A shear self-supporting crack mud pollution experimental device and method

Abstract

The present invention discloses a shear self-supporting fracture mud contamination experimental device and method, which belongs to the field of rock displacement experimental technology. A clamp and an intermediate container are provided to simulate the intrusion of mud in the shear self-supporting fracture. The clamp, the intermediate container, the measuring cylinder, the high-pressure gas storage tank and the confining pressure pump are used to realize the simulation of the whole process of shear self-supporting fracture pollution-blowout-reinjection of the repeated transformation well of heavy mud contamination. The device is easy to operate and is closely integrated with the working conditions of the mud-contaminated well. The experimental device of the present invention has a simple structure and is easy to operate. It can quickly realize the measurement of rock parameters on site; carry out the research on the mud contamination of shear self-supporting fractures, and through the innovative experimental device and method, break the mechanism and law of mud contamination of shear self-supporting fractures, and provide support for the transformation of such wells.

Description

Technical Field

[0001] The invention belongs to the technical field of rock displacement experiments, and in particular relates to a shear self-supporting fracture mud pollution experimental device and method. Background Art

[0002] Research has shown that mud clay can invade formation pores and natural fractures to varying degrees, particularly in high-yield carbonate reservoirs. The extent of this invasion is related to drilling time, formation permeability, mud type, and the number of trips during drilling operations. Mud filtrate can also cause clay swelling and migration. HCO₃⁻ ions in formation water can also react with Ca₂⁺ ions from high-calcium mud to form precipitates that clog the wellbore. Existing patents and papers primarily study mud contamination and invasion of natural fractures during drilling operations, primarily considering mud invasion processes under in-situ or drilling conditions. Fracture contamination, however, does not consider natural fracture shear dislocation, mud invasion, blowout, and re-injection processes. For heavily mud-contaminated, repeatedly stimulated wells, the initial stimulation results in stress perturbations and shear dislocations in the subsurface. How mud invades these self-supporting shear dislocations, whether blowouts can remove blockages, and whether mud affects subsequent fracturing pressures remain unclear, and testing equipment and methods are lacking. Summary of the Invention

[0003] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a shear self-supporting fracture mud contamination experimental device and method to solve the technical problems that the simulation research in the prior art does not take into account the shear dislocation of natural fractures and the mud invasion, blowout and re-injection process, how the mud invades in the shear dislocation self-support, whether it can be blown out to unblock, whether the mud affects the subsequent fracturing construction pressure, etc., and there is a lack of testing devices and testing methods.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A shear self-supporting fracture mud pollution experimental device includes: a clamp, the inlet end of the clamp is connected to an intermediate container, the intermediate container is connected to a high-pressure gas storage tank, and a pressure gauge is provided between the two, the outlet end of the clamp is connected to a measuring cylinder, a core is placed inside the clamp, and the clamp is also connected to a confining pressure pump.

[0006] Preferably, a circulation device is further provided between the intermediate container and the inlet end of the holder.

[0007] Preferably, the circulation device comprises a shell, the inside of the shell is connected to the pressure providing device via an air inlet pipe, the air inlet pipe is provided with a valve, and the shell is provided with an outlet.

[0008] Preferably, a six-way valve is connected between the clamper and the high-pressure gas storage tank to replace the intermediate container.

[0009] Preferably, the core is a fractured core.

[0010] The present invention also discloses a shear self-supporting fracture mud contamination test method, which uses any of the above-mentioned experimental devices to conduct the test, and specifically includes the following steps:

[0011] Placing the slurry in an intermediate container and connecting the inlet end of the holder to the intermediate container;

[0012] Adjust the high-pressure gas storage tank so that the pressure gauge reading reaches the set value and record the start time;

[0013] When no more liquid flows out of the holder outlet, record the amount of liquid in the measuring cylinder and the end time;

[0014] Turn off the gas source, remove the pressure at the inlet of the holder and calculate the intrusion permeability;

[0015] Replace the inlet and outlet ends of the clamp, repeat the above steps to simulate reverse flow and end the experiment.

[0016] Preferably, the intrusion permeability is calculated based on the start time, the end time, the liquid output and the pressure gauge reading.

[0017] Preferably, the calculation method of the intrusion permeability is as follows:

[0018]

[0019] Where: Δp is the pressure difference before and after the fluid passes through the core, Q is the flow rate through the sand body under the action of the pressure difference, μ is the viscosity of the fluid passing through the core, L is the length of the core, and A is the cross-sectional area of ​​the core perpendicular to the flow direction.

[0020] Preferably, after the inlet and outlet ends of the clamp are replaced, when simulating reverse discharge, a six-way valve is used to replace the intermediate container, which specifically includes the following steps:

[0021] Swap the inlet and outlet ends of the holder, connect the holder, six-way valve and high-pressure gas tank in sequence, and connect the other end of the holder to the measuring cylinder;

[0022] Adjust the high-pressure gas storage tank so that the pressure gauge reading reaches the set value and record the start time;

[0023] When no more liquid flows out of one end of the measuring cylinder, record the amount of liquid discharged and the end time; close the high-pressure gas storage tank and calculate the reverse permeability.

[0024] Preferably, the reverse flow permeability is calculated based on the start time, end time, liquid output and pressure gauge reading after the inlet and outlet ends of the holder are exchanged.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention discloses a mud contamination experimental device for shear self-supporting fractures, which is provided with a clamp and an intermediate container for simulating the intrusion of mud into shear self-supporting fractures. The clamp, the intermediate container, the measuring cylinder, the high-pressure gas storage tank and the confining pressure pump are used to realize the simulation of the whole process of shear self-supporting fracture contamination-blowout-reinjection of a well repeatedly reformed by heavy mud contamination. The device is easy to operate and is closely integrated with the working conditions of mud-contaminated wells. The experimental device of the present invention has a simple structure and is easy to operate, and can quickly realize the measurement of rock parameters on site; the mud contamination research of shear self-supporting fractures is carried out, and the mechanism and law of mud contamination of shear self-supporting fractures are cracked through innovative experimental devices and methods, providing support for the reform of such wells.

[0027] Furthermore, a six-way valve is used to replace the intermediate container to simulate the backflow of mud in shear self-supporting fractures, which is conducive to simulating the entire process of shear self-supporting fracture pollution-blowing-reinjection in wells repeatedly reformed with heavy mud pollution.

[0028] The experimental method of the present invention is easy to operate, closely combined with the working conditions of mud-contaminated wells, and can relatively simply obtain permeability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the intrusion structure of the experimental device of the present invention;

[0030] Figure 2 This is a schematic diagram of the flowback structure of the experimental device of the present invention;

[0031] Figure 3 Schematic diagram of the circulation device in the experimental device of the present invention;

[0032] Figure 4 Schematic diagram of permeability changes under different conditions of the present invention;

[0033] Figure 5 Flow chart of the experimental method of the present invention;

[0034] Figure 6 This is a flow chart of the experimental method of an embodiment of the present invention.

[0035] Among them: 1- graduated cylinder; 2- core; 3- holder; 4- confining pressure pump; 5- circulation device; 6- pressure gauge; 71- intermediate container; 72- six-way valve; 8- high-pressure gas storage tank. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described 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 should fall within the scope of protection of the present invention.

[0037] It should be noted that the terms "first", "second", etc. in the description and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0038] The present invention is described in further detail below with reference to the accompanying drawings:

[0039] See also Figure 1 A shear self-supporting fracture mud contamination experimental device includes a core 2 disposed within a holder 3; a confining pressure pump 4 for providing the required pressure to the core 2; the inlet of the holder 3 is connected to an intermediate container 71, and the outlet is connected to a measuring cylinder 1; the intermediate container 71 is connected to a pressure gauge 6; and a high-pressure gas tank 8 is provided for supplying nitrogen. The inlet of the holder 3 is connected to the intermediate container 71, which is connected to the high-pressure gas tank 8, with a pressure gauge 6 disposed therebetween; the outlet of the holder 3 is connected to a measuring cylinder 1; the holder 3 contains the core 2 and is connected to the confining pressure pump 4. The holder 3 and the intermediate container 71 are used to simulate mud intrusion into a shear self-supporting fracture. The holder 3, the intermediate container 71, the measuring cylinder 1, the high-pressure gas tank 8, and the confining pressure pump 4 are used to simulate the entire process of contamination, blowdown, and reinjection of a shear self-supporting fracture in a well repeatedly reformed by heavy mud contamination. The device is easy to operate and closely integrates with the working conditions of mud-contaminated wells. The experimental device of the present invention has a simple structure and is easy to operate, and can quickly measure rock parameters on site. It conducts research on mud contamination of shear self-supporting fractures. Through innovative experimental devices and methods, the mechanism and law of mud contamination of shear self-supporting fractures are analyzed, providing support for the transformation of such wells.

[0040] Furthermore, a circulation device 5 is provided at the inlet end of the holder 3 for circulating the mud on the end face of the core 2 during the experiment.

[0041] Furthermore, the core 2 is a fractured core 2.

[0042] See also Figure 2 A shear self-propping fracture mud contamination experimental device includes a core 2 disposed within a holder 3; a confining pressure pump 4 for providing the required pressure to the core 2; the inlet and outlet ends of the holder 3 are swapped, with the original outlet replacing an intermediate container 71 and connected to a six-way valve 72; the other end is connected to a graduated cylinder 1, which is connected to a pressure gauge 6; and a high-pressure gas tank 8 for providing nitrogen gas. The new inlet end of the holder 3 is connected to the six-way valve 72, which is connected to the high-pressure gas tank 8, with a pressure gauge 6 disposed therebetween; the new outlet end of the holder 3 is connected to the graduated cylinder 1, the core 2 is contained within the holder 3, and the confining pressure pump 4 is connected thereto. Replacing the intermediate container 71 with the six-way valve 72 simulates mud flowback in shear self-propping fractures, facilitating simulation of the entire process of contamination, blowdown, and reinjection in shear self-propping fractures of wells repeatedly reformed with heavy mud contamination.

[0043] In some embodiments, the inlet end of the holder 3 is provided with a circulation device 5 for circulating mud on the end face of the core 2 during the experiment.

[0044] See also Figure 3 The circulation device 5 includes a shell 9, the shell 9 is connected to the pressure providing device through an air inlet pipe 10, the air inlet pipe 10 is provided with a valve 11, and the shell 9 is provided with an outlet 12.

[0045] The present invention also discloses a shear self-supporting fracture slurry contamination test method, which specifically includes the following steps:

[0046] S1: Place the slurry in the intermediate container 71 and connect the inlet end of the holder 3 to the intermediate container 71;

[0047] S2: Adjust the high-pressure gas storage tank 8 so that the pressure gauge 6 reading reaches the set value and record the start time;

[0048] S3: When no more liquid flows out of the outlet of the holder 3, the amount of liquid discharged from the measuring cylinder 1 is recorded and the end time is recorded;

[0049] S4: Turn off the gas source, remove the pressure at the inlet of the holder 3 and calculate the intrusion permeability;

[0050] S5: Replace the inlet and outlet ends of the clamp 3, repeat the above steps to simulate reverse flow and end the experiment.

[0051] The experimental method of the present invention is easy to operate, closely integrated with the working conditions of mud-contaminated wells, and can relatively simply obtain permeability. It is used to simulate the intrusion and backflow of mud in shear self-supporting fractures. The clamp 3, intermediate container 71, measuring cylinder 1, high-pressure gas storage tank 8 and confining pressure pump 4 are used to realize the simulation of the entire process of shear self-supporting fracture pollution-blowout-reinjection of heavy mud-contaminated repeated transformation wells. The device is easy to operate and closely integrated with the working conditions of mud-contaminated wells. The experimental device of the present invention has a simple structure and is easy to operate. It can quickly realize the measurement of rock parameters on site; carry out research on mud pollution in shear self-supporting fractures, and through innovative experimental devices and methods, break the mechanism and law of mud pollution on shear self-supporting fractures, and provide support for the transformation of such wells.

[0052] In some embodiments, the intrusion permeability is calculated based on the start time, the end time, the liquid output, and the pressure gauge reading.

[0053] Preferably, the calculation method of the intrusion permeability is as follows:

[0054]

[0055] Where: Δp is the pressure difference before and after the fluid passes through the core, Q is the flow rate through the sand body under the action of the pressure difference, μ is the viscosity of the fluid passing through the core, L is the length of the core, and A is the cross-sectional area of ​​the core perpendicular to the flow direction.

[0056] Preferably, the Δp is the pressure gauge reading minus standard atmospheric pressure.

[0057] In some embodiments, after swapping the inlet and outlet ends of the clamp 3, a six-way valve 72 is used to replace the intermediate container 71 to simulate the flowback of mud in a shear self-propping fracture. This facilitates the simulation of the entire process of contamination, blowdown, and re-injection of shear self-propping fractures in a well repeatedly reformed with heavy mud contamination. Specifically, the following steps are included:

[0058] S6: Swap the inlet and outlet ends of the holder 3, connect the holder 3, the six-way valve 72 and the high-pressure gas storage tank 8 in sequence, and connect the other end of the holder 3 to the measuring cylinder 1;

[0059] S7: Adjust the high-pressure gas storage tank 8 so that the pressure gauge 6 reading reaches the set value and record the start time;

[0060] S8: When no more liquid flows out from one end of the measuring cylinder 1, record the liquid output and the end time; close the high-pressure gas storage tank 8 and calculate the reverse permeability.

[0061] In some embodiments, the reverse permeability is calculated based on the start time, end time, liquid output and pressure gauge reading after the inlet and outlet ends of the holder 3 are exchanged.

[0062] In some embodiments, after the experiment is completed, the pressure at the inlet end of the holder 3 is released, the pipeline is disassembled, the holder 3 and the core 2 are removed and cleaned; and the measuring cylinder 1 is removed and cleaned.

[0063] [Example 1]

[0064] A shear self-supporting fracture mud pollution experimental device is characterized in that it includes: a clamp 3, the inlet end of the clamp 3 is connected to the intermediate container 71, the intermediate container 71 is connected to the high-pressure gas storage tank 8, and a pressure gauge 6 is also arranged between the two, the outlet end of the clamp 3 is connected to the measuring cylinder 1, the core 2 is placed inside the clamp 3, and it is also connected to the confining pressure pump 4.

[0065] An experimental method for a shear self-supporting fracture mud contamination experimental device, see Figure 5 , including the following steps:

[0066] S1: Place the slurry in the intermediate container 71 and connect the inlet end of the holder 3 to the intermediate container 71;

[0067] S2: Adjust the high-pressure gas storage tank 8 so that the pressure gauge 6 reading reaches the set value and record the start time;

[0068] S3: When no more liquid flows out of the outlet of the holder 3, the amount of liquid discharged from the measuring cylinder 1 is recorded and the end time is recorded;

[0069] S4: Turn off the gas source, remove the pressure at the inlet of the holder 3 and calculate the intrusion permeability;

[0070] S5: Replace the inlet and outlet ends of the clamp 3, repeat the above steps to simulate reverse flow and end the experiment.

[0071] The intrusion permeability is calculated based on the start time, end time, liquid output and pressure gauge reading; the calculation method of the intrusion permeability is as follows:

[0072]

[0073] Where: Δp is the pressure difference before and after the fluid passes through the core, Q is the flow rate through the sand body under the action of the pressure difference, μ is the viscosity of the fluid passing through the core, L is the length of the core, and A is the cross-sectional area of ​​the core perpendicular to the flow direction.

[0074] The Δp is the pressure gauge reading minus the standard atmospheric pressure.

[0075] [Example 2]

[0076] like Figure 1 and Figure 2As shown, a shear self-supporting fracture mud contamination experimental device includes a core 2 set in a clamp 3; also includes a confining pressure pump 4 for providing the required pressure to the core 2; the inlet end of the clamp 3 is connected to an intermediate container 71 or a six-way valve 72, and the outlet end is connected to a measuring cylinder 1; the intermediate container 71 or the six-way valve 72 is connected to a pressure gauge 6, and also includes a high-pressure gas tank 8 for providing nitrogen. The inlet end of the clamp 3 is provided with a circulation device 5 for circulating mud on the end face of the core 2 during the experiment. The core 2 is a fractured core. The principle of the circulation device 5 is as follows Figure 3 As shown, any device that can achieve the above functions can be used. Figure 3 As shown, it includes a circulation device shell, the shell is connected to a pressure providing device through an air inlet pipe, and a valve is provided on the air inlet pipe. An outlet is provided on the shell.

[0077] An experimental method for a shear self-supporting fracture mud contamination experimental device, see Figure 6 , including the following steps:

[0078] S1: Place the slurry in the intermediate container 71 and connect the inlet end of the holder 3 to the intermediate container 71;

[0079] S2: Adjust the high-pressure gas storage tank 8 so that the pressure gauge 6 reading reaches the set value and record the start time;

[0080] S3: When no more liquid flows out of the outlet of the holder 3, the amount of liquid discharged from the measuring cylinder 1 is recorded and the end time is recorded;

[0081] S4: Turn off the gas source, remove the pressure at the inlet of the holder 3 and calculate the intrusion permeability;

[0082] S5: Replace the inlet and outlet ends of the holder 3; replace the intermediate container 71 with a six-way valve 72, connect the holder 3, the six-way valve 72 and the high-pressure gas tank 8 in sequence, and connect the other end of the holder 3 to the measuring cylinder 1;

[0083] S6: Adjust the high-pressure gas storage tank 8 so that the pressure gauge 6 reading reaches the set value and record the start time;

[0084] S7: When no more liquid flows out from one end of the measuring cylinder 1, record the liquid output and the end time; close the high-pressure gas storage tank 8 and calculate the reverse permeability.

[0085] The intrusion permeability is calculated based on the start time, end time, liquid output and pressure gauge reading. The permeability test is carried out according to Darcy's law. When water passes through the core, its flow rate Q is proportional to the cross-sectional area of ​​the core and the inlet and outlet pressure difference, and inversely proportional to the length of the core.

[0086] The calculation method of intrusion permeability is as follows:

[0087]

[0088] Where: Δp is the pressure difference before and after the fluid passes through the core, Q is the flow rate through the sand body under the action of the pressure difference, μ is the viscosity of the fluid passing through the core, L is the length of the core, and A is the cross-sectional area of ​​the core perpendicular to the flow direction.

[0089] The Δp is the pressure gauge reading minus the standard atmospheric pressure.

[0090] The reverse permeability is calculated based on the start time, end time, liquid output and pressure gauge reading after the inlet and outlet ends of the holder 3 are replaced.

[0091] During the experiment, 24 groups of experiments were conducted according to the above method and the parameter conditions in Table 1.

[0092] Table 1. Experimental parameters and conditions

[0093]

[0094]

[0095] By comparing the core photos after mud contamination and the calculated permeability values, the results are as follows Figure 4 As shown in Table 2, Figure 4 As can be seen from Table 2, mud damages the permeability of shear-displaced natural fractures to a certain extent. The permeability of the cores before and after mud contamination decreases by 10% to 20%. The damage does not show a clear pattern with increasing confining pressure, as the surface roughness of the fractures varies within each experimental group after fracture dislocation.

[0096] Table 2. Permeability of self-propped fractures before and after mud contamination

[0097] Experimental conditions Permeability before mud contamination / mD Permeability after mud contamination / mD Low-density mud + confining pressure 5MPa 39.85969 31.78842 Low-density mud + confining pressure 7MPa 105.3053 104.9803 Low-density mud + confining pressure 9MPa 106.2925 93.78752 High-density mud + confining pressure 5MPa 53.59286 53.35746 High-density mud + confining pressure 7MPa 49.15261 39.48948 High-density mud + confining pressure 9MPa 0.01155 0.008529

[0098] The experimental device of the present invention has a simple structure and is easy to operate, and can quickly measure rock parameters on site; the experimental method can relatively simply obtain permeability.

[0099] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A shear self-supporting fracture mud contamination test method, characterized in that: The experiment was conducted using an experimental device, which comprises: a holder (3), an inlet end of the holder (3) being connected to an intermediate container (71), the intermediate container (71) being connected to a high-pressure gas storage tank (8), and a pressure gauge (6) being provided between the two; an outlet end of the holder (3) being connected to a measuring cylinder (1), a core (2) being placed inside the holder (3), and being connected to a confining pressure pump (4); a six-way valve (72) being connected between the holder (3) and the high-pressure gas storage tank (8); and the method specifically comprises the following steps: Placing the slurry in an intermediate container (71) and connecting the inlet end of the holder (3) to the intermediate container (71); Adjust the high-pressure gas storage tank (8) so that the pressure gauge (6) reading reaches the set value and record the start time; When no more liquid flows out of the outlet of the holder (3), the amount of liquid discharged from the measuring cylinder (1) is recorded and the end time is recorded; Turn off the gas source, remove the pressure at the inlet end of the holder (3) and calculate the intrusion permeability; calculate the intrusion permeability based on the start time, end time, liquid output and pressure gauge reading. The calculation method is as follows: Where: is the pressure difference before and after the fluid passes through the core, Q is the flow rate through the core under the action of the pressure difference, μ is the viscosity of the fluid passing through the core, L is the length of the core, and A is the cross-sectional area of ​​the core perpendicular to the flow direction; When the inlet and outlet ends of the clamp (3) are exchanged and reverse discharge is simulated, the intermediate container (71) is replaced by a six-way valve (72), which specifically includes the following steps: The inlet and outlet ends of the holder (3) are swapped, and the holder (3), the six-way valve (72) and the high-pressure gas storage tank (8) are connected in sequence, and the other end of the holder (3) is connected to the measuring cylinder (1); Adjust the high-pressure gas storage tank (8) so that the pressure gauge (6) reading reaches the set value and record the start time; When no more liquid flows out of one end of the measuring cylinder (1), the liquid output and the end time are recorded; the high-pressure gas storage tank (8) is closed, and the reverse permeability is calculated.

2. A shear self-supporting fracture mud contamination test method according to claim 1, characterized in that: A circulation device (5) is also provided between the intermediate container (71) and the inlet end of the holder (3).

3. A shear self-supporting fracture mud contamination test method according to claim 2, characterized in that: The circulation device (5) comprises a housing (9), the housing (9) is connected to a pressure supply device via an air inlet pipe (10), a valve (11) is provided on the air inlet pipe (10), and an outlet (12) is provided on the housing (9).

4. A shear self-supporting fracture mud contamination test method according to claim 1, characterized in that: The core (2) is a fractured core.

5. A shear self-supporting fracture slurry contamination test method according to claim 1, characterized in that: The backflow permeability is calculated based on the start time, end time, liquid output and pressure gauge reading after the inlet and outlet ends of the holder (3) are replaced.

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