Shale reservoir inter-well pressure channeling identification method

Abstract

The invention belongs to the technical field of shale oil and gas exploration and development, and particularly relates to a shale reservoir inter-well pressure channeling identification method which comprises the following steps: establishing a fracturing crack propagation model, and assigning values to connecting nodes after dividing the connecting nodes of the fracturing crack propagation model; according to the actual fracturing scale, initial fracturing parameters are input; the forward flowing bottomhole pressure # imgabs0 # and the reverse flowing bottomhole pressure # imgabs1 # are obtained based on the fracturing crack propagation model, the reverse flowing bottomhole pressure # imgabs2 # serves as a constraint variable to constrain the forward flowing bottomhole pressure # imgabs3 #, crack parameters are changed to complete dynamic fitting of the crack form, and the target crack form is output; obtaining a fracture boundary seepage radius based on the target fracture form so as to obtain a fracture transformation volume; and according to the fracture reformation volume, obtaining a repeated reformation volume and a repeated reformation volume coefficient, and taking the repeated reformation volume coefficient as a pressure channeling identification evaluation index. According to the technical scheme, the pressure channeling position and the crosstalk degree of the gas well can be rapidly predicted, and theoretical support is provided for anti-channeling optimization design and rapid drainage recovery after pressure channeling.

Description

Technical Field

[0001] The invention belongs to the technical field of shale oil and gas exploration and development, and particularly relates to a method for identifying inter-well pressure crossover in shale reservoirs. Background Art

[0002] Fracturing is a necessary means to achieve commercial development of shale reservoirs. However, affected by the development model and well location, fracturing of later wells can easily lead to fracture communication between new wells and old wells, resulting in inter-well pressure channeling, which seriously affects the production of the parent well or adjacent wells and causes a large amount of economic losses. At present, the methods for identifying pressure channeling are mainly divided into three types: microseismic monitoring technology, tracer tracking technology, and dynamic analysis method.

[0003] Microseismic monitoring technology is an important technology for oilfield exploration and development. This method determines the location of cracks by receiving induced microseismic events generated during the fracturing process. This method is mainly used for dynamic imaging of fracturing cracks in low-permeability reservoirs, tracking the fracturing range, and objectively evaluating the fracturing effect and location. However, with the advancement of technology, people have found that the error of microseismic monitoring technology is large, and the actual cracks are only between 30% and 70% of the monitoring results. The credibility of fracturing evaluation using microseismic monitoring will be greatly reduced.

[0004] Tracer tracking technology is a method to directly measure reservoir communication. This method reflects reservoir fluid flow and inter-well communication information through the tracer concentration breakthrough curve monitored by the production well. With subsequent development, the types of tracers have become more diverse, and the information that can be evaluated has gradually increased, such as fracture type, reservoir seepage capacity, and inter-well crosstalk. However, tracer tracking technology requires a lot of time to draw tracer concentration curves, the cycle is too long, and the economic cost of tracers is high. Therefore, this method is relatively rarely used in evaluating inter-well pressure crosstalk.

[0005] The dynamic analysis method mainly analyzes the degree of pressure channeling based on the dynamic data of production wells or fracturing wells, such as changes in the production capacity of the parent well and changes in the construction pressure of the child well. The dynamic analysis method is widely used in the analysis of pressure channeling between wells due to its advantages such as low cost and simple operation. However, this method also has the disadvantage of being time-consuming, and is affected by multiple wells and external factors, resulting in large analysis errors.

[0006] In addition, the above three methods are qualitative evaluations of fracturing channeling and cannot accurately identify the location of fracturing channeling. Therefore, it is urgent to adopt new technologies to achieve quantitative identification of inter-well fracturing channeling in reservoirs. Summary of the invention

[0007] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and to propose a method for identifying inter-well pressure channeling in shale reservoirs, which can quickly predict the location of gas well pressure channeling and the degree of crosstalk, and provide theoretical support for the optimization design of anti-channeling and the rapid drainage and resumption of production after pressure channeling.

[0008] The present invention is achieved by adopting the following technical solutions:

[0009] A method for identifying pressure crossover between wells in a shale reservoir comprises the following steps:

[0010] S1, establishing a fracturing crack extension model based on basic address parameters, dividing the connection nodes of the fracturing crack extension model according to the size of the shale reservoir, and assigning values ​​to the connection nodes;

[0011] S2, based on the fracturing crack extension model and the actual fracturing scale, input the initial fracturing parameters;

[0012] S3, in the fracturing crack extension model, the bottom hole flow pressure at the next time step is obtained according to the construction pump pressure parameters and the wellbore fluid flow parameters, which is marked as the positive bottom hole flow pressure P wp ;

[0013] S4, in the fracturing fracture extension model, the bottom hole pressure obtained according to the operation displacement parameters and the current fracture morphology, marked as the reverse bottom hole pressure P wf ;

[0014] S5, reverse the bottom hole flow pressure P wf As a constraint variable, constrain the positive bottom hole pressure P wp , changing the crack parameters to complete the dynamic fitting of the crack morphology and output the target crack morphology;

[0015] S6, obtaining the fracture boundary seepage radius based on the target fracture morphology, and obtaining the fracture transformation volume according to the fracture boundary seepage radius;

[0016] S7, obtaining a repeated transformation volume and a repeated transformation volume coefficient according to the fracture transformation volume, and taking the repeated transformation volume coefficient as an evaluation index for pressure channeling identification.

[0017] Preferably, in step S1, the connection nodes of the fracturing fracture extension model are divided by discretizing the shale reservoir and the rock into continuous connection nodes, and communication relationships are established between adjacent nodes through connections, and different types of nodes are used to represent different shale reservoir properties and fracture properties.

[0018] Preferably, in step S3, the forward bottom hole flow pressure P is obtained. wp The following steps are involved:

[0019] S31, detect and record the fracturing operation pump pressure P s ;

[0020] S32, detecting and recording the fluid density and the wellbore depth, and obtaining the net liquid column pressure P based on the fluid density and the wellbore depth H ;

[0021] S33, obtaining the oil pipe friction resistance P according to the first preset formula pf ; Wherein, the first preset formula is expressed as:

[0022]

[0023] Among them, l p represents the length of the fracturing string, in m; v represents the flow velocity of the fracturing fluid in the tubing, in m / s; ρ1 represents the density of the fracturing fluid, in kg / m 3 ; f represents the dimensionless friction coefficient; d represents the inner diameter of the fracturing string, in meters;

[0024] S34, obtaining the positive bottom hole flow pressure P according to the second preset formula wp ; Wherein, the second preset formula is expressed as:

[0025] P wp =P s +P H +P pf

[0026] Among them, P wp , P s , P H and P pf The unit is MPa.

[0027] Preferably, in step S32, the net liquid column pressure P is obtained by the following formula: H :

[0028]

[0029] Among them, ρ(h) represents the fluid density. When the density changes with depth, the density is a constant value obtained through field monitoring; h is the well depth; g is the gravitational acceleration.

[0030] Preferably, in step S4, the reverse bottom hole flow pressure P is obtained. wf The following steps are involved:

[0031] S41, obtain the net pressure P at the crack mouth f , the closing pressure of rock P c ;

[0032] S42, obtain the friction P generated by the fluid on the rock wall ff ;

[0033] S43, obtaining the reverse bottom hole flow pressure P according to the third preset formula wf ; Wherein, the third preset formula is expressed as:

[0034] P wf=P f +P c +P ff ;

[0035] Among them, P wf , P f , P c , P ff The unit is MPa.

[0036] Preferably, in step S41, the net pressure P of the crack at the crack opening is obtained. f The following steps are involved:

[0037] S411, obtaining the equivalent flow rate q injected into the fracture in the current step according to the fourth preset formula; wherein the fourth preset formula is expressed as:

[0038]

[0039] Where q(t) represents the equivalent flow rate injected into the fracture at time t, and the unit is m 3 / min; Q represents the injection flow rate of fracturing fluid under actual conditions, the unit is m 3 / min; C represents the filtration coefficient, the unit is m / min 0.5 ; t represents the current time, the unit is min; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of the cracks generated in the current time step, in meters; H represents the height of the cracks, in meters; t frac Indicates the time when crack filtration begins;

[0040] S412, based on a fifth preset formula, obtaining a net pressure at the crack opening according to the reduced flow rate q injected into the crack; wherein the fifth preset formula is expressed as:

[0041]

[0042] Among them, p f (t) represents the net pressure at the seam at time t, in MPa; K represents the consistency coefficient, in MPa / min; n represents the rheological index, which is dimensionless; E represents Young's modulus, in MPa.

[0043] Preferably, in step S42, the friction P generated by the fluid on the rock wall is obtained by the sixth preset formula ff ; Wherein, the sixth preset formula is expressed as:

[0044]

[0045] Among them, p ff(t) represents the friction resistance generated on the rock wall at time t, in MPa; a and b represent the resistance coefficients under different states, in MPa / m; L f (t) is the total length of the crack, in meters; t represents the current time, in minutes; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of cracks generated in the current time step, in meters; L(t * ) represents the total length of cracks generated in the previous time step, in m.

[0046] Preferably, in step S6, the method for obtaining the fracture boundary seepage radius based on the target fracture morphology is: firstly obtaining the target fracture morphology, fracture permeability and fluid viscosity, and then obtaining the fracture boundary seepage radius according to the seventh preset formula; wherein the seventh preset formula is expressed as:

[0047]

[0048] Among them, r is the seepage radius of the fracture boundary, the unit is m; k is the fracture permeability, the unit is D; t′ is the time, the unit is s; μ is the fluid viscosity, the unit is MPa•s.

[0049] Preferably, in step S7, the method for obtaining the repeated transformation volume coefficient is: obtaining the number of fracture segments and the repeated transformation volume, and then obtaining the repeated transformation volume coefficient according to an eighth preset formula; wherein the eighth preset formula is expressed as:

[0050]

[0051] Where R represents the repeated reconstruction volume coefficient; N represents the number of fracture segments; V c Indicates the repeated transformation volume, in m 3 ; V i is the transformation volume of the i-th fracture segment, in m 3 .

[0052] Beneficial technical effects brought by the present invention:

[0053] This technical solution proposes a method for identifying inter-well pressure channeling in shale reservoirs. It constructs a fracture propagation model and a method for identifying pressure channeling based on the connected unit method. In the model, the fracture morphology is fitted by means of bottom hole flow pressure constraints. The bottom hole flow pressure calculated by the construction displacement and the fracture morphology is used as a constraint variable, and the dynamic fitting of the fracture morphology is achieved by changing the fracture parameters. At the same time, the fracture boundary seepage radius is introduced to calculate the fracture transformation volume, and the repeated transformation volume coefficient is used as a quantitative evaluation index for pressure channeling, so as to achieve an accurate description of the pressure channeling position and the degree of crosstalk. In summary, this method has the advantages of low cost, simple operation, short cycle, and small error. It can quickly determine the location and degree of crosstalk of gas well pressure channeling, and provide theoretical support for the optimization design of anti-channeling and rapid drainage and resumption of production after pressure channeling. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is the basic implementation flow chart of this technical solution;

[0055] Figure 2 This is a schematic diagram of reservoir and fracture attribute division using the connection unit method of this technology;

[0056] Figure 3 This is a schematic diagram of the impact of cracks in this technical solution;

[0057] Figure 4 This is a more specific implementation principle flow chart of this technical solution;

[0058] Figure 5 This is a schematic diagram of shale reservoir fracture transformation using this technical solution. DETAILED DESCRIPTION

[0059] In order to make the purpose, technical solution and advantages of the invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings in the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0060] Therefore, the following detailed description of the invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] Example 1

[0062] This embodiment discloses a method for identifying pressure channeling between wells in shale reservoirs. In the numerical simulation process, it is necessary to first establish a model containing basic geological parameters, and subsequent simulations are all performed on the basis of the model. Based on this, as a basic implementation scheme of the present invention, the following steps are included:

[0063] S1, establish a fracturing crack extension model based on the basic address parameters, and divide the connection nodes of the fracturing crack extension model according to the size of the shale reservoir, and assign values ​​to the connection nodes. That is, establish the user's own node model based on the geological model, and equate the geological model to different nodes in the model. The nodes have attributes, which can be understood as nodes are equivalent to a geological area, and the mechanical parameters of this geological area are assigned to the nodes, such as stress value, Young's modulus, depth, etc. These are the parameters to be used in calculating the fracture extension model, which is the process corresponding to step S5 of this technical solution.

[0064] S2, based on the fracturing crack expansion model, according to the actual fracturing scale, input the initial fracturing parameters. The actual fracturing scale includes the total number of fracturing sections in a well, the length of each section, the number of perforation clusters between sections, and the cluster spacing. These parameters are important construction parameters and the key to locating the fracturing position. Subsequent simulations are performed after locating these positions. The aforementioned parameters are a well-designed plan at the initial stage of fracturing. It is a clear parameter that can be obtained directly from the construction report. These parameters are also initial conditions, that is, the initial fracturing parameters that need to be input. The parameters first define which nodes are perforation cracks and nodes corresponding to the location of the well. Subsequent calculations start from the perforation position.

[0065] S3, in the fracturing crack extension model, according to the construction pump pressure parameters (the construction pump pressure is monitored on-site, the surface pump group is used to pump fluid into the underground, and the pressure change is monitored by instruments at the wellhead, which is a known value) and the wellbore fluid flow parameters (the wellbore fluid flow parameters include fluid density and wellbore depth. Wellbore depth and fluid density are known parameters, and the fluid density can be obtained through experiments. The wellbore depth is monitored during logging or drilling. These parameters are necessary conditions. As a known quantity in the model, these parameters must also be clarified before on-site construction) to obtain the bottom hole flow pressure at the next time step, marked as the positive bottom hole flow pressure P wp .

[0066] S4, in the fracturing fracture extension model, the bottom hole pressure obtained according to the operation displacement parameters and the current fracture morphology, marked as the reverse bottom hole pressure P wf ;

[0067] S5, reverse the bottom hole flow pressure P wf As a constraint variable, constrain the positive bottom hole pressure P wp , changing the crack parameters to complete the dynamic fitting of the crack morphology and output the target crack morphology;

[0068] S6, obtaining the fracture boundary seepage radius based on the target fracture morphology, and obtaining the fracture transformation volume according to the fracture boundary seepage radius;

[0069] S7, obtaining a repeated transformation volume and a repeated transformation volume coefficient according to the fracture transformation volume, and taking the repeated transformation volume coefficient as an evaluation index for pressure channeling identification.

[0070] Example 2

[0071] This embodiment discloses a method for identifying pressure channeling between wells in a shale reservoir, which, as a preferred embodiment of the present invention, comprises the following steps:

[0072] S1, establish a fracturing crack extension model based on basic address parameters, and divide the connection nodes of the fracturing crack extension model according to the size of the shale reservoir, and assign values ​​to the connection nodes. The connection nodes of the fracturing crack extension model are divided by discretizing the shale reservoir and the rock into continuous connection nodes, and the adjacent nodes are connected to establish a communication relationship, and different types of nodes are used to represent different shale reservoir properties and fracture properties.

[0073] S2, based on the fracturing crack extension model and the actual fracturing scale, input the initial fracturing parameters.

[0074] S3, in the fracturing crack extension model, the bottom hole flow pressure at the next time step is obtained according to the construction pump pressure parameters and the wellbore fluid flow parameters, which is marked as the positive bottom hole flow pressure P wp , specifically including the following steps:

[0075] S31, detect and record the fracturing operation pump pressure P s ;

[0076] S32, detecting and recording the fluid density and the wellbore depth, and obtaining the net liquid column pressure P based on the fluid density and the wellbore depth H ; Specifically, the net liquid column pressure P is obtained by the following formula H :

[0077]

[0078] Among them, ρ(h) represents the fluid density. When the density changes with depth, the density is a constant value obtained through field monitoring; h is the well depth; g is the gravitational acceleration.

[0079] S33, obtaining the oil pipe friction resistance P according to the first preset formula pf ; Wherein, the first preset formula is expressed as:

[0080]

[0081] Among them, l p represents the length of the fracturing string, in m; v represents the flow velocity of the fracturing fluid in the tubing, in m / s; ρ1 represents the density of the fracturing fluid, in kg / m 3; f represents the dimensionless friction coefficient; ; d represents the inner diameter of the fracturing string, in meters.

[0082] S34, obtaining the positive bottom hole flow pressure P according to the second preset formula wp ; Wherein, the second preset formula is expressed as:

[0083] P wp =P s +P H +P pf

[0084] Among them, P wp , P s , P H and P pf The unit is MPa.

[0085] S4, in the fracturing fracture extension model, the bottom hole pressure obtained according to the operation displacement parameters and the current fracture morphology, marked as the reverse bottom hole pressure P wf , specifically including the following steps:

[0086] S41, obtain the net pressure P at the crack mouth f , the closing pressure of rock P c ;

[0087] S42, obtain the friction P generated by the fluid on the rock wall ff ;

[0088] S43, obtaining the reverse bottom hole flow pressure P according to the third preset formula wf ; Wherein, the third preset formula is expressed as:

[0089] P wf =P f +P c +P ff ;

[0090] Among them, P wf , P f , P c , P ff The unit is MPa.

[0091] S5, reverse the bottom hole flow pressure P wf As a constraint variable, constrain the positive bottom hole pressure P wp , change the crack parameters to complete the dynamic fitting of the crack morphology and output the target crack morphology.

[0092] S6, obtaining the fracture boundary seepage radius based on the target fracture morphology, and obtaining the fracture transformation volume according to the fracture boundary seepage radius.

[0093] S7, obtaining a repeated transformation volume and a repeated transformation volume coefficient according to the fracture transformation volume, and taking the repeated transformation volume coefficient as an evaluation index for pressure channeling identification.

[0094] In this technical solution, in order to accurately and quickly simulate the shale reservoir, the l-connected unit method is used to characterize the reservoir model. In the model, the reservoir and the rock are discretized into continuous connection nodes, and the nodes and adjacent nodes establish communication relationships through connections, such as Figure 2 The heterogeneity in the reservoir can be represented by heterogeneous nodes, and the node values ​​can be obtained by interpolation of the geological model. Figure 2 Nodes of different colors represent reservoir attributes with different parameters and fracture attributes.

[0095] Example 3

[0096] This embodiment discloses a method for identifying pressure channeling between wells in a shale reservoir, which, as a preferred embodiment of the present invention, comprises the following steps:

[0097] S1, establish a fracturing crack extension model based on basic address parameters, and divide the connection nodes of the fracturing crack extension model according to the size of the shale reservoir, and assign values ​​to the connection nodes. The connection nodes of the fracturing crack extension model are divided by discretizing the shale reservoir and the rock into continuous connection nodes, and the adjacent nodes are connected to establish a communication relationship, and different types of nodes are used to represent different shale reservoir properties and fracture properties.

[0098] S2, based on the fracturing crack extension model and the actual fracturing scale, input the initial fracturing parameters;

[0099] S3, in the fracturing crack extension model, the bottom hole flow pressure at the next time step is obtained according to the construction pump pressure parameters and the wellbore fluid flow parameters, which is marked as the positive bottom hole flow pressure P wp , specifically including the following steps:

[0100] S31, detect and record the fracturing operation pump pressure P s ;

[0101] S32, detecting and recording the fluid density and the wellbore depth, and obtaining the net liquid column pressure P based on the fluid density and the wellbore depth H ;

[0102] S33, obtaining the oil pipe friction resistance P according to the first preset formula pf ; Wherein, the first preset formula is expressed as:

[0103]

[0104] Among them, l prepresents the length of the fracturing string, in m; v represents the flow velocity of the fracturing fluid in the tubing, in m / s; ρ1 represents the density of the fracturing fluid, in kg / m 3 ; f represents the dimensionless friction coefficient; d represents the inner diameter of the fracturing string, in meters;

[0105] S34, obtaining the positive bottom hole flow pressure P according to the second preset formula wp ; Wherein, the second preset formula is expressed as:

[0106] P wp =P s +P H +P pf

[0107] Among them, P wp , P s , P H and P pf The unit is MPa.

[0108] S4, in the fracturing fracture extension model, the bottom hole pressure obtained according to the operation displacement parameters and the current fracture morphology, marked as the reverse bottom hole pressure P wf , specifically including the following steps:

[0109] S41, obtain the net pressure P at the crack mouth f , the closing pressure of rock P c ; Among them, the closing pressure of the rock is a determined value obtained through physical experiments, which is a known value and also the initial condition; further, the net pressure P at the crack mouth is obtained f The following steps are involved:

[0110] S411, obtaining the equivalent flow rate q injected into the fracture in the current step according to the fourth preset formula; wherein the fourth preset formula is expressed as:

[0111]

[0112] Where q(t) represents the equivalent flow rate injected into the fracture at time t, and the unit is m 3 / min; Q represents the injection flow rate of fracturing fluid under actual conditions, the unit is m 3 / min; C represents the filtration coefficient, the unit is m / min 0.5 ; t represents the current time, the unit is min; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of the cracks generated in the current time step, in meters; H represents the height of the cracks, in meters; t frac Indicates the time when crack filtration begins;

[0113] S412, based on a fifth preset formula, obtaining a net pressure at the crack opening according to the reduced flow rate q injected into the crack; wherein the fifth preset formula is expressed as:

[0114]

[0115] Among them, p f (t) represents the net pressure at the seam at time t, in MPa; K represents the consistency coefficient, in MPa / min; n represents the rheological index, which is dimensionless; E represents Young's modulus, in MPa.

[0116] S42, obtain the friction P generated by the fluid on the rock wall ff Specifically, the friction P generated by the fluid on the rock wall is obtained by the sixth preset formula ff ; Wherein, the sixth preset formula is expressed as:

[0117]

[0118] Among them, p ff (t) represents the friction resistance generated on the rock wall at time t, in MPa; a and b represent the resistance coefficients under different states, in MPa / m; L f (t) is the total length of the crack, in meters; t represents the current time, in minutes; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of cracks generated in the current time step, in meters; L(t * ) represents the total length of cracks generated in the previous time step, in m.

[0119] S43, obtaining the reverse bottom hole flow pressure P according to the third preset formula wf ; Wherein, the third preset formula is expressed as:

[0120] P wf =P f +P c +P ff ;

[0121] Among them, P wf , P f , P c , P ff The unit is MPa.

[0122] S5, reverse the bottom hole flow pressure P wf As a constraint variable, constrain the positive bottom hole pressure P wp , change the crack parameters to complete the dynamic fitting of the crack morphology and output the target crack morphology; specifically:

[0123] S51, the reverse bottom hole flow pressure P at time step t+dt has been obtained through step S4. wf , which is converted from the construction pump pressure at the t+dt time step and the liquid column pressure inside the wellbore;

[0124] S52, assuming that the fracture morphology at the current time step is the real fracture morphology, using the construction displacement data of the t+dt time step, using the fourth preset formula to calculate the equivalent displacement, using the fifth preset formula to calculate the pressure at the fracture mouth, which is expressed as the positive bottom hole flow pressure P wp ;

[0125] S53, compare whether the two pressures are equal (these two pressures must be equal, one is calculated by pump pressure, which is actual data, and the other is calculated by construction displacement and crack morphology, which is just converted to the pressure of one point, and each step needs to be fitted). If they are not equal, the number of crack nodes needs to be increased, that is, the crack expansion process;

[0126] S54, when the number of fractures is increased, the forward bottom hole pressure P is calculated by using the fracture morphology and the displacement at the t+dt time step. wp .

[0127] S55, repeat the above process (step S51 to step S4) until the two pressures meet the accuracy requirements.

[0128] S6, obtaining the fracture boundary seepage radius based on the target fracture morphology, and obtaining the fracture transformation volume according to the fracture boundary seepage radius.

[0129] S7, obtaining a repeated transformation volume and a repeated transformation volume coefficient according to the fracture transformation volume, and taking the repeated transformation volume coefficient as an evaluation index for pressure channeling identification.

[0130] Example 4

[0131] This embodiment discloses a method for identifying pressure channeling between wells in a shale reservoir, which, as a preferred embodiment of the present invention, comprises the following steps:

[0132] S1, establish a fracturing crack extension model based on basic address parameters, and divide the connection nodes of the fracturing crack extension model according to the size of the shale reservoir, and assign values ​​to the connection nodes. The connection nodes of the fracturing crack extension model are divided by discretizing the shale reservoir and the rock into continuous connection nodes, and the adjacent nodes are connected to establish a communication relationship, and different types of nodes are used to represent different shale reservoir properties and fracture properties.

[0133] S2, based on the fracturing crack extension model and the actual fracturing scale, input the initial fracturing parameters;

[0134] S3, in the fracturing crack extension model, the bottom hole flow pressure at the next time step is obtained according to the construction pump pressure parameters and the wellbore fluid flow parameters, which is marked as the positive bottom hole flow pressure P wp , specifically including the following steps:

[0135] S31, detect and record the fracturing operation pump pressure P s ;

[0136] S32, detecting and recording the fluid density and the wellbore depth, and obtaining the net liquid column pressure P based on the fluid density and the wellbore depth H ;

[0137] S33, obtaining the oil pipe friction resistance P according to the first preset formula pf ; Wherein, the first preset formula is expressed as:

[0138]

[0139] Among them, l p represents the length of the fracturing string, in m; v represents the flow velocity of the fracturing fluid in the tubing, in m / s; ρ1 represents the density of the fracturing fluid, in kg / m 3 ; f represents the dimensionless friction coefficient; d represents the inner diameter of the fracturing string, in meters;

[0140] S34, obtaining the positive bottom hole flow pressure P according to the second preset formula wp ; Wherein, the second preset formula is expressed as:

[0141] P wp =P s +P H +P pf

[0142] Among them, P wp , P s , P H and P pf The unit is MPa.

[0143] S4, in the fracturing fracture extension model, the bottom hole pressure obtained according to the operation displacement parameters and the current fracture morphology, marked as the reverse bottom hole pressure P wf , specifically including the following steps:

[0144] S41, obtain the net pressure P at the crack mouth f , the closing pressure of rock P c Specifically, the net pressure P at the crack mouth is obtained f The following steps are involved:

[0145] S411, obtaining the equivalent flow rate q injected into the fracture in the current step according to the fourth preset formula; wherein the fourth preset formula is expressed as:

[0146]

[0147] Where q(t) represents the equivalent flow rate injected into the fracture at time t, and the unit is m 3 / min; Q represents the injection flow rate of fracturing fluid under actual conditions, the unit is m 3 / min; C represents the filtration coefficient, the unit is m / min 0.5 ; t represents the current time, the unit is min; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of the cracks generated in the current time step, in meters; H represents the height of the cracks, in meters; t frac Indicates the time when crack filtration begins;

[0148] S412, based on a fifth preset formula, obtaining a net pressure at the crack opening according to the reduced flow rate q injected into the crack; wherein the fifth preset formula is expressed as:

[0149]

[0150] Among them, p f (t) represents the net pressure at the seam at time t, in MPa; K represents the consistency coefficient, in MPa / min; n represents the rheological index, which is dimensionless; E represents Young's modulus, in MPa.

[0151] S42, obtain the friction P generated by the fluid on the rock wall ff Specifically, the friction P generated by the fluid on the rock wall is obtained by the sixth preset formula ff ; Wherein, the sixth preset formula is expressed as:

[0152]

[0153] Among them, p ff (t) represents the friction resistance generated on the rock wall at time t, in MPa; a and b represent the resistance coefficients under different states, in MPa / m; L f (t) is the total length of the crack, in meters; t represents the current time, in minutes; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of cracks generated in the current time step, in meters; L(t * ) represents the total length of cracks generated in the previous time step, in m.

[0154] S43, obtaining the reverse bottom hole flow pressure P according to the third preset formula wf ; Wherein, the third preset formula is expressed as:

[0155] P wf =P f +P c +P ff ;

[0156] Among them, P wf , P f , P c , P ff The unit is MPa.

[0157] S5, reverse the bottom hole flow pressure P wf As a constraint variable, constrain the positive bottom hole pressure P wp , changing the crack parameters to complete the dynamic fitting of the crack morphology and output the target crack morphology;

[0158] S6, based on the target fracture morphology, obtain the fracture boundary seepage radius, and obtain the fracture transformation volume according to the fracture boundary seepage radius. Among them, for the fracture transformation volume, after completing step S5, that is, the construction pressure is fitted, the fracture morphology is considered to be the real fracture morphology, and then the seventh preset formula is used to calculate the seepage area of ​​each fracture node, and the accumulation of each seepage area is the fracture transformation volume. It can be understood as: (1) step S5 has output the fracture morphology; (2) the seventh preset formula calculates the seepage radius of each node; (3) accumulates all reservoir areas or volumes within the seepage radius. Based on this, the method for obtaining the fracture boundary seepage radius based on the target fracture morphology is: first obtain the target fracture morphology, fracture permeability and fluid viscosity, and then obtain the fracture boundary seepage radius according to the seventh preset formula; wherein the seventh preset formula is expressed as:

[0159]

[0160] Among them, r represents the fracture boundary seepage radius, in m; k represents the fracture permeability, in D; t' represents the time, in s; μ represents the fluid viscosity, in MPa•s. Further, the fracture permeability and fluid viscosity are measured experimentally or estimated by empirical methods, and can be assumed to be a known and determined value. The fracture morphology can be obtained by fitting calculation in the above steps of the technical solution.

[0161] S7, obtain the repeated transformation volume and repeated transformation volume coefficient according to the fracture transformation volume, and use the repeated transformation volume coefficient as an evaluation index for pressure channeling identification. Among them, for obtaining the repeated transformation volume, the transformation range of the fracture has been calculated by the fracture morphology and seepage radius in step S6. Since the position of each well is fixed, when two wells facing each other are fractured, the fractures between the respective wells may intersect, and the fracture transformation areas calculated by each well may also overlap. It is only necessary to count a certain area that belongs to the transformation range of well 1 and the transformation range of well 2. The volume of this part of the area is the repeated transformation volume. Furthermore, the method for obtaining the repeated transformation volume coefficient is: obtain the number of fracture segments and the repeated transformation volume, and then obtain the repeated transformation volume coefficient according to the eighth preset formula; wherein the eighth preset formula is expressed as:

[0162]

[0163] Where R represents the repeated reconstruction volume coefficient; N represents the number of fracture segments; V c Indicates the repeated transformation volume, the unit is m 3 ; V i is the transformation volume of the i-th fracture segment, in m 3 .

[0164] In summary, this technical solution proposes a method for identifying inter-well pressure channeling in shale reservoirs. In the model, the bottom hole flow pressure is constrained to fit the fracture morphology. The bottom hole flow pressure calculated by the construction pump pressure and the fluid wellbore flow is mainly considered as the true solution, and the bottom hole flow pressure calculated by the construction displacement and the fracture morphology is used as the constraint variable. The dynamic fitting of the fracture morphology is achieved by changing the fracture parameters. At the same time, the fracture boundary seepage radius is introduced, the fracture transformation volume is calculated, and the repeated transformation volume coefficient is used as a quantitative evaluation index for pressure channeling, so as to achieve an accurate description of the pressure channeling position and the degree of interference.

[0165] Example 5

[0166] This embodiment discloses a method for identifying pressure channeling between wells in a shale reservoir, which, as a preferred embodiment of the present invention, comprises the following steps:

[0167] Step 102, based on the fracture connection unit method, divide the connection nodes of the fracturing fracture extension model according to the size of the shale reservoir, and assign values ​​to the connection nodes. Further, step 102 includes: in the fracturing fracture extension model, discretize the shale reservoir and the rock into continuous connection nodes, and establish a communication relationship between the nodes and the adjacent nodes through connection; use different types of nodes to characterize different shale reservoir properties and fracture properties. Based on this, the technical solution simplifies the processing of the shale reservoir for accurate and fast simulation, and uses the connection unit method to characterize the reservoir model. In the model, the reservoir and the rock are discretized into continuous connection nodes, and the communication relationship between the nodes and the adjacent nodes is established through connection, such as Figure 2 The heterogeneity in the reservoir can be represented by heterogeneous nodes, and the node values ​​can be obtained by interpolation of the geological model. Figure 2 Nodes of different colors represent reservoir attributes with different parameters and fracture attributes.

[0168] In the fracture initiation mechanics model, considering the rock as a porous elastic medium, the principal stress parameters of the rock can be obtained by combining the logging data, which can be expressed as:

[0169]

[0170] Among them, σ h is the minimum horizontal principal stress, in MPa; σ H is the maximum horizontal principal stress, in MPa; σ v is the vertical stress, in MPa; α vert , α hor is the vertical and horizontal Biot coefficient; ξ H , h is the strain coefficient of the maximum principal stress and the minimum principal stress; ν is Poisson's ratio; E is the elastic modulus, in GPa; P p is the pore pressure, in MPa.

[0171] This technical solution considers that rock cracking is affected by opening and shearing, which is a composite type I-II crack. Rock failure is affected by the horizontal principal stress σ h , σ H and the combined effect of fluid pressure in the fracture, such as Figure 3 As shown in (a). According to the superposition principle, the complex problem can be decomposed into two independent problems. Figure 3 In (b), the crack is subjected to far-field stress; Figure 3 (c) The crack is subjected to the fluid pressure inside the crack. Figure 3 (a) is a schematic diagram showing the influence of far-field stress and flow pressure in the fracture provided by an embodiment of the present invention; Figure 3 (b) is a schematic diagram of a crack affected by far-field stress provided by an embodiment of the present invention; Figure 3 (c) is a schematic diagram of the effect of flow pressure in a crack provided by an embodiment of the present invention.

[0172] Further, based on Figure 3 The crack force is decomposed into:

[0173] against Figure 3 (b) Problem, the stress intensity factor at the crack tip can be expressed as:

[0174]

[0175] against Figure 3 (c) Problem, the stress intensity factor at the crack tip can be expressed as:

[0176]

[0177] The final stress intensity factor at the crack tip can be obtained by superposition. Since the pressure inside the crack and the far-field stress have opposite effects on the crack, the direction problem needs to be paid attention to, which is finally expressed as:

[0178]

[0179] Among them, K Ib for Figure 3 (b) Mode I stress intensity factor of the problem, in MPa m0.5; K ∏b for Figure 3 (b) The type II stress intensity factor of the problem, in MPa m0.5; σy is the y-axis principal stress, in MPa; τ xy is the shear stress, in MPa; a is the half-length of the crack, in m; β is the angle between the crack and the x-axis; p is the static pressure in the crack, in MPa.

[0180] Taking the critical crack initiation stress as the crack initiation criterion, which is related to the fracture toughness of the rock, the crack extension condition is:

[0181]

[0182] Among them, σ fr is the residual crack initiation stress, in MPa; σ cr is the critical crack initiation stress, in MPa.

[0183] Step 104: input initial fracturing parameters according to the actual fracturing scale.

[0184] Step 106, based on the construction pump pressure parameters and the fluid wellbore flow parameters, the bottom hole flow pressure at the next time step is obtained, which is marked as the positive bottom hole flow pressure (P wp ). Further, step 106 includes: obtaining a fracturing operation pump pressure, denoted as Ps ; According to the obtained fluid density and wellbore depth, the net liquid column pressure is obtained, expressed as P H ; Obtain the oil pipe friction resistance according to the first preset formula, marked as P pf , the first preset formula is:

[0185]

[0186] According to the second preset formula, the positive bottom hole pressure (P wp ), the second preset formula is:

[0187] P wp =P s +P H +P pf

[0188] Among them, l p represents the length of the fracturing string, in m; v represents the flow velocity of the fracturing fluid in the tubing, in m / s; ρ1 represents the density of the fracturing fluid, in kg / m3; d represents the inner diameter of the fracturing string, in m; f is the dimensionless friction coefficient, P wp , P s , P H , P pf The unit is MPa.

[0189] Based on this, this technical solution provides a process for calculating the bottom hole flow pressure based on the pump pressure, which mainly considers the bottom hole flow pressure (P wp ) as the true solution.

[0190] Step 108, the bottom hole pressure is obtained according to the operation displacement parameter and the current fracture morphology, and is marked as the reverse bottom hole pressure (P wf ); Further, step 108 includes: obtaining the net pressure of the crack at the crack mouth, marked as p f ; Get the closing pressure of the rock, marked as P c ; Obtain the friction generated by the fluid on the rock wall, marked as P ff According to the third preset formula, the reverse bottom hole pressure (P wf ), the third preset formula is:

[0191] P wf =P f +P c +P ff ;

[0192] Among them, P wf , P f , P c , P ff The unit is MPa.

[0193] Based on this, this technical solution provides a process for calculating the bottom hole pressure based on the displacement, and combines the bottom hole pressure (P wf ) as constraint variables.

[0194] Further, the step of obtaining the net pressure of the crack at the crack opening includes: obtaining the equivalent flow rate q injected into the crack in the current step according to a fourth preset formula, and the fourth preset formula is:

[0195]

[0196] Where q(t) represents the equivalent flow rate injected into the fracture at time t, and the unit is m 3 / min; Q represents the injection flow rate of fracturing fluid under actual conditions, the unit is m 3 / min; C represents the filtration coefficient, the unit is m / min 0.5 ; t represents the current time, the unit is min; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of the cracks generated in the current time step, in meters; H represents the height of the cracks, in meters; t frac Indicates the time when the crack starts to lose fluid; the net pressure at the crack mouth is obtained according to the reduced flow rate q injected into the crack, which is expressed by the fifth preset formula. The fifth preset formula is:

[0197]

[0198] Among them, p f (t) represents the net pressure at the seam at time t, in MPa; K represents the consistency coefficient, in MPa / min; n represents the rheological index, which is dimensionless; E represents Young's modulus, in MPa.

[0199] Furthermore, the fluid pressure in the fracture can be calculated by using the injection displacement of the fracturing fluid during the actual fracturing construction process and the form of the fracture expansion at time t. Considering the filtration of the fluid on the rock wall, the actual flow rate injected into the fracture changes.

[0200] Furthermore, the step of obtaining the frictional resistance generated by the fluid on the rock wall surface includes: obtaining the frictional resistance generated by the fluid on the rock wall surface according to a sixth preset formula, wherein the sixth preset formula is:

[0201]

[0202] Among them, p ff(t) represents the friction resistance generated on the rock wall at time t, in MPa; a and b represent the resistance coefficients under different states, in MPa / m; L f (t) is the total length of the crack, in meters; t represents the current time, in minutes; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of cracks generated in the current time step, in meters; L(t * ) represents the total length of the fracture generated in the previous time step, in meters. Considering the flow resistance effect caused by the fluid in the fracture contacting the fracture wall, and assuming that the fluid resistance in the fracture does not change with the fracture position, the friction resistance P is obtained. ff .

[0203] Step 110, reverse bottom hole flow pressure (P wf ) as a constraint variable to constrain the positive bottom hole pressure (P wp ), changing the crack parameters to complete the dynamic fitting of the crack morphology and output the target crack morphology;

[0204] Step 112, obtaining a fracture boundary seepage radius based on the target fracture morphology, and obtaining a fracture reconstruction volume based on the fracture boundary seepage radius; specifically, the step of obtaining a fracture boundary seepage radius based on the target fracture morphology includes: obtaining a target fracture morphology, a fracture permeability, and a fluid viscosity; obtaining a fracture boundary seepage radius according to a seventh preset formula, wherein the seventh preset formula is:

[0205]

[0206] Among them, r represents the fracture boundary seepage radius, the unit is m; k represents the fracture permeability, the unit is D; t' represents the time, the unit is s; μ is the fluid viscosity, the unit is MPa•s. That is, in this technical solution, when the fracture morphology and fracture permeability are known, the fracture seepage radius facing the reservoir can be obtained.

[0207] Step 114, obtaining the repeated transformation volume and the repeated transformation volume coefficient according to the fracture transformation volume, and using the repeated transformation volume coefficient as a pressure channeling identification evaluation index. The step of obtaining the repeated transformation volume coefficient includes: obtaining the number of fracture segments and the repeated transformation volume; obtaining the repeated transformation volume coefficient according to the eighth preset formula, and the eighth preset formula is:

[0208]

[0209] Where R represents the repeated reconstruction volume coefficient; N represents the number of fracture segments; V c Indicates the repeated transformation volume, in m 3 ; Vi is the transformation volume of the i-th fracture segment, in m 3 .

[0210] This technical solution constructs a fracture propagation model and a fracturing crosstalk identification method based on the connected unit method. In the model, the fracture morphology is fitted by means of bottom hole flow pressure constraints. The bottom hole flow pressure calculated by the construction pump pressure and the fluid wellbore flow is mainly considered as the true solution, and the bottom hole flow pressure calculated by the construction displacement and the fracture morphology is used as the constraint variable. The dynamic fitting of the fracture morphology is achieved by changing the fracture parameters. At the same time, the fracture boundary seepage radius is introduced, the fracture transformation volume is calculated, and the repeated transformation volume coefficient is used as a quantitative evaluation index for crosstalk, so as to achieve an accurate description of the crosstalk location and the degree of crosstalk.

[0211] Furthermore, the technical solution can calculate the transformation volume of the cracks and the repeated transformation volume coefficient between the cracks through the seepage radius of the cracks. Based on the fracture inversion model, the seepage radius of the cracks is considered, and the repeated transformation volume coefficient is used as a quantitative evaluation index for pressure channeling, thereby establishing a quantitative identification model for pressure channeling. Through conceptual example calculations, the model can accurately identify the location and degree of channeling.

[0212] Example 6

[0213] This embodiment discloses a shale reservoir well pressure channeling identification system, as a preferred embodiment of the present invention, comprising:

[0214] A node module is used to divide the connection nodes of the fracturing fracture extension model according to the size of the shale reservoir based on the fracture connection unit method, and assign values ​​to the connection nodes;

[0215] An input module, used to input initial fracturing parameters according to the actual fracturing scale;

[0216] The forward module is used to obtain the bottom hole pressure at the next time step according to the construction pump pressure parameters and the fluid wellbore flow parameters, which is marked as the forward bottom hole pressure (P wp );

[0217] The reverse module is used to obtain the bottom hole pressure according to the operation displacement parameters and the current fracture morphology, which is marked as reverse bottom hole pressure (P wf );

[0218] Fitting module, used to convert the reverse bottom hole pressure (P wf ) as a constraint variable to constrain the positive bottom hole pressure (P wp ), changing the crack parameters to complete the dynamic fitting of the crack morphology and output the target crack morphology;

[0219] A calculation module, used to obtain a fracture boundary seepage radius based on a target fracture morphology, and to obtain a fracture transformation volume according to the fracture boundary seepage radius;

[0220] The evaluation module is used to obtain the repeated transformation volume and the repeated transformation volume coefficient according to the fracture transformation volume, and the repeated transformation volume coefficient is used as the pressure channeling identification evaluation index.

[0221] The above-mentioned device corresponds to the implementation method of the present technical solution. For the corresponding and related parts, please refer to the partial description of the method embodiment. The device embodiment described above is only schematic, in which the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the present embodiment. Ordinary technicians in this field can understand and implement it without creative work.

[0222] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

[0223] Example 7

[0224] This embodiment discloses a method for identifying pressure channeling between wells in a shale reservoir. As a preferred implementation scheme of the present invention, any one of the technical schemes in Examples 1-5 is adopted, such as Figure 4 As shown, it is a flowchart of the implementation principle of this technical solution, combined with Figure 5 As shown in the figure, well-to-well crosstalk is related to the distribution of fractures and the seepage intersection area between fractures. Therefore, based on the well-to-well fracture distribution morphology obtained by fracturing fracture extension simulation, the irregular fracture transformation volume is calculated, and the intersection between parent and child fractures is considered. The repeated transformation volume coefficient is used to evaluate the degree of crosstalk between fractures, thus forming a method for identifying crosstalk between fractures in shale gas reservoirs.

[0225] Furthermore, Figure 4In the calculation process of the inter-well fracturing crack interference identification method of this embodiment, the specific calculation steps are as follows: 1) divide the connection nodes according to the actual reservoir size, and the connection nodes will be used as subsequent calculation individuals; 2) assign values ​​to the connection nodes in combination with geological data, which can be obtained by interpolation of existing geological models, including physical parameters and mechanical parameters; 3) set perforation data and initial crack parameters according to the actual fracturing scale; 4) calculate the bottom hole flow pressure at the next time step according to the construction pump pressure parameters; 4) calculate the bottom hole flow pressure under the current crack morphology according to the construction displacement; 5) compare the bottom hole flow pressure values ​​calculated by forward calculation and reverse calculation, if they are not equal, add a new fracture connection node; 6) repeat steps 4 to 5 until the fitting error is less than the specified error value, and output the fracture morphology; 7) calculate the fracture seepage radius; 8) calculate the repeated transformation volume of the parent and child wells; 9) calculate the repeated transformation volume coefficient (interference coefficient), and finally realize the quantitative identification of inter-well pressure interference.

[0226] In this embodiment, a quantitative analysis of pressure channeling was performed on an actual pressure channeling well group, and a total of 108 fracture sections were simulated. By analyzing that the inverted fracture length was greater than the well spacing, the pressure channeling fracture sections were quantitatively identified by combining the fracture repeated transformation volume, and the reasons for cross-well pressure channeling were analyzed. The conclusions were consistent with the actual results.

Claims

1. A method for identifying pressure crossover between wells in shale reservoirs, characterized in that: The following steps are involved: S1, establishing a fracturing crack extension model based on basic address parameters, dividing the connection nodes of the fracturing crack extension model according to the size of the shale reservoir, and assigning values ​​to the connection nodes; S2, based on the fracturing crack extension model and the actual fracturing scale, input the initial fracturing parameters; S3, in the fracturing crack extension model, the bottom hole flow pressure at the next time step is obtained according to the construction pump pressure parameters and the wellbore fluid flow parameters, which is marked as the positive bottom hole flow pressure P wp ; S4, in the fracturing fracture extension model, the bottom hole pressure obtained according to the operation displacement parameters and the current fracture morphology, marked as the reverse bottom hole pressure P wf ; S5, reverse the bottom hole flow pressure P wf As a constraint variable, constrain the positive bottom hole pressure P wp , changing the crack parameters to complete the dynamic fitting of the crack morphology and output the target crack morphology; S6, obtaining the fracture boundary seepage radius based on the target fracture morphology, and obtaining the fracture transformation volume according to the fracture boundary seepage radius; S7, obtaining a repeated transformation volume and a repeated transformation volume coefficient according to the fracture transformation volume, and taking the repeated transformation volume coefficient as an evaluation index for pressure channeling identification.

2. A method for identifying pressure crossover between wells in a shale reservoir as claimed in claim 1, characterized in that: In step S1, the connection nodes of the fracturing fracture extension model are divided, which is to discretize the shale reservoir and the rock into continuous connection nodes, establish communication relationships between adjacent nodes through connections, and use different types of nodes to represent different shale reservoir properties and fracture properties.

3. A method for identifying pressure crossover between wells in a shale reservoir as claimed in claim 1, characterized in that: In step S3, the forward bottom hole flow pressure P is obtained. wp The following steps are involved: S31, detect and record the fracturing operation pump pressure P s ; S32, detecting and recording the fluid density and the wellbore depth, and obtaining the net liquid column pressure P based on the fluid density and the wellbore depth H ; S33, obtaining the oil pipe friction resistance P according to the first preset formula pf ; Wherein, the first preset formula is expressed as: Among them, l p represents the length of the fracturing string, in m; v represents the flow velocity of the fracturing fluid in the tubing, in m / s; ρ1 represents the density of the fracturing fluid, in kg / m 3 ; f represents the dimensionless friction coefficient; d represents the inner diameter of the fracturing string, in meters; S34, obtaining the positive bottom hole flow pressure P according to the second preset formula wp ; Wherein, the second preset formula is expressed as: P wp =P s +P H +P pf Among them, P wp , P s , P H and P pf The unit is MPa.

4. A method for identifying pressure crossover between wells in a shale reservoir as claimed in claim 3, characterized in that: In step S32, the net liquid column pressure P is obtained by the following formula: H : Among them, ρ(h) represents the fluid density. When the density changes with depth, the density is a constant value obtained through field monitoring; h is the well depth; g is the gravitational acceleration.

5. A method for identifying pressure crossover between wells in a shale reservoir as claimed in claim 3, characterized in that: In step S4, the reverse bottom hole flow pressure P is obtained. wf The following steps are involved: S41, obtain the net pressure P at the crack mouth f , the closing pressure of rock P c ; S42, obtain the friction P generated by the fluid on the rock wall ff ; S43, obtaining the reverse bottom hole flow pressure P according to the third preset formula wf ; Wherein, the third preset formula is expressed as: P wf =P f +P c +P ff ; Among them, P wf , P f , P c , P ff The unit is MPa.

6. A method for identifying pressure crossover between wells in a shale reservoir as claimed in claim 5, characterized in that: In step S41, the net pressure P of the crack at the crack opening is obtained. f The following steps are involved: S411, obtaining the equivalent flow rate q injected into the fracture in the current step according to the fourth preset formula; wherein the fourth preset formula is expressed as: Where q(t) represents the equivalent flow rate injected into the fracture at time t, and the unit is m 3 / min; Q represents the injection flow rate of fracturing fluid under actual conditions, the unit is m 3 / min; C represents the filtration coefficient, the unit is m / min 0.5 ; t represents the current time, the unit is min; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of the cracks generated in the current time step, in meters; H represents the height of the cracks, in meters; t frac Indicates the time when crack filtration begins; S412, based on a fifth preset formula, obtaining a net pressure at the crack opening according to the reduced flow rate q injected into the crack; wherein the fifth preset formula is expressed as: Among them, p f (t) represents the net pressure at the seam at time t, in MPa; K represents the consistency coefficient, in MPa / min; n represents the rheological index, which is dimensionless; E represents Young's modulus, in MPa.

7. A method for identifying pressure crossover between wells in a shale reservoir as claimed in claim 5, characterized in that: In step S42, the friction P generated by the fluid on the rock wall is obtained by the sixth preset formula. ff ; Wherein, the sixth preset formula is expressed as: Among them, p ff (t) represents the friction resistance generated on the rock wall at time t, in MPa; a and b represent the resistance coefficients under different states, in MPa / m; L f (t) is the total length of the crack, in meters; t represents the current time, in minutes; t * Indicates the time of the previous time step, in min; L(tt * ) represents the total length of cracks generated in the current time step, in meters; L(t * ) represents the total length of cracks generated in the previous time step, in m.

8. A method for identifying pressure crossover between wells in a shale reservoir as claimed in claim 1, characterized in that: In step S6, the method for obtaining the fracture boundary seepage radius based on the target fracture morphology is: firstly obtaining the target fracture morphology, fracture permeability and fluid viscosity, and then obtaining the fracture boundary seepage radius according to the seventh preset formula; wherein the seventh preset formula is expressed as: Among them, r is the seepage radius of the fracture boundary, the unit is m; k is the fracture permeability, the unit is D; t' is the time, the unit is s; μ is the fluid viscosity, the unit is MPa·s.

9. A method for identifying pressure crossover between wells in a shale reservoir as claimed in claim 7, characterized in that: In step S7, the method for obtaining the repeated reconstruction volume coefficient is: obtaining the number of fracture segments and the repeated reconstruction volume, and then obtaining the repeated reconstruction volume coefficient according to the eighth preset formula; wherein the eighth preset formula is expressed as: Where R represents the repeated reconstruction volume coefficient; N represents the number of fracture segments; V c Indicates the repeated transformation volume, in m 3 ; V i is the transformation volume of the i-th fracture segment, in m 3 .

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