Method and device for determining horizontal ground stress of reservoir and storage medium

Abstract

The invention discloses a method and device for determining the horizontal ground stress of a reservoir and a storage medium. The method comprises the steps that after fracturing fluid is stopped from being injected into a crack in a target reservoir, multiple construction pressures of a target well in the target reservoir in a preset time period and imaging data in the preset time period are obtained; based on a preset G function, determining a G function value corresponding to each construction pressure according to the plurality of construction pressures; according to the plurality of construction pressures and the plurality of G function values, determining a target time point when a crack closing point of the crack is in a closed state within a preset time period; determining a target construction pressure corresponding to the target time point according to the plurality of construction pressures; determining a crack inclination angle corresponding to the crack closing point according to the imaging data; and determining the horizontal ground stress of the target reservoir according to the target construction pressure and the crack inclination angle. According to the method, the horizontal crustal stress can be solved based on the closing pressure of the natural fractures with different inclination angles, and the prediction result is high in precision.

Description

Technical Field

[0001] The present application relates to the technical field of oil and gas field development, and in particular to a method, a device and a storage medium for determining horizontal geostress of a reservoir. Background Art

[0002] In the process of coal seam development, artificial fractures are extended by adopting certain hydraulic fracturing methods, thereby forming a complex fracture network in which artificial fractures and natural fractures are intertwined, increasing the reservoir transformation volume, and improving the single well production capacity and ultimate recovery rate. Therefore, in this process, it is necessary to evaluate the spatial geometry of the fractures after fracturing in order to carry out subsequent construction optimization design. However, the existing fracture geometry evaluation method can only achieve good results in a two-dimensional simple fracture evaluation scenario. When analyzing a complex fracture network, the inability to identify the closing point of the artificial fracture will result in a low accuracy of the determined horizontal ground stress, which will in turn result in poor optimization effects in the subsequent drilling and fracturing and drainage construction optimization design processes. Summary of the invention

[0003] The purpose of the embodiments of the present application is to provide a method, a device processor and a machine-readable storage medium for determining the horizontal geostress of a reservoir, so as to solve the problem that the horizontal geostress determined by the fracture geometry assessment method in the prior art is of low accuracy when analyzing a complex fracture network.

[0004] In order to achieve the above-mentioned object, a first aspect of an embodiment of the present application provides a method for determining horizontal geostress of a reservoir, the method comprising:

[0005] After stopping the injection of fracturing fluid into the cracks in the target reservoir, obtaining a plurality of construction pressures of the target well in the target reservoir within a preset time period and imaging data within a preset time period;

[0006] Based on a preset G function, a G function value corresponding to each construction pressure is determined according to multiple construction pressures;

[0007] Determining a target time point at which a crack closure point of the crack is in a closed state within a preset time period according to a plurality of construction pressures and a plurality of G function values;

[0008] Determine the target construction pressure corresponding to the target time point according to multiple construction pressures;

[0009] According to the imaging data, the fracture inclination angle corresponding to the fracture closure point is determined;

[0010] The horizontal geostress of the target reservoir is determined based on the target construction pressure and fracture inclination.

[0011] In an embodiment of the present application, a target time point at which a crack is in a closed state within a preset time period is determined based on multiple construction pressures and multiple G function values, including: determining a first curve based on multiple construction pressures and multiple G function values, the first curve being a first-order derivative curve drawn based on the first-order derivative value of the construction pressure to the G function value; determining a target time point based on the first curve, wherein the target time point is any time point when the first-order derivative value in the first curve is in a constant state.

[0012] In an embodiment of the present application, determining the target time point based on the first curve includes: multiplying the first-order derivative value in the first curve with the G function value to obtain a second curve, the second curve being a curve drawn based on the superimposed derivative value obtained by multiplying the first-order derivative value and the G function value; determining the target time point based on the second curve, wherein the target time point is any time point when the superimposed derivative value in the second curve is in a constant state.

[0013] In an embodiment of the present application, the horizontal geostress of the target reservoir is determined according to the target construction pressure and the fracture inclination, including: converting the target construction pressure to determine the target bottom hole closure pressure; determining the horizontal geostress according to the target bottom hole closure pressure and the fracture inclination based on a preset horizontal geostress determination model, wherein the preset horizontal geostress determination model is a relationship model between the target bottom hole closure pressure, the fracture inclination and the horizontal geostress.

[0014] In the embodiment of the present application, the target operation pressure is converted to determine the target bottom hole closing pressure, including determining the target bottom hole closing pressure according to formula (1):

[0015] σ n =σ′ n +P H -P M ; (1)

[0016] Among them, σ n is the target bottom hole closing pressure, σ′ n is the target construction pressure, P H is the liquid column pressure, P M For friction.

[0017] In an embodiment of the present application, the number of crack closure points is two, the number of target time points is two, and the horizontal geostress includes a maximum horizontal geostress and a minimum horizontal geostress; based on a preset horizontal geostress determination model, the horizontal geostress is determined according to the target bottom hole closure pressure and the crack inclination, including: based on the preset horizontal geostress determination model, the maximum horizontal geostress and the minimum horizontal geostress are determined according to the target bottom hole closure pressure obtained by converting the target construction pressures corresponding to the two target time points and the crack inclinations corresponding to the two crack closure points.

[0018] In the embodiment of the present application, the preset horizontal geostress determination model satisfies formula (2):

[0019] σ n =σ H sin 2 θ n +σ h cos 2 θ n ; (2)

[0020] Among them, σ n is the target bottom hole closing pressure, σ H is the maximum horizontal ground stress, σ h is the minimum horizontal ground stress, θ n is the crack inclination angle.

[0021] A second aspect of an embodiment of the present application provides a device for determining horizontal geostress of a reservoir, comprising:

[0022] A data acquisition module, used to acquire multiple construction pressures of a target well in the target reservoir within a preset time period and imaging data within a preset time period after stopping the injection of fracturing fluid into the cracks in the target reservoir;

[0023] A function value determination module, used to determine the G function value corresponding to each construction pressure according to a plurality of construction pressures based on a preset G function;

[0024] A target time point determination module, used to determine a target time point at which a crack closure point of a crack is in a closed state within a preset time period according to multiple construction pressures and multiple G function values;

[0025] A target construction pressure determination module is used to determine the target construction pressure corresponding to the target time point according to multiple construction pressures;

[0026] A target fracture dip angle determination module is used to determine the fracture dip angle corresponding to the fracture closure point according to the imaging data;

[0027] The horizontal geostress determination module is used to determine the horizontal geostress of the target reservoir according to the target construction pressure and the fracture inclination.

[0028] A third aspect of an embodiment of the present application provides a processor configured to execute the above-mentioned method for determining horizontal geostress of a reservoir.

[0029] A fourth aspect of an embodiment of the present application provides a machine-readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the above-mentioned method for determining horizontal geostress of a reservoir.

[0030] The above technical solution, after stopping the injection of fracturing fluid into the cracks in the target reservoir, obtains multiple construction pressures and imaging data within a preset time period for the target well in the target reservoir, and then determines the G function value corresponding to each construction pressure based on the preset G function according to the multiple construction pressures, and then determines the target time point at which the crack closure point of the crack is in a closed state within the preset time period according to the multiple construction pressures and the multiple G function values, and further determines the target construction pressure corresponding to the target time point according to the multiple construction pressures, and determines the crack inclination corresponding to the crack closure point according to the imaging data, and finally determines the horizontal geostress of the target reservoir according to the target construction pressure and the crack inclination. The present application can solve the horizontal geostress based on the closing pressure of natural fractures with different inclinations when the G function cannot identify the closing point of the main hydraulic fracturing fracture and obtain the minimum horizontal geostress, and the prediction result has a high accuracy.

[0031] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following specific implementations, they are used to explain the embodiments of the present application, but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings:

[0033] Figure 1 A schematic flow chart of a method for determining horizontal geostress of a reservoir provided in an embodiment of the present application;

[0034] Figure 2 A flow chart of a method for determining ground stress based on a pump-stop pressure drop curve in a deep coal seam is provided for a specific embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the embodiments of the present application, and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back...), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0037] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0038] Geostress is an important link throughout the drilling, fracturing, and production processes in oil fields. At present, the commonly used method for obtaining geostress in oil fields is small-scale fracturing test. A small amount of fracturing fluid is injected to open the formation cracks to form simple fractures. After stopping the pump, the pressure is monitored to obtain geostress information. Small-scale fracturing test has more accurate geostress detection results, but due to time and economic cost constraints, it is impossible to test every well. At the same time, it can only be used for simple fracture monitoring and is not suitable for the complex fracture network formed by volume fracturing at this stage.

[0039] Most current projects use the G function to analyze the pump-off pressure drop curve of a simple fracture to obtain the geostress. The closing time of a two-dimensional simple fracture is short and most of them have only one main fracture extending along the direction of the maximum horizontal principal stress. Therefore, the G function is used to find the closing point of the main fracture and read the closing pressure. The relationship between the closing pressure and the minimum horizontal geostress can determine the value of the minimum horizontal geostress.

[0040] When the filtration loss of microfracture fracturing fluid is not considered, the filtration coefficient can be approximately considered as a constant, and the G function can be obtained as shown in formula (3):

[0041]

[0042] When the reservoir is fractured, the fracturing fluid loss coefficient is usually regarded as a function related to pressure. The loss coefficient can be expressed as the following formula (4):

[0043]

[0044] Among them, α a is the parameter related to the filtration area, dimensionless; θ is the dimensionless time, t D is the shut-in time, min, t p is the pumping time, min; η′ s is the initial filtration loss fracturing fluid efficiency at the end of pumping, dimensionless; ΔP f (t p) is the net pressure of the fracture when the pump is stopped, MPa; Φ is the fracturing fluid loss parameter when the fracture extends; C(t) represents the loss coefficient at any time after the well is shut in, C(t p ) represents the filtration coefficient at the time of shut-in, P(t p ) represents the instantaneous pump stop pressure at the time of well shut-in, MPa; P(t) represents the bottom hole pressure at any time after well shut-in, MPa; P i Represents the original formation pressure, MPa.

[0045] According to the G function equation and the pressure drop equation, a rectangular coordinate system of G function-P (construction pressure) is established to fit the pressure p * is the slope of the curve, as shown in formulas (5) and (6):

[0046]

[0047] Among them, p * is the fitting pressure, MPa; P is the construction pressure, MPa; f p is the ratio of the effective crack loss surface area to the total crack area, dimensionless; C is the comprehensive loss coefficient, c f is the crack flexibility, m / MPa.

[0048] According to the formula, when the fitting pressure remains constant, for any formation, the parameters such as the filtration coefficient and the proportional coefficient remain unchanged, indicating that the fluid state in the fracture is stable and is just in the stage of gradual closing. Therefore, the fitting pressure p can be plotted. * -G function relationship curve, fitting pressure p * The constant interval is the crack closure interval, so the crack closure point can be determined. In order to more accurately identify the crack closure point, a superimposed derivative function GdP / dG is created to amplify the change trend of the curve. * When the horizontal segment in the GdP / dG-G relationship curve is difficult to distinguish, it can be judged based on the approximate linear relationship in the GdP / dG-G relationship curve.

[0049] The identification of the closure period is the basis for the interpretation of the G function pressure drop. However, compared with the simple fractures formed by traditional fracturing, the complex fracture network produced by volume fracturing shows obvious differences in closure behavior after pumping stops. According to the pump-off pressure drop data monitored on site, the fracture network produced by volume fracturing shows the characteristics of a late and long closure period, that is, the closure of the main fracture of volume fracturing can only be identified 60 to 250 hours after the pump is stopped. In contrast, the fractures of traditional single-stage fracturing will be completely closed within 3 to 70 hours of pumping. The pump-off time of volume fracturing on site is short. When the G function is used to analyze the pump-off pressure drop curve of the complex fracture network, the closure point of the hydraulic main fracture cannot be identified, but the closure points of multiple natural fractures will be identified. The corresponding closure pressure is no longer the minimum horizontal ground stress, but is related to the closure pressure of fractures at different angles. Therefore, it is urgent to establish the relationship between the closure pressure of natural fractures with different inclination angles and ground stress, and accurately obtain the ground stress.

[0050] In this regard, an embodiment of the present application provides a method for determining horizontal geostress of a reservoir, which can be used to determine situations of complex fracture networks, and the prediction results are highly accurate.

[0051] Figure 1 A schematic diagram of a method for determining horizontal geostress of a reservoir provided in an embodiment of the present application. Figure 1 As shown, an embodiment of the present application provides a method for determining horizontal geostress of a reservoir, which is described by taking the method applied to a processor as an example. The method may include the following steps.

[0052] Step S101, after stopping the injection of fracturing fluid into the fractures in the target reservoir, obtaining a plurality of construction pressures of a target well in the target reservoir within a preset time period and imaging data within a preset time period.

[0053] Specifically, in order to ensure that the pressure and imaging data observed subsequently can truly reflect the closure state of the fracture, after the fracture fracturing operation is completed, the injection of fracturing fluid into the fractures in the target reservoir is stopped. Then the construction pressure is collected, and the construction pressure of the target well is continuously or intermittently recorded within a preset time period. These pressure data will be used for subsequent analysis and calculation. At the same time, imaging technology, such as seismic imaging, microseismic monitoring, etc., is used to obtain imaging data of the target reservoir. These imaging data can be used to determine information such as the shape, location and inclination of the fracture.

[0054] Step S102: Based on a preset G function, a G function value corresponding to each construction pressure is determined according to a plurality of construction pressures.

[0055] It can be understood that in petroleum engineering and geological engineering, the G function is widely used in fracturing analysis, especially in determining the closure point of the fracture, reading the closure pressure, and obtaining the ground stress. Through the analysis of the G function, the fracturing effect can be evaluated, the fracturing parameters can be optimized, and the production capacity of oil and gas wells can be predicted. The G function is a mathematical model or formula used to describe the relationship between the construction pressure and the fracture state. It may be constructed based on experimental data, theoretical derivation or empirical formula. Specifically, the value of each construction pressure obtained above is substituted into the G function, and the corresponding G function value is calculated, that is, the G function value corresponding to each construction pressure among multiple construction pressures is obtained. These values ​​can be used for subsequent analysis and comparison.

[0056] Step S103, determining a target time point at which a crack closing point of the crack is in a closed state within a preset time period according to the multiple construction pressures and the multiple G function values.

[0057] It can be understood that after obtaining multiple G function values, the change of the G function values ​​can be analyzed. By analyzing the change trend of the G function values ​​over time, the points where the G function values ​​change significantly can be found. These points may correspond to the transition of the crack state, such as the transition from the open state to the closed state. Therefore, according to the change of the G function value, the target time point in the closed state within the preset time period can be determined, that is, the time point corresponding to the crack closed state can be found among the points where the G function value changes significantly. This is usually determined by comparing the size of the G function value, the change trend and the corresponding relationship with the known crack state.

[0058] Step S104: determining a target construction pressure corresponding to a target time point according to multiple construction pressures.

[0059] It can be understood that after determining the target time point, the target construction pressure corresponding to the target time point can be determined based on the corresponding relationship between the signed target time point and the G function value, and the corresponding relationship between the G function value and the construction pressure, so as to provide key parameters for the subsequent calculation of horizontal ground stress.

[0060] Step S105, determining the fracture inclination angle corresponding to the fracture closure point according to the imaging data.

[0061] Specifically, the morphology and distribution of cracks, including the inclination and direction of cracks, can be analyzed based on imaging data. Based on professional image processing software and geological interpretation technology, the inclination of cracks can be determined by measuring and analyzing the morphology of cracks in imaging data, thus providing key data for subsequent calculation of horizontal ground stress.

[0062] Step S106, determining the horizontal geostress of the target reservoir according to the target construction pressure and the fracture dip angle.

[0063] Specifically, after determining the target construction pressure and fracture inclination, a suitable mechanical model can be selected to calculate the horizontal geostress. This model should be able to take into account factors such as fracture inclination, construction pressure, and physical properties of the reservoir. Next, the target construction pressure and fracture inclination are substituted into the mechanical model to calculate the horizontal geostress of the target reservoir. This value will be used to evaluate the stability of the reservoir and the fluid flow characteristics.

[0064] In this way, by systematically collecting and analyzing construction pressure, imaging data and mechanical models, the closure state and related parameters of the fractures in the target reservoir can be accurately determined. These parameters are of great significance for subsequent reservoir development, fluid management and geological disaster prediction. At the same time, this method also demonstrates the application potential of multidisciplinary cross-cutting in the field of oil and gas exploration and development.

[0065] The above technical solution, after stopping the injection of fracturing fluid into the cracks in the target reservoir, obtains multiple construction pressures and imaging data within a preset time period for the target well in the target reservoir, and then determines the G function value corresponding to each construction pressure based on the preset G function according to the multiple construction pressures, and then determines the target time point at which the crack closure point of the crack is in a closed state within the preset time period according to the multiple construction pressures and the multiple G function values, and further determines the target construction pressure corresponding to the target time point according to the multiple construction pressures, and determines the crack inclination corresponding to the crack closure point according to the imaging data, and finally determines the horizontal geostress of the target reservoir according to the target construction pressure and the crack inclination. The present application can solve the horizontal geostress based on the closing pressure of natural fractures with different inclinations when the G function cannot identify the closing point of the main hydraulic fracturing fracture and obtain the minimum horizontal geostress, and the prediction result has a high accuracy.

[0066] In an embodiment of the present application, a target time point at which a crack is in a closed state within a preset time period is determined based on multiple construction pressures and multiple G function values, including: determining a first curve based on multiple construction pressures and multiple G function values, the first curve being a first-order derivative curve drawn based on the first-order derivative value of the construction pressure to the G function value; determining a target time point based on the first curve, wherein the target time point is any time point when the first-order derivative value in the first curve is in a constant state.

[0067] Specifically, for each construction pressure value, its corresponding G function value can be calculated, and the first-order derivative of the construction pressure is calculated for these G function values, that is, the slope of the G function value to the construction pressure is calculated. In this way, a series of first-order derivative values ​​can be obtained, each value corresponding to a construction pressure point. The construction pressure is used as the horizontal coordinate and the first-order derivative value is used as the vertical coordinate to draw a first-order derivative curve, that is, the first curve. The first curve can show the trend of the change rate of the G function value to the construction pressure over time (or the construction pressure sequence). Then, the shape and trend of the first-order derivative curve are analyzed to find the area in the curve where the first-order derivative value tends to be stable or constant. It can be understood that in the process of crack closure, the change rate of the G function value to the construction pressure (that is, the first-order derivative value) usually undergoes a significant change, and then tends to be stable or constant. This stable or constant state usually corresponds to the closed state of the crack. Therefore, in the first-order derivative curve, any time point where the first-order derivative value is in a constant state (or close to a constant state) can be found. This time point is the target time point when the crack is in a closed state within a preset time period.

[0068] In this way, by using multiple construction pressures and multiple G function values, the target time point at which the fracture is in a closed state within a preset time period can be accurately determined by drawing and analyzing the first-order derivative curve. This is of great significance for evaluating the stability of the reservoir and the fluid flow characteristics.

[0069] In an embodiment of the present application, determining the target time point based on the first curve includes: multiplying the first-order derivative value in the first curve with the G function value to obtain a second curve, the second curve being a curve drawn based on the superimposed derivative value obtained by multiplying the first-order derivative value and the G function value; determining the target time point based on the second curve, wherein the target time point is any time point when the superimposed derivative value in the second curve is in a constant state.

[0070] Specifically, after obtaining the first curve, each first-order derivative value in the first curve can be multiplied by its corresponding G function value to obtain a series of superimposed derivative values. It can be understood that this processing process is actually weighting the first-order derivative, and the weight is the G function value itself. Further, the construction pressure is used as the horizontal coordinate and the superimposed derivative value is used as the vertical coordinate to draw the superimposed derivative value curve to obtain the second curve. The second curve can show the change trend of the weighted first-order derivative value (i.e., the superimposed derivative value) with the construction pressure. Then, the shape and trend of the second curve are analyzed to find the area where the superimposed derivative value tends to be stable or constant in the curve. It can be understood that in the process of crack closure, the superimposed derivative value (i.e., the weighted first-order derivative value) usually undergoes a significant change and then tends to be stable or constant. This stable or constant state usually corresponds to the closed state of the crack. Therefore, any time point at which the superimposed derivative value is in a constant state (or close to a constant state) can be found in the second curve. This time point is the target time point at which the crack is in a closed state within a preset time period.

[0071] In an embodiment of the present application, the horizontal geostress of the target reservoir is determined according to the target construction pressure and the fracture inclination, including: converting the target construction pressure to determine the target bottom hole closure pressure; determining the horizontal geostress according to the target bottom hole closure pressure and the fracture inclination based on a preset horizontal geostress determination model, wherein the preset horizontal geostress determination model is a relationship model between the target bottom hole closure pressure, the fracture inclination and the horizontal geostress.

[0072] Specifically, in order to determine the horizontal geostress of the target reservoir, after determining the target construction pressure, the target construction pressure can be appropriately converted according to the fluid properties, temperature, pressure gradient and other factors of the wellbore and reservoir to determine the target bottom hole closure pressure. It can be understood that this process needs to consider factors such as the hydrostatic pressure in the wellbore, friction pressure loss and possible pressure recovery effect.

[0073] Furthermore, the target bottom hole closure pressure and fracture inclination are used as input parameters and substituted into the preset horizontal geostress determination model. The preset horizontal geostress determination model is used for calculation to obtain the horizontal geostress value of the target reservoir. It can be understood that the horizontal geostress value may be a scalar, representing the horizontal geostress in a single direction, or it may be a vector representing the horizontal geostress components in two orthogonal directions. Among them, the preset horizontal geostress determination model is a relational model, which describes the relationship between the target bottom hole closure pressure, fracture inclination and horizontal geostress. This model may be constructed based on experimental data, theoretical derivation or empirical formula, and takes into account the physical properties of the reservoir (such as rock strength, Poisson's ratio, etc.) and geological conditions (such as formation inclination, tectonic stress, etc.).

[0074] Preferably, after determining the horizontal geostress value, the calculated horizontal geostress value can also be verified to ensure that it conforms to geological and engineering common sense. Based on the calculation results, the possible impact of horizontal geostress on reservoir stability and fluid flow characteristics is explained.

[0075] In the embodiment of the present application, the target operation pressure is converted to determine the target bottom hole closing pressure, including determining the target bottom hole closing pressure according to formula (1):

[0076] σ n =σ′ n +P H -P M ; (1)

[0077] Among them, σ n is the target bottom hole closing pressure, σ′ n is the target construction pressure, P H is the liquid column pressure, P M It is the friction resistance, that is, the friction resistance of fracturing fluid filtration.

[0078] In one example, the target operation pressure may be read from a fracturing operation curve.

[0079] In one example, the liquid column pressure P H =ρgH, ρ is the density of the fracturing fluid, g is the acceleration of gravity, and H is the vertical length of the fracturing string.

[0080] In one example, the fracturing fluid loss friction P M =λ1.3866×10 6 D -4.8 Q 1.8 L; where λ is the drag reduction ratio of the fracturing fluid, obtained from experiments; g is the acceleration of gravity, taken as 9.8m / s 2 ; D is the inner diameter of the fracturing string; L is the length of the fracturing string; Q is the fracturing fluid loss volume, which is obtained based on experiments.

[0081] In an embodiment of the present application, the number of crack closure points is two, the number of target time points is two, and the horizontal geostress includes a maximum horizontal geostress and a minimum horizontal geostress; based on a preset horizontal geostress determination model, the horizontal geostress is determined according to the target bottom hole closure pressure and the crack inclination, including: based on the preset horizontal geostress determination model, the maximum horizontal geostress and the minimum horizontal geostress are determined according to the target bottom hole closure pressure obtained by converting the target construction pressures corresponding to the two target time points and the crack inclinations corresponding to the two crack closure points.

[0082] Specifically, when the number of crack closure points is two and the number of target time points is two, in order to determine the maximum horizontal geostress and the minimum horizontal geostress, the preset horizontal geostress determination model can be used to determine the target bottom hole closure pressure obtained by converting the target construction pressures corresponding to the two target time points and the crack inclinations corresponding to the two crack closure points, respectively, to determine the maximum horizontal geostress and the minimum horizontal geostress.

[0083] Specifically, two target time points are known, each of which corresponds to a target construction pressure. The two target construction pressures are converted respectively, and the fluid properties, temperature, pressure gradient and other factors of the wellbore and reservoir are considered to determine the two target bottom hole closure pressures. At the same time, two fracture closure points are known, and each point corresponds to a fracture inclination. The two target bottom hole closure pressures and two fracture inclinations are used as input parameters and substituted into the preset horizontal geostress determination model. The preset horizontal geostress determination model is used for calculation to obtain the maximum horizontal geostress and the minimum horizontal geostress. It can be understood that this process may involve solving a system of equations or optimization problems, because there are usually multiple parameters and variables that affect the calculation results of horizontal geostress at the same time. Among them, the preset horizontal geostress determination model is a relational model that describes the relationship between the target bottom hole closure pressure, fracture inclination and horizontal geostress. This model may be constructed based on experimental data, theoretical derivation or empirical formula, and takes into account the physical properties of the reservoir (such as rock strength, Poisson's ratio, etc.) and geological conditions (such as formation inclination, tectonic stress, etc.).

[0084] Preferably, after obtaining the maximum horizontal geostress and the minimum horizontal geostress, the calculated maximum horizontal geostress and the minimum horizontal geostress can be verified to ensure that they are consistent with geological and engineering common sense. Based on the calculation results, explain the possible impact of horizontal geostress on reservoir stability and fluid flow characteristics. If the calculation results do not meet expectations, it is necessary to recheck the input parameters, model selection or calculation process.

[0085] In the embodiment of the present application, the preset horizontal geostress determination model satisfies formula (2):

[0086] σ n =σ H sin 2 θ n +σ h cos 2 θ n ; (2)

[0087] Among them, σ n is the target bottom hole closing pressure, σ H is the maximum horizontal ground stress, σ h is the minimum horizontal stress, θ n is the crack inclination angle.

[0088] Figure 2 A flow chart of a method for determining ground stress based on a deep coal seam pump stop pressure drop curve is provided in a specific embodiment of the present application. Figure 2 As shown, the method may include the following steps:

[0089] Step 1: Use imaging logging data to determine the inclination range of natural fractures in the target well section (θ1, θn), and sort them accordingly: θ1<θ2<θ3<θ4<……<θ n-1 <θ n .

[0090] Step 2: Use the G function to analyze the pump-off pressure drop curve of the volume fracturing of the target well, and the closing pressure of the first fracture closing point identified is σ n1 , the fracture inclination is θn; the closing pressure of the second fracture closing point identified by the G function is σ n2 , the crack inclination is θn-1.

[0091] Step 4: Convert the surface closing pressure to the bottom hole closing pressure, as shown in formulas (7) to (9):

[0092] σ n =σ′ n +P H -P M ; (7)

[0093]

[0094] Δp M =1.3866×10 6 D -4.8 Q 1.8 Lλ; (9)

[0095] Among them, σ n is the bottom hole closing pressure, MPa; σ′ n is the ground closing pressure, MPa; P H is the liquid column pressure, MPa; P M is the friction, MPa; λ is the rent reduction ratio, dimensionless; P M is the friction, MPa; Δp M is the friction loss of fracturing fluid, MPa; Δp w is the friction loss of clean water, MPa; D is the casing diameter, mm; Q is the pumping displacement during the construction process, m 3 / min; L is the length of the column, m.

[0096] Step 5: Solve the system of equations to obtain the horizontal ground stress.

[0097] Specifically, the closure pressure is substituted into the above normal stress formula of the two-dimensional natural fracture surface to solve the maximum horizontal stress and the minimum horizontal stress, as shown in formulas (10) and (11):

[0098] σ n1 =σ H sin 2 θ n +σ h cos 2 θ n ; (10)

[0099] σ n2 =σ H sin 2 θ n-1 +σ h cos 2 θ n-1 (11)

[0100] In this way, the inclination range of natural fractures is determined using imaging logging data of known well sections, and the G function is used to identify the fracture closing point of the known well pump-off pressure drop curve. The closing pressure of two or more closing points can be obtained to solve the maximum horizontal geostress and the minimum horizontal geostress. Specifically, the inclination range of natural fractures is determined and sorted using imaging logging data of the target well section of the known well, and then the G function is used to identify the fracture closing point of the volume fracturing pump-off pressure drop curve of the known well. The first identified fracture closing point is the closing point of the natural fracture with the largest inclination, and the second identified fracture closing point is the closing point of the natural fracture with the second largest inclination. The closing pressures of the two closing points are read, and the maximum horizontal geostress and the minimum horizontal geostress can be solved. When the G function cannot identify the closing point of the main hydraulic fracturing fracture and obtain the minimum horizontal geostress, the embodiment of the present application can solve the horizontal geostress based on the closing pressure of natural fractures with different inclinations, and the prediction result has a high accuracy.

[0101] In another specific embodiment of the present application, the vertical depth of the target well section of a well is 2196-2204m, and the inclination range of the natural fractures determined by imaging logging data is (5°, 50°), which is arranged in sequence as follows: 5°<10°<30°<50°, to determine the geostress of the well.

[0102] Specifically, the G function is used to analyze the pump-off pressure drop curve of the target well volume fracturing, and the closing pressure of the first fracture closing point identified is σ n1 =32.09MPa, corresponding to a natural fracture inclination of 50°. The closing pressure of the second fracture closure point identified is σ n2 =30.40MPa, the corresponding natural fracture inclination is 30°.

[0103] Next, convert the surface closing pressure into the bottom hole closing pressure, and the result is:

[0104] σ n1 ′=32.09+1.02×2200×0.00981-1.3866×10 12 ×114 -4.8 ×2450×0.000018=45.91MPa;

[0105] σ n2 ′=30.40+1.02×2200×0.00981-1.3866×10 12 ×114 -4.8 ×2450×0.000018=44.22MPa.

[0106] Furthermore, the closing pressure is substituted into the normal stress formula of the two-dimensional natural fracture surface, and the minimum horizontal ground stress σ is obtained by solving the equations. h =42.98MPa, maximum horizontal ground stress σ H =47.95MPa.

[0107] Finally, the small-scale fracturing test results of the well were calculated to show the minimum horizontal ground stress σ h ′=45MPa, and the error of the ground stress value interpreted based on the pump stop pressure drop curve is:

[0108]

[0109] Therefore, the error is within 10%, proving the reliability of this method.

[0110] Figure 2 The schematic diagram of the structure of a device for determining horizontal geostress of a reservoir provided in an embodiment of the present application is shown in FIG. Figure 2 As shown, the embodiment of the present application also provides a device 200 for determining horizontal geostress of a reservoir, the device 200 comprising:

[0111] The data acquisition module 210 is used to acquire multiple construction pressures of a target well in the target reservoir within a preset time period and imaging data within a preset time period after stopping the injection of fracturing fluid into the fractures in the target reservoir.

[0112] The function value determination module 220 is used to determine the G function value corresponding to each construction pressure according to multiple construction pressures based on a preset G function.

[0113] The target time point determination module 230 is used to determine the target time point at which the crack closing point of the crack is in a closed state within a preset time period according to multiple construction pressures and multiple G function values.

[0114] The target construction pressure determination module 240 is used to determine the target construction pressure corresponding to the target time point according to multiple construction pressures.

[0115] The target fracture dip determination module 250 is used to determine the fracture dip corresponding to the fracture closure point according to the imaging data.

[0116] The horizontal geostress determination module 260 is used to determine the horizontal geostress of the target reservoir according to the target construction pressure and the fracture inclination.

[0117] The above-mentioned device 200 for determining the horizontal geostress of the reservoir, after stopping the injection of fracturing fluid into the cracks in the target reservoir, obtains multiple construction pressures and imaging data within a preset time period of the target well in the target reservoir, and then determines the G function value corresponding to each construction pressure based on the preset G function according to the multiple construction pressures, and then determines the target time point at which the crack closure point of the crack is in a closed state within the preset time period according to the multiple construction pressures and the multiple G function values, and further determines the target construction pressure corresponding to the target time point according to the multiple construction pressures, and determines the crack inclination corresponding to the crack closure point according to the imaging data, and finally determines the horizontal geostress of the target reservoir according to the target construction pressure and the crack inclination. The present application can solve the horizontal geostress based on the closing pressure of natural fractures with different inclinations when the G function cannot identify the closing point of the main hydraulic fracturing fracture and obtain the minimum horizontal geostress, and the prediction result has a high accuracy.

[0118] In one embodiment, the target time point determination module 230 is also used to: determine a first curve based on multiple construction pressures and multiple G function values, where the first curve is a first-order derivative curve drawn based on the first-order derivative value of the construction pressure to the G function value; determine the target time point based on the first curve, where the target time point is any time point when the first-order derivative value in the first curve is in a constant state.

[0119] In one embodiment, the target time point determination module 230 is also used to: multiply the first-order derivative value in the first curve by the G function value to obtain a second curve, where the second curve is a curve drawn based on the superimposed derivative value obtained by multiplying the first-order derivative value by the G function value; determine the target time point based on the second curve, wherein the target time point is any time point when the superimposed derivative value in the second curve is in a constant state.

[0120] In one embodiment, the horizontal geostress determination module 260 is also used to: convert the target construction pressure to determine the target bottom hole closure pressure; determine the horizontal geostress based on the preset horizontal geostress determination model according to the target bottom hole closure pressure and the fracture inclination, wherein the preset horizontal geostress determination model is a relationship model between the target bottom hole closure pressure, the fracture inclination and the horizontal geostress.

[0121] In one embodiment, the target operation pressure is converted to determine the target bottom hole closure pressure, including determining the target bottom hole closure pressure according to formula (1):

[0122] σ n =σ′ n +P H -P M ; (1)

[0123] Among them, σ n is the target bottom hole closing pressure, σ′ n is the target construction pressure, P H is the liquid column pressure, P M For friction.

[0124] In one embodiment, the number of crack closure points is two, the number of target time points is two, and the horizontal geostress includes a maximum horizontal geostress and a minimum horizontal geostress; the horizontal geostress determination module 260 is also used to: based on a preset horizontal geostress determination model, determine the maximum horizontal geostress and the minimum horizontal geostress according to the target bottom hole closure pressure obtained by converting the target construction pressures corresponding to the two target time points and the crack inclinations corresponding to the two crack closure points.

[0125] In one embodiment, the preset horizontal geostress determination model satisfies formula (2):

[0126] σ n =σ H sin 2 θ n +σ h cos 2 θ n ; (2)

[0127] Among them, σ n is the target bottom hole closing pressure, σ H is the maximum horizontal ground stress, σ h is the minimum horizontal stress, θ n is the crack inclination angle.

[0128] An embodiment of the present application also provides a processor configured to execute the method for determining horizontal geostress of a reservoir in the above-mentioned embodiment.

[0129] An embodiment of the present application also provides a machine-readable storage medium having instructions stored thereon, the instructions being used to enable a machine to execute the method for determining horizontal geostress of a reservoir in the above-mentioned embodiment.

[0130] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0131] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems) and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0132] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0133] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0134] In a typical configuration, a computing device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0135] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0136] Computer readable media include permanent and non-permanent, removable and non-removable media that can be implemented by any method or technology to store information. Information can be computer readable instructions, data structures, program modules 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 technology, compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassettes, magnetic tape disk storage or other magnetic storage devices or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer readable media does not include temporary computer readable media (transitory media), such as modulated data signals and carrier waves.

[0137] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0138] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A method for determining horizontal geostress of a reservoir, characterized in that: The method comprises: After stopping the injection of fracturing fluid into the cracks in the target reservoir, obtaining a plurality of construction pressures of the target well in the target reservoir within a preset time period and imaging data within the preset time period; Based on a preset G function, determining a G function value corresponding to each of the construction pressures according to the multiple construction pressures; Determining, according to the multiple construction pressures and the multiple G function values, a target time point at which the crack closing point of the crack is in a closed state within the preset time period; Determining a target construction pressure corresponding to the target time point according to the multiple construction pressures; Determining the fracture inclination angle corresponding to the fracture closure point according to the imaging data; The horizontal geostress of the target reservoir is determined according to the target construction pressure and the fracture inclination.

2. The method according to claim 1, characterized in that The step of determining, based on the multiple construction pressures and the multiple G function values, a target time point at which the crack is in a closed state within the preset time period comprises: Determine a first curve according to the multiple construction pressures and the multiple G function values, wherein the first curve is a first-order derivative curve drawn according to the first-order derivative value of the construction pressure to the G function value; The target time point is determined according to the first curve, wherein the target time point is any time point when the first-order derivative value in the first curve is in a constant state.

3. The method according to claim 2, characterized in that Determining the target time point according to the first curve includes: Multiplying the first-order derivative value in the first curve by the G function value to obtain a second curve, wherein the second curve is a curve drawn according to a superimposed derivative value obtained by multiplying the first-order derivative value by the G function value; The target time point is determined according to the second curve, wherein the target time point is any time point when the superposition derivative value in the second curve is in a constant state.

4. The method according to claim 1, characterized in that: Determining the horizontal geostress of the target reservoir according to the target construction pressure and the fracture inclination angle includes: Converting the target operation pressure to determine a target bottom hole closing pressure; Based on a preset horizontal geostress determination model, the horizontal geostress is determined according to the target bottom hole closure pressure and the fracture inclination, wherein the preset horizontal geostress determination model is a relationship model among the target bottom hole closure pressure, the fracture inclination and the horizontal geostress.

5. The method according to claim 4, characterized in that The converting the target operation pressure to determine the target bottom hole closing pressure includes determining the target bottom hole closing pressure according to formula (1): s n =σ′ n +P H -P M (1) Among them, σ n is the target bottom hole closure pressure, σ′ n is the target construction pressure, P H is the liquid column pressure, P M For friction.

6. The method according to claim 4, characterized in that The number of the crack closure points is two, the number of the target time points is two, and the horizontal ground stress includes a maximum horizontal ground stress and a minimum horizontal ground stress; The method of determining the horizontal geostress based on a preset horizontal geostress determination model and according to the target bottom hole closure pressure and the fracture inclination angle comprises: Based on a preset horizontal geostress determination model, the maximum horizontal geostress and the minimum horizontal geostress are determined according to the target bottom hole closure pressure obtained by converting the target construction pressures corresponding to the two target time points and the crack inclinations corresponding to the two crack closure points.

7. The method according to claim 6, characterized in that The preset horizontal geostress determination model satisfies formula (2): s n =s H sin 2 i n +s h cos 2 i n (2) Among them, σ n is the target bottom hole closing pressure, σ H is the maximum horizontal in-situ stress, σ h is the minimum horizontal stress, θ n is the inclination angle of the crack.

8. A device for determining horizontal geostress of a reservoir, characterized in that: include: A data acquisition module, for acquiring a plurality of construction pressures of a target well in the target reservoir within a preset time period and imaging data within the preset time period after stopping the injection of fracturing fluid into the cracks in the target reservoir; A function value determination module, configured to determine a G function value corresponding to each construction pressure according to the plurality of construction pressures based on a preset G function; A target time point determination module, used to determine a target time point at which the crack closing point of the crack is in a closed state within the preset time period according to the multiple construction pressures and the multiple G function values; A target construction pressure determination module, used to determine the target construction pressure corresponding to the target time point according to the multiple construction pressures; A target fracture dip angle determination module, used to determine the fracture dip angle corresponding to the fracture closure point according to the imaging data; The horizontal geostress determination module is used to determine the horizontal geostress of the target reservoir according to the target construction pressure and the fracture inclination.

9. A processor, characterized in that: The method is configured to perform the method for determining horizontal geostress of a reservoir according to any one of claims 1 to 7.

10. A machine-readable storage medium, characterized in that: The machine-readable storage medium stores instructions for causing a machine to execute the method for determining horizontal geostress of a reservoir according to any one of claims 1 to 7.

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