Beach bar sand reservoir sand-mud consubstantial fracturing crack height evaluation method

Abstract

The invention provides a beach and bar sand reservoir sand-mud consubstantial fracturing crack height evaluation method. The method comprises the following steps: step 1, extracting characteristic parameters of a target layer; 2, designing parameters of the physical model for sand-mud consubstantial fracturing, and pouring, forming and maintaining the physical model; 3, an acoustic emission monitoring scheme in the fracturing process is designed, and a fracturing test is conducted on a fracturing testing machine; step 4, performing three-dimensional coordinate positioning of the effective event; step 5, establishing a mathematical relationship between the fracture height of the fracturing fracture and the test factors; and step 6, engineering geology amplification and restoration are carried out, and nonlinear fitting between the fracture height data and the test factors is carried out according to the amplified and restored data. According to the beach and bar sand reservoir sand-mud consubstantial fracturing crack height evaluation method, the physical model is simple in design, the applicability is high, the prediction precision of the beach and bar sand reservoir sand-mud consubstantial fracturing crack height can be improved, the understanding of the crack height extension rule is improved, and guidance is provided for on-site fracturing construction.

Description

Technical Field

[0001] The invention relates to the technical field related to beach-bar sand reservoir development, and in particular to a method for high-quality evaluation of sand-mud composite fractures in beach-bar sand reservoirs. Background Art

[0002] my country's beach-bar sand reservoirs are rich in reserves and have great development potential. Beach-bar sand reservoirs are generally characterized by complex lithology, low permeability and low porosity, and strong heterogeneity. They usually require large-scale fracturing to achieve industrial production capacity. The geological reservoir distribution characteristics of beach-bar sand reservoirs are generally large in vertical span, with many thin layers. Such reservoirs need to be fractured to be effectively utilized. In general, they have the following characteristics: (1) The reservoir depth is below 1500m, and fracturing mainly produces longitudinal cracks; (2) There are many thin layers and there are differences in lithology, physical properties and geostress between the small layers; (3) The interlayer is thin and the reservoir permeability is low, which requires transformation before it can be put into production; (4) It is difficult for a single production layer to have productivity, and single-layer fracturing is not economical. Therefore, it is planned to implement sand-mud fracturing of the oil-bearing sandstone and oil-mudstone interlayers.

[0003] However, when designing the sand-mud fracturing operation, the following issues need to be clarified: (1) How much does the thickness of the oil mud layer affect the fracture height; (2) How much does the mud content of the oil mud layer affect the fracture height; and (3) Is it possible to achieve sand-mud fracturing by controlling the construction displacement to break through the oil mud layer?

[0004] Furthermore, the current evaluation of fracture height in multi-thin layer hydraulic fracturing of beach-bar sand is mostly based on numerical simulation. The input parameters, grid size, fluid-solid coupling constitutive model, fracture propagation strength criterion, etc. of the numerical simulation all affect the accuracy of the numerical simulation results, resulting in large differences in the assessment of fracture height.

[0005] Therefore, it is urgent to invent a new evaluation method for fracture height expansion of sand-mud co-existing fracturing to provide technical guidance for fracture height design and construction parameter limit determination of sand-mud co-existing fracturing in beach-bar sand reservoirs.

[0006] In the Chinese patent application with application number: CN202011616600.2, a method for finely evaluating the height of hydraulic fracturing cracks in offshore sandstone reservoirs is involved, which adopts the following steps: 1. Collect relevant data within a given depth interval; 2. Calculate the formation shear wave time difference and arrival time of array acoustic waves before and after fracturing; 3. Calculate the difference in shear wave amplitude of array acoustic waves before and after fracturing; 4. Invert the array acoustic wave data before and after fracturing; 5. Calculate the difference in its brittle fracture index; 6. Establish a fine evaluation chart of reservoir fracturing cracks based on shear wave amplitude and radial velocity profile; 7. Divide the fine evaluation chart of fracturing cracks into three intervals; 8. Repeat steps 1 to 5 to obtain the processing results of the full wave train data of single well array acoustic waves, and make a fine evaluation of the height of reservoir fracturing cracks based on the processing results. This invention can not only evaluate the fracturing effect of anisotropic technology; but also evaluate the height of hydraulic fracturing cracks to effectively improve the accuracy of hydraulic fracturing evaluation of offshore sandstone reservoirs.

[0007] In the Chinese patent application with application number: CN201910180892.0, a method for comprehensively evaluating fracture-pore carbonate reservoirs based on karst parameters is involved. First, a reservoir concept model is established to identify fracture-pore carbonate reservoirs; then, applicable classification and evaluation standards are formulated for the reservoir, and single-well reservoirs are semi-quantitatively and qualitatively divided and evaluated; then, through paleo-tectonic stress field analysis, carbonate fracture evaluation and prediction are carried out to obtain key fracture parameters for reservoir evaluation; two karst parameters, vertical karst rate and karst intensity, are characterized to calculate key karst parameters for reservoir evaluation; sedimentary microfacies types, key fracture parameters and key karst parameters are comprehensively considered, and a multi-factor reservoir development probability evaluation is performed using the "superposition probability evaluation method"; under the constraints of the fracture evaluation prediction plane map, the single-well reservoir evaluation results are combined with the reservoir development probability evaluation results to achieve reservoir evaluation and prediction on the plane; the invention has the advantages of strong comprehensiveness, quantitative evaluation and operability.

[0008] In the Chinese patent application with application number: CN201610940085.0, a method for quantitatively calculating fracture porosity in an array acoustic logging porous media model is involved, which belongs to the field of reservoir evaluation. The method includes: firstly establishing a pore aspect ratio spectrum distribution function, determining the pore distribution interval, then adding the pore aspect ratio spectrum distribution to the equivalent medium model, establishing an array acoustic logging porous media model, establishing an objective function in combination with the rock modulus calculated by the array acoustic logging, obtaining the morphological characteristics of the pore aspect ratio spectrum distribution by inversion means, and quantitatively calculating the fracture porosity using the fracture cutoff value. The invention can be applied to conventional sandstone and mudstone reservoirs, and can also be applied to the fracture effectiveness evaluation of complex reservoirs such as complex lithology and buried hills, realizing the quantitative calculation of reservoir fracture porosity, providing reliable fracture parameters for reservoir evaluation, becoming an important technology for reserve evaluation, and improving the accuracy of reserve evaluation.

[0009] In the Chinese patent application with application number: CN202010494993.8, a feasibility evaluation method for horizontal well through-layer fracturing is involved, which includes the following steps: S1 establishment of a single well geological model; S2 simulation of the expansion law of artificial fractures; S3 judgment of the feasibility of through-layer fracturing; S4 analysis of the passability of sand-carrying fluid in the artificial fractures of mudstone interlayers; S5 experimental evaluation of the conductivity of different sand concentrations in mudstone interlayers; S6 comprehensive evaluation of the feasibility of through-layer fracturing. It can not only evaluate whether the fracturing transformation of the target oil and gas layer can take into account the adjacent oil and gas layers, but also scientifically evaluate the passability of sand-carrying fluid in the artificial fractures of mudstone interlayers and the conductivity of mudstone interlayer fracturing, accurately analyze whether the adjacent oil and gas layers can be saturated with sand and whether the conductivity of mudstone interlayers after fracturing can meet the requirements of oil and gas seepage, and provide a reliable, comprehensive and scientific evaluation method for the feasibility of on-site implementation of horizontal well through-layer fracturing technology. The method provided by the invention can not only be used for pre-fracturing evaluation, but also for post-fracturing analysis and judgment.

[0010] The above existing technologies are all significantly different from the present invention and fail to solve the technical problem we want to solve. Therefore, we have invented a new high-evaluation method for sand-mud composite fractures in beach-bar sand reservoirs. Summary of the invention

[0011] The purpose of the present invention is to provide a method for evaluating the height of fractures in the sand-mud composite fracture of beach-bar sand reservoirs, which can solve the problems of insufficient understanding of fracture height expansion law, unclear main controlling factors of fracture height, and difficulty in determining the limits of construction parameters in the fracturing design project of beach-bar sand reservoirs.

[0012] The object of the present invention can be achieved by the following technical measures: a high evaluation method for beach-bar sand reservoir sand-mud composite fracture, the beach-bar sand reservoir sand-mud composite fracture high evaluation method comprising:

[0013] Step 1, extracting characteristic parameters of the target layer;

[0014] Step 2, designing parameters of the physical model of sand-mud fracturing, and casting, molding and curing the physical model;

[0015] Step 3, designing an acoustic emission monitoring scheme for the fracturing process and conducting a fracturing test on a fracturing test machine;

[0016] Step 4, locating the three-dimensional coordinates of the valid event;

[0017] Step 5, establishing a mathematical relationship between the fracturing crack height and the test factors;

[0018] Step 6: Perform engineering geological amplification and restoration, and perform nonlinear fitting between the fracture height data and the experimental factors based on the amplified and restored data.

[0019] The purpose of the present invention can also be achieved by the following technical measures:

[0020] In step 1, based on the logging data of the vertical and inclined wells in the beach-bar sand reservoir, the characteristic parameters of the target layer reservoir barrier, such as sand and mud content, reservoir barrier thickness, reservoir barrier interaction structure, reservoir barrier physical and mechanical parameters and initial ground stress, are extracted.

[0021] In step 1, the reservoir-interlayer interaction structure refers to the vertical inter-arrangement sequence of the oil-bearing reservoir and the oil mudstone interlayer.

[0022] In step 2, based on the principle of similarity, the material properties, geometric dimensions and boundary conditions of the physical model of sand-mud fracturing are designed, and the casting, molding and curing of the physical model are carried out to ensure a sufficient number of test samples.

[0023] In step 2, the material properties of the physical model include elastic modulus, Poisson's ratio, strength and porosity, wherein the sandstone layer is made of 425 composite silicate cement, and the mudstone layer is made of 425 composite silicate cement, river sand and kaolin in a mass ratio of 3:3:4.

[0024] In step 2, the larger the physical model, the better the effect of the physical model. If the size is too small, the statistical error of the subsequent acoustic emission event measurement gap height is difficult to eliminate. At the same time, the test cost and the operability of the test are considered to select the size of the physical model.

[0025] In step 2, a sufficient number of test samples means that for each individual research condition, the more physical phantom models prepared, the better, and the minimum number should not be less than 4 groups.

[0026] In step 3, based on the maintained physical model, an acoustic emission monitoring scheme for the fracturing process is designed, a fracturing test is carried out on a fracturing test machine, and the pump pressure curve and acoustic emission ringing events during the test are recorded throughout the process.

[0027] In step 3, the acoustic emission monitoring scheme refers to the relevant settings such as the placement of the acoustic emission sensor on the surface of the physical model, the initial wave velocity of the model, and the sampling frequency.

[0028] In step 4, the time axis of the pump pressure curve and the acoustic emission ringing event are aligned, the first rupture pressure point of the pressure curve is taken as the time initial point, the acoustic emission event after the time initial point is taken as the effective event, and the three-dimensional coordinate positioning of the effective event is performed.

[0029] In step 4, the initial time point is used to filter out discrete acoustic emission events that occur inside the model before the occurrence of fracturing cracks. These acoustic emission events are not fracture events, but initial defect damage points induced by fracturing fluid loss and pump pressure disturbance, which can increase the statistical error of fracture height.

[0030] In step 5, a nonlinear fitting is performed on multiple groups of fracture height monitoring data, generally a negative exponential relationship fitting, so as to establish a mathematical relationship between the fracture height of the hydraulic fracture and the test factors.

[0031] In step 5, according to the vertical coordinates of the located acoustic emission events in the sandstone reservoir and the mudstone interlayer, the longitudinal extension height of the fracture is calculated, and the mathematical relationship between the fracture height of the physical model and the experimental factors such as mudstone thickness, mud content, and construction parameters is established, as shown in formula (1).

[0032]

[0033] Where: y is the height of the fracture in the physical model; x is the mudstone thickness, mud content and pump pressure parameters of the physical model; A i , B i and C i (i=1) is the fitting coefficient.

[0034] In step 6, according to the similar proportions of the physical model and the in-situ engineering scale model, the parameters of the three designed geometric dimensions, namely, fracture height, mudstone thickness, and displacement, are enlarged and restored, and nonlinear fitting between the fracture height data and the experimental factors is performed based on the enlarged and restored data.

[0035] In step 6, according to the geometric similarity principle in the similarity principle, the engineering geological restoration is carried out to further establish the mathematical relationship between the actual fracture height of the hydraulic fracturing and the mudstone thickness, mud content, and construction parameters at the in-situ scale, as shown in formula (2):

[0036]

[0037] Where: F h is the actual formation fracture height; ω is mudstone thickness, mud content, and construction parameters; A i , B i and C i (i=2) is the fitting coefficient.

[0038] The method for evaluating fracture height of sand-mud composite fractures in beach-bar sand reservoirs of the present invention solves the problems of insufficient understanding of fracture height expansion law, unclear main controlling factors of fracture height, and difficulty in determining construction parameter limits in the fracturing design engineering of beach-bar sand reservoirs. The advantages and beneficial effects of the present invention are:

[0039] 1. The present invention makes full use of the mature and perfect similarity principle, and can realize the quantitative evaluation of the influence of any different mud content, different reservoir thickness, and different sand-mud interaction structure on the height of the fracturing crack. The physical model is simple in design and has strong applicability, which effectively avoids the difficult problems of input parameters, grid effects, and constitutive model uncertainty in theoretical calculations, numerical simulations and other methods.

[0040] 2. The present invention combines modern high-frequency and high-precision acoustic emission testing technology to fully capture the acoustic emission event data during the physical model experiment, and can achieve fine imaging and evaluation of crack height under conditions such as variable displacement and variable viscosity, which is beneficial to improving the prediction accuracy of fracture height of sand-mud hybrid hydraulic fracturing in beach-bar sand reservoirs, improving the understanding of fracture height expansion laws, and providing guidance for on-site fracturing construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a design diagram of a sand-mud composite fracturing model in a specific embodiment of the present invention;

[0042] Figure 2 This is a model diagram of a sand-mud composite fracturing model after curing and forming in a specific embodiment of the present invention;

[0043] Figure 3 It is a test factor diagram of mudstone interlayer thickness in a specific embodiment of the present invention;

[0044] Figure 4 It is a diagram of the layout of acoustic emission sensors in a specific embodiment of the present invention;

[0045] Figure 5 A pump pressure-time curve diagram during a fracturing simulation test in a specific embodiment of the present invention;

[0046] Figure 6 A fracture height map of a hydraulic fracture after acoustic emission event positioning in a specific embodiment of the present invention;

[0047] Figure 7 It is a statistical relationship diagram between the fracture height of the physical model and the thickness of the mudstone interlayer in a specific embodiment of the present invention;

[0048] Figure 8 It is a statistical relationship diagram between the in-situ engineering scale fracture height and the mudstone interlayer thickness after geological restoration in a specific embodiment of the present invention;

[0049] Fig. 9 A model diagram for testing the influence of lithology on fracture height in a specific embodiment of the present invention;

[0050] Fig.10 It is a schematic diagram of the height of the fracturing crack after the acoustic emission event is located in a specific embodiment of the present invention;

[0051] Fig.11 It is a schematic diagram of the influence of lithology on fracture height obtained by simulation in a specific embodiment of the present invention;

[0052] Fig.12 It is a schematic diagram of the influence of lithology on fracture height calculated according to the similarity criterion in a specific embodiment of the present invention;

[0053] Fig.13In one embodiment of the present invention, a fracture height map of a hydraulic fracture after locating an acoustic emission event in a specific embodiment;

[0054] Fig.14 A schematic diagram of the effect of displacement on seam height obtained by physical modeling in a specific embodiment of the present invention;

[0055] Fig.15 A schematic diagram of the effect of displacement on seam height calculated according to a similarity criterion in a specific embodiment of the present invention;

[0056] Fig.16 The present invention is a flow chart of a specific embodiment of the method for evaluating the high pressure fracture of the sand-mud composite of the beach-bar sand reservoir. DETAILED DESCRIPTION

[0057] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0058] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0059] like Fig.16 As shown, Fig.16 The flowchart of the method for evaluating the high performance of the sand-mud composite fracture of the beach-bar sand reservoir of the present invention is as follows. The method for evaluating the high performance of the sand-mud composite fracture of the beach-bar sand reservoir comprises:

[0060] Step 101: Extract characteristic parameters such as sand and mud content, thickness, interaction structure, physical and mechanical parameters and initial geostress of the target layer reservoir barrier according to the logging data of the vertical and inclined wells in the beach-bar sand reservoir; the interaction structure of the reservoir barrier refers to the vertical arrangement sequence of the oil-bearing reservoir and the mudstone barrier, and a single huge thick reservoir is not within the scope supported by the present invention.

[0061] Step 102: Based on the similarity principle, the material properties, geometric dimensions and boundary conditions of the physical model of the sand-mud fracturing are designed, and the physical model is cast, formed and cured to ensure a sufficient number of test samples;

[0062] The material properties of the physical model include elastic modulus, Poisson's ratio, strength and porosity, wherein the sandstone layer is made of 425 composite silicate cement, and the mudstone layer is made of 425 composite silicate cement, river sand and kaolin in a mass ratio of 3:3:4.

[0063] The larger the physical model, the better the effect. If the size is too small, the statistical error of the subsequent acoustic emission event measurement gap height will be difficult to eliminate. The size of the physical model should be selected considering the test cost and the operability of the test.

[0064] The geometric dimensions can be 30cm×30cm×30cm, or 40cm×40cm×40cm, or 50cm×50cm×50cm. The larger the size, the better the modeling effect. If the size is too small, the statistical error of the subsequent acoustic emission event measurement seam height is difficult to eliminate. Therefore, the side length of the physical model is not less than 30cm; but considering the test cost and the operability of the test, the side length of the physical model is not greater than 50cm.

[0065] The sufficient number of test samples means that for each individual research condition, the more physical phantom models prepared, the better, and the minimum number should not be less than 4 groups.

[0066] Step 103: Based on the maintained physical model, an acoustic emission monitoring scheme for the fracturing process is designed, a fracturing test is conducted on a fracturing test machine, and the pump pressure curve and acoustic emission ringing events during the test are fully recorded; the acoustic emission monitoring scheme refers to the surface layout position of the acoustic emission sensor on the physical model, the initial wave velocity of the model, the sampling frequency and other related settings.

[0067] Step 104: aligning the time axis of the pump pressure curve and the acoustic emission ringing event, taking the first rupture pressure point of the pressure curve as the time initial point, taking the acoustic emission event after the time initial point as the effective event, and performing three-dimensional coordinate positioning of the effective event;

[0068] The initial time point is to filter out discrete acoustic emission events that occur inside the model before the fracturing cracks appear. These acoustic emission events are not fracture events, but initial defect damage points induced by fracturing fluid loss and pump pressure disturbance, which can increase the statistical error of fracture height.

[0069] Step 105: Calculate the longitudinal extension height of the fracture according to the vertical coordinates of the located acoustic emission events in the sandstone reservoir and the mudstone interlayer, and establish a mathematical relationship between the fracture height of the physical model and experimental factors such as mudstone thickness, mud content, and construction parameters, as shown in formula (1).

[0070]

[0071] Where: y is the height of the fracture in the physical model; x is the mudstone thickness, mud content and pump pressure parameters of the physical model; A i , B i and C i (i=1) is the fitting coefficient.

[0072] The specific approach is to perform nonlinear fitting on multiple groups (at least 4 groups) of fracture height monitoring data, generally a negative exponential relationship fitting, so as to establish a mathematical relationship between the fracture height of the hydraulic fracture and the test factors.

[0073] Step 106: Based on the geometric similarity principle in the similarity principle, the engineering geological restoration is performed to further establish the mathematical relationship between the actual fracturing crack height and the mudstone thickness, mud content, and construction parameters at the in-situ scale (actual scale), as shown in formula (2).

[0074]

[0075] Where: F h is the actual formation fracture height; ω is mudstone thickness, mud content, and construction parameters; A i , B i and C i (i=2) is the fitting coefficient.

[0076] The specific approach is as follows: according to the similar proportions of the physical model and the in-situ engineering scale model, the three design geometric parameters of fracture height, mudstone thickness and displacement are enlarged and restored, and the nonlinear fitting between the fracture height data and the experimental factors is performed based on the enlarged and restored data.

[0077] The following are several specific embodiments of the present invention.

[0078] Example 1

[0079] In a specific embodiment 1 of the present invention, the method is used to evaluate the effect of the thickness of each layer on the fracture height in the sand-shale body fracturing, which includes the following steps:

[0080] Step 1: Taking a vertical well in the beach-bar sand reservoir of Shengli Oilfield as an example, and taking the thickness of the mudstone barrier as the physical model test factor for specific explanation, according to the well logging data of the vertical well, the characteristic parameters of the target layer reservoir barrier, such as sand and mud content, reservoir barrier thickness, reservoir barrier interaction structure, reservoir barrier physical and mechanical parameters and initial ground stress, are extracted;

[0081] Step 2: Based on the principle of similarity, the material properties of the physical model of sand-mud fracturing are designed. The sandstone layer uses 425 composite silicate cement, and the mudstone layer uses 425 composite silicate cement, river sand, and kaolin in a mass ratio of 3:3:4; the geometric size uses a 30cm×30cm×30cm cubic sample, such as Figure 1, the fracturing wellbore is preset in the center of the plane perpendicular to the reservoir barrier; after the physical model is cast, formed and cured, Figure 2 As shown in Figure 2, in order to ensure a sufficient number of test samples, four groups of models were designed according to the reservoir thickness characteristics of the logging data, as shown in Figure 2. Figure 3 As shown, the thickness of the mudstone interlayers are 100 mm, 70 mm, 40 mm and 20 mm respectively;

[0082] Step 3: Based on the completed physical model, design an acoustic emission monitoring scheme for the fracturing process, such as Figure 4 As shown, the sampling frequency is 2000kHz, and then it is placed on the fracturing test machine for fracturing test, and the pump pressure curve and acoustic emission ringing events during the test are recorded throughout the whole process;

[0083] Step 4: Benchmark the pump pressure curve and the time axis of the AE ringing event, such as Figure 5 , taking the first rupture pressure point of the pressure curve as the time initial point, taking the acoustic emission events after the time initial point as the effective events, and performing the three-dimensional coordinate positioning of the effective events, such as Figure 6 As shown;

[0084] Step 5: Calculate the longitudinal extension height of the fracture based on the vertical coordinates of the located acoustic emission events in the sandstone reservoir and mudstone interlayer. The test statistical data points are as follows: Figure 7 As shown in the figure, the mathematical relationship between the fracture height of the physical model and the thickness of the mudstone interlayer can be established, see formula (1),

[0085] y=204.4e -0.0072x +91.7 (1)

[0086] Where: y is the height of the fracturing crack in the physical model, in mm; x is the mudstone thickness in the physical model, in mm.

[0087] Step 6: According to the geometric similarity principle in the similarity principle, the engineering geological restoration is performed. In the embodiment, the geometric similarity ratio of the physical model is 1:125. The statistical data after restoration is as follows: Figure 8 As shown in the figure, the mathematical relationship between the actual fracture height and the mudstone thickness at the in-situ scale (actual scale) can be further established, as shown in formula (2):

[0088] F h =25.5e -0.22ω +11.5 (2)

[0089] Where: F h is the actual formation fracturing crack height, unit is m; ω is the mudstone thickness, unit is m.

[0090] Example 2

[0091] In the specific embodiment 2 of the present invention, the method is used to evaluate the influence of lithology on fracture height in sandstone-mudstone fracturing, which includes the following steps:

[0092] Step 1: Taking a vertical well in the beach-bar sand reservoir of Shengli Oilfield as an example, and taking the thickness of the mudstone barrier as the physical model test factor for specific explanation, according to the well logging data of the vertical well, the characteristic parameters of the target layer reservoir barrier, such as sand and mud content, reservoir barrier thickness, reservoir barrier interaction structure, reservoir barrier physical and mechanical parameters and initial ground stress, are extracted;

[0093] Step 2: Based on the principle of similarity, the material properties of the physical model of sand-mud fracturing are designed. The sandstone layer uses 425 composite silicate cement, and the mudstone layer uses 425 composite silicate cement, river sand, and kaolin in a mass ratio of 3:3:4; the geometric size uses a 30cm×30cm×30cm cubic sample, such as Figure 1 , the fracturing wellbore is preset in the center of the plane perpendicular to the reservoir barrier; after the physical model is cast, formed and cured, Figure 2 As shown in Figure 2, in order to ensure a sufficient number of test samples, 5 groups of models were designed according to the reservoir lithology characteristics of the logging data, as shown in Figure 2. Fig. 9 As shown, the sand content of the interlayer is gradually increased. The vertical stress of the five models is σ1 = 20MPa, the maximum horizontal principal stress is σ2 = 15MPa, the minimum horizontal principal stress is σ3 = 10MPa, the fracturing fluid is clean water, the perforation section is centered vertically, and the length of the perforation section is 3cm. The sand content of the mudstone interlayer is 0%, 20%, 40%, 60%, and 100% respectively.

[0094] Step 3: Based on the completed physical model, design an acoustic emission monitoring scheme for the fracturing process, such as Figure 4 As shown, the sampling frequency is 2000kHz, and then it is placed on the fracturing test machine for fracturing test, and the pump pressure curve and acoustic emission ringing events during the test are recorded throughout the whole process;

[0095] Step 4: Align the pump pressure curve and the time axis of the acoustic emission ringing event, take the first rupture pressure point of the pressure curve as the time initial point, take the acoustic emission event after the time initial point as the effective event, and locate the three-dimensional coordinates of the effective event, such as Fig.10 As shown;

[0096] Step 5: Calculate the longitudinal extension height of the fracture according to the vertical coordinates of the located acoustic emission events in the sandstone reservoir and the mudstone interlayer. The test statistical data points are shown in 11. The mathematical relationship between the fracture height of the physical model and the sand content of the mudstone interlayer can be established, see formula (3),

[0097] y=-163.1e -0.022x +228.1 (3)

[0098] Where: y is the height of the fracturing crack in the physical model, in mm; x is the sand content of the interlayer in the physical model, in %.

[0099] Step 6: According to the geometric similarity principle in the similarity principle, the engineering geological restoration is performed. In the embodiment, the geometric similarity ratio of the physical model is 1:125. The statistical data after restoration is as follows: Fig.12 As shown in the figure, the mathematical relationship between the actual fracture height and the mudstone thickness at the in-situ scale (actual scale) can be further established, as shown in formula (4):

[0100] y=-21.8e -0.022x +30.4 (4)

[0101] Where: F h is the actual formation fracturing crack height, unit is m; ω is the interlayer sand content, unit is %.

[0102] Example 3

[0103] In the specific embodiment 3 of the present invention, the method is applied to evaluate the effect of displacement on fracture height in sand-shale fracturing, which includes the following steps:

[0104] Step 1: Taking a vertical well in the beach-bar sand reservoir of Shengli Oilfield as an example, and taking the thickness of the mudstone barrier as the physical model test factor for specific explanation, according to the well logging data of the vertical well, the characteristic parameters of the target layer reservoir barrier, such as sand and mud content, reservoir barrier thickness, reservoir barrier interaction structure, reservoir barrier physical and mechanical parameters and initial ground stress, are extracted;

[0105] Step 2: Based on the principle of similarity, the material properties of the physical model of sand-mud fracturing are designed. The sandstone layer uses 425 composite silicate cement, and the mudstone layer uses 425 composite silicate cement, river sand, and kaolin in a mass ratio of 3:3:4; the geometric size uses a 30cm×30cm×30cm cubic sample, such as Figure 1 , the fracturing wellbore is preset in the center of the plane perpendicular to the reservoir barrier; after the physical model is cast, formed and cured, Figure 2 As shown in the figure, in order to ensure a sufficient number of test samples, four groups of models were designed according to the reservoir characteristics of the logging data. The vertical stress σ1 of the four models was 20MPa, the maximum horizontal principal stress σ2 was 15MPa, and the minimum horizontal principal stress σ3 was 10MPa. Fresh water fracturing was used. Four initial displacement values ​​were set: 40ml / min, 70ml / min, 135ml / min and 200ml / min. After reaching the initial fracture pressure, the displacement was increased to open the core.

[0106] Step 3: Based on the completed physical model, design an acoustic emission monitoring scheme for the fracturing process, such as Figure 4As shown, the sampling frequency is 2000 kHz, and then it is placed on a fracturing test machine for fracturing tests, and the pump pressure curve and acoustic emission ringing events during the test process are recorded throughout the process;

[0107] Step 4: Align the time axes of the pump pressure curve and the acoustic emission ringing events. Take the first fracture pressure point of the pressure curve as the initial time point, and take the acoustic emission events after this initial time point as valid events, and perform three-dimensional coordinate positioning of the valid events, as Fig.13 shown;

[0108] Step 5: Calculate the longitudinal extension height of the fracture according to the vertical coordinates of the located acoustic emission events in the sandstone reservoir and the mudstone interlayer. The experimental statistical data points are as Fig.14 shown. The mathematical relationship between the fracture height of the physical model and the displacement can be established, as shown in formula (5),

[0109] y = -232.9e -0.0073x + 233.7 (5)

[0110] In the formula: y is the fracture height of the physical model fracturing, unit mm; x is the sand content of the interlayer of the physical model, unit %.

[0111] Step 6: According to the geometric similarity principle in the similarity principle, perform engineering geological restoration. In the embodiment, the geometric similarity ratio of the physical model is 1:125. The restored statistical data is as Fig.15 shown. The mathematical relationship between the actual fracture height of the actual fracturing and the mudstone thickness at the in-situ scale (actual scale) can be further established, as shown in formula (6),

[0112] y = -31.1e -0.066x + 31.2 (6)

[0113] In the formula: F h is the actual fracture height of the actual formation fracturing, unit m; ω is the sand content of the interlayer, unit %.

[0114] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0115] Except for the technical features described in the specification, they are all known technologies to those skilled in the art.

Claims

1. Evaluation method of high pressure fracture of sand-mud composite in beach-bar sand reservoir, It is characterized in that The high evaluation method of the sand-mud composite fracture of the beach-bar sand reservoir includes: Step 1, extracting characteristic parameters of the target layer; Step 2, designing parameters of the physical model of sand-mud composite fracturing, and performing casting, molding and curing of the physical model; Step 3, designing an acoustic emission monitoring scheme for the fracturing process and conducting a fracturing test on a fracturing test machine; Step 4, locating the three-dimensional coordinates of the valid event; Step 5, establishing a mathematical relationship between the fracturing crack height and the test factors; Step 6: Perform engineering geological amplification and restoration, and perform nonlinear fitting between the fracture height data and the experimental factors based on the amplified and restored data.

2. The method for evaluating the high pressure fracture of the sand-mud composite of the beach-bar sand reservoir according to claim 1, It is characterized in that In step 1, based on the logging data of the vertical and inclined wells in the beach-bar sand reservoir, the characteristic parameters of the target layer reservoir barrier, such as sand and mud content, reservoir barrier thickness, reservoir barrier interaction structure, reservoir barrier physical and mechanical parameters and initial ground stress, are extracted.

3. The method for evaluating the high pressure fracture of the sand-mud composite of the beach-bar sand reservoir according to claim 2, It is characterized in that In step 1, the reservoir-interlayer interaction structure refers to the vertical inter-arrangement sequence of the oil-bearing reservoir and the oil mudstone interlayer.

4. The method for evaluating the high performance of the sand-mud composite fracture of the beach-bar sand reservoir according to claim 1, It is characterized in that In step 2, based on the principle of similarity, the material properties, geometric dimensions and boundary conditions of the physical model of sand-mud fracturing are designed, and the casting, molding and curing of the physical model are carried out to ensure a sufficient number of test samples.

5. The method for evaluating the high pressure fracture of the sand-mud composite of the beach-bar sand reservoir according to claim 4, It is characterized in that In step 2, the material properties of the physical model include elastic modulus, Poisson's ratio, strength and porosity, wherein the sandstone layer is made of 425 composite silicate cement, and the mudstone layer is made of 425 composite silicate cement, river sand and kaolin in a mass ratio of 3:3:

4.

6. The method for evaluating the high performance of the sand-mud composite fracture of the beach-bar sand reservoir according to claim 4, It is characterized in that In step 2, the larger the physical model, the better the effect of the physical model. If the size is too small, the statistical error of the subsequent acoustic emission event measurement gap height is difficult to eliminate. At the same time, the test cost and the operability of the test are considered to select the size of the physical model.

7. The method for evaluating the high pressure fracture of the sand-mud composite fracture of the beach-bar sand reservoir according to claim 4, It is characterized in that In step 2, a sufficient number of test samples means that for each individual research condition, the more physical phantom models prepared, the better, and the minimum number should not be less than 4 groups.

8. The method for evaluating the high performance of the sand-mud composite fracture of the beach-bar sand reservoir according to claim 1, It is characterized in that In step 3, based on the maintained physical model, an acoustic emission monitoring scheme for the fracturing process is designed, a fracturing test is carried out on a fracturing test machine, and the pump pressure curve and acoustic emission ringing events during the test are recorded throughout the process.

9. The method for evaluating the high pressure fracture of the sand-mud composite of the beach-bar sand reservoir according to claim 8, It is characterized in that In step 3, the acoustic emission monitoring scheme refers to the relevant settings such as the placement of the acoustic emission sensor on the surface of the physical model, the initial wave velocity of the model, and the sampling frequency.

10. The method for evaluating the high pressure fracture of the sand-mud composite of the beach-bar sand reservoir according to claim 1, It is characterized in that In step 4, the time axis of the pump pressure curve and the acoustic emission ringing event are aligned, the first rupture pressure point of the pressure curve is taken as the time initial point, the acoustic emission event after the time initial point is taken as the effective event, and the three-dimensional coordinate positioning of the effective event is performed.

11. The method for evaluating the high pressure fracture of the sand-mud composite of the beach-bar sand reservoir according to claim 10, It is characterized in that In step 4, the initial time point is used to filter out discrete acoustic emission events that occur inside the model before the occurrence of fracturing cracks. These acoustic emission events are not fracture events, but initial defect damage points induced by fracturing fluid loss and pump pressure disturbance, which can increase the statistical error of fracture height.

12. The method for evaluating the high performance of the sand-mud composite fracture of the beach-bar sand reservoir according to claim 1, It is characterized in that In step 5, nonlinear fitting is performed on multiple groups of fracture height monitoring data, generally a negative exponential relationship fitting, so as to establish a mathematical relationship between the fracture height of the hydraulic fracture and the test factors.

13. The method for evaluating the high pressure fracture of the sand-mud composite of the beach-bar sand reservoir according to claim 12, It is characterized in that In step 5, according to the vertical coordinates of the located acoustic emission events in the sandstone reservoir and the mudstone interlayer, the longitudinal extension height of the fracture is calculated, and the mathematical relationship between the fracture height of the physical model and the experimental factors such as mudstone thickness, mud content, and construction parameters is established, as shown in formula (1). Where: y is the height of the fracture in the physical model; x is the mudstone thickness, mud content and pump pressure parameters of the physical model; A i , B i and C i (i=1) is the fitting coefficient.

14. The method for evaluating the high performance of the sand-mud composite fracture of the beach-bar sand reservoir according to claim 1, It is characterized in that In step 6, according to the similar proportions of the physical model and the in-situ engineering scale model, the parameters of the three designed geometric dimensions, namely, fracture height, mudstone thickness, and displacement, are enlarged and restored, and nonlinear fitting between the fracture height data and the experimental factors is performed based on the enlarged and restored data.

15. The method for evaluating the high pressure fracture of the sand-mud composite of the beach-bar sand reservoir according to claim 14, It is characterized in that In step 6, according to the geometric similarity principle in the similarity principle, the engineering geological restoration is carried out to further establish the mathematical relationship between the actual fracture height of the hydraulic fracturing and the mudstone thickness, mud content, and construction parameters at the in-situ scale, as shown in formula (2): Where: F h is the actual formation fracture height; ω is mudstone thickness, mud content, and construction parameters; A i , B i and C i (i=2) is the fitting coefficient.

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