Experimental system for predicting fracturing fluid invasion depth and method for predicting fracturing fluid invasion depth

Abstract

The embodiment of the present application provides an experimental system for predicting fracturing fluid invasion depth and a method for predicting fracturing fluid invasion depth, and belongs to the field of chemical engineering technology.The experimental system for predicting fracturing fluid invasion depth comprises an ultrahigh-pressure high-precision displacement pump, an ultrahigh-temperature ultrahigh-pressure intermediate container, an ultrahigh-temperature ultrahigh-pressure core holder, a pressure detection device, a fracturing fluid simulation invasion device and a control device.The pressure difference between the inlet end and the outlet end of the ultrahigh-temperature ultrahigh-pressure intermediate container can be changed to obtain the change relationship between different pressure differences and fracturing fluid breakthrough core time, so that the fracturing fluid invasion depth in the formation can be predicted.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and more specifically to an experimental system and method for predicting the depth of fracturing fluid penetration. Background Technology

[0002] Multi-stage horizontal well fracturing has become an important method for developing tight oil reservoirs. Fracturing significantly enhances reservoir permeability and improves oil recovery, making fracturing effectiveness evaluation a crucial step in tight oil reservoir development. The fracturing fluid penetration depth not only relates to the fracturing fluid sweep area but is also a parameter that must be considered in subsequent flowback production, and even plays a role in considering the absorption area during the shut-in phase. Therefore, penetration depth is undoubtedly an important indicator of fracturing effectiveness. However, the fracturing process is influenced by various geological and engineering factors, and the penetration depth of the fracturing fluid varies under different pressures and times, making it difficult to obtain a precise value for the penetration depth.

[0003] Therefore, a comprehensive and effective solution for obtaining fracturing fluid penetration depth data is needed to provide a reference for evaluating fracturing performance. Summary of the Invention

[0004] The purpose of this invention is to provide an experimental system for predicting the depth of fracturing fluid penetration, which can comprehensively and effectively acquire fracturing fluid penetration depth data.

[0005] To achieve the above objectives, embodiments of the present invention provide an experimental system for predicting the depth of fracturing fluid invasion. The experimental system for predicting the depth of fracturing fluid invasion includes an ultra-high pressure high-precision displacement pump, an ultra-high temperature and ultra-high pressure intermediate container, an ultra-high temperature and ultra-high pressure core holder, a pressure detection device, a fracturing fluid simulation invasion device, and a control device. The ultra-high pressure, high-precision displacement pump is connected to the ultra-high temperature, ultra-high pressure intermediate container. The ultra-high temperature, ultra-high pressure intermediate container holds the experimental core in place using an ultra-high temperature, ultra-high pressure core holder. The ultra-high temperature, ultra-high pressure intermediate container is connected to the pressure detection device, and its inlet and outlet are connected to the fracturing fluid simulation intrusion device. The pressure detection device is used to detect the pressure inside the ultra-high temperature, ultra-high pressure intermediate container and the pressure at its inlet and outlet. The fracturing fluid simulation intrusion device is used to simulate fracturing fluid intrusion into the experimental core. The control device is electrically connected to the ultra-high pressure, high-precision displacement pump, the ultra-high temperature, ultra-high pressure intermediate container, the pressure detection device, and the fracturing fluid simulation intrusion device. It is used to predict the depth of fracturing fluid intrusion into the formation by changing the pressure difference between the inlet and outlet of the ultra-high temperature, ultra-high pressure intermediate container and the relationship between different pressure differences and the time it takes for the fracturing fluid to penetrate the core.

[0006] This invention also provides an experimental method for predicting the fracturing fluid penetration depth. The method is performed using the aforementioned experimental system for predicting fracturing fluid penetration depth. The method includes: for one core sample from a pre-selected set of core samples, drying the core with clean oil and placing it in an ultra-high temperature and ultra-high pressure core holder; closing the valve at the inlet of the ultra-high temperature and ultra-high pressure intermediate container; controlling an ultra-high pressure high-precision displacement pump to evacuate the ultra-high temperature and ultra-high pressure intermediate container; and after a first preset time, closing the valve at the outlet of the ultra-high temperature and ultra-high pressure intermediate container. The process involves: opening the valve at the inlet of the ultra-high temperature and ultra-high pressure intermediate vessel; controlling the fracturing fluid simulation intrusion device to perform crude oil saturation operation on the experimental core; controlling the fracturing fluid simulation intrusion device to perform water drive operation on the experimental core to simulate the oil saturation of the core under formation conditions through water drive; controlling the pressure at the inlet and outlet of the ultra-high temperature and ultra-high pressure intermediate vessel to obtain the time for the fracturing fluid to penetrate the experimental core; repeating the above experimental process for the remaining experimental cores in the pre-selected group of experimental cores to obtain the time for the fracturing fluid to penetrate the corresponding experimental cores under different pressure differentials, in order to predict the depth of fracturing fluid intrusion into the formation.

[0007] Optionally, the controlled fracturing fluid simulated invasion device performs crude oil saturation operation on the experimental core, including: controlling the fracturing fluid simulated invasion device to perform crude oil saturation operation on the experimental core at a first preset speed within a second preset time period; performing crude oil saturation operation on the experimental core at a second preset speed within a third preset time period; and controlling the operation preset time and operation preset speed to continue performing crude oil saturation operation on the experimental core until the experimental core is saturated.

[0008] Optionally, controlling the pressure at the inlet and outlet of the ultra-high temperature and ultra-high pressure intermediate container to obtain the time for fracturing fluid to penetrate the experimental core includes: gradually increasing the confining pressure of the ultra-high temperature and ultra-high pressure core holder, the pressure at the inlet, and the pressure at the outlet by controlling the valves at the inlet and outlet of the ultra-high temperature and ultra-high pressure intermediate container, wherein the confining pressure of the ultra-high temperature and ultra-high pressure core holder is higher than the pressure at the inlet; closing the valves at the inlet and outlet of the ultra-high temperature and ultra-high pressure intermediate container after the pressure at the outlet reaches a preset state; controlling the fracturing fluid simulation intrusion device to perform water drive operation on the experimental core, and opening the valves at the inlet and outlet of the ultra-high temperature and ultra-high pressure intermediate container after the confining pressure of the ultra-high temperature and ultra-high pressure core holder reaches a preset pressure; and recording the time for fracturing fluid to penetrate the experimental core.

[0009] Optionally, the prediction of fracturing fluid penetration depth into the formation includes: obtaining the penetration velocity of fracturing fluid under different pressure differentials based on the time it takes for the fracturing fluid to penetrate the corresponding experimental core under different pressure differentials; obtaining the relationship between the penetration depth of fracturing fluid in the formation near the fracture and the fracturing time based on the penetration velocity of fracturing fluid under different pressure differentials; and obtaining the relationship between the penetration amount and the fracturing time based on the obtained relationship between the penetration depth of fracturing fluid in the formation near the fracture and the fracturing time.

[0010] This invention also provides a method for predicting the depth of fracturing fluid invasion. The method includes: constructing a two-dimensional filtration model of fracturing fluid invasion into the formation based on the equilibrium relationship of the fracturing fluid invasion material; calculating the depth of fracturing fluid invasion under different pressures using the two-dimensional filtration model and the mesh model; and verifying the calculated depth of fracturing fluid invasion using the experimental method for predicting the depth of fracturing fluid described above.

[0011] Optionally, the construction of the two-dimensional filtration model of fracturing fluid intrusion into the formation includes:

[0012] Based on the continuity equation and Darcy's law, the differential equation for the occurrence of fracturing fluid seepage is derived as follows:

[0013]

[0014] The boundary conditions include:

[0015] The closed outer boundary is:

[0016]

[0017] The constant pressure outer boundary is:

[0018]

[0019] The inner boundary conditions are:

[0020]

[0021] The initial conditions of the model are:

[0022] P| t＝0 =P i

[0023] Solve the five-diagonal equation system consisting of the seepage differential equation and additional conditions, and use a strongly implicit method to obtain the pressure at each grid point;

[0024] The formula for filtration rate is:

[0025]

[0026] Based on the pressure difference between the grid points near the fracture and the fracture pressure, the fracturing fluid loss per unit time is obtained as follows:

[0027]

[0028] The two-dimensional filtering model is as follows:

[0029]

[0030] Where μ is the viscosity of the fracturing fluid, C f Let G be the overall rock compressibility coefficient, and G be the starting pressure gradient. P represents rock porosity. i and P f These represent the original formation pressure and fracture pressure, respectively, with Δy1 being the length of the first row of grids in the y-direction. Let m be the filter loss at time n, m be the number of meshes in the crack, and k be the filter loss. d Where is the formation permeability, h is the fracturing fluid filtration height, and l is the formation permeability. xi L is the length of the mesh in the x-direction of the crack. x and L y These are the boundary coordinates in the x and y directions, respectively, l f v is the total length of the crack. i Let P be the filtration velocity of the i-th crack mesh. i,1 The pressure of the first row of grids in the y direction.

[0031] Optionally, the mesh model is divided into: horizontal well X-direction meshing and fracture Y-direction meshing. Horizontal well X-direction meshing: Two clusters of fractures within a segment are simultaneously fractured. Based on the pressure changes between clusters, a symmetrical mesh is adopted; the closer to the fracture, the greater the pressure gradient, so a denser mesh is used, with the mesh length increasing sequentially from the fracture to the inter-cluster distance; the total length of the inter-cluster mesh should be equal to the inter-cluster distance, and the mesh length and number are selected based on computational accuracy and speed. Fracture Y-direction meshing: The fracture extends outward segment by segment, and the length of the expanding mesh gradually decreases within the same time frame, adopting a decreasing mesh length; the mesh expansion rate is determined based on the injection time, and fracture expansion is completed within the injection time; the total length of the fracture mesh is equal to the fracture length.

[0032] Optionally, calculating the fracturing fluid penetration depth under different pressures using the two-dimensional filtration model and the mesh model includes: calculating the filtration loss of the fracturing fluid based on the two-dimensional filtration model and the mesh model; obtaining the fracturing fluid injection volume using the filtration loss of the fracturing fluid and the volume change of the fracture, wherein the volume change of the fracture is calculated using a fracture volume model; and obtaining the fracturing fluid penetration depth based on the injection volume of the fracturing fluid.

[0033] Optionally, the method for predicting the fracturing fluid invasion depth further includes: establishing a pressure diffusion model for a fracturing horizontal well using the grid model; and calculating the formation pressure change of the near-horizontal well based on the pressure diffusion model for the fracturing horizontal well.

[0034] Through the above technical solution, the experimental system for fracturing fluid invasion depth provided by the embodiments of the present invention includes an ultra-high pressure high-precision displacement pump, an ultra-high temperature and ultra-high pressure intermediate container, an ultra-high temperature and ultra-high pressure core holder, a pressure detection device, a fracturing fluid simulation invasion device, and a control device. By changing the pressure difference between the inlet and outlet of the ultra-high temperature and ultra-high pressure intermediate container, the relationship between different pressure differences and the fracturing fluid breakthrough core time can be obtained, thereby predicting the fracturing fluid invasion depth into the formation.

[0035] Other features and advantages of the embodiments of the present invention will be described in detail in the following detailed description section. Attached Figure Description

[0036] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0037] Figure 1 This is a schematic diagram of an example experimental system for predicting fracturing fluid penetration depth provided in Embodiment 1 of the present invention;

[0038] Figure 2 This is a flowchart illustrating the experimental method for predicting fracturing fluid penetration depth provided in Embodiment 2 of the present invention.

[0039] Figure 3 This is a schematic diagram of the prepared experimental core.

[0040] Figure 4 This is a graph showing the relationship between the fracturing fluid intrusion rate and the experimental pressure difference;

[0041] Figure 5 This is a schematic diagram of the intrusion velocity fitting obtained from the experiment;

[0042] Figure 6 It shows the relationship between the penetration depth of fracturing fluid and fracturing time;

[0043] Figure 7 This is the relationship between the amount of intrusion and the fracturing time;

[0044] Figure 8 This is a schematic flowchart of the method for predicting the fracturing fluid penetration depth provided in Embodiment 3 of the present invention;

[0045] Figure 9 This is a schematic diagram showing the change in the penetration depth of fracturing fluid with fracturing time under different pressures during the fracturing process;

[0046] Figure 10 This is a schematic diagram showing the pressure changes during fracturing of two clusters of fractures in a horizontal well section. Detailed Implementation

[0047] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0048] This invention employs a comprehensive approach combining laboratory experiments, numerical simulations, and theoretical analysis to predict the penetration depth of fracturing fluid under different pressures. First, to simulate the high pressure characteristics of actual fractures, laboratory experiments were conducted using equipment conforming to high formation pressure conditions. Considering the changing pressure difference between the fracture and reservoir during fracturing operations, a variable inlet / outlet pressure difference method was used to test and analyze fracturing fluid penetration into the reservoir under different pressure differences (e.g., 30 MPa, 25 MPa, 20 MPa, 15 MPa, 10 MPa). Experiments were performed to determine the penetration depth of fracturing fluid under different pressures, thus establishing the relationship between pressure difference and fracturing fluid penetration depth. Second, a two-dimensional fracturing fluid filtration model and a mesh model were established. Numerical simulations of fracturing fluid penetration were used to clarify the penetration depth of fracturing fluid under different operational pressures. Finally, combining experimental measurements, numerical simulations, and theoretical analysis, the prediction of the fracturing fluid penetration depth was completed.

[0049] Embodiment 1 of the present invention provides an experimental system for predicting the depth of fracturing fluid invasion. The experimental system for predicting the depth of fracturing fluid invasion includes an ultra-high pressure high-precision displacement pump, an ultra-high temperature and ultra-high pressure intermediate container, an ultra-high temperature and ultra-high pressure core holder, a pressure detection device, a fracturing fluid simulation invasion device, and a control device.

[0050] The ultra-high pressure, high-precision displacement pump is connected to the ultra-high temperature, ultra-high pressure intermediate container. The ultra-high temperature, ultra-high pressure intermediate container holds the experimental core in place using an ultra-high temperature, ultra-high pressure core holder. The ultra-high temperature, ultra-high pressure intermediate container is connected to the pressure detection device, and its inlet and outlet are connected to the fracturing fluid simulation intrusion device. The pressure detection device is used to detect the pressure inside the ultra-high temperature, ultra-high pressure intermediate container and the pressure at its inlet and outlet. The fracturing fluid simulation intrusion device is used to simulate fracturing fluid intrusion into the experimental core. The control device is electrically connected to the ultra-high pressure, high-precision displacement pump, the ultra-high temperature, ultra-high pressure intermediate container, the pressure detection device, and the fracturing fluid simulation intrusion device. It is used to predict the depth of fracturing fluid intrusion into the formation by changing the pressure difference between the inlet and outlet of the ultra-high temperature, ultra-high pressure intermediate container and the relationship between different pressure differences and the time it takes for the fracturing fluid to penetrate the core.

[0051] The actual bottom hole fracture pressure during the tight reservoir fracturing process can reach 70-90 MPa. To meet the high pressure requirements, Embodiment 1 of this invention provides an experimental system for predicting the fracturing fluid invasion depth. The experimental process design is completed using a displacement system, and a series of fracturing fluid invasion experiments are conducted using actual pressure values.

[0052] Figure 1 This is a schematic diagram of an example experimental system for predicting fracturing fluid penetration depth provided in Embodiment 1 of the present invention. Please refer to it. Figure 1 Experimental systems for predicting fracturing fluid penetration depth may include: an ultra-high pressure, high-precision displacement pump (e.g., a confining pressure pump) with an experimental range of 0–200 MPa; an ultra-high temperature, ultra-high pressure intermediate vessel with a maximum pressure of 200 MPa and a test temperature of up to 200 °C; and an ultra-high temperature, ultra-high pressure core holder (e.g., a core holder) with a maximum pressure of 200 MPa and a test temperature of up to 200 °C.

[0053] The experimental system for predicting the depth of fracturing fluid invasion may also include: a pressure detection device, a fracturing fluid invasion simulation device, and a control device (e.g., a metering system).

[0054] During in-situ fracturing operations, the formation pressure gradually increases as the fracturing fluid diffuses, leading to a continuous increase in the fracturing fluid's penetration depth within the formation. To study the fracturing fluid's penetration into the formation during the fracturing process, the experimental system provided in Embodiment 1 of this invention can be used to test the relationship between different pressure differentials between the fracture and the reservoir and the fracturing fluid's core breakthrough time. Based on this, numerical interpolation methods can be used, combined with experimentally determined pressure differential-time relationships, to predict the fracturing fluid's penetration depth into the formation.

[0055] Figure 2 This is a flowchart illustrating the experimental method for predicting fracturing fluid penetration depth provided in Embodiment 2 of the present invention. Please refer to it. Figure 2 The experimental method for predicting the fracturing fluid penetration depth can be performed using the experimental system for fracturing fluid penetration depth provided in Embodiment 1 of the present invention, and the experimental method for predicting the fracturing fluid penetration depth may include the following steps:

[0056] Step S110: For one of the pre-selected experimental cores, after the experimental core is dried by oil removal, it is placed in the ultra-high temperature and ultra-high pressure core holder, and the valve at the inlet end of the ultra-high temperature and ultra-high pressure intermediate container is closed.

[0057] Taking a set of experimental cores taken from the horizontal section of a horizontal well in the X well area of ​​Xinjiang Oilfield after fracturing as an example, this paper explains the experimental method for predicting the fracturing fluid invasion depth provided in Example 2 of the present invention.

[0058] Please refer to the local characteristics of the experimental core. Figure 3 Five 1-inch × 5-cm test cores were drilled, and the basic parameter data of the test cores are shown in Table 1.

[0059] Table 1 Basic parameters of the experimental core

[0060]

[0061] Taking one of the experimental cores from the above group as an example, after the experimental core is dried and cleaned, it is placed in an ultra-high temperature and ultra-high pressure core holder, and the valve at the inlet end of the ultra-high temperature and ultra-high pressure intermediate container is closed.

[0062] Step S120: Control the ultra-high pressure and high-precision displacement pump to evacuate the ultra-high temperature and ultra-high pressure intermediate container. After a first preset time, close the valve at the outlet end of the ultra-high temperature and ultra-high pressure intermediate container.

[0063] Following the above example, the outlet end of the ultra-high temperature and ultra-high pressure intermediate container is connected to an ultra-high pressure and high-precision displacement pump. The ultra-high pressure and high-precision displacement pump is controlled to evacuate the ultra-high temperature and ultra-high pressure intermediate container. After a first preset time (e.g., 24 hours), the valve at the outlet end of the ultra-high temperature and ultra-high pressure intermediate container is closed, and the high-pressure and high-precision displacement pump is stopped.

[0064] Step S130: Open the valve at the inlet end of the ultra-high temperature and ultra-high pressure intermediate vessel and control the fracturing fluid simulation intrusion device to perform crude oil saturation operation on the experimental core.

[0065] Please refer to Figure 1 The fracturing fluid intrusion simulation device includes a displacement pump and two channels. The right channel is used to saturate the experimental core with crude oil under the drive of the displacement pump (e.g., a horizontal flow pump), and the left channel is used to simulate fracturing fluid intrusion under the drive of the displacement pump.

[0066] Preferably, the controlled fracturing fluid simulated invasion device for saturating the experimental core with crude oil may include: controlling the fracturing fluid simulated invasion device to saturate the experimental core with crude oil at a first preset speed within a second preset time period; saturating the experimental core with crude oil at a second preset speed within a third preset time period; and controlling the preset operation time and preset operation speed to continue saturating the experimental core with crude oil until the experimental core is saturated.

[0067] Following the above example, the fracturing fluid simulation intrusion device can be controlled to saturate the experimental core with crude oil at a rate of 0.05 ml / min for 12 hours; then at a rate of 0.1 ml / min for 6 hours; and then the saturation rate can be gradually increased while the saturation time is decreased until the experimental core is saturated.

[0068] Step S140: Control the fracturing fluid simulation intrusion device to perform water drive operation on the experimental core, so as to construct a simulation of the core oil saturation under formation conditions through water drive.

[0069] In Embodiment 2 of the present invention, slickwater is used to simulate fracturing fluid. Therefore, the fracturing fluid simulation intrusion device is controlled, and under the drive of its displacement pump, water-drive operation is performed on the experimental core through the left channel to simulate the oil saturation of the core under formation conditions through water-drive.

[0070] Following the example above, a simulation of core oil saturation under formation conditions was constructed, and the experimental core was aged for, for example, 48 hours.

[0071] Step S150: Control the pressure at the inlet and outlet of the ultra-high temperature and ultra-high pressure intermediate vessel to obtain the time it takes for the fracturing fluid to penetrate the experimental core.

[0072] A preferred step S150 may include: gradually increasing the confining pressure, inlet pressure, and outlet pressure of the ultra-high temperature and high pressure core holder by controlling the valves at the inlet and outlet of the ultra-high temperature and high pressure intermediate container, wherein the confining pressure of the ultra-high temperature and high pressure core holder is higher than the inlet pressure; closing the valves at the inlet and outlet of the ultra-high temperature and high pressure intermediate container after the outlet pressure reaches a preset state; controlling the fracturing fluid simulation intrusion device to perform water drive operation on the experimental core, and opening the valves at the inlet and outlet of the ultra-high temperature and high pressure intermediate container after the confining pressure of the ultra-high temperature and high pressure core holder reaches a preset pressure; and recording the time when the fracturing fluid breaks through the experimental core.

[0073] Following the example above, gradually increase the confining pressure, the pressure at the inlet end of the ultra-high temperature and ultra-high pressure core holder, and the pressure at the outlet end, while ensuring that the confining pressure of the ultra-high temperature and ultra-high pressure core holder is higher than (for example, 2-3 MPa higher) the pressure at the inlet end.

[0074] The experimental core in this embodiment of the invention is cylindrical. The confining pressure of the ultra-high temperature and ultra-high pressure core holder refers to the pressure wrapped around the core to prevent the fracturing fluid from flowing radially along the core during the displacement process. Therefore, the confining pressure should be 2-3 MPa higher than the core inlet pressure.

[0075] Step S160: For the remaining experimental cores in the pre-selected set of experimental cores, repeat the above experimental process to obtain the time of fracturing fluid penetration of the corresponding experimental cores under different pressure differentials, so as to predict the depth of fracturing fluid penetration into the formation.

[0076] Repeat steps S110-S150. According to the preset experimental requirements, the pressure of the back pressure valve at the outlet end of the ultra-high temperature and ultra-high pressure core holder can be gradually increased to obtain the time for fracturing fluid to penetrate the corresponding experimental core under different pressure differentials. For example, according to the pressure control shown in Table 2, the time for sluice water to penetrate the experimental core under different pressure differentials is recorded. Table 2 shows the fracturing fluid flow velocity under different production pressure differentials (inlet pressure - outlet pressure) by fixing the inlet pressure and adjusting the outlet pressure, thereby calculating the distance of fracturing fluid penetration into the core within a certain time. The results are shown in Table 3.

[0077] Table 2. Experimental pressure differential and inlet / outlet pressure

[0078]

[0079] Experiments were conducted under different pressure differentials, and the core breakthrough time was recorded as follows:

[0080] Experimental core No. 1, inlet pressure 70MPa, outlet pressure 40MPa, experimental pressure difference 30MPa, breakthrough time 1'25"23;

[0081] Core No. 2, inlet pressure 70MPa, outlet pressure 45MPa, experimental pressure difference 25MPa, breakthrough time 1'50"54;

[0082] Core No. 3, inlet pressure 70MPa, outlet pressure 50MPa, experimental pressure difference 20MPa, breakthrough time 1'48"26;

[0083] Core No. 4, inlet pressure 70MPa, outlet pressure 55MPa, experimental pressure difference 15MPa, breakthrough time 2′01″07;

[0084] Core No. 5, inlet pressure 70MPa, outlet pressure 60MPa, experimental pressure difference 10MPa, breakthrough time 2′17″50.

[0085] Table 3. Breakthrough time statistics of experimental core samples

[0086]

[0087] Preferably, the prediction of fracturing fluid penetration depth may further include: obtaining the penetration velocity of fracturing fluid under different pressure differentials based on the time it takes for the fracturing fluid to penetrate the corresponding experimental core under different pressure differentials; obtaining the relationship between the penetration depth of fracturing fluid in the formation near the fracture and the fracturing time based on the penetration velocity of fracturing fluid under different pressure differentials; and obtaining the relationship between the penetration amount and the fracturing time based on the obtained relationship between the penetration depth of fracturing fluid in the formation near the fracture and the fracturing time.

[0088] According to the results shown in Table 3, the larger the pressure differential corresponding to the core experiment, the faster the fracturing fluid invades and the shorter the breakthrough time. As the experimental pressure differential increases gradually from 10 MPa to 30 MPa, the time required for the fracturing fluid to penetrate the experimental core gradually decreases. Based on the selected experimental core length of 5 cm, the invasion velocity under different experimental pressure differentials can be calculated, as shown in Table 4.

[0089] Figure 4 The graph shows the relationship between the fracturing fluid intrusion rate and the experimental pressure differential. Figure 4 It can be seen that the intrusion rate of fracturing fluid is different under different experimental pressure differentials, and the intrusion rate tends to increase with the increase of pressure differential. However, the range of variation of fracturing fluid intrusion rate is relatively small within the range of experimental pressure differential variation.

[0090] Table 4. Fracturing fluid intrusion rate under different experimental pressure differentials.

[0091]

[0092] Fracturing fluid penetrates the formation through fractures under different pressures. Experimental data can be used to obtain the penetration velocity of the fracturing fluid under different pressures, from which the penetration depth and volume can be calculated. Specifically, the penetration velocity obtained from the experiments is fitted, such as... Figure 5 As shown.

[0093] The formula for calculating the fitted fracturing fluid intrusion velocity y and the experimental pressure difference x can be expressed by the following equation:

[0094] y=10-5x3-0.0006x2+0.011x-0.0265, R 2 =0.962 (1)

[0095] Among them, R 2 The fitting coefficients are denoted as .

[0096] The penetration depth of fracturing fluid in the formation near the fracture during fracturing operations can be obtained by multiplying the penetration rate and the pressure differential duration over different time periods. Figure 6 This shows the relationship between the penetration depth of the fracturing fluid and the fracturing time. For example... Figure 6 As shown, within 72 minutes of fracturing time, the penetration depth of the fracturing fluid continuously increases with the increase of the pressure differential. After 72 minutes of fracturing, the penetration depth of the fracturing fluid reaches 1.317 m.

[0097] During the fracturing operation of well X-1 in this well area, the fracture half-length was 80m and the supporting fracture height was 31.60m. After determining the invasion depth on one side of a cluster of fractures, the invasion volume could be calculated based on the fracture geometry and formation porosity. That is, the invasion volume equals the product of the invasion depth, the fracture cross-section, and the porosity. The calculation results of the invasion volume are as follows: Figure 7As shown, at the end of 72 minutes of fracturing, the invasion depth on one side of the fracture, calculated based on the invasion rate, was approximately 157.11 m. 3 .

[0098] Accordingly, in Embodiment 2 of the present invention, the experimental system for predicting the depth of fracturing fluid invasion provided in Embodiment 1 of the present invention is used to simulate the process of continuous increase in formation pressure near the fracturing fracture by designing an inlet and outlet pressure difference, keeping the inlet pressure constant and increasing the outlet pressure, thereby establishing the relationship between the fracturing fluid invasion velocity under different pressure differences between the fracture and the reservoir, and then calculating the depth of fracturing fluid invasion into the formation.

[0099] Furthermore, taking into full account the actual intrusion of the entire fracture into deeper formations, a two-dimensional fracturing fluid filtration model can be established using numerical simulation tests. This model can construct the fracturing fluid injection material balance relationship, calculate and analyze the formation pressure changes at a certain distance during the fracturing process, and obtain fracturing fluid intrusion depth data under different construction pressures.

[0100] Figure 8 This is a schematic flowchart of the method for predicting fracturing fluid penetration depth provided in Embodiment 3 of the present invention. Please refer to it. Figure 8 The method for predicting the fracturing fluid penetration depth may include the following steps:

[0101] Step S210: Based on the equilibrium relationship of fracturing fluid intrusion material, construct a two-dimensional filtration model of fracturing fluid intrusion into the formation.

[0102] During formation fracturing, fracturing fluid is continuously injected into the formation along the fracture under high pressure, resulting in pressure changes based on the original formation pressure. Embodiment 3 of this invention, considering the two-dimensional filtration loss and flow of fracturing fluid within the wellbore, constructs a fracturing fluid injection material balance relationship based on relevant theories of rock mechanics and fluid mechanics, and establishes a fracturing fluid injection model based on the following pre-defined conditions:

[0103] (1) Fracturing construction system: Set the injection rate and total injection time of fracturing fluid.

[0104] For example, the injection rate of fracturing fluid is set to 5m. 3 / min / cluster, total injection time is 72min.

[0105] (2) It is preferred to take a quarter of the reservoir as the research object, establish a two-dimensional filtering model, and use different methods to determine the grid length of the grid model in the XY direction.

[0106] For example, in the X direction: during fracturing operations, the length of the fracture pressed per unit time gradually decreases with time, so the fracture grid length in the X direction adopts a decreasing sequence; in the Y direction: the grid in the Y direction is determined according to the distribution of formation pressure. The closer to the fracture, the greater the pressure gradient, so a denser grid is used, and the farther away from the fracture, the sparser grid is used.

[0107] (3) The formation grid near the fracture is equal to the fracture pressure (i.e., the grid with y=1), and the fracture pressure remains constant during construction.

[0108] (4) Set the crack propagation time.

[0109] For example, set the crack to advance one mesh every 6 minutes.

[0110] Preferably, the construction of the two-dimensional filtration model for fracturing fluid intrusion into the formation may include:

[0111] Based on the continuity equation and Darcy's law, the differential equation for the occurrence of fracturing fluid seepage can be derived as follows:

[0112]

[0113] The boundary conditions include:

[0114] The closed outer boundary is:

[0115]

[0116] The constant pressure outer boundary is:

[0117]

[0118] The inner boundary conditions are:

[0119]

[0120] The initial conditions of the model are:

[0121] P| t＝0 =P i (6)

[0122] Solve the five-diagonal equation system consisting of the seepage differential equation and additional conditions, and use a strongly implicit method to obtain the pressure at each grid point;

[0123] The formula for filtration rate is:

[0124]

[0125] Based on the pressure difference between the grid points near the fracture and the fracture pressure, the fracturing fluid loss per unit time is obtained as follows:

[0126]

[0127] The two-dimensional filtering model is as follows:

[0128]

[0129] Where μ is the viscosity of the fracturing fluid (unit: mPa·s); C f The comprehensive compressibility coefficient of the rock (unit: MPa) －1 G represents the starting pressure gradient (unit: MPa / m); P represents rock porosity. i and P f These represent the original formation pressure and fracture pressure (unit: MPa); Δy1 is the length of the first row of grids in the y direction (unit: m); Filter loss at time n (unit: m) 3 ); m is the number of meshes for the crack; k d Formation permeability (unit: μm) 2 h is the fracturing fluid filtration height (unit: m); l xi L represents the length of the grid along the crack's x-direction (in meters). x and L y These are the boundary coordinates in the x and y directions (unit: m); l f v represents the total length of the crack (in meters). i The filtration velocity of the i-th crack mesh (unit: m) 3 / s); P i,1 The pressure of the first row of grids in the y direction (unit: MPa).

[0130] During the fracturing fluid injection stage, based on the material balance relationship, it can be known that part of the fracturing fluid injected into the formation is retained in the fracture volume, while the other part is lost into the formation surrounding the fracture. The injected fracturing fluid volume is equal to the fracturing fluid loss plus the fracture volume change. A two-dimensional fracturing fluid loss model is established and the loss is calculated. The fracture volume change is calculated using the fracture volume model.

[0131] Step S220: Calculate the penetration depth of fracturing fluid under different pressures using the two-dimensional filtration model and the mesh model.

[0132] Step S230: The calculated fracturing fluid penetration depth is verified using the experimental method for predicting fracturing fluid penetration depth described in steps S110-S160.

[0133] Preferably, the mesh model is divided into:

[0134] Horizontal well X-axis meshing:

[0135] 1) Two clusters of fractures within the segment are simultaneously subjected to pressure fracturing. Based on the pressure changes between the clusters, a symmetrical grid is adopted.

[0136] 2) The closer to the crack, the greater the pressure gradient. Therefore, a denser mesh should be used, with the mesh length increasing sequentially from the crack to the inter-cluster mesh.

[0137] 3) The total length of the inter-cluster grid should be equal to the inter-cluster distance. The grid length and number are selected based on computational accuracy and speed.

[0138] Mesh the crack in the Y direction:

[0139] 1) The cracks expand outward segment by segment, and the length of the expanding mesh gradually decreases within the same time period. The mesh length is reduced accordingly.

[0140] 2) Determine the mesh expansion rate based on the injection time; crack expansion is completed within the injection time.

[0141] 3) The total length of the crack mesh is equal to the crack length.

[0142] Preferably, step S220 may include: calculating the filtration loss of fracturing fluid based on the two-dimensional filtration loss model and the mesh model; obtaining the injection volume of fracturing fluid through the filtration loss of fracturing fluid and the volume change of the fracture, wherein the volume change of the fracture is calculated through the fracture volume model; and obtaining the fracturing fluid penetration depth based on the injection volume of fracturing fluid.

[0143] Taking the second stage of fracturing fractures in Well X-1 in the X well area of ​​Xinjiang Oilfield as an example, this paper explains the process of calculating the penetration depth of fracturing fluid under different pressures using the two-dimensional filtration model and grid model. The basic parameters of the well (X-1 well) (e.g., geological, engineering design, and construction data) are shown in Table 5. This stage of fracturing consists of two clusters of half-fractures, each 80m long, with a cluster spacing of 34m. The system is set to allow the fracture to expand forward by one grid every 6 minutes, and the fracture continuously expands to 80m within a 72-minute injection time.

[0144] Table 5 Basic Parameters of Well X-1

[0145]

[0146]

[0147] Based on the established grid model and two-dimensional filtration model example, the depth of fracturing fluid penetration into the reservoir in well X-1 under different construction pressures (e.g., 70MPa, 65MPa, 60MPa, 55MPa, 50MPa) is calculated. The pressure difference formed with the original formation pressure corresponds to the experimental pressure difference in the experimental method for predicting the fracturing fluid penetration depth described in steps S110-S160. The relationship between the penetration depth of fracturing fluid and fracturing time under different pressures is statistically analyzed.

[0148] For example, by expanding the grid by one unit every 6 minutes, the fracture penetration distance is longer and thus greater in the first artificial fracture grid due to the longer filtration time. The penetration distance gradually decreases in subsequent grids. Along the fracture length, a progressively discrete grid is used, allowing the fracturing fluid to advance continuously from the root of the artificial fracture to its tip. The root of the artificial fracture (i.e., the first grid) is also where the fracturing fluid leaches the most. Table 6 shows the calculated penetration distance during the grid fracturing process, and the relationship between the fracturing fluid penetration depth and fracturing time is as follows: Figure 9 As shown.

[0149] Table 6. Fracturing fluid penetration depth data under different pressures.

[0150]

[0151]

[0152] At a pressure of 70 MPa, the fracturing fluid penetration depth calculated according to Example 2 of this invention reached 1.317 m. According to the numerical simulation analysis of the two-dimensional filtration model and the grid model, the fracturing fluid penetration depth was approximately 1.434 m after 72 min of fracturing, with an error of approximately 8.8% compared to the indoor experimental results. The error length was within 0.15 m. This indicates that the mathematical model calculation results are close to the range of fracturing fluid penetration depths in the indoor experiments, and the fracturing fluid penetration depth values ​​are reliable, which can provide a reference for subsequent well shut-in and flowback production.

[0153] The actual fracturing process of well X-1 can reach 26 stages, with the interval between stages ranging from 28 to 87 meters. Based on the numerical simulation method of Embodiment 3 of this invention, the invasion depth data of all stages of horizontal well fracturing were simulated. Since the initial pressure of each fracturing stage is affected by the formation pressure changes of the preceding stage, the formation pressure after the preceding stage fracturing is assigned to the next stage for pressure calculation. Therefore, the fracturing fluid invasion depth varies during each fracturing stage, as shown in Table 7. The invasion depth of each stage ranges from 1.158 to 1.434 meters, with the average invasion depth of later fracturing stages being smaller. The total invasion volume of each fracturing stage was calculated to be 21,560.05 cubic meters, while the actual total fluid volume injected into the well was 24,019.6 cubic meters, indicating that most of the fracturing fluid was lost during fracturing and fracture creation and entered the formation.

[0154] Table 7 Numerical simulation intrusion depth of each of the 26 sections of the horizontal well.

[0155]

[0156] In a preferred embodiment of the present invention, the method for predicting the fracturing fluid invasion depth may further include: establishing a pressure diffusion model for a fracturing horizontal well using the grid model; and calculating the formation pressure change of the near-horizontal well based on the pressure diffusion model for the fracturing horizontal well.

[0157] To illustrate, by studying the seepage mechanism during the fracturing injection process, a pressure diffusion model for a fracturing horizontal well is established. This model calculates the formation pressure changes near the wellbore and simulates the pressure changes between two clusters of fractures in the horizontal well section. Figure 10 As shown, during fracturing, as the fracture continues to extend forward, the pressure along the fracture direction and on both sides of the fracture gradually propagates outward. The fracturing pressure is high and the propagation speed is fast, resulting in large pressure changes between clusters after fracturing. The pressure increases rapidly in a short period of time. When the distance between fracture clusters decreases, pressure disturbances during injection may affect the entire inter-cluster area.

[0158] Continue to refer to Figure 10 In the case of simultaneous fracturing of two clusters, the pressure inside the fracture is equal to the fracturing pressure. The high pressure is indicated by the red part. The pressure in the adjacent areas on both sides and between the clusters increases, and the pressure propagation can be seen covering the area between the clusters. The pressure distribution on both sides is symmetrical.

[0159] Taking a multi-stage fractured horizontal well in the X well area of ​​Xinjiang Oilfield as an example, the fracturing fluid invasion depth is predicted based on laboratory experiments and mathematical models, and at least the following results are obtained:

[0160] (1) Fracturing fluid intrusion experiments with pressure differentials of, for example, 30 MPa, 25 MPa, 20 MPa, 15 MPa and 10 MPa showed that when the pressure differential increased, the breakthrough time shortened and the intrusion rate decreased.

[0161] (2) Within 72 minutes of fracturing time, the experimentally measured fracturing fluid penetration depth can reach 1.317m, while the fracturing fluid penetration depth calculated by the mathematical model is about 1.434m, with an error of about 8.8% and an error length within 0.15m, which verifies the accuracy of the mathematical model.

[0162] (3) The pressure diffusion results of the fractured horizontal well show that the pressure propagation speed is fast. When the spacing between fracture clusters decreases, the pressure disturbance during the injection process may affect the entire inter-cluster area.

[0163] Accordingly, embodiments of the present invention can obtain the fracturing fluid penetration depth under different pressures through both experimental methods and mathematical models. The experimental method involves controlling the inlet and outlet pressure difference, keeping the inlet pressure constant while increasing the outlet pressure to simulate the continuous increase in formation pressure near the fracturing fracture. This establishes the relationship between the fracturing fluid penetration velocity and different pressure differences between the fracture and the reservoir, thereby calculating the fracturing fluid penetration depth. The mathematical model employs numerical simulation to establish a two-dimensional fracturing fluid loss model, constructing a fracturing fluid injection mass balance relationship, calculating the formation pressure change at a certain distance during the fracturing process, and obtaining fracturing fluid penetration depth data under different operating pressures.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0169] Memory may include non-persistent memory in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0170] 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, magnetic magnetic 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.

[0171] 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.

[0172] 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. An experimental method of predicting the invasion depth of a fracturing fluid, characterized in that, The experimental method for predicting the fracturing fluid invasion depth is completed by an experimental system for fracturing fluid invasion depth, and the experimental method for predicting the fracturing fluid invasion depth comprises the following steps: For one experimental core in a preselected group of experimental cores, the experimental core is dried by oil baking and then arranged in an ultrahigh-temperature and ultrahigh-pressure core holder, and a valve at an inlet end of the ultrahigh-temperature and ultrahigh-pressure intermediate container is closed; The ultrahigh-pressure and high-precision displacement pump is controlled to perform vacuumization on the ultrahigh-temperature and ultrahigh-pressure intermediate container, and after a first preset time, a valve at an outlet end of the ultrahigh-temperature and ultrahigh-pressure intermediate container is closed; The valve at the inlet end of the ultrahigh-temperature and ultrahigh-pressure intermediate container is opened, and the fracturing fluid simulation invasion device is controlled to perform oil saturation operation on the experimental core; The fracturing fluid simulation invasion device is controlled to perform water flooding operation on the experimental core to build a core oil saturation simulation under formation conditions by water flooding; The pressures at the inlet end and the outlet end of the ultrahigh-temperature and ultrahigh-pressure intermediate container are controlled to obtain a time when the fracturing fluid breaks through the experimental core; For the remaining experimental cores in the preselected group of experimental cores, the above experimental process is repeated to obtain the times when the fracturing fluid breaks through the corresponding experimental cores under different pressure differentials, so as to predict the fracturing fluid invasion depth in the formation; The fracturing fluid invasion depth prediction comprises the following steps: according to the times when the fracturing fluid breaks through the corresponding experimental cores under different pressure differentials, the invasion speeds of the fracturing fluid under different pressure differentials are obtained; According to the invasion speeds of the fracturing fluid under different pressure differentials, a relationship between the invasion depth of the fracturing fluid in the formation near the fracture and the fracturing time is obtained; According to the obtained relationship between the invasion depth of the fracturing fluid in the formation near the fracture and the fracturing time, a relationship between the invasion amount and the fracturing time is obtained; The experimental system for fracturing fluid invasion depth comprises an ultrahigh-pressure and high-precision displacement pump, an ultrahigh-temperature and ultrahigh-pressure intermediate container, an ultrahigh-temperature and ultrahigh-pressure core holder, a pressure detection device, a fracturing fluid simulation invasion device, and a control device, The ultrahigh-pressure and high-precision displacement pump is connected to the ultrahigh-temperature and ultrahigh-pressure intermediate container, The ultrahigh-temperature and ultrahigh-pressure intermediate container fixes the experimental core through the ultrahigh-temperature and ultrahigh-pressure core holder, and is connected to the pressure detection device, and the inlet end and the outlet end thereof are connected to the fracturing fluid simulation invasion device, The pressure detection device is used to detect the pressure in the ultrahigh-temperature and ultrahigh-pressure intermediate container, and the pressures at the inlet end and the outlet end thereof, The fracturing fluid simulation invasion device is used to perform fracturing fluid invasion simulation operation on the experimental core, The control device is electrically connected to the ultrahigh-pressure and high-precision displacement pump, the ultrahigh-temperature and ultrahigh-pressure intermediate container, the pressure detection device, and the fracturing fluid simulation invasion device, and is used to obtain the change relationship between different pressure differentials and the fracturing fluid breakthrough core time by changing the pressure differentials at the inlet end and the outlet end of the ultrahigh-temperature and ultrahigh-pressure intermediate container, so as to predict the fracturing fluid invasion depth in the formation.

2. The experimental method of predicting invasion depth of a fracturing fluid according to claim 1, wherein, The control of the fracturing fluid simulation invasion device to perform oil saturation operation on the experimental core comprises the following steps: The fracturing fluid simulation invasion device is controlled to perform oil saturation operation on the experimental core at a first preset speed within a second preset time; saturate the experimental core with crude oil at a second preset speed within a third preset time; and controlling the preset time and the preset speed of the operation, and continuing to saturate the experimental core with crude oil until the experimental core is saturated.

3. The experimental method of predicting invasion depth of a fracturing fluid of claim 1, wherein, The method for controlling the pressure of the inlet end and the outlet end of the ultra-high temperature and ultra-high pressure intermediate container to obtain the time when the fracturing fluid breaks through the experimental core comprises: gradually increasing the confining pressure, the pressure of the inlet end and the pressure of the outlet end of the ultra-high temperature and ultra-high pressure core holder by controlling the valves of the inlet end and the outlet end of the ultra-high temperature and ultra-high pressure intermediate container, wherein the confining pressure of the ultra-high temperature and ultra-high pressure core holder is higher than the pressure of the inlet end; when the pressure of the outlet end reaches a preset state, closing the valves of the inlet end and the outlet end of the ultra-high temperature and ultra-high pressure intermediate container; controlling the fracturing fluid simulation invasion device to perform water flooding operation on the experimental core, opening the valves of the inlet end and the outlet end of the ultra-high temperature and ultra-high pressure intermediate container when the confining pressure of the ultra-high temperature and ultra-high pressure core holder reaches a preset pressure; recording the time when the fracturing fluid breaks through the experimental core.

4. A method of predicting fracture fluid invasion depth, characterized by, The method for predicting the invasion depth of the fracturing fluid comprises: constructing a two-dimensional filtration model of the fracturing fluid invading the formation according to the equilibrium relationship of the fracturing fluid invasion material; calculating the invasion depth of the fracturing fluid under different pressures through the two-dimensional filtration model and a grid model; verifying the calculated invasion depth of the fracturing fluid through the experimental method for predicting the invasion depth of the fracturing fluid according to any one of claims 1-3.

5. The method of predicting fracture fluid invasion depth according to claim 4, wherein, The method for constructing the two-dimensional filtration model of the fracturing fluid invading the formation comprises: deducing the differential equation of the fracturing fluid seepage according to the continuity equation and Darcy's law as: wherein the boundary conditions comprise: the closed outer boundary is: ， the constant pressure outer boundary is: the inner boundary condition is: （y=0） the model initial condition is: solving the five-diagonal equation group of the seepage differential equation and the additional conditions to obtain the pressure of each grid point by using the strong implicit method; the filtration velocity formula is: obtaining the filtration amount of the fracturing fluid per unit time according to the pressure difference between the grid point close to the fracture and the fracture pressure: the two-dimensional filtration model is: in, This refers to the viscosity of the fracturing fluid. Let G be the overall rock compressibility coefficient, and G be the starting pressure gradient. For rock porosity, and These are the original formation pressure and the fracture pressure, respectively. for Length of the first row of grids in the direction. Let be the filtering loss at time n, and m be the number of meshes in the crack. For formation permeability, This refers to the fracturing fluid filtration height. For cracks Length of directional grid, L x and L y They are respectively x and y Directional boundary coordinates, l f The total length of the crack. v i For the first i The filtration velocity of a cracked mesh P i,1 for y Directional pressure on the first row of grids.

6. The method of predicting fracture fluid invasion depth according to claim 4, wherein, the division of the grid model comprises: dividing the grid in the X direction of the horizontal well: when two clusters of fractures in a section are fractured at the same time, symmetrical grid is adopted based on the pressure change between the clusters; the closer to the fracture, the greater the pressure gradient, and the denser the grid, and the grid length gradually increases from the fracture to the cluster; the total length of the grid divided between the clusters should be equal to the distance between the clusters, and the grid length and quantity are selected based on the calculation accuracy and speed; dividing the grid in the Y direction of the fracture: the grid length gradually decreases in the same time when the fracture expands outward section by section, and the decreasing grid length is adopted; the grid expansion speed is determined according to the injection time, and the fracture expansion is completed within the injection time; the total length of the grid divided in the fracture is equal to the length of the fracture.

7. The method of predicting invasion depth of a fracturing fluid of claim 6, wherein, The method for calculating the invasion depth of the fracturing fluid under different pressures through the two-dimensional filtration model and the grid model comprises: calculating the filtration amount of the fracturing fluid according to the two-dimensional filtration model and the grid model; obtaining the injection amount of the fracturing fluid through the filtration amount of the fracturing fluid and the volume change amount of the fracture, The volume change amount of the crack is calculated by a crack volume model. The fracturing fluid invasion depth is obtained according to the injection amount of the fracturing fluid.

8. The method of predicting invasion depth of a fracturing fluid of claim 5, wherein, The method for predicting the fracturing fluid invasion depth further comprises: A fracturing horizontal well pressure diffusion model is established by the grid model; and The formation pressure change near the horizontal well is calculated according to the fracturing horizontal well pressure diffusion model.

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