An equivalent method for hydraulic fracturing fractures in horizontal wells of tight oil and gas reservoirs

Abstract

The present invention provides an equivalent method for hydraulic fracturing cracks in horizontal wells of tight oil and gas reservoirs, and relates to the technical field of oil and gas field development. In the method of the present invention, a step adjustment value of the length of a natural crack is determined in combination with a pump-off pressure difference and a preset step value, and a step adjustment value of the intersection angle between a natural crack and an artificial crack is determined in combination with an extension pressure difference and a preset step value, and a step adjustment value of the spacing between natural cracks is determined in combination with a fracture length difference and a preset step value, so as to achieve adaptive adjustment of the step adjustment values ​​of various parameters of the natural cracks. Compared with setting the step adjustment values ​​of the natural crack parameters to fixed values, it is easy to find the best natural crack parameters and reduce the amount of calculation spent on finding the best natural crack parameters.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field development, and in particular to an equivalent method based on hydraulic fracturing of horizontal wells in tight oil and gas reservoirs. Background Art

[0002] The matrix permeability of tight oil and gas reservoirs such as shale and conglomerate is low. If horizontal well staged fracturing technology is not used, it will be far from meeting the requirements of economic exploitation. However, the increase in the length of horizontal wells and the scale of hydraulic fracturing construction makes the construction cost of fracturing horizontal wells much higher than that of conventional wells. In the United States, the cost of drilling a new horizontal well is about 1.5 to 2.5 times that of a vertical well. Therefore, improving the fracturing effect is of great significance for improving the production capacity and economic benefits of fracturing wells. Researchers have found through observation that the interaction between fracturing cracks and natural cracks may form a complex fracture network structure. Reasonable prediction of the complex fracture network morphology after fracturing is crucial to optimizing fracturing construction. By simulating the fracturing process, the geometric morphology of the fractures after fracturing can be obtained. The nature of the fractures directly determines the size of the later production capacity and also determines the pros and cons of the fracturing scheme.

[0003] In the prior art, the publication number is "CN114186439B", which is a large-scale hydraulic fracturing equivalent simulation method for conglomerate reservoirs, including the following steps: S1: determine the basic form of hydraulic fractures in the target work area; S2: randomly set a set of natural fracture parameters and embed them into the geological model of the target work area; S3: carry out hydraulic fracturing simulation to obtain hydraulic fracturing simulation pressure curve and simulated fracture length; S4: according to the results of hydraulic fracturing simulation pressure curve, adjust the natural fracture length and the intersection angle between natural fractures and artificial fractures in the natural fracture parameters; S5: according to the presence or absence of microseismic monitoring results, according to the size of the fracture length difference or the fracture length prediction model, adjust the natural fracture density in the natural fracture parameters; S6: based on the adjusted natural fracture parameters, carry out large-scale hydraulic fracturing equivalent simulation for other fracturing sections or fracturing wells. In this way, macroscopic large-scale hydraulic fracturing simulation of horizontal wells in conglomerate reservoirs is realized, which is of great significance to the production guidance and commercial development of conglomerate oil and gas reservoirs.

[0004] However, the prior art still has major defects. For example, when adjusting the parameters of natural fractures (such as the length of natural fractures, the angle between natural fractures and artificial fractures, and the spacing between natural fractures), the prior art performs adjustments with a certain step size without taking into account the error deviation between the simulated pressure and the actual pressure. It is impossible to adaptively change the adjustment step size of the natural fracture parameters according to the error deviation between the simulated pressure and the actual pressure. There are problems such as difficulty in finding the optimal value of the natural fracture parameters and too many times of adjusting the natural fracture parameters, resulting in excessive model training calculation. Summary of the invention

[0005] The object of the present invention is to provide an equivalent method for hydraulic fracturing of horizontal wells in tight oil and gas reservoirs to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] An equivalent method for hydraulic fracturing of horizontal wells in tight oil and gas reservoirs comprises the following steps:

[0008] S1, obtaining the actual fracturing construction curve characteristics of the existing fracturing wells in the target work area, and determining the basic form of the hydraulic fractures in the target work area, wherein the actual fracturing construction curve includes the actual construction pressure curve;

[0009] S2, setting a set of natural fracture parameters including natural fracture length, intersection angle between natural fracture and artificial fracture, and natural fracture spacing, and embedding the natural fracture parameters into the geological model of the target work area to be equivalent to the mineral particles in the tight oil and gas reservoir geology, and based on the fracturing construction data of existing fracturing wells, using a large-scale boundary element model to perform hydraulic fracturing simulation on the geological model embedded with the natural fracture parameters, and generating a hydraulic fracturing simulation pressure curve and a simulated fracture length;

[0010] S3, comparing the actual construction pressure curve of the existing fracturing well with the hydraulic fracturing simulation pressure curve obtained in step S2, calculating the average error coefficient, the maximum error coefficient, and the minimum error coefficient between the simulation pressure and the actual construction pressure, and combining the average error coefficient, the maximum error coefficient, and the minimum error coefficient to generate a comprehensive error coefficient, and when the comprehensive error coefficient is greater than a first preset threshold, entering step S4, and when the comprehensive error coefficient is not greater than the first preset threshold, entering step S6;

[0011] S4, calculating the pump-off pressure difference between the actual construction pressure curve and the hydraulic fracturing simulation curve obtained in step S2, and entering step S5 when the pump-off pressure difference is equal to 0, and determining the step adjustment value of the natural fracture length by combining the pump-off pressure difference and the preset step value when the pump-off pressure difference is not equal to 0, and reducing the natural fracture length by the step adjustment value when the pump-off pressure difference is greater than 0 and returning to step S2 to reset the natural fracture length, and increasing the natural fracture length by the step adjustment value when the pump-off pressure difference is less than 0 and returning to step S2 to reset the natural fracture length;

[0012] S5, calculating the extension pressure difference between the actual construction pressure curve and the hydraulic fracturing simulation curve obtained in step S2, and entering step S6 when the extension pressure difference is equal to 0, and determining the step adjustment value of the intersection angle between the natural fracture and the artificial fracture in combination with the extension pressure difference and the preset step value when the extension pressure difference is not equal to 0, increasing the intersection angle between the natural fracture and the artificial fracture according to the step adjustment value when the extension pressure difference is greater than 0 and returning to step S2 to reset the intersection angle between the natural fracture and the artificial fracture, and reducing the intersection angle between the natural fracture and the artificial fracture according to the step adjustment value when the extension pressure difference is less than 0 and returning to step S2 to reset the intersection angle between the natural fracture and the artificial fracture;

[0013] S6, according to the actual construction status of the existing fracturing wells in the target work area, determine whether the existing fracturing wells have monitoring results of the fracture length; if there are no monitoring results of the fracture length, establish a mathematical model for predicting the fracture length of the tight oil and gas reservoir, and obtain a predicted value of the fracture length according to the mathematical model for predicting the fracture length;

[0014] S7, calculating the difference between the simulated fracture length obtained in step S2 and the predicted fracture length or the monitoring result of the fracture length, and taking the absolute value of the ratio of the fracture length difference to the predicted fracture length or the monitoring result of the fracture length as the fracture length deviation coefficient, and when the fracture length deviation coefficient is less than the second preset threshold value, taking the natural fracture parameters at this time as the optimal natural fracture parameters and entering step S8, otherwise determining the step adjustment value of the natural fracture spacing in combination with the fracture length difference and the preset step value, when the fracture length difference is greater than 0, reducing the natural fracture spacing according to the step adjustment value and returning to step S2 to reset the natural fracture spacing, and when the fracture length difference is less than 0, increasing the natural fracture spacing according to the step adjustment value and returning to step S2 to reset the natural fracture spacing, and directly entering step S7 after step S2 ends;

[0015] S8, based on the optimal natural fracture parameters, perform hydraulic fracturing equivalent simulation on other fracturing wells in the target work area.

[0016] Furthermore, in step S2, the natural fracture parameters initially set are: natural fracture length 20 meters, intersection angle between natural fracture and artificial fracture 45 degrees, and natural fracture spacing 10 meters.

[0017] Furthermore, the actual construction pressure at the i-th acquisition time in the actual construction pressure curve is calibrated as Fsj i , will be compared with the actual construction pressure Fsj i The corresponding simulated pressure is calibrated as Fsj i , i represents the number of different collection moments, and i = 1, 2, ..., m, m represents the total number of collection moments, and m∈N + .

[0018] Furthermore, the calculation formula of the comprehensive error coefficient is as follows:

[0019]

[0020] Among them, λ1, λ2, and λ3 are all preset proportional coefficients, and λ1+λ2+λ3=1, and 0<λ3<λ2<λ1<1, and WCzh represents the comprehensive error coefficient.

[0021] Furthermore, the value range of λ1 is 0.5-0.7, the value range of λ2 is 0.2-0.3, and the value range of λ3 is 0.1-0.2.

[0022] Furthermore, the calculation formula of the step adjustment value of the natural fracture length is as follows:

[0023]

[0024] Wherein, BCcd1 represents the step adjustment value of the natural fracture length determined after processing in step S4 when the pressure difference value of the first pump stop is not equal to 0, BCcd0 represents the preset step value of the natural fracture length, and BCcd x represents the step adjustment value of the natural fracture length determined after processing in step S4 when the pressure difference value of the pump stopping for the xth time is not equal to 0, Fsj i1 represents the actual pump stop pressure in the actual construction pressure curve, and i1∈(1,m), Indicates the difference between the hydraulic fracturing simulation curve and the actual pump stop pressure Fsj when the xth pump stop pressure difference is not equal to 0 i1 The corresponding simulated pump stop pressure, x represents the number of different times when the pump stop pressure difference is not equal to 0, and x = 1, 2, ..., X, X represents the total number of times the pump stop pressure difference is not equal to 0, and X∈N + .

[0025] Furthermore, the calculation formula of the step length adjustment value of the intersection angle between the natural fracture and the artificial fracture is as follows:

[0026]

[0027] Wherein, BCjj1 represents the step adjustment value of the intersection angle between the natural fracture and the artificial fracture determined after the processing in step S5 when the first extension pressure difference is not equal to 0, BCjj0 represents the preset step value of the intersection angle between the natural fracture and the artificial fracture, and BCjj y represents the step adjustment value of the intersection angle between the natural fracture and the artificial fracture determined after processing in step S5 when the yth extension pressure difference is not equal to 0, Fsj i2 represents the actual extension pressure in the actual construction pressure curve, and i2∈(1,m), Indicates the difference between the hydraulic fracturing simulation curve and the actual extension pressure Fsj when the yth extension pressure difference is not equal to 0i2 The corresponding simulated extension pressure, y represents the number of different times when the extension pressure difference is not equal to 0, and y = 1, 2, ..., Y, Y represents the total number of times the extension pressure difference is not equal to 0, and Y∈N + .

[0028] Furthermore, the calculation formula of the step adjustment value of the natural fracture spacing is as follows:

[0029]

[0030] Wherein, BCju1 represents the step adjustment value of the natural fracture spacing determined after processing in step S7 when the first fracture length deviation coefficient is not less than the second preset threshold value, BCju0 represents the preset step value of the natural fracture spacing, and BCju z represents the step adjustment value of the natural fracture spacing determined after processing in step S7 when the z-th fracture length deviation coefficient is not less than the second preset threshold value, Lju1 represents the fracture length prediction value or the fracture length value in the fracture length monitoring result, and Lju z represents the simulated seam length outputted in step S2 when the seam length deviation coefficient is not less than the second preset threshold value for the zth time, z represents the number of different times when the seam length deviation coefficient is not less than the second preset threshold value, and z=1, 2, ..., Z, Z represents the total number of times when the seam length deviation coefficient is not less than the second preset threshold value, and Z∈N + .

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The equivalent method of hydraulic fracturing cracks in horizontal wells of tight oil and gas reservoirs of the present invention determines the step adjustment value of the natural fracture length in combination with the pump-off pressure difference and the preset step value, determines the step adjustment value of the intersection angle between the natural fracture and the artificial fracture in combination with the extension pressure difference and the preset step value, and determines the step adjustment value of the natural fracture spacing in combination with the fracture length difference and the preset step value, thereby achieving adaptive adjustment of the step adjustment values ​​of various parameters of the natural fracture. Compared with setting the step adjustment values ​​of the natural fracture parameters to fixed values, it is easy to find the optimal natural fracture parameters and reduce the amount of calculation spent on finding the optimal natural fracture parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the equivalent method flow of hydraulic fracturing fractures in horizontal wells of tight oil and gas reservoirs in the present invention. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0035] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present invention should be understood by people with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0036] Embodiment 1:

[0037] See also Figure 1 The present invention provides an equivalent method for hydraulic fracturing of horizontal wells in tight oil and gas reservoirs, comprising the following steps:

[0038] S1, obtaining the actual fracturing construction curve characteristics of the existing fracturing wells in the target work area, and determining the basic form of the hydraulic fractures in the target work area, wherein the actual fracturing construction curve includes the actual construction pressure curve;

[0039] It should be noted that the fracturing construction curve includes a construction pressure curve, a sand concentration curve, and a construction displacement curve that change with the increase of construction time. The fracturing construction curve can be obtained by processing and integrating the construction log data. It is an existing technology to judge the basic form of hydraulic fractures according to the characteristics of the fracturing construction curve, which will not be elaborated here.

[0040] It should be noted that the construction pressure curve includes two parameters: pump stop pressure and extension pressure. This is common knowledge and will not be elaborated here.

[0041] S2, setting a set of natural fracture parameters including natural fracture length, intersection angle between natural fracture and artificial fracture, and natural fracture spacing, and embedding the natural fracture parameters into the geological model of the target work area to be equivalent to the mineral particles in the tight oil and gas reservoir geology, and based on the fracturing construction data of existing fracturing wells, using a large-scale boundary element model to perform hydraulic fracturing simulation on the geological model embedded with the natural fracture parameters, and generating a hydraulic fracturing simulation pressure curve and a simulated fracture length;

[0042] As an implementation method, the initially set natural crack parameters can be set to: natural crack length 20 meters, natural crack and artificial crack intersection angle 45 degrees, natural crack spacing 10 meters. Of course, the natural crack parameters can also be set to other values, which will not be described in detail here;

[0043] It should be noted that when hydraulic fracturing simulation is carried out on a geological model embedded with natural fracture parameters using a large-scale boundary element model, if large-scale faults or natural fractures are found in the strata of the target work area through geophysical interpretation, they need to be embedded in the three-dimensional geomechanical model together with the equivalent natural fractures. The use of large-scale boundary element models for hydraulic fracturing simulation is an existing technology, and the specific method will not be repeated here.

[0044] S3, comparing the actual construction pressure curve of the existing fracturing well with the hydraulic fracturing simulation pressure curve obtained in step S2, calculating the average error coefficient, the maximum error coefficient, and the minimum error coefficient between the simulation pressure and the actual construction pressure, and combining the average error coefficient, the maximum error coefficient, and the minimum error coefficient to generate a comprehensive error coefficient, and when the comprehensive error coefficient is greater than a first preset threshold, entering step S4, and when the comprehensive error coefficient is not greater than the first preset threshold, entering step S6;

[0045] Among them, the calculation formula of the comprehensive error coefficient is as follows:

[0046]

[0047] It should be noted that Fsj i Indicates the actual construction pressure at the i-th acquisition time in the actual construction pressure curve, Fmn i Indicates that Fsj i The corresponding simulated pressure, i represents the number of different acquisition moments, and i = 1, 2, ..., m, m represents the total number of acquisition moments, and m∈N + ;

[0048] It should be noted that represents the average error coefficient, WCmax represents the maximum error coefficient, WCmin represents the minimum error coefficient, and the average error coefficient The larger the maximum error coefficient WCmax and the minimum error coefficient WCmin, the greater the error between the simulated pressure and the actual construction pressure, and the worse the accuracy of the simulated pressure;

[0049] It should be noted that λ1, λ2, and λ3 are all preset proportional coefficients, and λ1 represents the average error coefficient The weight of the comprehensive error coefficient WCzh, λ2 represents the weight of the maximum error coefficient WCmax in the calculation of the comprehensive error coefficient WCzh, λ3 represents the weight of the minimum error coefficient WCmin in the calculation of the comprehensive error coefficient WCzh, and λ1+λ2+λ3=1, and 0<λ3<λ2<λ1<1, the specific values ​​of λ1 and λ2 are generally determined by those skilled in the art according to actual conditions;

[0050] As an implementation mode, the value range of λ1 is 0.5-0.7, the value range of λ2 is 0.2-0.3, and the value range of λ3 is 0.1-0.2;

[0051] It should be noted that WCzh represents the comprehensive error coefficient, which is composed of the average error coefficient The maximum error coefficient WCmax and the minimum error coefficient WCmin are composed of the average error coefficient The maximum error coefficient WCmax and the minimum error coefficient WCmin are multiplied by different preset proportional coefficients to comprehensively consider the deviation characteristics between the simulated pressure and the actual construction pressure, so that the comprehensive error coefficient WCzh can more comprehensively reflect the error degree between the simulated pressure and the actual construction pressure;

[0052] It should be noted that the specific value of the first preset threshold is generally determined by those skilled in the art according to actual conditions. For example, the first preset threshold may be 5%, 8%, 10%, etc., which is not limited here.

[0053] S4, calculating the pump-off pressure difference between the actual construction pressure curve and the hydraulic fracturing simulation curve obtained in step S2, and entering step S5 when the pump-off pressure difference is equal to 0, and determining the step adjustment value of the natural fracture length by combining the pump-off pressure difference and the preset step value when the pump-off pressure difference is not equal to 0, and reducing the natural fracture length by the step adjustment value when the pump-off pressure difference is greater than 0 and returning to step S2 to reset the natural fracture length, and increasing the natural fracture length by the step adjustment value when the pump-off pressure difference is less than 0 and returning to step S2 to reset the natural fracture length;

[0054] Among them, the calculation formula of the step adjustment value of the natural fracture length is as follows:

[0055]

[0056] It should be noted that BCcd1 represents the step adjustment value of the natural fracture length determined after processing in step S4 when the pressure difference value of the first pump stop is not equal to 0, and BCcd0 represents the preset step value of the natural fracture length. The preset step value BCcd0 can be 1m, 2m, 3m, etc., and is not limited here;

[0057] It should be noted that BCcd x represents the step adjustment value of the natural fracture length determined after processing in step S4 when the pressure difference value of the pump stopping for the xth time is not equal to 0, Fsj i1 represents the actual pump stop pressure in the actual construction pressure curve, and i1∈(1,m), Indicates the difference between the hydraulic fracturing simulation curve and the actual pump stop pressure Fsj when the xth pump stop pressure difference is not equal to 0i1 The corresponding simulated pump stop pressure, x represents the number of different times when the pump stop pressure difference is not equal to 0, and x = 1, 2, ..., X, X represents the total number of times the pump stop pressure difference is not equal to 0, and X∈N + ;

[0058] It should be noted that Indicates the simulated pump stop pressure when the xth pump stop pressure difference is not equal to 0 And the actual pump stop pressure Fsj i1 The absolute difference between Indicates the simulated pump stop pressure when the xth pump stop pressure difference is not equal to 0 The simulated pump stop pressure when the difference between the pump stop pressure and the x-1th pump stop pressure is not equal to 0 The absolute difference between x-1 It represents the step adjustment value of the natural fracture length determined when the pressure difference of the pump stop for the x-1th time is not equal to 0. The effect of the step adjustment value of the natural fracture length on the simulated pump stop pressure change is found by For different times Calculate the average value to find the average value of the effect of the step adjustment value of the natural fracture length on the simulated pump stop pressure change, and then multiply the average value by To determine the step adjustment value BCcd of the natural fracture length determined after processing in step S4 when the pressure difference value of the pump stopping for the xth time is not equal to 0 x , achieving automatic adjustment of the step adjustment value of the natural fracture length, compared with setting the step adjustment value of the natural fracture length to a fixed value, it is easier to find the optimal natural fracture length and reduce the amount of calculation spent on finding the optimal natural fracture length;

[0059] S5, calculating the extension pressure difference between the actual construction pressure curve and the hydraulic fracturing simulation curve obtained in step S2, and entering step S6 when the extension pressure difference is equal to 0, and determining the step adjustment value of the intersection angle between the natural fracture and the artificial fracture in combination with the extension pressure difference and the preset step value when the extension pressure difference is not equal to 0, increasing the intersection angle between the natural fracture and the artificial fracture according to the step adjustment value when the extension pressure difference is greater than 0 and returning to step S2 to reset the intersection angle between the natural fracture and the artificial fracture, and reducing the intersection angle between the natural fracture and the artificial fracture according to the step adjustment value when the extension pressure difference is less than 0 and returning to step S2 to reset the intersection angle between the natural fracture and the artificial fracture;

[0060] Among them, the calculation formula of the step adjustment value of the intersection angle between natural fractures and artificial fractures is as follows:

[0061]

[0062] It should be noted that BCjj1 represents the step adjustment value of the intersection angle between the natural fracture and the artificial fracture determined after the processing of step S5 when the first extension pressure difference is not equal to 0, and BCjj0 represents the preset step value of the intersection angle between the natural fracture and the artificial fracture. The preset step value BCjj0 can be 7 degrees, 10 degrees, 13 degrees, etc., and is not limited here.

[0063] It should be noted that BCjj y represents the step adjustment value of the intersection angle between the natural fracture and the artificial fracture determined after processing in step S5 when the yth extension pressure difference is not equal to 0, Fsj i2 represents the actual extension pressure in the actual construction pressure curve, and i2∈(1,m), Indicates the difference between the hydraulic fracturing simulation curve and the actual extension pressure Fsj when the yth extension pressure difference is not equal to 0 i2 The corresponding simulated extension pressure, y represents the number of different times when the extension pressure difference is not equal to 0, and y = 1, 2, ..., Y, Y represents the total number of times the extension pressure difference is not equal to 0, and Y∈N + ;

[0064] It should be noted that Indicates the simulated extension pressure when the yth extension pressure difference is not equal to 0 and actual extension pressure Fsj i2 The absolute difference between Indicates the simulated extension pressure when the yth extension pressure difference is not equal to 0 Simulated extension pressure when the difference between the y-1 extension pressure and the y-1 extension pressure is not equal to 0 The absolute difference between y-1 It represents the step adjustment value of the intersection angle between natural fractures and artificial fractures when the y-1th extension pressure difference is not equal to 0. The setting of the step size adjustment value of the intersection angle between natural fractures and artificial fractures is used to find the influence of the simulated extension pressure change. For different times Calculate the average value to find the average value of the effect of the step adjustment value of the intersection angle between natural fractures and artificial fractures on the simulated extension pressure change, and then multiply the average value by To determine the step adjustment value BCjj of the intersection angle between the natural fracture and the artificial fracture determined after processing in step S5 when the yth extension pressure difference is not equal to 0 y , achieving automatic adjustment of the step adjustment value of the intersection angle between natural fractures and artificial fractures, compared with setting the step adjustment value of the intersection angle between natural fractures and artificial fractures to a fixed value, it is easier to find the best intersection angle between natural fractures and artificial fractures, and reduces the amount of calculation spent on finding the best intersection angle between natural fractures and artificial fractures;

[0065] S6, according to the actual construction status of the existing fracturing wells in the target work area, determine whether the existing fracturing wells have monitoring results of the fracture length. If there are no monitoring results of the fracture length, establish a mathematical model for predicting the fracture length of the tight oil and gas reservoir, and obtain a predicted value of the fracture length according to the mathematical model for predicting the fracture length.

[0066] It should be noted that the existing technology can be used to establish a mathematical model for predicting the fracture length of tight oil and gas reservoirs, and to obtain the predicted value of the fracture length based on the mathematical model for predicting the fracture length. For example, based on the particle size characteristics of the mineral particles in the tight oil and gas reservoirs, a laboratory small-scale fracture extension mechanism model is constructed. Under the different property characteristics of the minerals and matrix of the tight oil and gas reservoirs, the finite element method and the cohesive force unit are combined to carry out hydraulic fracturing simulation. By averaging the growth trend of the fracture length obtained by simulation at different positions, the coefficient of the traditional PKN fracture length prediction model is corrected to make the predicted fracture length consistent with the simulation result, and then the mathematical model for predicting the fracture length of tight oil and gas reservoirs as shown in the following formula is established;

[0067]

[0068] It should be noted that L is the predicted value of fracture length output by the fracture length prediction mathematical model, a is the correction coefficient, q is the injection rate, E' is the plane strain Young's modulus, μ is the fluid viscosity, h is the fracture height, and t is the injection time. The specific construction process of the fracture length prediction mathematical model for tight oil and gas reservoirs will not be described in detail here;

[0069] S7, calculating the difference between the simulated fracture length obtained in step S2 and the predicted fracture length or the monitoring result of the fracture length, and taking the absolute value of the ratio of the fracture length difference to the predicted fracture length or the monitoring result of the fracture length as the fracture length deviation coefficient, and when the fracture length deviation coefficient is less than the second preset threshold value, taking the natural fracture parameters at this time as the optimal natural fracture parameters and entering step S8, otherwise determining the step adjustment value of the natural fracture spacing in combination with the fracture length difference and the preset step value, when the fracture length difference is greater than 0, reducing the natural fracture spacing according to the step adjustment value and returning to step S2 to reset the natural fracture spacing, and when the fracture length difference is less than 0, increasing the natural fracture spacing according to the step adjustment value and returning to step S2 to reset the natural fracture spacing, and directly entering step S7 after step S2 ends;

[0070] It should be noted that the specific value of the second preset threshold is generally determined by those skilled in the art according to actual conditions. For example, the second preset threshold may be 15%, 20%, 25%, etc., which is not limited here.

[0071] The calculation formula for the step adjustment value of the natural fracture spacing is as follows:

[0072]

[0073] It should be noted that BCju1 represents the step adjustment value of the natural fracture spacing determined after processing in step S7 when the first fracture length deviation coefficient is not less than the second preset threshold value, BCju0 represents the preset step value of the natural fracture spacing, and the preset step value BCju0 can be 1m, 2m, 3m, etc., which is not limited here;

[0074] It should be noted that BCjuz represents the step adjustment value of the natural fracture spacing determined after processing in step S7 when the fracture length deviation coefficient is not less than the second preset threshold for the zth time, Lju1 represents the fracture length prediction value or the fracture length value in the fracture length monitoring result, Ljuz represents the simulated fracture length output in step S2 when the fracture length deviation coefficient is not less than the second preset threshold for the zth time, z represents the number of different times when the fracture length deviation coefficient is not less than the second preset threshold, and z=1, 2, ..., Z, Z represents the total number of times when the fracture length deviation coefficient is not less than the second preset threshold, and Z∈N + ;

[0075] It should be noted that Ljuz-Lju1 represents the absolute difference between the simulated fracture length and the predicted value of the hydraulic fracture length or the monitoring result of the hydraulic fracture length when the z-th fracture length deviation coefficient is not less than the second preset threshold, Ljuz-Ljuz-1 represents the absolute difference between the simulated fracture length Ljuz when the z-th fracture length deviation coefficient is not less than the second preset threshold and the simulated fracture length Ljuz-1 when the z-1-th fracture length deviation coefficient is not less than the second preset threshold, BCjuz-1 represents the step adjustment value of the natural fracture spacing determined when the z-1-th fracture length deviation coefficient is not less than the second preset threshold, and The effect of the step adjustment value of the natural fracture spacing on the simulated fracture length change is found by For different times Calculate the average value to find the average value of the effect of the step adjustment value of the natural fracture spacing on the simulated fracture length change, and then multiply the average value by Lju z -Lju1|To determine the step adjustment value BCju of the natural fracture spacing determined after processing in step S7 when the z-th fracture length deviation coefficient is not less than the second preset threshold z , achieving automatic adjustment of the step adjustment value of the natural fracture spacing, compared with setting the step adjustment value of the natural fracture spacing to a fixed value, it is easier to find the optimal natural fracture spacing and reduce the amount of calculation spent on finding the optimal natural fracture spacing;

[0076] S8, based on the optimal natural fracture parameters, perform hydraulic fracturing equivalent simulation on other fracturing wells in the target work area;

[0077] It should be noted that step S8 may adopt existing technologies, such as the method steps mentioned in the background technology, which will not be described in detail here.

[0078] The above formulas are all dimensionless and numerical calculations. The formula is a formula for the most recent real situation obtained by collecting a large amount of data and performing software simulation. The preset parameters in the formula are set by technicians in this field according to actual conditions.

[0079] The above embodiments may be implemented in whole or in part by software, hardware, firmware or any other combination thereof. When implemented by software, the above embodiments may be implemented in whole or in part in the form of a computer program product. Those skilled in the art may appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein may be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed by hardware or software methods depends on the specific application and design constraints of the technical solution.

[0080] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, and may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0081] The above description is only a specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application.

Claims

1. An equivalent method for hydraulic fracturing of horizontal wells in tight oil and gas reservoirs, characterized in that: The steps include: S1, obtaining the actual fracturing construction curve characteristics of the existing fracturing wells in the target work area, and determining the basic form of the hydraulic fractures in the target work area, wherein the actual fracturing construction curve includes the actual construction pressure curve; S2, setting a set of natural fracture parameters including natural fracture length, intersection angle between natural fracture and artificial fracture, and natural fracture spacing, and embedding the natural fracture parameters into the geological model of the target work area to be equivalent to the mineral particles in the tight oil and gas reservoir geology, and based on the fracturing construction data of existing fracturing wells, using a large-scale boundary element model to perform hydraulic fracturing simulation on the geological model embedded with the natural fracture parameters, and generating a hydraulic fracturing simulation pressure curve and a simulated fracture length; S3, comparing the actual construction pressure curve of the existing fracturing well with the hydraulic fracturing simulation pressure curve obtained in step S2, calculating the average error coefficient, the maximum error coefficient, and the minimum error coefficient between the simulation pressure and the actual construction pressure, and combining the average error coefficient, the maximum error coefficient, and the minimum error coefficient to generate a comprehensive error coefficient, and when the comprehensive error coefficient is greater than a first preset threshold, entering step S4, and when the comprehensive error coefficient is not greater than the first preset threshold, entering step S6; S4, calculating the pump-off pressure difference between the actual construction pressure curve and the hydraulic fracturing simulation curve obtained in step S2, and entering step S5 when the pump-off pressure difference is equal to 0, and determining the step adjustment value of the natural fracture length by combining the pump-off pressure difference and the preset step value when the pump-off pressure difference is not equal to 0, and reducing the natural fracture length by the step adjustment value when the pump-off pressure difference is greater than 0 and returning to step S2 to reset the natural fracture length, and increasing the natural fracture length by the step adjustment value when the pump-off pressure difference is less than 0 and returning to step S2 to reset the natural fracture length; S5, calculating the extension pressure difference between the actual construction pressure curve and the hydraulic fracturing simulation curve obtained in step S2, and entering step S6 when the extension pressure difference is equal to 0, and determining the step adjustment value of the intersection angle between the natural fracture and the artificial fracture in combination with the extension pressure difference and the preset step value when the extension pressure difference is not equal to 0, increasing the intersection angle between the natural fracture and the artificial fracture according to the step adjustment value when the extension pressure difference is greater than 0 and returning to step S2 to reset the intersection angle between the natural fracture and the artificial fracture, and reducing the intersection angle between the natural fracture and the artificial fracture according to the step adjustment value when the extension pressure difference is less than 0 and returning to step S2 to reset the intersection angle between the natural fracture and the artificial fracture; S6, according to the actual construction status of the existing fracturing wells in the target work area, determine whether the existing fracturing wells have monitoring results of the fracture length; if there are no monitoring results of the fracture length, establish a mathematical model for predicting the fracture length of the tight oil and gas reservoir, and obtain a predicted value of the fracture length according to the mathematical model for predicting the fracture length; S7, calculating the difference between the simulated fracture length obtained in step S2 and the predicted fracture length or the monitoring result of the fracture length, and taking the absolute value of the ratio of the fracture length difference to the predicted fracture length or the monitoring result of the fracture length as the fracture length deviation coefficient, and when the fracture length deviation coefficient is less than the second preset threshold value, taking the natural fracture parameters at this time as the optimal natural fracture parameters and entering step S8, otherwise determining the step adjustment value of the natural fracture spacing in combination with the fracture length difference and the preset step value, when the fracture length difference is greater than 0, reducing the natural fracture spacing according to the step adjustment value and returning to step S2 to reset the natural fracture spacing, and when the fracture length difference is less than 0, increasing the natural fracture spacing according to the step adjustment value and returning to step S2 to reset the natural fracture spacing, and directly entering step S7 after step S2 ends; S8, based on the optimal natural fracture parameters, perform hydraulic fracturing equivalent simulation on other fracturing wells in the target work area; The actual construction pressure at the i-th acquisition time in the actual construction pressure curve is calibrated as Fsj i , will be compared with the actual construction pressure Fsj i The corresponding simulated pressure is calibrated as Fsj i , i represents the number of different collection moments, and i = 1, 2, ..., m, m represents the total number of collection moments, and m∈N + ; The calculation formula of the step adjustment value of the natural fracture length is as follows: Wherein, BCcd1 represents the step adjustment value of the natural fracture length determined after processing in step S4 when the pressure difference value of the first pump stop is not equal to 0, BCcd0 represents the preset step value of the natural fracture length, and BCcd x represents the step adjustment value of the natural fracture length determined after processing in step S4 when the pressure difference value of the pump stopping for the xth time is not equal to 0, Fsj i1 represents the actual pump stop pressure in the actual construction pressure curve, and i1∈(1,m), Indicates the difference between the hydraulic fracturing simulation curve and the actual pump stop pressure Fsj when the xth pump stop pressure difference is not equal to 0 i1 The corresponding simulated pump stop pressure, x represents the number of different times when the pump stop pressure difference is not equal to 0, and x = 1, 2, ..., X, X represents the total number of times the pump stop pressure difference is not equal to 0, and X∈N + ; The calculation formula of the step length adjustment value of the intersection angle between natural fractures and artificial fractures is as follows: Wherein, BCjj1 represents the step adjustment value of the intersection angle between the natural fracture and the artificial fracture determined after the processing in step S5 when the first extension pressure difference is not equal to 0, BCjj0 represents the preset step value of the intersection angle between the natural fracture and the artificial fracture, and BCjj y represents the step adjustment value of the intersection angle between the natural fracture and the artificial fracture determined after processing in step S5 when the yth extension pressure difference is not equal to 0, Fsj i2 represents the actual extension pressure in the actual construction pressure curve, and i2∈(1,m), Indicates the difference between the hydraulic fracturing simulation curve and the actual extension pressure Fsj when the yth extension pressure difference is not equal to 0 i2 The corresponding simulated extension pressure, y represents the number of different times when the extension pressure difference is not equal to 0, and y = 1, 2, ..., Y, Y represents the total number of times the extension pressure difference is not equal to 0, and Y∈N + ; The calculation formula of the step adjustment value of the natural fracture spacing is as follows: Wherein, BCju1 represents the step adjustment value of the natural fracture spacing determined after processing in step S7 when the first fracture length deviation coefficient is not less than the second preset threshold value, BCju0 represents the preset step value of the natural fracture spacing, and BCju z represents the step adjustment value of the natural fracture spacing determined after processing in step S7 when the z-th fracture length deviation coefficient is not less than the second preset threshold value, Lju1 represents the fracture length prediction value or the fracture length value in the fracture length monitoring result, and Lju z represents the simulated seam length outputted in step S2 when the seam length deviation coefficient is not less than the second preset threshold value for the zth time, z represents the number of different times when the seam length deviation coefficient is not less than the second preset threshold value, and z=1, 2, ..., Z, Z represents the total number of times when the seam length deviation coefficient is not less than the second preset threshold value, and Z∈N + .

2. The equivalent method of hydraulic fracturing cracks in horizontal wells of tight oil and gas reservoirs according to claim 1, characterized in that: In step S2, the natural fracture parameters initially set are: natural fracture length 20 meters, intersection angle between natural fracture and artificial fracture 45 degrees, and natural fracture spacing 10 meters.

3. The equivalent method of hydraulic fracturing cracks in horizontal wells of tight oil and gas reservoirs according to claim 1, characterized in that: The calculation formula of the comprehensive error coefficient is as follows: Among them, λ1, λ2, and λ3 are all preset proportional coefficients, and λ1+λ2+λ3=1, and 0<λ3<λ2<λ1<1, and WCzh represents the comprehensive error coefficient.

4. The equivalent method of hydraulic fracturing cracks in horizontal wells of tight oil and gas reservoirs according to claim 3 is characterized in that: The value range of λ1 is 0.5-0.7, the value range of λ2 is 0.2-0.3, and the value range of λ3 is 0.1-0.2.

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