore, it is crucial to evaluate the strength performance of the temporary plugging agent. Summary of the invention

[0005] The purpose of the present invention is to provide a device for evaluating the strength of a temporary plugging agent, which solves the problem of poor reproducibility of temporary plugging agent evaluation test results using fractured cores, and also solves the problem of whether the pressure increase generated after monitoring temporary plugging can open new fractures.

[0006] The technical solution adopted by the present invention to solve the technical problem is as follows: the temporary plugging agent strength evaluation device comprises a piston container, a pressure sensor, a high-pressure pipe, a double-bar pump, a core clamp, a steel fracture core model, a steel core, and a waste liquid recovery tank; the piston container has a pressure bearing capacity of 40MPa, the plug of the piston container is connected to the double-bar pump, the lower port of the piston container is connected to a valve mechanism, and the end of the valve mechanism is connected to the inlet of the high-pressure pipe; the high-pressure pipe is provided with a pressure sensor at its inlet end, and the end of the high-pressure pipe is connected to the core clamp; the core clamp is provided with a steel fracture core model and a steel core, the outlet end of the steel fracture core model is connected to the steel core, and the end of the steel core is connected to the waste liquid recovery tank; a displacement experiment is carried out by using the temporary plugging agent strength evaluation device to simulate the plugging condition of the temporary plugging agent in the fracture, monitor the change of pressure after the temporary plugging agent enters the fracture, determine whether the pressure standard of 40MPa can be reached, and accurately simulate and evaluate the temporary plugging performance of the temporary plugging agent.

[0007] In the above scheme, the piston container includes two types: 500mL piston container and 2000mL piston container, there is one 2000mL piston container and three 500mL piston containers; the valve mechanism is composed of four valve groups arranged in the valve frame, and a rolling wheel is arranged at the bottom of the valve frame. The four valve groups are connected in parallel to the upper side of the bottom connecting pipe, among which three valve groups are respectively connected to a 500mL piston container, and one valve group is connected to the 2000mL piston container; the valve group connected to the 2000mL piston container is connected to the starting end of the bottom connecting pipe through a two-way connection, and the other three valve groups are all connected to the bottom connecting pipe through a three-way connection, and the end of the bottom connection is connected to the inlet of the high-pressure pipe; the plug of the 2000mL piston container is connected to the double-bar pump; the valve group is composed of two valves in series.

[0008] In the above scheme, the high-pressure pipe has an outer diameter of 25 mm, an inner diameter of 15 mm, and a length of 1000 mm.

[0009] In the above scheme, the core holder is 1000 mm long, and contains a steel fracture core model and a steel core. The steel fracture core model and the steel core are coaxially connected. The steel fracture core model is located at the inlet end of the core holder, and the steel core is located at the outlet end of the core holder.

[0010] The steel fracture core model in the above scheme is a tapered steel fracture core model with a square inlet of 15×15 mm, a rectangular outlet of 15×1 mm, and a total length of 900 mm, which is composed of three sections of steel fracture core models.

[0011] In the above scheme, the steel core is a hollow cylinder with an outer diameter of 25 mm, an inner diameter of 6 mm and a length of 100 mm.

[0012] Method for evaluating temporary plugging agent using the temporary plugging agent strength evaluation device: (1) Prepare fracturing fluid: thickener 0.6%, surfactant 0.2%; (2) Check the air tightness of the temporary plugging agent strength evaluation device; (3) A total of 30 g of yellow granular temporary plugging agent and white powder temporary plugging agent were selected and placed in a steel fracture core model in a ratio of 5:5; the particle size of the yellow granular temporary plugging agent was 3.16-3.4 mm, and the particle size of the white powder temporary plugging agent was 1.08-1.84 mm; the fracturing fluid was poured into the piston container, and a displacement experiment was carried out at an injection rate of 50 mL / min. The pressure data was collected through a pressure sensor to determine whether the pressure standard of 40 MPa could be reached.

[0013] The beneficial effects brought by the technical solution provided by the present invention are: 1. The temporary plugging agent evaluation device provided by the present invention can realize the indoor simulation experiment evaluation of the pressure bearing strength of the temporary plugging agent. The pressure change after the temporary plugging agent enters the crack can be monitored to determine whether the pressure standard of 40MPa can be reached. The achievement of this pressure level is a key indicator for evaluating the strength of the temporary plugging agent. By accurately evaluating the performance of the temporary plugging agent, the use of temporary plugging agents with poor effects can be avoided, reducing the cost and time of oil field development.

[0014] 2. The present invention can use the device to simulate the plugging condition of the temporary plugging agent in the crack by conducting a displacement experiment, and monitor the pressure increase after plugging, so as to accurately simulate and evaluate the pressure bearing strength of the temporary plugging agent.

[0015] 3. The present invention uses steel fracture plates and steel cores to simulate formation fractures for displacement experiments, which can more realistically simulate the plugging of temporary plugging agents in fractures and monitor the net pressure generated after plugging to see whether it can reach 40 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings: Figure 1 It is a structural schematic diagram of a temporary plugging agent strength evaluation device; Figure 2 It is a steel fracture core model and a schematic diagram of the steel core structure; Figure 3 It is a schematic diagram of the piston container structure; Figure 4 It is a schematic diagram of the piston container cylinder structure; Figure 5 It is a schematic diagram of the plug structure; Figure 6 Schematic diagram of piston structure; Figure 7 It is a schematic diagram of the lower port structure of the container; Figure 8It is a schematic diagram of the pressure cap structure.

[0017] Numbers in the figure: 1-double-bar pump, 2-2000mL piston container, 3-500mL piston container, 4-pressure sensor, 5-connector, 6-core holder, 7-steel fracture core model, 8-steel core, 9-waste liquid recovery tank, 10-high-pressure pipe, 11-plug, 12-pressure cap, 13-piston, 14-lower port of container. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solution of the present invention, the present invention is further described below in conjunction with the accompanying drawings: Combination Figure 1-Figure 8 As shown, the temporary plugging agent strength evaluation device includes a 2000mL piston container 2, a 500mL piston container 3, a pressure sensor 4, a high-pressure pipe 10, a double-bar pump 1, a core holder 6, a steel fracture core model 7, a steel core 8, and a waste liquid recovery tank 9. The plug of the piston container 2 is connected to the double-bar pump 1, the lower port of the piston container 2 is connected to a system consisting of a pipeline and a valve, and the end of the pipeline is connected to the inlet of the high-pressure pipe 10. The high-pressure pipe 10 is provided with a pressure sensor 4 at its inlet end to monitor the change of pressure, and the end of the high-pressure pipe 10 is connected to the core holder 6. The core holder 6 is equipped with a steel fracture core model 7 and a steel core 8. The outlet end of the steel fracture core model 7 is connected to the steel core 8. The end of the steel core 8 is connected to the waste liquid recovery tank 9. The piston container includes a cylinder, a pressure cap 12, a plug 11, a lower port 14 of the container, a piston 13, and an O-ring.

[0019] The piston container includes two types: 500mL piston container and 2000mL piston container. There is one 2000mL piston container and three 500mL piston containers. The valve mechanism is composed of four valve groups arranged in the valve frame. A rolling wheel is arranged at the bottom of the valve frame. The four valve groups are connected in parallel to the upper side of the bottom connecting pipe, among which three valve groups are respectively connected to a 500mL piston container, and one valve group is connected to the 2000mL piston container. The valve group connected to the 2000mL piston container is connected to the starting end of the bottom connecting pipe through a two-way connection, and the other three valve groups are connected to the bottom connecting pipe through a three-way connection, and the end of the bottom connection is connected to the inlet of the high-pressure pipe; the plug of the 2000mL piston container is connected to the double-bar pump; the valve group is composed of two valves in series.

[0020] The steel fracture core model is a tapered steel fracture core model with a square inlet of 15×15mm, a rectangular outlet of 15×1mm, and a total length of 900mm. It is composed of three sections of steel fracture core models. The steel core is a hollow cylinder with an outer diameter of 25mm, an inner diameter of 6mm, and a length of 100mm.

[0021] The temporary plugging agent strength evaluation device provided in this embodiment is used to perform an experimental test on the temporary plugging agent, and the specific steps are as follows: (1) Prepare fracturing fluid: 0.6% thickener and 0.2% surfactant.

[0022] (2) Check the air tightness of the connecting device; (3) Select 30g of yellow granular temporary plugging agent and white powder temporary plugging agent and put them into the steel fracture core model in a ratio of 5:5. The particle size of the yellow granular temporary plugging agent is 3.16~3.4mm, and the particle size of the white powder temporary plugging agent is 1.08~1.84mm. Pour the fracturing fluid into the piston container, carry out the displacement experiment at an injection rate of 50mL / min, and collect pressure data through the pressure sensor to determine whether the pressure standard of 40MPa can be reached. The achievement of this pressure level is a key indicator for evaluating the strength of the temporary plugging agent.

[0023] The results show that the pressure reaches 43.97MPa at 4 minutes of the experimental test, indicating that the strength of the temporary plugging agent reaches the pressure standard of 40MPa. The achievement of this pressure level is a key indicator for evaluating the strength of the temporary plugging agent. The present invention determines whether the pressure standard of 40MPa can be reached by monitoring the change of the net pressure after the temporary plugging agent enters the crack. By accurately evaluating the performance of the temporary plugging agent, the use of temporary plugging agents with poor effects can be avoided, reducing the cost and time of oil field development.

Claims

1. A temporary plugging agent strength evaluation device, characterized in that: The temporary plugging agent strength evaluation device comprises a piston container, a pressure sensor, a high-pressure pipe, a double-bar pump, a core clamp, a steel fracture core model, a steel core, and a waste liquid recovery tank; the piston container has a pressure bearing capacity of 40MPa, the plug of the piston container is connected to the double-bar pump, the lower port of the piston container is connected to a valve mechanism, and the end of the valve mechanism is connected to the inlet of the high-pressure pipe; the high-pressure pipe is provided with a pressure sensor at its inlet end, and the end of the high-pressure pipe is connected to the core clamp; the core clamp is provided with a steel fracture core model and a steel core, the outlet end of the steel fracture core model is connected to the steel core, and the end of the steel core is connected to the waste liquid recovery tank; a displacement experiment is carried out by using the temporary plugging agent strength evaluation device to simulate the plugging condition of the temporary plugging agent in the fracture, monitor the change of pressure after the temporary plugging agent enters the fracture, determine whether the pressure standard of 40MPa can be reached, and accurately simulate and evaluate the temporary plugging performance of the temporary plugging agent.

2. The temporary plugging agent strength evaluation device according to claim 1, characterized in that: The piston container includes two types, namely a 500mL piston container and a 2000mL piston container, with one 2000mL piston container and three 500mL piston containers; the valve mechanism is composed of four valve groups arranged in the valve frame, a rolling wheel is arranged at the bottom of the valve frame, and the four valve groups are connected in parallel to the upper side of the bottom connecting pipe, among which three valve groups are respectively connected to a 500mL piston container, and one valve group is connected to the 2000mL piston container; the valve group connected to the 2000mL piston container is connected to the starting end of the bottom connecting pipe through a two-way connection, and the other three valve groups are all connected to the bottom connecting pipe through a three-way connection, and the end of the bottom connection is connected to the inlet of the high-pressure pipe; the plug of the 2000mL piston container is connected to the double-bar pump; the valve group is composed of two valves in series.

3. The temporary plugging agent strength evaluation device according to claim 2, characterized in that: The high-pressure pipe has an outer diameter of 25 mm, an inner diameter of 15 mm and a length of 1000 mm.

4. The temporary plugging agent strength evaluation device according to claim 3, characterized in that: The core holder is 1000 mm long and contains a steel fracture core model and a steel core. The steel fracture core model and the steel core are coaxially connected. The steel fracture core model is located at the inlet end of the core holder and the steel core is located at the outlet end of the core holder.

5. The temporary plugging agent strength evaluation device according to claim 4, characterized in that: The steel fracture core model is a tapered steel fracture core model with a square inlet of 15×15 mm, a rectangular outlet of 15×1 mm, and a total length of 900 mm, and is formed by splicing three sections of steel fracture core models.

6. The temporary plugging agent strength evaluation device according to claim 5, characterized in that: The steel core is a hollow cylinder with an outer diameter of 25 mm, an inner diameter of 6 mm and a length of 100 mm.

7. The temporary plugging agent strength evaluation device according to claim 6, characterized in that: The method for evaluating a temporary plugging agent by the temporary plugging agent strength evaluation device comprises the following steps: (1) Prepare fracturing fluid: thickener 0.6%, surfactant 0.2%; (2) Check the air tightness of the temporary plugging agent strength evaluation device; (3) A total of 30 g of yellow granular temporary plugging agent and white powder temporary plugging agent were selected and placed in a steel fracture core model in a ratio of 5:5; the particle size of the yellow granular temporary plugging agent was 3.16-3.4 mm, and the particle size of the white powder temporary plugging agent was 1.08-1.84 mm; the fracturing fluid was poured into the piston container, and a displacement experiment was carried out at an injection rate of 50 mL / min. The pressure data was collected through a pressure sensor to determine whether the pressure standard of 40 MPa could be reached.

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