Controlled backflow methods, devices, equipment and media

Abstract

This application relates to the field of controlled flowback technology, and discloses a controlled flowback method, apparatus, equipment, and medium, including: obtaining the wellhead flow rate for a preset well opening time based on the initial formation pressure, initial formation water saturation, initial bottom hole pressure, and wellhead flow rate at the end of fracturing; obtaining the initial drag reduction ratio based on the wellhead flow rate for the preset well opening time; obtaining the frictional resistance of the flowback fluid in the wellbore based on the wellhead flow rate for the preset well opening time and the initial drag reduction ratio; obtaining the initial nozzle diameter based on the target bottom hole pressure, initial wellhead pressure, wellhead flow rate for the preset well opening time, and frictional resistance of the flowback fluid in the wellbore; iteratively updating the initial drag reduction ratio, frictional resistance of the flowback fluid in the wellbore, and the initial nozzle diameter to obtain the bottom hole pressure after flowback; and determining the nozzle diameter for controlled flowback based on the target bottom hole pressure and the bottom hole pressure after flowback. This application precisely controls the bottom hole pressure of controlled flowback.

Description

Technical Field

[0001] This application relates to the field of pressure-controlled backflow technology, specifically to a pressure-controlled backflow method, apparatus, equipment, and medium. Background Technology

[0002] Controlled flowback after fracturing is a crucial step in oil and gas field development, especially in low-permeability and ultra-low-permeability reservoirs. A reasonable flowback rate helps improve the flowback efficiency of fracturing fluid, effectively control proppant backflow, and enhance the effective conductivity of fractures, thereby improving the overall effectiveness of fracturing stimulation.

[0003] The fracturing fluid flowback rate is related to the bottom hole pressure. Excessive bottom hole pressure results in slow flowback, leading to formation contamination; conversely, insufficient bottom hole pressure results in rapid flowback, causing proppant backflow and reducing fracture conductivity. To ensure faster flowback of fracturing fluid while maintaining as much proppant as possible within the fracture, precise control of the bottom hole pressure is necessary. However, current technology cannot directly monitor bottom hole pressure, posing significant challenges to pressure-controlled flowback. Summary of the Invention

[0004] The purpose of this application is to provide a pressure-controlled flowback method, apparatus, equipment, and medium to solve the problem that the existing technology cannot directly monitor the bottom hole pressure, which brings great difficulties to pressure-controlled flowback.

[0005] To achieve the above objectives, the first aspect of this application provides a pressure-controlled backflow method, comprising:

[0006] Obtain the initial formation pressure, initial formation water saturation, initial bottom hole pressure, initial wellhead pressure, and target bottom hole pressure at the end of fracturing;

[0007] Based on the initial formation pressure, initial formation water saturation, initial bottom hole pressure, and wellhead flow rate at the end of fracturing, the wellhead flow rate for the preset well opening time is obtained;

[0008] The initial drag reduction ratio is obtained based on the wellhead flow rate during the preset well opening time;

[0009] Based on the wellhead flow rate and initial drag reduction ratio during the preset well opening time, the frictional resistance of the return fluid in the wellbore is obtained;

[0010] The initial nozzle diameter is obtained based on the target bottom hole pressure, initial wellhead pressure, wellhead flow rate for the preset well opening time, and frictional resistance of the return fluid in the wellbore.

[0011] The initial drag reduction ratio, the frictional resistance of the backflow fluid in the wellbore, and the initial nozzle diameter are iteratively updated to obtain the bottom hole pressure after backflow.

[0012] The diameter of the nozzle for controlled pressure return is determined based on the target bottom hole pressure and the bottom hole pressure after return flow.

[0013] In this embodiment of the application, the wellhead flow rate for a preset well opening time is obtained based on the initial formation pressure, initial formation water saturation, initial bottom hole pressure, and wellhead flow rate at the end of fracturing, including:

[0014] Based on the wellhead flow rate at the end of fracturing, the formation pressure and formation water saturation for the preset well opening time are obtained;

[0015] Based on the initial formation pressure, the formation pressure at the preset well opening time, the initial formation water saturation, and the formation water saturation at the preset well opening time, the total fluid volume returned at the preset well opening time is obtained.

[0016] The wellhead flow rate for the preset well opening time is obtained based on the ratio of the preset well opening time to the total fluid volume.

[0017] In this embodiment of the application, the initial drag reduction ratio is obtained based on the wellhead flow rate during a preset well opening time, including:

[0018] Based on the wellhead flow rate for the preset well opening time and the first formula, the initial drag reduction ratio is obtained, wherein the first formula includes:

[0019]

[0020] In the formula, A0 represents the initial drag reduction ratio, D represents the wellbore diameter, Q0 represents the wellhead flow rate for the preset well opening time, B represents the fracturing fluid thickener concentration, and C represents the fracturing fluid proppant concentration.

[0021] In this embodiment of the application, the frictional resistance of the flowback fluid in the wellbore is obtained based on the wellhead flow rate and the initial drag reduction ratio after a preset well opening time, including:

[0022] Based on the wellhead flow rate for the preset well opening time, the initial drag reduction ratio, and the second formula, the frictional resistance of the flowback fluid within the wellbore is obtained. The second formula includes:

[0023] P jt0 =1.39×10 12 A0D -4.8 Q0 1.8 H

[0024] In the formula, P jt0 The value represents the frictional resistance of the flowback fluid within the wellbore, A0 represents the initial resistance reduction ratio, D represents the wellbore diameter, Q0 represents the wellhead flow rate for the preset well opening time, and H represents the vertical distance from the bottom of the well to the wellhead.

[0025] In this embodiment of the application, the initial nozzle diameter is obtained based on the target bottom hole pressure, the initial wellhead pressure, the wellhead flow rate for the preset well opening time, and the frictional resistance of the flowback fluid in the wellbore, including:

[0026] Based on the target bottomhole pressure, initial wellhead pressure, wellhead flow rate for the preset well opening time, frictional resistance of the flowback fluid in the wellbore, and the third formula, the initial nozzle diameter is obtained. The third formula includes:

[0027]

[0028] In the formula, d0 represents the initial nozzle diameter, Q0 represents the wellhead flow rate for the preset well opening time, ρ represents the flowback fluid density, and P jd* P represents the target bottom hole pressure. jk0 P represents the initial wellhead pressure. jt0 The value represents the frictional resistance of the flowback fluid within the wellbore, g represents the gravitational constant, and H represents the vertical distance from the bottom of the well to the wellhead.

[0029] In this embodiment, the initial drag reduction ratio, the frictional resistance of the flowback fluid in the wellbore, and the initial nozzle diameter are iteratively updated to obtain the bottom hole pressure after flowback, including:

[0030] Obtain the real-time wellhead flow rate and real-time wellhead pressure after the preset well opening time;

[0031] The updated drag reduction ratio is obtained based on the real-time wellhead flow rate after the preset well opening time;

[0032] Based on the real-time wellhead flow rate after the preset well opening time and the updated drag reduction ratio, the updated frictional resistance of the flowback fluid in the wellbore is obtained;

[0033] Based on the preset value and the initial nozzle diameter, the updated nozzle diameter is obtained;

[0034] The nozzle friction is obtained based on the real-time wellhead flow rate after the preset well opening time and the updated nozzle diameter;

[0035] The bottom hole pressure after well opening is obtained based on the real-time wellhead pressure after the preset well opening time, the friction of the updated flowback fluid in the wellbore, and the friction of the nozzle.

[0036] In this embodiment of the application, the diameter of the nozzle for controlled flowback is determined based on the target bottom hole pressure and the bottom hole pressure after flowback, including:

[0037] The error is obtained based on the target bottom-hole pressure and the bottom-hole pressure after backflow.

[0038] If the error is greater than the preset threshold, the updated drag reduction ratio, the updated friction of the flowback fluid in the wellbore, and the updated nozzle diameter will be iteratively updated until the error is less than or equal to the preset threshold.

[0039] When the error is equal to the preset threshold, the nozzle diameter at the end of the iteration update is determined to be the nozzle diameter for pressure control and backflow.

[0040] If the error is less than the preset threshold, the average of the nozzle diameter at the end of the iteration update and the nozzle diameter before the end of the iteration update is determined as the nozzle diameter for pressure control and backflow.

[0041] A second aspect of this application provides a pressure-controlled backflow device, comprising:

[0042] The acquisition module is used to acquire the initial formation pressure, initial formation water saturation, initial bottom hole pressure, initial wellhead pressure, and target bottom hole pressure at the end of fracturing.

[0043] The first module is used to obtain the wellhead flow rate for a preset well opening time based on the initial formation pressure, initial formation water saturation, initial bottom hole pressure, and wellhead flow rate at the end of fracturing.

[0044] The second module is used to obtain the initial drag reduction ratio based on the wellhead flow rate during the preset well opening time;

[0045] The third module is used to obtain the frictional resistance of the return fluid in the wellbore based on the wellhead flow rate and the initial drag reduction ratio during the preset well opening time.

[0046] The fourth module is used to obtain the initial nozzle diameter based on the target bottom hole pressure, initial wellhead pressure, wellhead flow rate for the preset well opening time, and frictional resistance of the flowback fluid in the wellbore.

[0047] The iterative update module is used to iteratively update the initial drag reduction ratio, the frictional resistance of the flowback fluid in the wellbore, and the initial nozzle diameter to obtain the bottom hole pressure after flowback.

[0048] The determination module is used to determine the nozzle diameter for controlled pressure return based on the target bottom hole pressure and the bottom hole pressure after return.

[0049] A third aspect of this application provides a pressure-controlled backflow device, comprising:

[0050] The memory is configured to store instructions;

[0051] The processor is configured to retrieve instructions from memory and, when executing instructions, to implement the control pressure backflow method described in the first aspect above.

[0052] A third aspect of this application provides a machine-readable storage medium storing instructions that cause a machine to perform the controlled pressure return method of the first aspect described above.

[0053] The above technical solution precisely controls the bottom hole pressure of controlled pressure return by controlling the diameter of the nozzle, thereby avoiding formation contamination caused by excessively slow return and proppant backflow caused by excessively fast return.

[0054] Other features and advantages of the embodiments of this application will be described in detail in the following detailed description section. Attached Figure Description

[0055] The accompanying drawings are provided to further illustrate the embodiments of this application and form part of the specification. They are used together with the following detailed description to explain the embodiments of this application, but do not constitute a limitation on the embodiments of this application. In the drawings:

[0056] Figure 1 The schematic diagram illustrates a flow chart of a pressure-controlled backflow method according to an embodiment of this application;

[0057] Figure 2 A schematic diagram of a formation-fracture geometry model according to an embodiment of this application is shown.

[0058] Figure 3 A schematic diagram illustrating the bottom hole pressure variation according to an embodiment of this application is shown.

[0059] Figure 4 The diagram illustrates the formation pressure distribution after 34 iterations of the calculations in this application embodiment. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only for illustration and explanation of the embodiments of this application and are not intended to limit the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0061] It should be noted that the acquisition, transmission, storage, use, and processing of data in the technical solution of this application all comply with the relevant provisions of national laws and regulations. In the embodiments of this application, certain existing industry solutions such as software, components, and models may be mentioned. These should be considered exemplary, intended only to illustrate the feasibility of implementing the technical solution of this application, and do not imply that the applicant has already used or necessarily used such solutions.

[0062] It should be noted that if the embodiments of this application involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0063] Furthermore, if the embodiments of this application involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0064] Figure 1 A schematic flowchart of a pressure-controlled backflow method according to an embodiment of this application is shown. Figure 1 As shown in the figure, this application provides a pressure-controlled backflow method, which may include the following steps.

[0065] Step S110: Obtain the initial formation pressure, initial formation water saturation, initial bottom hole pressure, initial wellhead pressure, and target bottom hole pressure at the end of fracturing.

[0066] In this embodiment, the initial formation pressure, initial formation water saturation, initial bottom hole pressure, and initial wellhead pressure at the end of fracturing are all parameters that are readily obtainable during fracturing operations. The target bottom hole pressure is preset based on the actual fracturing conditions and the proppant.

[0067] Step S120: Based on the initial formation pressure, initial formation water saturation, initial bottom hole pressure, and wellhead flow rate at the end of fracturing, obtain the wellhead flow rate for the preset well opening time.

[0068] In this embodiment of the application, the wellhead flow rate for the preset well opening time is determined based on the initial formation pressure, initial formation water saturation, initial bottom hole pressure and wellhead flow rate at the end of fracturing obtained in step S110.

[0069] Furthermore, step S120 includes the following steps:

[0070] Step S121: Based on the wellhead flow rate at the end of fracturing, obtain the formation pressure and formation water saturation for the preset well opening time.

[0071] Step S122: Based on the initial formation pressure, the formation pressure at the preset well opening time, the initial formation water saturation, and the formation water saturation at the preset well opening time, obtain the total fluid volume returned at the preset well opening time.

[0072] Step S123: Based on the ratio of the preset well opening time to the total fluid volume, obtain the wellhead flow rate for the preset well opening time.

[0073] In step S121, the wellhead is not yet open at the end of fracturing, and the wellhead flow rate at the end of fracturing is equal to 0. Based on the wellhead flow rate at the end of fracturing, the following equation is constructed:

[0074]

[0075] In the above formula, φ represents the formation porosity, and S w c represents the water saturation of the formation. to p represents the compressibility coefficient of the oil phase fluid. c ′ c represents the derivative of capillary force with respect to water saturation. t The coefficient of mass represents the overall compressibility of the formation, and m represents the formation matrix. This represents the derivative of formation pressure with respect to time. K represents the derivative of formation water saturation with respect to time. m Indicates the permeability of the formation matrix. λ represents the oil phase flow coefficient. w p represents the water phase flow coefficient. w q represents formation pressure. o q represents the oil phase yield. w This indicates the amount of aqueous phase produced.

[0076] Transforming the above equation, we obtain the solution matrix equation, which includes:

[0077]

[0078] In the above formula, q represents the fluid source term, and G and K represent the numerical matrices to be solved.

[0079] The formation pressure and formation water saturation at each time point after well opening were determined using the finite element method.

[0080]

[0081] In the above formula, N represents the shape function used in the finite element method. In the finite element method, the shape function is used to approximate the unknowns within the element and transform the problem from a continuous domain to a discrete domain. Through the shape function, the finite element method transforms partial differential equations into a system of linear algebraic equations, and finally solves for the nodal unknowns.

[0082] From the formation pressure and formation water saturation obtained at each moment after well opening, the formation pressure and formation water saturation for the preset well opening time are extracted. For example, setting the preset well opening time to 1 minute yields the formation pressure and formation water saturation after 1 minute of well opening. The following discussion uses a 1-minute preset well opening time as an example; however, it is understood that the preset well opening time can be set according to actual needs, and this application does not limit this setting.

[0083] In step S122, spatial integration is performed based on the initial formation pressure, the formation pressure after 1 minute of well opening, the initial formation water saturation, and the formation water saturation after 1 minute of well opening to obtain the total fluid volume returned after 1 minute of well opening. The spatial integration formula for the total fluid volume includes:

[0084]

[0085] In the above formula, V0 represents the total fluid volume returned per minute after well opening, and S w0 p represents the initial water saturation of the formation at the end of fracturing. w0 S represents the initial formation pressure at the end of fracturing. w1 p represents the formation water saturation 1 minute after well opening. w0 This indicates the formation pressure one minute after well opening.

[0086] In step S123, the wellhead flow rate for the preset well opening time is obtained based on the ratio of the preset well opening time to the total fluid volume:

[0087]

[0088] In the above formula, Q0 represents the wellhead flow rate in 1 minute of well opening, and Δt represents the preset duration.

[0089] Step S130: Obtain the initial drag reduction ratio based on the wellhead flow rate during the preset well opening time.

[0090] In this embodiment of the application, the initial drag reduction ratio is obtained based on the wellhead flow rate obtained in step 120 after one minute of well opening.

[0091] Furthermore, step S130 includes the following steps:

[0092] Step S131: Based on the wellhead flow rate for the preset well opening time and the first formula, obtain the initial drag reduction ratio, wherein the first formula includes:

[0093]

[0094] In the formula, A0 represents the initial drag reduction ratio, D represents the wellbore diameter, Q0 represents the wellhead flow rate for the preset well opening time, B represents the fracturing fluid thickener concentration, and C represents the fracturing fluid proppant concentration. For illustrative purposes, Q0 is the wellhead flow rate for 1 minute after well opening.

[0095] Step S140: Based on the wellhead flow rate and initial drag reduction ratio during the preset well opening time, obtain the frictional resistance of the return fluid in the wellbore.

[0096] In this embodiment of the application, the frictional resistance of the return fluid in the wellbore is obtained based on the wellhead flow rate and the initial drag reduction ratio during the preset well opening time.

[0097] Furthermore, step S140 includes the following steps:

[0098] Step S141: Based on the wellhead flow rate during the preset well opening time, the initial drag reduction ratio, and the second formula, obtain the frictional resistance of the flowback fluid within the wellbore. The second formula includes:

[0099] P jt0 =1.39×10 12 A0D -4.8 Q0 1.8 H

[0100] In the formula, P jt0 The formula represents the frictional resistance of the flowback fluid within the wellbore. A0 represents the initial drag reduction ratio, D represents the wellbore diameter, Q0 represents the wellhead flow rate for the preset well opening time, and H represents the vertical distance from the bottom of the well to the wellhead. For illustrative purposes, Q0 represents the wellhead flow rate after one minute of well opening.

[0101] Step S150: Based on the target bottom hole pressure, initial wellhead pressure, wellhead flow rate for the preset well opening time, and frictional resistance of the return fluid in the wellbore, obtain the initial nozzle diameter.

[0102] In this embodiment of the application, the initial nozzle diameter is obtained based on the target bottom hole pressure, the initial wellhead pressure, the wellhead flow rate after 1 minute of well opening, and the frictional resistance of the return fluid in the wellbore.

[0103] Furthermore, step S150 includes the following steps:

[0104] Step S151: Based on the target bottom hole pressure, initial wellhead pressure, wellhead flow rate for the preset well opening time, frictional resistance of the flowback fluid in the wellbore, and the third formula, obtain the initial nozzle diameter, wherein the third formula includes:

[0105]

[0106] In the formula, d0 represents the initial nozzle diameter, Q0 represents the wellhead flow rate for the preset well opening time, ρ represents the flowback fluid density, and P jd* P represents the target bottom hole pressure. jk0P represents the initial wellhead pressure. jt0 The flow rate represents the frictional resistance of the flowback fluid within the wellbore, g represents the gravitational constant, and H represents the vertical distance from the bottom of the well to the wellhead. For illustrative purposes, Q0 represents the wellhead flow rate in one minute after well opening.

[0107] Step S160: Iteratively update the initial drag reduction ratio, the frictional resistance of the flowback fluid in the wellbore, and the initial nozzle diameter to obtain the bottom hole pressure after flowback.

[0108] In this embodiment, the initial drag reduction ratio, the frictional resistance of the flowback fluid in the wellbore, and the initial nozzle diameter are iteratively updated to determine the bottom hole pressure after flowback.

[0109] Furthermore, step S160 includes the following steps:

[0110] Step S161: Obtain the real-time wellhead flow rate and real-time wellhead pressure after the preset well opening time;

[0111] Step S162: Based on the real-time wellhead flow rate after the preset well opening time, obtain the updated drag reduction ratio;

[0112] Step S163: Based on the real-time wellhead flow rate after the preset well opening time and the updated drag reduction ratio, obtain the updated frictional resistance of the flowback fluid in the wellbore;

[0113] Step S164: Based on the preset value and the initial nozzle diameter, obtain the updated nozzle diameter;

[0114] Step S165: Based on the real-time wellhead flow rate after the preset well opening time and the updated nozzle diameter, obtain the nozzle friction.

[0115] Step S166: Based on the real-time wellhead pressure after the preset well opening time, the friction of the updated flowback fluid in the wellbore, and the friction of the nozzle, obtain the bottom hole pressure after flowback.

[0116] In step S161, the real-time wellhead flow rate 1 minute after well opening is measured in real time by a flow rate meter, and the real-time wellhead pressure 1 minute after well opening is measured in real time by a pressure gauge.

[0117] In step S162, the drag reduction ratio is updated based on the wellhead flow rate one minute after well opening and the fourth formula. The fourth formula includes:

[0118]

[0119] In the formula, A i Let Q represent the drag reduction ratio after the i-th iteration update, D represent the wellbore diameter, and Q represent the drag reduction ratio after the i-th iteration update. i Q represents the real-time wellhead flow rate after the preset well opening time, B represents the fracturing fluid thickener concentration, and C represents the fracturing fluid proppant concentration. (Illustrative example) iThis represents the real-time wellhead flow rate one minute after well opening.

[0120] In step S163, the frictional resistance of the flowback fluid in the wellbore is updated based on the wellhead flow rate one minute after well opening, the updated drag reduction ratio, and the fifth formula. The fifth formula includes:

[0121] P jti =1.39×10 12 A i D -4.8 Q i 1.8 H

[0122] In the formula, P jti Let A represent the frictional resistance of the flowback fluid in the wellbore after the i-th iteration update. i Let Q represent the drag reduction ratio after the i-th iteration update, D represent the wellbore diameter, and Q represent the drag reduction ratio after the i-th iteration update. i This represents the real-time wellhead flow rate after a preset well opening time, where H represents the vertical distance from the bottom of the well to the wellhead. (Illustrative example, Q...) i This represents the real-time wellhead flow rate one minute after well opening.

[0123] In step S164, the updated nozzle diameter is obtained by multiplying the preset value 1.01 by the initial nozzle diameter. This update is achieved using a sixth formula, which includes:

[0124] d i =d i-1 *1.01

[0125] In the above formula, d i Let d represent the nozzle diameter after the i-th iteration update. i-1 This represents the nozzle diameter after the (i-1)th iteration update.

[0126] In step S165, the nozzle friction is determined based on the real-time wellhead flow rate after the preset well opening time, the updated nozzle diameter, and the seventh formula. The seventh formula includes:

[0127]

[0128] In the above formula, P yzi Let Q represent the friction resistance of the nozzle after the i-th iteration update. i The flow rate at the wellhead is represented by ρ after the preset well opening time, and d represents the flowback fluid density. i Let Q represent the nozzle diameter after the i-th iteration update. (Illustratively, Q...) i This represents the real-time wellhead flow rate one minute after well opening.

[0129] In step S166, the bottom hole pressure after backflow is determined based on the eighth formula, the real-time wellhead pressure after the preset well opening time, the friction of the updated flowback fluid in the wellbore, and the friction of the nozzle. The eighth formula includes:

[0130] P jdi =P jki +P jti +P yzi +ρgH

[0131] In the above formula, P jdi P represents the bottom hole pressure after backflow. jki P represents the real-time wellhead pressure after a preset well opening time. jti P represents the frictional resistance of the flowback fluid in the wellbore after the i-th iteration update. yzi Let ρ represent the nozzle friction after the i-th iteration update, ρ represent the flowback fluid density, g represent the gravity constant, and H represent the vertical distance from the bottom of the well to the wellhead.

[0132] Step S170: Determine the diameter of the nozzle for controlled pressure return based on the target bottom hole pressure and the bottom hole pressure after return flow.

[0133] In this embodiment of the application, the diameter of the pressure-controlled return nozzle can be determined based on the target bottom hole pressure and the bottom hole pressure after return flow. The bottom hole pressure is controlled to be maintained near the target bottom hole pressure by controlling the diameter of the pressure-controlled return nozzle.

[0134] Furthermore, step S170 includes the following steps:

[0135] Step S171: Based on the target bottom hole pressure and the bottom hole pressure after backflow, obtain the error;

[0136] Step S172: If the error is greater than the preset threshold, the updated drag reduction ratio, the updated friction of the flowback fluid in the wellbore, and the updated nozzle diameter are iteratively updated until the error is less than or equal to the preset threshold.

[0137] Step S173: If the error is equal to the preset threshold, determine the nozzle diameter at the end of the iteration update as the nozzle diameter for pressure control and backflow.

[0138] Step S174: If the error is less than the preset threshold, the average of the nozzle diameter at the end of the iteration update and the nozzle diameter before the end of the iteration update is determined as the nozzle diameter for pressure control and backflow.

[0139] In step S171, the error calculation formula includes:

[0140]

[0141] In the above formula, P jdiP represents the bottom hole pressure after backflow. jd* This indicates the target bottom hole pressure.

[0142] In step S172, schematically, the preset threshold is 0, if ω i If the error is greater than 0, the updated drag reduction ratio, the updated friction of the flowback fluid in the wellbore, and the updated nozzle diameter will be iteratively updated until the error is less than or equal to the preset threshold.

[0143] In step S173, if ω i =0, the nozzle diameter at the end of the iteration update is used as the nozzle diameter for pressure control and backflow.

[0144] In step S174, if ω i If the value is less than 0, the average of the nozzle diameter at the end of the iteration update and the nozzle diameter before the end of the iteration update is determined as the nozzle diameter for pressure control and backflow.

[0145] The embodiments of this application can control the bottom hole pressure near the target bottom hole pressure to prevent formation contamination due to slow flowback and proppant backflow due to excessively fast flowback.

[0146] Indicatively, after determining the diameter of the pressure-controlled return nozzle in step S170, timing begins until a preset time is reached. Then, the process returns to step S160 and repeats the subsequent steps to maintain the bottom hole pressure consistently near the target bottom hole pressure. The preset time can be set according to actual needs; this embodiment does not impose a specific limitation.

[0147] Figure 2 This schematically illustrates a formation-fracture geometry model according to an embodiment of this application. When using the finite element analysis method, the following is employed: Figure 2 The formation-fracture geometry model shown can be used to determine the reservoir size, fracture length, and fracture interval based on the wellbore sweep range and fracturing evaluation effect. Schematic, in this embodiment, the reservoir size of the formation-fracture geometry model is 100m, and the fracture length and fracture interval are both 20m.

[0148] Utilize Figure 2 The formation-fracture geometry model shown yields the changes in bottom hole pressure. Figure 3 A schematic diagram illustrating the bottom hole pressure variation according to an embodiment of this application is shown, such as... Figure 3 As shown, as the nozzle diameter increases, the bottom hole pressure gradually decreases. After 34 iterations of update calculations, the bottom hole pressure was controlled from 27,800,000 Pa to a specific value of 20,000,000 Pa.

[0149] Figure 4This schematic diagram illustrates the formation pressure distribution after 34 iterations of the calculation in an embodiment of this application. Figure 4 As shown, the bottom pressure at this time is 20,000,000 Pa.

[0150] This application embodiment also provides a pressure-controlled backflow device, including:

[0151] The acquisition module is used to acquire the initial formation pressure, initial formation water saturation, initial bottom hole pressure, initial wellhead pressure, and target bottom hole pressure at the end of fracturing.

[0152] The first module is used to obtain the wellhead flow rate for a preset well opening time based on the initial formation pressure, initial formation water saturation, initial bottom hole pressure, and wellhead flow rate at the end of fracturing.

[0153] The second module is used to obtain the initial drag reduction ratio based on the wellhead flow rate during the preset well opening time;

[0154] The third module is used to obtain the frictional resistance of the return fluid in the wellbore based on the wellhead flow rate and the initial drag reduction ratio during the preset well opening time.

[0155] The fourth module is used to obtain the initial nozzle diameter based on the target bottom hole pressure, initial wellhead pressure, wellhead flow rate for the preset well opening time, and frictional resistance of the flowback fluid in the wellbore.

[0156] The iterative update module is used to iteratively update the initial drag reduction ratio, the frictional resistance of the flowback fluid in the wellbore, and the initial nozzle diameter to obtain the bottom hole pressure after flowback.

[0157] The determination module is used to determine the nozzle diameter for controlled pressure return based on the target bottom hole pressure and the bottom hole pressure after return.

[0158] It is understood that the pressure-controlled backflow device provided in this application embodiment can realize each process of the pressure-controlled backflow method in the above embodiment and achieve the same technical effect. To avoid repetition, it will not be described again here.

[0159] This application embodiment also provides a pressure-controlled backflow device, including:

[0160] The memory is configured to store instructions;

[0161] The processor is configured to retrieve instructions from memory and, when executing instructions, to implement the pressure-controlled backflow method described above. It achieves the same technical effect, and to avoid repetition, will not be elaborated upon here.

[0162] This application also provides a machine-readable storage medium storing instructions that cause a machine to execute the controlled-pressure runout method described above. This achieves the same technical effect, and to avoid repetition, it will not be described again here.

[0163] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0164] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0165] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0166] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0167] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0168] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, like read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0169] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information using any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0170] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0171] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A pressure-controlled backflow method, characterized in that, include: Obtain the initial formation pressure, initial formation water saturation, initial bottom hole pressure, initial wellhead pressure, and target bottom hole pressure at the end of fracturing; Based on the initial formation pressure, the initial formation water saturation, the initial bottom hole pressure, and the wellhead flow rate at the end of fracturing, the wellhead flow rate for the preset well opening time is obtained; The initial drag reduction ratio is obtained based on the wellhead flow rate during the preset well opening time; Based on the wellhead flow rate during the preset well opening time and the initial drag reduction ratio, the frictional resistance of the return fluid in the wellbore is obtained; The initial nozzle diameter is obtained based on the target bottom hole pressure, the initial wellhead pressure, the wellhead flow rate during the preset well opening time, and the frictional resistance of the return fluid in the wellbore. The initial drag reduction ratio, the frictional resistance of the backflow fluid in the wellbore, and the initial nozzle diameter are iteratively updated to obtain the bottom hole pressure after backflow. Based on the target bottom hole pressure and the bottom hole pressure after backflow, determine the nozzle diameter for pressure-controlled backflow; The step of obtaining the wellhead flow rate for a preset well opening duration based on the initial formation pressure, the initial formation water saturation, the initial bottom hole pressure, and the wellhead flow rate at the end of fracturing includes: Based on the wellhead flow rate at the end of the fracturing, the formation pressure and formation water saturation for the preset well opening time are obtained; Based on the initial formation pressure, the formation pressure at the preset well opening time, the initial formation water saturation, and the formation water saturation at the preset well opening time, the total fluid volume returned at the preset well opening time is obtained; Based on the ratio of the total fluid volume to the preset well opening time, the wellhead flow rate for the preset well opening time is obtained; The step of obtaining the initial nozzle diameter based on the target bottom hole pressure, the initial wellhead pressure, the wellhead flow rate for the preset well opening time, and the frictional resistance of the flowback fluid in the wellbore includes: Based on the target bottomhole pressure, the initial wellhead pressure, the wellhead flow rate for the preset well opening time, the frictional resistance of the flowback fluid in the wellbore, and a third formula, the initial nozzle diameter is obtained, wherein the third formula includes: In the formula, This indicates the initial nozzle diameter. The wellhead flow rate represents the preset well opening time. Indicates the density of the backflow fluid. This indicates the target bottom hole pressure. This indicates the initial wellhead pressure. This indicates the frictional resistance of the flowback fluid within the wellbore. Represents the gravitational constant. This indicates the vertical distance from the bottom of the well to the wellhead.

2. The method according to claim 1, characterized in that, The initial drag reduction ratio is obtained based on the wellhead flow rate during the preset well opening time, including: Based on the wellhead flow rate during the preset well opening time and the first formula, the initial drag reduction ratio is obtained, wherein the first formula includes: In the formula, This represents the initial drag reduction ratio. represents the wellbore diameter, The wellhead flow rate represents the preset well opening time. This indicates the concentration of the fracturing fluid thickener. This indicates the concentration of proppant in the fracturing fluid.

3. The method according to claim 1, characterized in that, The method of obtaining the frictional resistance of the flowback fluid in the wellbore based on the wellhead flow rate of the preset well opening time and the initial drag reduction ratio includes: Based on the wellhead flow rate during the preset well opening time, the initial drag reduction ratio, and the second formula, the frictional resistance of the flowback fluid within the wellbore is obtained, wherein the second formula includes: In the formula, This indicates the frictional resistance of the flowback fluid within the wellbore. This represents the initial drag reduction ratio. represents the wellbore diameter, The wellhead flow rate represents the preset well opening time. This indicates the vertical distance from the bottom of the well to the wellhead.

4. The method according to claim 1, characterized in that, The step of iteratively updating the initial drag reduction ratio, the frictional resistance of the flowback fluid in the wellbore, and the initial nozzle diameter to obtain the bottom hole pressure after flowback includes: Obtain the real-time wellhead flow rate and real-time wellhead pressure after the preset well opening time; Based on the real-time wellhead flow rate after the preset well opening time, the updated drag reduction ratio is obtained; Based on the real-time wellhead flow rate after the preset well opening time and the updated drag reduction ratio, the updated frictional resistance of the flowback fluid in the wellbore is obtained; The updated nozzle diameter is obtained by multiplying the preset value and the initial nozzle diameter. Based on the real-time wellhead flow rate after the preset well opening time and the updated nozzle diameter, the nozzle friction is obtained; The bottom hole pressure after well opening is obtained based on the real-time wellhead pressure after the preset well opening time, the friction of the updated flowback fluid in the wellbore, and the friction of the nozzle.

5. The method according to claim 4, characterized in that, The determination of the nozzle diameter for controlled-pressure return based on the target bottom-hole pressure and the bottom-hole pressure after return includes: The error is obtained based on the target bottom hole pressure and the bottom hole pressure after backflow. If the error is greater than the preset threshold, the updated drag reduction ratio, the updated friction of the flowback fluid in the wellbore, and the updated nozzle diameter will be iteratively updated until the error is less than or equal to the preset threshold. When the error is equal to the preset threshold, the nozzle diameter at the end of the iteration update is determined to be the nozzle diameter for pressure control and backflow. If the error is less than the preset threshold, the average of the nozzle diameter at the end of the iteration update and the nozzle diameter before the end of the iteration update is determined as the nozzle diameter for pressure control and backflow.

6. A pressure-controlled backflow device, characterized in that, include: The acquisition module is used to acquire the initial formation pressure, initial formation water saturation, initial bottom hole pressure, initial wellhead pressure, and target bottom hole pressure at the end of fracturing. The first obtaining module is used to obtain the wellhead flow rate for a preset well opening time based on the initial formation pressure, the initial formation water saturation, the initial bottom hole pressure, and the wellhead flow rate at the end of the fracturing. The second obtaining module is used to obtain the initial drag reduction ratio based on the wellhead flow rate during the preset well opening time; The third module is used to obtain the frictional resistance of the return fluid in the wellbore based on the wellhead flow rate during the preset well opening time and the initial drag reduction ratio; The fourth module is used to obtain the initial nozzle diameter based on the target bottom hole pressure, the initial wellhead pressure, the wellhead flow rate during the preset well opening time, and the frictional resistance of the flowback fluid in the wellbore. The iterative update module is used to iteratively update the initial drag reduction ratio, the frictional resistance of the backflow fluid in the wellbore, and the initial nozzle diameter to obtain the bottom hole pressure after backflow. The determination module is used to determine the nozzle diameter for controlled-pressure return based on the target bottom hole pressure and the bottom hole pressure after return; The step of obtaining the wellhead flow rate for a preset well opening duration based on the initial formation pressure, the initial formation water saturation, the initial bottom hole pressure, and the wellhead flow rate at the end of fracturing includes: Based on the wellhead flow rate at the end of the fracturing, the formation pressure and formation water saturation for the preset well opening time are obtained; Based on the initial formation pressure, the formation pressure at the preset well opening time, the initial formation water saturation, and the formation water saturation at the preset well opening time, the total fluid volume returned at the preset well opening time is obtained; Based on the ratio of the total fluid volume to the preset well opening time, the wellhead flow rate for the preset well opening time is obtained; The step of obtaining the initial nozzle diameter based on the target bottom hole pressure, the initial wellhead pressure, the wellhead flow rate for the preset well opening time, and the frictional resistance of the flowback fluid in the wellbore includes: Based on the target bottomhole pressure, the initial wellhead pressure, the wellhead flow rate for the preset well opening time, the frictional resistance of the flowback fluid in the wellbore, and a third formula, the initial nozzle diameter is obtained, wherein the third formula includes: In the formula, This indicates the initial nozzle diameter. The wellhead flow rate represents the preset well opening time. Indicates the density of the backflow fluid. This indicates the target bottom hole pressure. This indicates the initial wellhead pressure. This indicates the frictional resistance of the flowback fluid within the wellbore. Represents the gravitational constant. This indicates the vertical distance from the bottom of the well to the wellhead.

7. A pressure-controlled backflow device, characterized in that, include: The memory is configured to store instructions; The processor is configured to retrieve the instructions from the memory and, when executing the instructions, to implement the controlled pressure backflow method according to any one of claims 1 to 5.

8. A machine-readable storage medium, characterized in that, The machine-readable storage medium stores instructions for causing the machine to perform the controlled pressure run-out method according to any one of claims 1 to 5.

Images