Fractured multi-layer rock core combined displacement device and method

Abstract

The invention belongs to the technical field of rock core displacement experiments, and particularly relates to a fracturing multilayer rock core combined displacement device and method, an ISCO pump and an intermediate container are connected through a pipeline, the pipeline between the ISCO pump and the intermediate container is provided with a control valve, and an outlet is connected with an injection port of a longitudinal heterogeneous multilayer rock core through an injection pipeline; an extraction port of the longitudinal heterogeneous multi-layer rock core is connected with an upper inlet of the output metering system through an injection pipeline, the longitudinal heterogeneous multi-layer rock core is arranged in the confining pressure device, and the injection port, the extraction port and the true triaxial compressor are connected with the confining pressure device respectively; a plurality of steel pipes are placed in the core, penetrate through different physical property reservoirs and are connected with an injection port to form a circulation pipeline, a pipeline at one end of the injection port is connected with an acoustic emission system, and the devices are all connected with a computer control system and are controlled by the computer control system. According to the invention, the transformation effect of the fracture size and the fracture network form after fracturing on the reservoir can be truly detected.

Description

Technical Field

[0001] The invention belongs to the technical field of core displacement experiments, and in particular relates to a fractured multi-layer core combined displacement device and method. Background Art

[0002] Extensive geological surveys and field studies have revealed that the irregular arrangement of mineral particles creates significant heterogeneity in unconventional reservoirs. This heterogeneity is a significant obstacle to efficient oilfield development and production, particularly the inability to quantitatively measure the effectiveness of enhanced oil recovery after hydraulic fracturing.

[0003] Currently, conventional fracturing experiments are unable to resolve these challenges. However, simulated multi-layer heterogeneous fracturing physical model tests and large-scale physical model flat core displacement experiments are effective technical means to understand rock fracture morphology, reservoir fracturing transformation, and improve oil recovery efficiency. Summary of the Invention

[0004] The present invention effectively solves the above-mentioned problems and breaks the technical barriers to reservoir transformation and oil layer development. The main purpose of the present invention is to provide a combined fractured multi-layer core displacement experimental device and method for solving and observing fractured reservoir transformation and the enhanced recovery rate after transformation during oil field production. The innovative proposal integrates hydraulic fracturing experiments and multi-layer flat core displacement to achieve the effect of simulating reservoirs and improving recovery rate after transformation.

[0005] In order to achieve the above objectives, the present invention provides a combined displacement device and method for fracturing multi-layer cores, wherein the combined displacement device for fracturing multi-layer cores comprises: a pumping system, a multi-layer core device, an output metering device system, and an acoustic emission detection system.

[0006] The pump injection system is mainly composed of an ISCO pump, an intermediate container, a control valve and corresponding injection pipelines.

[0007] The multi-layer core device is mainly composed of casing, injection port and production port. A plurality of steel pipes are placed inside the core to penetrate different physical reservoirs to simulate the fracturing casing in the oil field production process and are connected to the flat injection port to form a circulation pipeline. The injection port is connected to the pumping system, and the production port is connected to the output metering system. When the displacement fluid is injected into the core, the external output metering system can calculate the gas flow, oil output, liquid output, etc. At the same time, the hydraulic pump is used to apply confining pressure in the X, Y and Z directions to the core to simulate the real stress state. The loading plate is the same size as the sample surface to ensure uniform pressure. The loading process adopts variable frequency loading technology, which is quickly pressurized by the hydraulic station, and then accurately pressurized by the control system, and can realize servo tracking of pressure.

[0008] The output metering system is mainly composed of a gas flow meter, a pressure gauge, a high-pressure transmission pipeline, a measuring cylinder, a gas collection device, a valve and a corresponding injection pipeline.

[0009] The acoustic emission detection system detects stress changes in the rock mass and the resulting acoustic wave signals of tiny cracks and fractures, thereby determining the rock mass's failure process and the time point of failure, so as to achieve the purpose of predicting and forecasting the stability and safety of the rock mass.

[0010] As can be seen from the above technical solution, the present invention provides a combined displacement experimental device for fracturing multi-layer cores, comprising: a pumping system, a multi-layer core device, an output metering device system, and an acoustic emission detection system. The outlet of the pumping system is connected to the injection end of the longitudinal heterogeneous multi-layer core through an injection pipeline, and the production end of the longitudinal heterogeneous multi-layer core is connected to the upper inlet of the output metering system through an injection pipeline. The experimental core is connected to the true triaxial loading system, and the experimental core is placed in the true triaxial loading system at the same time. The injection end, the production end, and the true triaxial loading are respectively connected to the confining pressure device. The above-mentioned device system and the acoustic emission detection system are all connected to the computer system through corresponding pipelines and are controlled by the computer control system.

[0011] The present invention further proposes a combined displacement method for a fractured multi-layer core, using the combined displacement device for a fractured multi-layer core as described above. The combined displacement method for a fractured multi-layer core comprises:

[0012] Step 1: Place the core (with movable oil volume a) into the casing, place it in the confining pressure device, start the ISCO pump, and inject the displacement fluid in the intermediate container into the injection port of the core.

[0013] Step 2: When there is no liquid output from the production port, use a pipeline to connect the production port to the output metering system to achieve gas-liquid separation, and measure the gas, produced liquid, and oil volume (the oil volume is b) respectively. The recovery factor R before fracturing is calculated using the following formula: b for:

[0014]

[0015] Step 3: The computer control system sets the hydraulic pump pressure to simulate formation stress. The fracturing pump is activated and injected according to the programmed pattern using a signal generator. During the fracturing process, an acoustic emission device is used to detect the timing and type of fractures within the core. The system then feeds the acoustic emission signal to a signal amplifier, which processes the signal and provides the corresponding numerical value to the computer.

[0016] Step 4: When the pressure curve drops sharply, stop injection, retract the three-axis loading hydraulic cylinder, start the confining pressure device and inject proppant at the same time. After shutting in the well, drive the displacement fluid to displace the sand-carrying fluid to complete the reservoir transformation.

[0017] Step 5: Start the ISCO pump and inject the displacement fluid from the intermediate container into the injection port of the core. The produced fluid flows to the separation device through the production port. Observe the amount of produced gas and oil (the oil volume is c) and the amount of produced liquid. Calculate the enhanced oil recovery R after fracturing using the following formula: a for:

[0018]

[0019] According to the above technical solution, the present invention provides a combined fracturing multi-layer core displacement device and method, which has the following beneficial effects:

[0020] 1) The present invention can simulate the fracturing process of heterogeneous multi-layer cores under different ground stresses.

[0021] 2) The present invention can truly detect the size of cracks and the morphology of the fracture network after fracturing, and the transformation effect on the reservoir.

[0022] 3) The present invention can simulate core displacement and observe the effect of enhanced oil recovery after fracturing transformation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention.

[0025] Description of reference numerals:

[0026] 1-Computer control system; 2-Intermediate container; 3-ISCO pump; 4-Control valve; 5-Fracturing pump; 6-Hydraulic pump; 7-Casing; 8-True three-axis compressor; 9-Gas flow meter; 10-Graduating cylinder; 11-Output metering system; 12-Separator; 13-Production port; 14-Pressure gauge; 15-Signal amplifier; 16-Acoustic emission device; 17-Injection port; 18-Top reservoir; 19-Type II reservoir; 20-Type III reservoir; 21-Bottom reservoir; 22-Confining pressure device. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0028] Example 1

[0029] The present invention provides a fracturing multi-layer core combined displacement experimental device and method, which specifically includes the following contents:

[0030] The fracturing multi-layer core combined displacement experimental device includes: a pump injection system, a multi-layer core device, an output metering device system, and an acoustic emission detection system.

[0031] The pumping system consists of an intermediate container 2, an ISCO pump 3, a control valve 4 and a transmission pipeline.

[0032] The multi-layer core device is assembled by manufacturing materials to form an injection port 17, a production port 13, a top reservoir 18, a second reservoir 19, a third type reservoir 20, a bottom reservoir 21, and a casing 7.

[0033] The output metering device system consists of a gas flow meter 9 , a measuring cylinder 10 , and a separator 12 .

[0034] The acoustic emission system is composed of an acoustic emission device 16 and a signal amplifier 15 .

[0035] The combined fracturing and multi-layer core displacement method includes:

[0036] Step 1: First, place the core (with a movable oil volume of a) into the casing 7 and place it in the confining pressure device 22. Start the ISCO pump 3 and inject the displacement fluid from the intermediate container 2 into the injection port 17 of the core.

[0037] Step 2: When there is no liquid output from the production port, use a pipeline to connect the production port 13 to the output metering system to achieve gas-liquid separation, measure the gas and produced liquid, and oil volume (the oil volume is b) respectively, and calculate the recovery factor R before fracturing using the following formula: b for:

[0038]

[0039] Step 3: The computer control system 1 sets the pressure value of the hydraulic pump 6 to simulate the formation stress. The fracturing pump 6 is started and the signal generator is used to make the pump inject according to the set method. During the fracturing process, the acoustic emission device 16 detects the timing and type of fractures within the core. The system feeds the acoustic emission signal to the signal amplifier 15, which processes the signal and feeds the corresponding value to the computer.

[0040] Step 4: When the pressure curve drops sharply, stop injection, retract the three-axis loading hydraulic cylinder, start the confining pressure device 22 and inject proppant at the same time, shut in the well and drive the displacement fluid to displace the sand-carrying fluid to complete the reservoir transformation.

[0041] Step 5: Start the ISCO pump 3 and inject the displacement fluid from the intermediate container 2 into the injection port 17 of the core. The produced fluid flows to the separator 12 through the production port 13. Observe the amount of produced gas and oil (the oil amount is c) and the amount of produced liquid. Calculate the enhanced oil recovery R after fracturing using the following formula: a for:

[0042]

[0043] The specific experimental steps are:

[0044] During the experiment, the core was first placed in the casing 7 and placed in the confining pressure device 22. The ISCO pump 3 was started, and the displacement fluid in the intermediate container 2 was injected into the injection port 17 of the core. When there was no liquid output from the production port 13, a pipeline was used to connect the production port 13 to the output metering system 11 to achieve gas-liquid separation, measure the gas and output liquid and oil respectively, and calculate the recovery factor Rb before fracturing. The hydraulic pump device 6 was set on the computer control system 1 to simulate the formation stress by numerical pressure, and the fracturing pump 5 was started to inject according to the set method through the signal generator. The acoustic emission device 16 was used to detect the fracture timing and fracture type inside the core, and the system fed back to the signal amplifier 15 to process the acoustic emission signal. When the pressure curve suddenly dropped, the injection was stopped, the three-axis loading hydraulic cylinder was withdrawn, and the confining pressure device was started to inject proppant and then shut down the well to displace it. Close the control valve 4 and start the ISCO pump 3 to inject the injection liquid from the intermediate container 2 into the core injection port 17. Use a pipeline to connect the production port 13 to the output metering system 11 to achieve gas-liquid separation. After measuring the gas, produced liquid and oil respectively, calculate the recovery factor Ra before fracturing. Finally, calculate the enhanced recovery factor R after fracturing transformation. This is used to quantitatively analyze the enhanced recovery effect after the transformation, and the experiment ends.

[0045] In this specification, terms such as "comprises", "comprising" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. It should be noted that, unless there is a conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention is not limited to any single aspect, nor to any single embodiment, nor to any combination and / or permutation of these aspects and / or embodiments. Moreover, each aspect and / or embodiment of the present invention may be used alone or in combination with one or more other aspects and / or embodiments thereof.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. A fracturing multi-layer core joint displacement device, characterized in that IS The CO pump (3) and the intermediate container (2) are connected by a pipeline. The pipeline between them is provided with a control valve (4). The outlet is connected to the injection port (17) of the longitudinal heterogeneous multilayer core through the injection pipeline. The production port (13) of the longitudinal heterogeneous multilayer core is connected to the upper inlet of the output metering system (11) through the injection pipeline. The longitudinal heterogeneous multilayer core is placed in a confining pressure device (22). The injection port (17), the production port (13) and the true three-axis compressor (8) are respectively connected to the confining pressure device (22). Multiple steel pipes are placed inside the core to penetrate different physical properties of reservoirs to simulate the fracturing casing (7) of the oil field production process and are connected to the injection port (17) to form a circulation pipeline. The pipeline at one end of the injection port (17) is connected to the acoustic emission system. The above devices are all connected to a computer control system (1) and are controlled by the computer control system (1).

2. The multi-layer fractured core combined displacement device according to claim 1 is characterized in that: The longitudinal heterogeneous multi-layer core is divided into four parts from top to bottom: top reservoir (18), second type reservoir (19), third type reservoir (20), and bottom reservoir (21).

3. The multi-layer fractured core combined displacement device according to claim 1 is characterized in that: The output metering system (11) includes a gas flow meter (9), a measuring cylinder (10), and a separator (12).

4. The multi-layer fractured core combined displacement device according to claim 1 is characterized in that: The acoustic emission system consists of an acoustic emission device (16) and a signal amplifier (15).

5. A combined fracturing and multi-layer core displacement method, characterized in that: The following steps are involved: Step 1: First, place the core in the casing (7) and place it in the confining pressure device (22). The movable oil volume of the core is a. Start the ISCO pump (3) and inject the displacement fluid in the intermediate container (2) into the injection port (17) of the core. Step 2: When there is no liquid output from the production port, use a pipeline to connect the production port (13) to the output metering system to achieve gas-liquid separation, measure the gas and output liquid and oil volume b respectively, and calculate the recovery factor R before fracturing b ; Step 3: Set the pressure value of the hydraulic pump (6) on the computer control system (1) to simulate the formation stress, start the fracturing pump (6) and use the signal generator to make the pump inject in the set manner. During the fracturing process, use the acoustic emission device (16) to detect the fracture timing and crack type inside the core, and feed back the acoustic emission signal to the signal amplifier (15) through the system to realize the processing of the acoustic emission signal and feed back the corresponding value to the computer; Step 4: When the pressure curve drops sharply, stop the injection, retract the three-axis loading hydraulic cylinder, start the confining pressure device (22) and inject the proppant at the same time, shut down the well and drive the displacement fluid to displace the sand-carrying fluid to complete the reservoir transformation; Step 5: Start the ISCO pump (3) and inject the displacement fluid in the intermediate container (2) into the injection port (17) of the core. The produced fluid flows to the separator (12) through the production port (13). Observe the amount of produced gas and oil c and the amount of produced liquid, and calculate the enhanced recovery factor R after fracturing. a .

6. The fractured multi-layer core combined displacement method according to claim 1, characterized in that: Recovery factor R b for:

7. The fractured multi-layer core combined displacement method according to claim 1, characterized in that: Recovery factor R a for:

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