Quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length

Abstract

The invention provides a quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length, which comprises the following steps of: 1, collecting basic data of a water injection well, and calculating underflow pressure Pw of the water injection well; 2, a Pw / Q-1 / Q water injection indication curve before pressure flooding is drawn, and the average reservoir pressure Pe before pressure flooding water injection is calculated; 3, drawing a pressure-driving water injection Hall curve, and revealing a change rule of a skin coefficient S *; step 4, calculating half-fracture length Xf / 2 values of different pressure-driving water injection stages; and 5, drawing a real-time expansion and future development trend prediction map of the half-seam length Xf / 2 of pressure flooding water injection. According to the quantitative characterization method for real-time expansion and future prediction of the pressure-driving water injection crack length, the influence of discontinuous pressure-driving operation time, injection parameter change and the like can be eliminated, the real-time expansion rule of the crack length in the pressure-driving water injection process is analyzed for the first time, the future development trend of the crack is predicted according to the real-time expansion rule, and the blank of research in the field is filled.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development, and in particular to a quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length. Background Art

[0002] Pressure-driven water injection is an emerging technology for improving oil recovery in low-permeability reservoirs. This technology involves injecting water at high pressure and high flow rates into injection wells. This overpressure causes rock fractures, forming cracks. The injected water then filters deep into the reservoir pores along the cracks, rapidly replenishing formation energy and expanding the impact range. Extensive laboratory core experiments and production practices have demonstrated that fracture length is a key factor influencing the effectiveness of pressure-driven water injection. Because actual fracture length measurement is difficult, numerical simulation methods are commonly used to calculate fracture length. These methods primarily include traditional hydraulic fracturing simulations and numerical simulations based on fluid-structure interaction models.

[0003] Traditional hydraulic fracturing simulation methods are suitable for addressing the rapid expansion of fractures. Field microseismic monitoring technology shows that pressure-driven fractures exhibit uniform expansion, significantly different from the long fracture formation process under hydraulic fracturing. The research results, "Practical and Insights into Pressure-Drive Development Technology in Shengli Oilfield," were published in the journal Oil and Gas Geology and Recovery, Vol. 3, 2023, pp. 87-93. This method is not suitable for determining the length of fractures generated by pressure-driven water injection and cannot accurately simulate the expansion and extension of fractures during pressure-driven water injection.

[0004] The pressure-driven numerical simulation method based on the fluid-solid coupling model has just started. Its core technology is to build a physical model of reservoir pressure-driven water injection. The main research methods include: based on the assumption of slightly compressible fluid and Griffith's material fracture theory, establishing an expansion cycle model for fracture expansion water injection and a fracture half-fracture length expansion increment model. The research results "Research on Fracture Extension Laws in Fracture Extension Water Injection Technology" were published in "Petroleum Drilling Technology" Issue 6, 2011, Pages 82-85; based on Biot's linear elastic contact theory, establishing the constitutive equation between fluid and matrix, The virtual unit method is used to discretely solve the rock stress and strain field. The research results "Numerical simulation method of pressure-driven water injection based on virtual unit method and damage model" were published in "Computational Physics" in the first issue of 2023, P81~P90; based on the dynamic crack extension law during pressure-driven development, the crack extension model is organically coupled with the oil-water two-phase seepage model of tight oil reservoirs, and a pressure-driven water injection model is established. The finite difference method is used to solve it. The research results "Establishment and Application of Pressure-Driven Dynamic Fracture Model in Tight Oil Reservoirs" were published in "Special Oil and Gas Reservoirs" in the fourth issue of 2023, P87~P95.

[0005] In the Chinese patent application with application number 202010876538.4, a method and device for numerical simulation of water injection growth fractures of embedded discrete fractures are disclosed. The method includes: based on geological parameters and engineering parameters, using dynamic theoretical analysis to establish a dynamic model of fracture initiation, extension and closure; the dynamic model of fracture initiation, extension and closure is iteratively coupled with a reservoir numerical simulation program with EDFM fracture modeling function to simulate the evolution process of water injection growth fracture initiation, extension and closure.

[0006] In the Chinese patent application with application number 202211189021.3, a method, device and medium for numerical simulation of fluid-solid coupling of pressure-driven water injection in low-permeability reservoirs are disclosed. The method includes: obtaining the physical parameters of seepage and rock mechanics parameters of the low-permeability reservoir; establishing a geometric model of the low-permeability reservoir, and meshing the geometric model using a structured method; for the high-pressure injection of pressure-driven agents into the injection well and the shut-in stage of the production well, the phase field method is used to accurately describe the slow expansion process of the cracks, and a fluid-solid coupling model of the fracturing crack expansion is established; for the production stage of the injection well and water injection into the production well, a water-oil two-phase flow model is established to calculate the cumulative oil production and recovery rate of the low-permeability reservoir.

[0007] In the Chinese patent application with application number 202211290051.3, a device and method for testing the distribution morphology of pressure-driven fractures in low-permeability reservoirs are disclosed. The method includes: using a 3D printer to produce a pressure-driven model of a reservoir containing fractures and using a testing device to conduct a water drive experiment on it to obtain the fracture distribution morphology before and after pressure-driven water injection.

[0008] The above existing technologies are unable to calculate the fracture length in real time during the pressure-driven water injection process and cannot simulate the future dynamic expansion changes of the fracture length, failing to solve the technical problems we want to solve. To this end, we have invented a new quantitative characterization method for the real-time expansion and future prediction of the fracture length of pressure-driven water injection. Summary of the Invention

[0009] The purpose of the present invention is to provide a quantitative characterization method for the real-time expansion and future prediction of pressure-driven water injection crack length, which uses mathematical deduction and deduction to solve the reservoir seepage model for analysis and solves the deterministic problem of the real-time length of cracks and their future dynamic expansion changes during pressure-driven water injection.

[0010] The object of the present invention can be achieved by the following technical measures: a quantitative characterization method for the real-time expansion and future prediction of the length of a pressure-driven water injection crack, the quantitative characterization method for the real-time expansion and future prediction of the length of a pressure-driven water injection crack comprising:

[0011] Step 1: Collect basic data of injection wells and calculate the bottom flow pressure P of injection wells w ;

[0012] Step 2: Draw the pressure drive front P w / Q-1 / Q water injection indicator curve, calculate the average reservoir pressure P before pressure drive water injection e ;

[0013] Step 3: Draw the pressure-driven water injection Hall curve to reveal the skin factor S * the law of change;

[0014] Step 4: Calculate the half-fracture length X at different pressure-driven water injection stages. f / 2 value;

[0015] Step 5: Draw the half crack length X of the pressure drive water injection f / 2Real-time expansion and future development trend forecast chart.

[0016] The purpose of the present invention can also be achieved by the following technical measures:

[0017] In step 1, basic information such as reservoir properties, downhole tubing, and production data are collected to calculate the bottomhole flowing pressure during production before pressure drive and during pressure drive water injection.

[0018] In step 1, according to the wellhead oil pressure P of the water injection well, o and water injection rate q, calculate the bottom flow pressure P of the injection well w The formula is:

[0019] P w =P o +P H -P f (1)

[0021] Where, P w -Bottomhole pressure of water injection well, MPa; P o -Injection wellhead oil pressure, MPa; P H -Hydrostatic pressure in the injection well, = ρ w gH, MPa; ρ w -Injection water density, 10 3 kg / m 3 ; g-gravitational acceleration, 9.8m / s 2 ; H-well depth, m; P f -Pressure loss along the water injection string, MPa.

[0022] In step 1, the pressure loss along the injection string is P f Calculation formula:

[0023] P f =Cq 2 H (2)

[0025] Where, q-water injection rate, m 3 / h; C-coefficient related to pipe diameter.

[0026] In step 2, the linear fit P w / Q-1 / Q water injection indicator curve, its slope is the average reservoir pressure before pressure drive water injection, that is, the horizontal axis is 1 / Q and the vertical axis is P w / Q;P w / Q is a linear function of 1 / Q, and the slope of this function curve is the average reservoir pressure P around the injection zone. e :

[0027] P w / Q=P e / Q+b (3)

[0029] Where, Q-daily water injection volume, m 3 / d;P e - average reservoir pressure, MPa; b- intercept, constant.

[0030] In step 3, the average reservoir pressure P before pressure injection obtained in step 2 is used. e , and combined with the daily pressure-driven water injection data obtained in step 1 and the corresponding bottom hole flowing pressure data, draw the pressure-driven water injection Hall curve; the Hall curve form:

[0031]

[0032] in:

[0033]

[0034]

[0035]

[0036]

[0037] Where, ΔP-pressure drive water injection pressure difference, =P w -P e , MPa; τ, t-pressure drive water injection time and cumulative pressure drive water injection time, d; μ-pressure drive injection water viscosity, mPa·s; B-pressure drive injection water volume coefficient; K-reservoir permeability, 10 -3 μm 2 ;h-reservoir thickness, m; W i -Cumulative water injection volume, including before pressure drive, m 3 ; r e -Radius of the pressure-driven waterflooding front, m; r w -Wellbore radius, m; S *-skin coefficient; φ-reservoir porosity; S or -Reservoir residual oil saturation.

[0038] In step 3, the Hall curve is drawn using the numerical integration method, with the horizontal axis being ∑Q and the vertical axis being

[0039]

[0040] In the curve, yes Linear function; using linear fitting method, obtain the slope M of the curve H data;

[0041] According to M H formula:

[0042] M H =α[ln(r e / r w )-0.5+S * ] (9)

[0044] Where M H -Hall curve slope, constant;

[0045] Then, the skin coefficient S during the pressure-driven water injection process is obtained. * change:

[0046]

[0047] Linear fitting of the Hall curve to obtain its slope M H The skin coefficient S of the wellbore at different pressure-driven water injection stages is calculated using formulas (7) and (10). * The real-time change value of the pressure-driven water injection displacement front radius r is calculated using formula (7) e When the cumulative water injection volume W of the previous moment is used i data.

[0048] In step 4, calculate the effective wellbore radius r wa :

[0049] r wa =r w exp(-S * ) (11)

[0051] Where r wa -Effective radius of the wellbore, m;

[0052] r w -Wellbore radius, m;

[0053] S* -Skin factor;

[0054] Pressure drive water injection half seam length X f / 2Quantitative representation form:

[0055] X f / 2=r wa (12)

[0057] Where, X f / 2-pressure drive water injection half-slit length, m;

[0058] Use the wellbore skin factor S obtained in step 3 * Real-time data, combined with formula (11) (12), calculate the half crack length X in different pressure drive water injection stages. f / 2 value.

[0059] In step 5, according to different pressure-driven water injection speeds, select the corresponding M H The value, combined with formulas (7)(10)(11)(12), can be used to simulate and calculate the future development trend of pressure-driven crack length:

[0060] X f / 2=FW i 0.5 (13)

[0062] Where, F-coefficient,

[0063] In step 5, the half crack length X obtained in step 4 is used to f / 2 real-time data, and combined with formula (13), predict the half-slit length X when the cumulative pressure-driven water injection volume reaches a certain limit value under the set pressure-driven water injection speed in the next stage f / 2 data, and draw the pressure drive water injection half crack length X f / 2Real-time expansion and future development trend forecast chart.

[0064] The purpose of the present invention can also be achieved through the following technical measures: a quantitative characterization system for the real-time expansion of pressure-driven water injection crack length and the prediction of future development trends. The quantitative characterization system for the real-time expansion of pressure-driven water injection crack length and the prediction of future development trends adopts a quantitative characterization method for the real-time expansion of pressure-driven water injection crack length and the prediction of future development trends to analyze the real-time expansion law of the crack length during the pressure-driven water injection process and predict the future development trend of the crack.

[0065] In order to solve the problem that the existing technology cannot calculate the crack length in real time and cannot simulate the future dynamic expansion of the crack length during the pressure-driven water injection process, the present invention proposes a quantitative characterization method for the real-time expansion and future prediction of the pressure-driven water injection crack length. First, the historical production information of the water injection well and the real-time injection data during the pressure-driven process are used to calculate the average reservoir pressure P before the pressure-driven water injection. e and the bottom hole flow pressure P during pressure drive water injection w Secondly, based on the analysis of the pressure-driven water injection Hall curve, the slope M H The reservoir physical change information contained in the data is used to obtain the real-time expansion law of the pressure-driven water injection fracture length, and then predict the future development degree of the fracture.

[0066] Compared with the prior art, the present invention has the following advantages:

[0067] The water injection P used in the present invention w The / Q-1 / Q indicator curve method is an improvement on the existing water injection indicator curve method. It can effectively eliminate the phenomenon of unclear linear relationship between water injection pressure and water injection volume. The calculated reservoir average pressure result is highly accurate. The independently derived pressure loss P along the water injection string is f The fitting formula is based on the hydraulic friction calculation formula under various flow states. Unlike the Blasius empirical formula commonly used in mining practice, it has the advantages of a wide range of applicability and high calculation accuracy. The Hall curve analysis method can eliminate the effects of discontinuous pressure-driven operation time and changes in injection parameters. For the first time, the real-time expansion law of crack length during pressure-driven water injection is analyzed, and the future development trend of cracks is predicted based on this, filling the research gap in this field.

[0068] Based on actual production data from pressure-driven water injection, this paper provides an economical, convenient, and reliable pressure-driven water injection analysis method for reservoir development and engineering professionals. By revealing the real-time expansion pattern of pressure-driven water injection fracture length, it can make timely and accurate simulations and predictions of its future development trends. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 A flowchart of a specific embodiment of the quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection fracture length according to the present invention;

[0070] Figure 2 A schematic diagram of the geological structure of the well area in a specific embodiment 1 of the present invention;

[0071] Figure 3 The pressure-driven front P is drawn in a specific embodiment 1 of the present invention. w / Q-1 / Q water injection indication curve diagram;

[0072] Figure 4A Hall curve diagram of pressure-driven water injection drawn in a specific embodiment 1 of the present invention;

[0073] Figure 5 The half crack length X of the pressure-driven water injection drawn in a specific embodiment 1 of the present invention f / 2Real-time expansion and future development trend forecast chart;

[0074] Figure 6 A schematic diagram of the geological structure of the well area in a specific embodiment 2 of the present invention;

[0075] Figure 7 The pressure-driven front P is drawn in a specific embodiment 2 of the present invention. w / Q-1 / Q water injection indication curve diagram;

[0076] Figure 8 P before recovery pressure driving drawn in a specific embodiment 2 of the present invention w / Q-1 / Q water injection indication curve diagram;

[0077] Figure 9 A Hall curve diagram of pressure-driven water injection drawn in a specific embodiment 2 of the present invention;

[0078] Figure 10 The pressure-driven water injection half-slit length X drawn in a specific embodiment 2 of the present invention f / 2Real-time expansion and future development trend forecast chart;

[0079] Figure 11 A schematic diagram of the geological structure of the well area in a specific embodiment 3 of the present invention;

[0080] Figure 12 The pressure-driven front P is drawn in a specific embodiment 3 of the present invention. w / Q-1 / Q water injection indication curve diagram;

[0081] Figure 13 A Hall curve diagram of pressure-driven water injection drawn in a specific embodiment 3 of the present invention;

[0082] Figure 14 The half crack length X of the pressure-driven water injection drawn in a specific embodiment 3 of the present invention f / 2Real-time expansion and future development trend forecast chart. DETAILED DESCRIPTION

[0083] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0084] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations and / or combinations thereof.

[0085] like Figure 1 As shown, Figure 1 The following is an analysis flow chart of a quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length includes the following steps:

[0086] Step 101: Collect basic data such as reservoir properties, downhole tubing, and production data, and calculate the bottomhole flowing pressure during production before pressure drive and during pressure drive water injection.

[0087] According to the wellhead oil pressure P o and water injection rate q, calculate the bottom flow pressure P of the injection well w The formula is:

[0088] P w =P o +P H -P f (1)

[0090] Where, P w -Bottomhole pressure of water injection well, MPa; P o -Injection wellhead oil pressure, MPa; P H -Hydrostatic pressure in the injection well, = ρ w gH, MPa; ρ w -Injection water density, 10 3 kg / m 3 ; g-gravitational acceleration, 9.8m / s 2 ; H-well depth, m; P f -Pressure loss along the water injection string, MPa.

[0091] Among them, the pressure loss along the water injection string is P f Calculation formula:

[0092] P f =Cq 2 H (2)

[0094] Where, q-water injection rate, m 3 / h; C-coefficient related to pipe diameter. The C values ​​of Φ60.3, Φ73.0, and Φ88.9 oil pipes are 4.89×10 -6 , 1.69×10 -6 , 5.85×10 -7 .

[0095] Step 102: Using the water injection volume before pressure drive obtained in step 101 and the corresponding bottom hole flow pressure data, draw the P before pressure drive. w / Q-1 / Q water injection curve. Linear fitting P w / Q-1 / Q water injection curve, its slope is the average reservoir pressure P before pressure drive water injection e .

[0096] The horizontal axis is 1 / Q and the vertical axis is P w / Q;P w / Q is a linear function of 1 / Q, and the slope of this function curve is the average reservoir pressure P around the injection zone. e :

[0097] P w / Q=P e / Q+b (3)

[0099] Where, Q-daily water injection volume, m 3 / d;P e - average reservoir pressure, MPa; b- intercept, constant.

[0100] Step 103: Using the average reservoir pressure P before pressure injection obtained in step 102 e , and draw a pressure-driven water injection Hall curve by combining the pressure-driven water injection daily data obtained in step 101 and the corresponding bottom hole flowing pressure data.

[0101] Hall curve form:

[0102]

[0103] in:

[0104]

[0105]

[0106]

[0107] Where, ΔP-pressure drive water injection pressure difference, =P w -P e, MPa; τ, t-pressure drive water injection time and cumulative pressure drive water injection time, d; μ-pressure drive injection water viscosity, mPa·s; B-pressure drive injection water volume coefficient; K-reservoir permeability, 10 -3 μm 2 ;h-reservoir thickness, m; W i -Cumulative water injection volume (including before pressure drive), m 3 ; r e -Radius of the pressure-driven waterflooding front, m; r w -Wellbore radius, m; S * -skin coefficient; φ-reservoir porosity; S or -Reservoir residual oil saturation.

[0108] The Hall curve is drawn using the numerical integration method, with the horizontal axis being ∑Q and the vertical axis being

[0109]

[0110] In the curve, yes A linear function of . Using the linear fitting method, the slope of the curve M is obtained H data.

[0111] According to M H formula:

[0112] M H =α[ln(r e / r w )-0.5+S * ] (9)

[0114] Where M H -Hall curve slope, constant.

[0115] Then, the skin coefficient S during the pressure-driven water injection process is obtained. * change:

[0116]

[0117] Linear fitting of the Hall curve to obtain its slope M H The skin coefficient S of the wellbore at different pressure-driven water injection stages is calculated using formulas (7) and (10). * The real-time change value of . Use formula (7) to calculate the pressure drive water injection displacement front radius r e When the cumulative water injection volume W of the previous moment is used i data.

[0118] Step 104: Use the wellbore skin coefficient S obtained in step 103 *Real-time data, combined with formula (11) (12), calculate the half crack length X in different pressure drive water injection stages. f / 2 value.

[0119] Calculate the effective radius r of the wellbore wa :

[0120] r wa =r w exp(-S * ) (11)

[0122] Where r wa -Effective radius of the wellbore, m.

[0123] Pressure drive water injection half seam length X f / 2Quantitative representation form:

[0124] X f / 2=r wa (12)

[0126] Where, X f / 2-pressure-driven water injection half-slit length, m.

[0127] Step 105: Use the pressure-driven water injection half-slit length X obtained in step 104 to calculate the water injection half-slit length X. f / 2 real-time data, and combined with formula (13), predict the half-slit length X when the cumulative pressure-driven water injection volume reaches a certain limit value under the set pressure-driven water injection speed in the next stage f / 2 data, and draw the pressure drive water injection half crack length X f / 2Real-time expansion and future development trend forecast chart.

[0128] The horizontal axis is The vertical axis is X f / 2.

[0129] According to different pressure drive water injection speeds, select the corresponding M H The value, combined with formulas (7)(10)(11)(12), can be used to simulate and calculate the future development trend of pressure-driven crack length:

[0130]

[0131] Where, F-coefficient,

[0132] The following are several specific embodiments of the present invention:

[0133] Example 1:

[0134] like Figure 2 As shown, Figure 2This is a schematic diagram of the geological structure of the well area where specific embodiment 1 is located.

[0135] In step 101, basic data such as reservoir properties, downhole tubing, and production data of a specific embodiment are collected to calculate the bottom hole flowing pressure during production before pressure drive and the bottom hole flowing pressure during pressure drive water injection.

[0136] For example, the water injection pipe diameter is Φ73.0 and the pipe string depth is 3360m.

[0137] Using formulas (1) and (2), the monthly water injection data for the 12 months before pressure drive is taken to calculate the bottom hole pressure data during production before pressure drive. The daily water injection data for pressure drive is used to calculate the bottom hole pressure data during pressure drive water injection. The process proceeds to step 102.

[0138] In step 102, the water injection volume before pressure drive and the corresponding bottom hole pressure data obtained in step 101 are used to draw the P before pressure drive. w / Q-1 / Q water injection indication curve, such as Figure 3 shown.

[0139] exist Figure 3 Middle, pressure drive front P w The linear regression equation of the / Q-1 / Q water injection curve is:

[0140] P w / Q=61.8370·1 / Q+0.8000,R 2 =0.9990

[0141] Among them, R 2 -Correlation coefficient.

[0142] Therefore, the average reservoir pressure before pressure drive water injection is 61.8 MPa. The process proceeds to step 103.

[0143] In step 103, the average reservoir pressure P before pressure injection obtained in step 102 is used. e , and draw the pressure-driven water injection Hall curve by combining the pressure-driven water injection daily data obtained in step 101 and the corresponding bottom hole flow pressure data, as shown in FIG. Figure 4 shown.

[0144] exist Figure 4 In the above example, the curve is piecewise linearly fitted according to the variation law of the second-order derivative of Hall integral. The regression equations after fitting are:

[0145] Section I: Y = 0.01920X, R 2 =0.9902

[0146] Section II: Y = 0.004281X + 18.2946, R 2=0.9872

[0147] Section III: Y = 0.02044X - 403.5584, R 2 =0.9872

[0148] Section IV: Y = 0.01493X - 225.8480, R 2 =0.9991

[0149] Section V: Y = 0.01962X - 417.4409, R 2 =0.9975

[0150] Section VI: Y = 0.02292X - 586.8964, R 2 =0.9981

[0151] Where,

[0152] The slope value of the above linear equation is the slope value M of the Hall curve at different pressure-driven water injection stages. H .

[0153] For example, the reservoir thickness is 18.7m, the reservoir porosity is 18%, and the reservoir permeability is 8.2×10 -3 μm 3 , the residual oil saturation of the reservoir is 0.23, the wellbore radius is 0.06985m, and the cumulative water injection volume before pressure drive is 5.8716×10 4 m 3 .

[0154] Calculate the skin coefficient S of the pressure-driven water injection wellbore at a certain moment * When the cumulative water injection volume W of the previous moment is i Substitute the data into formula (7) to calculate the pressure drive water injection front radius r e , together with the slope M of the pressure-driven water injection Hall curve corresponding to this moment H Substitute the values ​​into formula (10) to calculate the wellbore skin coefficient S at this moment * Calculate the wellbore skin coefficient S during the entire pressure drive water injection phase. * After the value is obtained, the process proceeds to step 104.

[0155] In step 104, the wellbore skin coefficient S obtained in step 103 is used * Real-time data, combined with formula (11) (12), calculate the half crack length X in different pressure drive water injection stages. f / 2 value. The process proceeds to step 105.

[0156] Step 105: Use the pressure-driven water injection half-slit length X obtained in step 104 to calculate the water injection half-slit length X. f / 2 real-time data, combined with formula (13), can predict the half-slit length X when the cumulative pressure-driven water injection volume reaches a certain limit value under the set pressure-driven water injection speed in the next stage. f / 2 data.

[0157] For example, the actual pressure drive water injection volume is 5.8464×10 5 m 3 When the pressure drive water injection half crack length X f / 2 is 10.80m. When the pressure drive injection speed is 0.4m 3 / min、0.6m 3 / min、0.8m 3 / min, the coefficient F values ​​in the calculation formula for predicting the future development of crack length are 0.03155, 0.06133, and 0.1488 respectively.

[0158] The actual pressure-driven water injection volume is 5.8464×10 5 m 3 When the pressure drive water injection speed is set to 0.6m 3 / min、0.8m 3 / min, predicted pressure drive water injection half crack length X f / 2 are 20.98m and 50.92m respectively.

[0159] When the cumulative water injection volume of pressure drive reaches 1.0×10 5 m 3 When the pressure drive water injection speed is set to 0.4m 3 / min、0.6m 3 / min、0.8m 3 / min, predicted pressure drive water injection half crack length X f / 2 are 12.57m, 24.43m and 59.24m respectively.

[0160] Draw the half crack length X of pressure drive water injection f / 2Real-time expansion and future development trend forecast chart, such as Figure 5 As shown. Figure 5 Middle, half seam length X f / 2 Pressure drive water injection speed and pressure drive water injection volume Influence.

[0161] Example 2:

[0162] like Figure 6 As shown, Figure 6 This is a schematic diagram of the geological structure of the well area where specific embodiment 2 is located.

[0163] In step 101, basic data such as reservoir properties, downhole tubing, and production data of a specific embodiment are collected to calculate the bottom hole flowing pressure during production before pressure drive and the bottom hole flowing pressure during pressure drive water injection.

[0164] For example, the water injection pipe diameter is Φ73.0 and the pipe string depth is 3132.62m.

[0165] Using formulas (1) and (2), we take the daily water injection data for the three months before the pressure drive and calculate the bottomhole pressure data during production before the pressure drive. Using the daily water injection data for the pressure drive, we calculate the bottomhole pressure data during the pressure drive water injection process. The process then proceeds to step 102.

[0166] In step 102, the water injection volume before pressure drive and the corresponding bottom hole pressure data obtained in step 101 are used to draw the P before pressure drive. w / Q-1 / Q water injection curve, such as Figure 7 shown.

[0167] exist Figure 7 Middle, pressure drive front P w The linear regression equation of the / Q-1 / Q water injection indicator curve is:

[0168] P w / Q=61.1723·1 / Q+0.05649,R 2 =0.9987

[0169] Therefore, the average reservoir pressure before pressure-driven water injection is 61.2 MPa.

[0170] For example, the cumulative water injection volume of pressure drive reaches 6819m 3 When the pump is stopped, normal water injection is resumed for a period of time, and then pressure drive is continued.

[0171] Using formulas (1) and (2), we take the daily water injection data from the period of normal water injection after pressure drive to calculate the bottomhole pressure data before the second pressure drive. We also use the daily water injection data from the second pressure drive to calculate the bottomhole pressure data during the second pressure drive water injection process. The process then proceeds to step 102.

[0172] In step 102, the water injection volume before the second pressure drive and the corresponding bottom hole pressure data obtained in step 101 are used to draw the P before the second pressure drive. w / Q-1 / Q water injection curve, such as Figure 8 shown.

[0173] exist Figure 8 In the middle, press the front P again w The linear regression equation of the / Q-1 / Q water injection indicator curve is:

[0174] P w / Q=61.2825·1 / Q+0.005765,R 2 =0.9997

[0175] Therefore, the average reservoir pressure before the second pressure drive water injection is 61.3 MPa.

[0176] The process enters step 103.

[0177] In step 103, the average reservoir pressure P before pressure injection obtained in step 102 is used. e , and draw the pressure-driven water injection Hall curve by combining the pressure-driven water injection daily data obtained in step 101 and the corresponding bottom hole flow pressure data, as shown in FIG. Figure 9 shown.

[0178] exist Figure 9 In the above example, the curve is piecewise linearly fitted according to the variation law of the second-order derivative of Hall integral. The regression equations after fitting are:

[0179] Section I: Y = 0.06634X, R 2 =1

[0180] Section II: Y = 0.008571X + 6.7403, R 2 =0.9588

[0181] Section III: Y = 0.005725X + 14.8476, R 2 =0.9993

[0182] Section IV: Y = 0.02630X - 135.1359, R 2 =0.9972

[0183] The slope value of the above linear equation is the slope value M of the Hall curve at different pressure-driven water injection stages. H .

[0184] For example, the reservoir thickness is 23.2m, the reservoir porosity is 15.5%, and the reservoir permeability is 28.5×10 -3 μm 3 , the residual oil saturation of the reservoir is 0.28, the wellbore radius is 0.06985m, and the cumulative water injection volume before pressure drive is 5.59708×10 4 m 3 The cumulative water injection volume before pressure drive restoration was 6.43264×10 4 m 3 .

[0185] Calculate the skin coefficient S of the pressure-driven water injection wellbore at a certain moment * When the cumulative water injection volume W of the previous moment is iSubstitute the data into formula (7) to calculate the pressure drive water injection front radius r e , together with the slope M of the pressure-driven water injection Hall curve corresponding to this moment H Substitute the values ​​into formula (10) to calculate the wellbore skin coefficient S at this moment * Calculate the wellbore skin coefficient S during the entire pressure drive water injection phase. * After the value is obtained, the process proceeds to step 104.

[0186] In step 104, the wellbore skin coefficient S obtained in step 103 is used * Real-time data, combined with formula (11) (12), calculate the half crack length X in different pressure drive water injection stages. f / 2 value. The process proceeds to step 105.

[0187] Step 105: Use the pressure-driven water injection half-slit length X obtained in step 104 to calculate the water injection half-slit length X. f / 2 real-time data, combined with formula (13), can predict the half-slit length X when the cumulative pressure-driven water injection volume reaches a certain limit value under the set pressure-driven water injection speed in the next stage. f / 2 data.

[0188] For example, the actual pressure drive water injection volume is 1.98257×10 5 m 3 When the pressure drive water injection half crack length X f / 2 is 0.005m. When the pressure drive water injection speed is 0.6m 3 / min、0.8m 3 / min, the coefficient F values ​​in the calculation formula for predicting the future development of crack length are 0.009816 and 0.02725 respectively.

[0189] The actual pressure-driven water injection volume is 1.98257×10 5 m 3 When the pressure drive water injection speed is set to 0.6m 3 / min、0.8m 3 / min, predicted pressure drive water injection half crack length X f / 2 are 2.70m and 7.50m respectively.

[0190] When the cumulative water injection volume of pressure drive reaches 5.0×10 4 m 3 When the pressure drive water injection speed is set to 0.6m 3 / min、0.8m 3 / min, predicted pressure drive water injection half crack length X f / 2 are 3.19m and 8.87m respectively.

[0191] Draw the half crack length X of pressure drive water injectionf / 2Real-time expansion and future development trend forecast chart, such as Figure 10 As shown. Figure 10 Middle, half seam length X f / 2 Pressure drive water injection rate q and cumulative pressure drive water injection volume Influence.

[0192] Example 3:

[0193] like Figure 11 As shown, Figure 11 This is a schematic diagram of the geological structure of the well area where specific embodiment 3 is located.

[0194] In step 101, basic data such as reservoir properties, downhole tubing, and production data of a specific embodiment are collected to calculate the bottom hole flowing pressure during production before pressure drive and the bottom hole flowing pressure during pressure drive water injection.

[0195] For example, the water injection pipe diameter is Φ88.9 and the pipe string depth is 3079.09m.

[0196] Using formulas (1) and (2), the daily water injection data from August 21, 2020, to September 11, 2020, before pressure drive, are taken to calculate the bottomhole flow pressure data during production before pressure drive. The bottomhole flow pressure data during pressure drive water injection are calculated using the daily water injection data. The process proceeds to step 102.

[0197] In step 102, the water injection volume before pressure drive and the corresponding bottom hole pressure data obtained in step 101 are used to draw the P before pressure drive. w / Q-1 / Q water injection curve, such as Figure 12 shown.

[0198] exist Figure 12 Middle, pressure drive front P w The linear regression equation of the / Q-1 / Q water injection indicator curve is:

[0199] P w / Q=50.083·1 / Q+0.0328,R 2 =0.9976

[0200] Therefore, the average reservoir pressure before pressure drive water injection is 50.1 MPa. The process proceeds to step 103.

[0201] In step 103, the average reservoir pressure P before pressure injection obtained in step 102 is used. e , and draw the pressure-driven water injection Hall curve by combining the pressure-driven water injection daily data obtained in step 101 and the corresponding bottom hole flow pressure data, as shown in FIG. Figure 13 shown.

[0202] exist Figure 13In the figure, the curve is piecewise linearly fitted according to the variation law of the second-order derivative of Hall integral, and the regression equations after fitting are

[0203] Section I: Y = 0.01001X, R 2 =0.9984

[0204] Section II: Y = 0.006236X + 6.1772, R 2 =1

[0205] Section III: Y = 0.01028X - 13.4267, R 2 =0.9991

[0206] Section IV: Y = 0.01091X - 26.1139, R 2 =0.9978

[0207] Section V: Y = 0.01374X - 112.1459, R 2 =0.9992

[0208] Section VI: Y = 0.01103X - 7.5575, R 2 =0.9913

[0209] The slope value of the above linear equation is the slope value M of the Hall curve at different pressure-driven water injection stages. H .

[0210] For example, the reservoir thickness is 7m, the reservoir porosity is 17.5%, and the reservoir permeability is 69.8×10 -3 μm 3 , the residual oil saturation of the reservoir is 0.22, the wellbore radius is 0.06985m, and the cumulative water injection volume before pressure drive is 1.8956×10 4 m 3 .

[0211] Calculate the skin coefficient S of the pressure-driven water injection wellbore at a certain moment * When the cumulative water injection volume W of the previous moment is i Substitute the data into formula (7) to calculate the pressure drive water injection front radius r e , together with the slope M of the pressure-driven water injection Hall curve corresponding to this moment H Substitute the values ​​into formula (10) to calculate the wellbore skin coefficient S at this moment * Calculate the wellbore skin coefficient S during the entire pressure drive water injection phase. * After the value is obtained, the process proceeds to step 104.

[0212] In step 104, the wellbore skin coefficient S obtained in step 103 is used *Real-time data, combined with formula (11) (12), calculate the half crack length X in different pressure drive water injection stages. f / 2 value. The process proceeds to step 105.

[0213] Step 105: Use the pressure-driven water injection half-slit length X obtained in step 104 to calculate the water injection half-slit length X. f / 2 real-time data, combined with formula (13), can predict the half-slit length X when the cumulative pressure-driven water injection volume reaches a certain limit value under the set pressure-driven water injection speed in the next stage. f / 2 data.

[0214] For example, the actual pressure drive water injection volume is 4.3967×10 5 m 3 When the pressure drive water injection half crack length X f / 2 is 4.64m. When the pressure drive water injection speed is 1.2m 3 / min、1.5m 3 / min、1.6m 3 / min, the coefficient F values ​​in the calculation formula for predicting the future development of crack length are 0.009152, 0.01875, and 0.06692 respectively.

[0215] The actual pressure-driven water injection volume is 4.3967×10 5 m 3 When the pressure drive water injection speed is set to 1.2m 3 / min、1.6m 3 / min, predicted pressure drive water injection half crack length X f / 2 are 2.27m and 16.56m respectively.

[0216] When the cumulative water injection volume of pressure drive reaches 1.0×10 5 m 3 When the pressure drive water injection speed is set to 1.2m 3 / min、1.5m 3 / min、1.6m 3 / min, predicted pressure drive water injection half crack length X f / 2 are 3.15m, 6.45m and 23.06m respectively.

[0217] Draw the half crack length X of pressure drive water injection f / 2Real-time expansion and future development trend forecast chart, such as Figure 14 As shown. Figure 14 Middle, half seam length X f / 2 Pressure drive water injection rate q and cumulative pressure drive water injection volume Influence.

[0218] The specific examples show that large-volume pressure injection will produce longer cracks, and the higher the pressure injection volume, the more conducive it is to the expansion of cracks. or Reservoir physical parameters such as the formation coefficient Kh determine the order of magnitude of the fracture length.

[0219] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art may modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features therein. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

[0220] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection fracture length, characterized by: The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection fracture length includes: Step 1: Collect basic data of injection wells and calculate the bottom flow pressure P of injection wells w ; Step 2: Draw the pressure drive front P w / Q-1 / Q water injection indicator curve, calculate the average reservoir pressure P before pressure drive water injection e ; Step 3: Draw the pressure-driven water injection Hall curve to reveal the skin factor S * the law of change; Step 4: Calculate the half-fracture length X at different pressure-driven water injection stages. f / 2 value; Step 5: Draw the half crack length X of the pressure-driven water injection f / 2Real-time expansion and future development trend forecast chart.

2. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to claim 1 is characterized in that: In step 1, basic information such as reservoir properties, downhole tubing, and production data are collected to calculate the bottomhole flowing pressure during production before pressure drive and during pressure drive water injection.

3. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to claim 2 is characterized in that: In step 1, according to the wellhead oil pressure P of the water injection well, o and water injection rate q, calculate the bottom flow pressure P of the injection well w The formula is: P w =P o +P H -P f (1) Where, P w -Bottomhole pressure of water injection well, MPa; P o -Injection wellhead oil pressure, MPa; P H -Hydrostatic pressure in the injection well, = ρ w gH, MPa; ρ w -Injection water density, 10 3 kg / m 3 ; g-gravitational acceleration, 9.8m / s 2 ; H-well depth, m; P f -Pressure loss along the water injection string, MPa.

4. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to claim 3 is characterized in that: In step 1, the pressure loss along the injection string is P f Calculation formula: P f =Cq 2 H (2) Where, q-water injection rate, m 3 / h; C-coefficient related to pipe diameter.

5. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to claim 1 is characterized in that: In step 2, the linear fit P w / Q-1 / Q water injection indicator curve, its slope is the average reservoir pressure before pressure drive water injection, that is, the horizontal axis is 1 / Q and the vertical axis is P w / Q;P w / Q is a linear function of 1 / Q, and the slope of this function curve is the average reservoir pressure P around the injection zone. e : P w / Q=P e / Q+b (3) Where, Q-daily water injection volume, m 3 / d;P e - average reservoir pressure, MPa; b- intercept, constant.

6. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to claim 1 is characterized in that: In step 3, the average reservoir pressure P before pressure injection obtained in step 2 is used. e , and combined with the daily pressure-driven water injection data obtained in step 1 and the corresponding bottom hole flowing pressure data, draw the pressure-driven water injection Hall curve; the Hall curve form: in: Where, ΔP-pressure drive water injection pressure difference, =P w -P e , MPa; τ, t-pressure drive water injection time and cumulative pressure drive water injection time, d; μ-pressure drive injection water viscosity, mPa·s; B-pressure drive injection water volume coefficient; K-reservoir permeability, 10 -3 μm 2 ;h-reservoir thickness, m; W i -Cumulative water injection volume, including before pressure drive, m 3 ; r e -Radius of the pressure-driven waterflooding front, m; r w -Wellbore radius, m; S * -skin coefficient; φ-reservoir porosity; S or -Reservoir residual oil saturation.

7. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to claim 6, characterized in that: In step 3, the Hall curve is drawn using the numerical integration method, with the horizontal axis being ∑Q and the vertical axis being In the curve, yes A linear function; using the linear fitting method, the slope of the curve M is obtained H data; According to M H formula: M H =α[ln(r e / r w )-0.5+S * ] (9) Where M H -Hall curve slope, constant; Then, the skin coefficient S during the pressure-driven water injection process is obtained. * change: Linear fitting of the Hall curve to obtain its slope M H The skin coefficient S of the wellbore at different pressure-driven water injection stages is calculated using formulas (7) and (10). * The real-time change value of the pressure-driven water injection displacement front radius r is calculated using formula (7) e When the cumulative water injection volume W of the previous moment is used i data.

8. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to claim 7, characterized in that: In step 4, calculate the effective wellbore radius r wa : r wa =r w exp(-S * ) (11) Where r wa -Effective radius of the wellbore, m; r w - well radius, m; S * -Skin factor; Pressure drive water injection half seam length X f / 2Quantitative representation form: X f / 2＝r wa (12) Where, X f / 2-pressure drive water injection half-slit length, m; Use the wellbore skin factor S obtained in step 3 * Real-time data, combined with formula (11) (12), calculate the half crack length X in different pressure drive water injection stages. f / 2 value.

9. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to claim 8, characterized in that: In step 5, according to different pressure-driven water injection speeds, select the corresponding M H The value, combined with formulas (7)(10)(11)(12), can be used to simulate and calculate the future development trend of pressure-driven crack length: X f / 2=FW i 0.5 (13) Where, F-coefficient, 10. The quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to claim 9, characterized in that: In step 5, the half crack length X obtained in step 4 is used to f / 2 real-time data, and combined with formula (13), predict the half-slit length X when the cumulative pressure-driven water injection volume reaches a certain limit value under the set pressure-driven water injection speed in the next stage f / 2 data, and draw the pressure drive water injection half crack length X f / 2Real-time expansion and future development trend forecast chart.

11. A quantitative characterization system for real-time expansion of pressure-driven water injection crack length and prediction of future development trends, characterized by: The quantitative characterization system for real-time expansion and future development trend prediction of pressure-driven water injection crack length adopts the quantitative characterization method for real-time expansion and future prediction of pressure-driven water injection crack length according to any one of claims 1 to 10 to analyze the real-time expansion law of crack length during pressure-driven water injection and predict the future development trend of cracks.

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