Experimental method and device for proppant flowback performance test

Abstract

The invention discloses an experimental method and device for testing flowback performance of a proppant, and belongs to the technical field of hydraulic fracturing in oil exploitation, the method comprises the following steps: step 1, stirring prepared slurry by a stirring tank, and pressurizing and injecting the slurry into a simulated formation fracture flat plate model by a liquid injection pump; 2, when the fracturing fluid containing the propping agent is discharged at the constant flow speed, fracturing is completed; step 3, closing an emptying valve on a fracturing fluid output pipeline, closing a sealing plate by a simulated fracture closing module under the action of a gas source, applying closing pressure to simulate fracture closing, inputting liquid into a stratum at a certain pressure after the input gas source passes through a gas path containing an intermediate container, and simulating formation fluid production; and step 4, after the input gas source passes through the gas path only containing the pressure regulating valve, inputting gas into the stratum at a certain pressure, and simulating gas production of the stratum. The invention further discloses an experimental device for testing the flowback performance of the proppant. The invention studies the flowback conditions of the proppant under different conditions, and provides reference for reasonable preparation of the proppant.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic fracturing in petroleum exploitation, and relates to an experimental method and a device for testing proppant spitting performance. Background Art

[0002] For oil wells with formation pressure coefficients above 0.6 in unconventional oil and gas reservoirs, more than 70% of the construction wells have serious proppant spitting. With the increase of fracturing fluid backflow and production pressure difference, part of the proppant is also brought into the wellbore, which brings many problems. It is mainly manifested in the following four aspects: ① Part of the backflow proppant enters the pump barrel with the liquid flow, causing pump jamming and pump inspection, which not only increases the workload but also delays the timing of fracturing fluid backflow. ② The backflow of proppant will cause the proppant crack to narrow, causing the fracture conductivity to decrease, thereby affecting the fracturing production increase effect. If most of the proppant is spit out in the near-joint zone, the crack will be completely closed, resulting in the failure of fracturing construction. ③ In the normal production process, since the backflow of proppant in the construction well is proportional to the pumping volume, excessive production parameters will aggravate the backflow of proppant and shorten the effective period of production increase, while taking smaller working parameters will limit the production of the oil well and inhibit the production increase capacity of the construction well.

[0003] Based on the above situation, in order to control proppant spitting, maximize the capacity of fracturing to increase production, and extend the effectiveness of the measures, we have carried out research on the process of controlling proppant spitting. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to solve the above technical problems and provide an experimental method and device for testing the proppant spitting performance. By changing the proppant material ratio parameters and pumping flow rate, the proppant spitting under different conditions is studied to provide a reference for the reasonable preparation of proppant.

[0005] In order to solve the above technical problems, on the one hand, an embodiment of the present invention provides an experimental method for testing proppant spit-out performance, comprising the following steps:

[0006] Step 1: The mixing tank of the proppant spitting test device stirs the prepared mud and then injects it into the simulated formation fracture flat plate model under pressure through the injection pump;

[0007] Step 2: When the proppant-containing fracturing fluid is discharged at a constant flow rate, the fracturing is completed;

[0008] Step 3: The drain valve on the fracturing fluid output pipeline is closed, and the simulated fracture closure module closes the sealing plate under the action of the gas source to start applying closing pressure to simulate fracture closure. At the same time, after the input gas source passes through the gas circuit containing the intermediate container, the liquid is input into the formation at a certain pressure under the action of the pressure regulating valve to simulate formation fluid production;

[0009] Step 4: After the input gas source passes through the gas circuit containing only the pressure regulating valve, the gas is input into the formation at a certain pressure under the action of the pressure regulating valve to simulate formation gas production.

[0010] Furthermore, in step 1, throttling and speed regulation are performed by the back pressure valve and pressure relief is performed by the safety valve before injection.

[0011] Furthermore, in step 1, the flat plate model simulating the formation fracture is adjusted in phase angle under the action of the flip support to simulate different fracture angles.

[0012] Furthermore, in step 1, the simulated wellbore of the flat plate model simulating the formation fracture has different perforation densities at different phase angles, and the number of holes is adjusted by rotating the perforating inner tube.

[0013] Furthermore, after the proppant-containing fracturing fluid is spitted back, the drain valve on the fracturing fluid input pipeline is closed, and then the fracturing fluid is discharged through the filter, and the proppant content in the spitted back fluid is filtered out to evaluate the proppant effect.

[0014] On the other hand, an embodiment of the present invention further provides an experimental device for testing the proppant spitting performance, comprising: a motor is installed above the stirring tank and fixed with threads to drive the stirring paddle in the stirring tank to rotate; the outlet of the lower part of the stirring paddle is connected to a metal pipe with threads, and the other end of the metal pipe is connected to a tee with threads, and the tee is respectively connected to a drain valve and an injection pump with threads; the injection pump is connected to a simulated wellbore of a fracture plate model through a metal pipe, the drain valve, the inlet pressure gauge, the safety valve, and the filter are respectively connected to the metal pipe with threads, and the lower part of the filter is connected to a back pressure valve with threads; the electric flip bracket in the fracture plate model is connected to the fracture plate with a bearing, and the simulated wellbore and the outlet are connected to the fracture plate with a sealing clamp; the front and rear ends of the fracture plate are respectively connected to a gas source and an intermediate container with metal pipes with threads to control the closing pressure of the fracture plate; the pressure regulating valve, the pressure gauge, and the intermediate container are respectively connected to the metal pipe with threads; the fracture plate outlet is connected to a tee, and is respectively connected to a filter and a cleaning bypass with metal pipes; the filter is connected to a flow meter and an outlet pressure gauge with a metal pipe, and is finally connected to the upper part of the stirring tank; the cleaning bypass is connected to a metal pipe, and is finally connected to the upper part of the stirring tank.

[0015] Furthermore, the simulated formation fracture plate model includes: simulated horizontal wells and fracture plate outlets are distributed at both ends of the fracture plate, and an electric rotating bracket is connected to the fracture plate with a bearing; the upper part of the fracture plate is fixed and visible, and the lower part is sealed with a movable metal closed sealing plate; the outer layer of the closed sealing plate is a fixed metal shell, and by injecting high-pressure gas or liquid between the metal shell and the closed sealing plate, the closed sealing plate can be pushed to move and pressure can be applied to the medium in the wellbore; the simulated horizontal well is measured with holes to simulate horizontal well perforation; by adjusting the rotation angle of the electric rotating bracket, vertical seams, horizontal seams and cracks at other angles can be simulated.

[0016] The above technical solution of the embodiment of the present invention has the following beneficial technical effects:

[0017] The technical solution of the present invention studies the paving morphology of proppant under different fracturing fluid pumping flow rates, can simulate the proppant spitting under different gas and liquid production pressures, and can study whether the proppant spitting can be effectively controlled after adding different new materials to the fracturing fluid. The present invention studies the proppant spitting under different conditions by changing the proppant material ratio parameters and pumping flow rate, and provides a reference for the rational preparation of proppant. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The figure shows a schematic diagram of the process of the proppant spitting test experimental device of the present invention;

[0019] Figure 2 Schematic diagram of the structure of the flat plate model for simulating formation fractures of the present invention; wherein A is a perforation diagram on a simulated horizontal well casing, B is a plan view of a simulated vertical fracture, C is a side view of a simulated vertical fracture, D is a plan view of a simulated horizontal fracture, and E is a side view of a simulated horizontal fracture. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0021] like Figure 1The schematic diagram of the proppant spitting test experimental device is shown. After the fracturing fluid carrying proppant comes out of the stirring tank 1, it is injected into the simulated formation fracture flat plate model at a certain pressure (inlet pressure 19 is stable) through the injection pump 2. Then it flows back to the stirring tank 1 through the filter 6 and the flow meter 16 after passing through the outlet 17 pipeline of the simulated formation fracture flat plate model. After the circulation of the proppant fracturing fluid is stable, that is, the solid phase filtered out by the filter remains unchanged, the liquid phase of the flow meter remains unchanged, and the outlet pressure 18 remains stable, it is considered that the fracturing is completed. Then close the inlet emptying valve 3, and adjust the closed sealing plate under the action of the gas source 11 to adjust the crack width to start applying the closing pressure to simulate the crack closing module 12. The safety valve 15 is used to prevent the closing spitting hydraulic pressure from being too large to protect the pipeline; then, after the input gas source passes through the gas circuit containing the intermediate container 7, the liquid is input into the formation at a certain pressure under the action of the pressure regulating valve 10 to simulate the formation liquid production; after the input gas source passes through the gas circuit containing only the pressure regulating valve, the gas is input into the formation at a certain pressure under the action of the pressure regulating valve to simulate the formation gas production. The vomited fracturing fluid carrying proppant is filtered out of the solid phase through the filter at the entrance of the simulated wellbore to evaluate the proppant effect, and the vomited fluid is discharged through the back pressure valve 4; after the experiment, the cleaning bypass 5 is opened to clean the residual fracturing fluid and proppant in the pipeline and flow into the mixing tank.

[0022] like Figure 2 As shown, A is a perforation diagram on a simulated horizontal well casing, B is a plan view of a simulated vertical seam, C is a side view of a simulated vertical seam, D is a plan view of a simulated horizontal seam, and E is a side view of a simulated horizontal seam. The simulated formation fracture flat plate model mainly comprises a PC visual cover plate, a PC visual flat plate, a sealing ring, a closed sealing plate 21, a sealing cavity, and the like. The visible range 24 is 1000*300mm.

[0023] The simulated wellbore of the simulated formation fracture flat plate model can be perforated with different holes at different phase angles, and the hole size and density can be adjusted by rotating the inner tube of the perforator 20 .

[0024] The simulated formation fracture flat plate model can adjust the angle by means of the electric flip support 14 to simulate the proppant spitting condition under the fracturing of the horizontal fracture 22 and the vertical fracture 23 .

[0025] The electric flip bracket can be installed on an independent mobile bracket, and adopts ergonomic design, which is convenient for direct observation in the most comfortable posture during the experiment and easy to operate.

[0026] The simulated stratum fracture flat plate model is a single-sided fully visible structure, and is sealed and fixed with a double-layer fully transparent PC plate, which is convenient for experimental observation and recording.

[0027] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. An experimental method for testing proppant spit-out performance, characterized in that: The steps include: Step 1: The mixing tank of the proppant spitting test device stirs the prepared mud and then injects it into the simulated formation fracture flat plate model under pressure through the injection pump; Step 2: When the proppant-containing fracturing fluid is discharged at a constant flow rate, the fracturing is completed; Step 3: The drain valve on the fracturing fluid output pipeline is closed, and the simulated fracture closure module closes the sealing plate under the action of the gas source to start applying closing pressure to simulate fracture closure. At the same time, after the input gas source passes through the gas circuit containing the intermediate container, the liquid is input into the formation at a certain pressure under the action of the pressure regulating valve to simulate formation fluid production; Step 4: After the input gas source passes through the gas circuit containing only the pressure regulating valve, the gas is input into the formation at a certain pressure under the action of the pressure regulating valve to simulate formation gas production.

2. The experimental method for testing proppant spit-out performance according to claim 1, characterized in that: In step 1, throttling and speed regulation are performed through the back pressure valve and pressure relief is performed through the safety valve before injection.

3. The experimental method for testing proppant spit-out performance according to claim 1, characterized in that: In step 1, the flat plate model simulating the formation fracture is adjusted to adjust the phase angle under the action of the flip support to simulate different fracture angles.

4. The experimental method for testing proppant spit-out performance according to claim 1, characterized in that: In step 1, the simulated wellbore of the flat plate model simulating the formation fracture has different perforation densities at different phase angles, and the number of holes is adjusted by rotating the perforating inner tube.

5. The experimental method for testing proppant spit-out performance according to claim 1, characterized in that: After the fracturing fluid containing proppant is spitted back, the drain valve on the fracturing fluid input pipeline is closed, and then the fracturing fluid is discharged through the filter, and the proppant content in the spitted back fluid is filtered out to evaluate the proppant effect.

6. An experimental device for testing proppant disgorgement performance of the method according to any one of claims 1 to 5, characterized in that: include: A motor is installed above the stirring tank and fixed with threads to drive the stirring paddle in the stirring tank to rotate; the lower outlet of the stirring paddle is connected to a metal pipe with threads, and the other end of the metal pipe is connected to a tee with threads, and the tee is connected to the drain valve and the injection pump with threads respectively; the injection pump is connected to the simulated wellbore of the fracture plate model through a metal pipe, the drain valve, the inlet pressure gauge, the safety valve, and the filter are connected to the metal pipe with threads respectively, and the lower part of the filter is connected to the back pressure valve with threads; the electric flip bracket in the fracture plate model is connected to the fracture plate with a bearing, and the simulated wellbore and the outlet are connected to the fracture plate with a sealing splint; the front and rear ends of the fracture plate are connected to the gas source and the intermediate container with metal pipes with threads respectively, which are used to control the closing pressure of the fracture plate; the pressure regulating valve, the pressure gauge, and the intermediate container are connected to the metal pipe with threads respectively; the fracture plate outlet is connected to the tee, and is connected to the filter and the cleaning bypass with metal pipes respectively; the filter is connected to the flow meter and the outlet pressure gauge with a metal pipe, and is finally connected to the upper part of the stirring tank; the cleaning bypass is connected to the metal pipe, and is finally connected to the upper part of the stirring tank.

7. The experimental device for testing proppant disgorgement performance according to claim 6, characterized in that: The simulated formation fracture plate model comprises: simulated horizontal wells and fracture plate outlets are distributed at both ends of the fracture plate, and an electric rotating bracket is connected to the fracture plate by a bearing; the upper part of the fracture plate is fixed and visible, and the lower part is sealed by a movable metal closed sealing plate; the outer layer of the closed sealing plate is a fixed metal shell, and by injecting high-pressure gas or liquid between the metal shell and the closed sealing plate, the closed sealing plate can be pushed to move and pressure can be applied to the medium in the wellbore; holes are distributed inside the simulated horizontal well to simulate horizontal well perforation; and by adjusting the rotation angle of the electric rotating bracket, vertical seams, horizontal seams and fractures at other angles can be simulated.

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