A method for quantitatively interpreting multipoint tracing technology curves of water injection and production well pattern

Abstract

The present application belongs to the field of oil and gas field development, and relates to a water-straight combined injection-production well pattern multi-point tracer technology curve quantitative interpretation method. The water-straight combined injection-production well pattern multi-point tracer technology curve quantitative interpretation method is as follows: the flow of the tracer in the water-straight combined injection-production well pattern is classified and equivalent; the classified and equivalent results are classified respectively; the tracer production curve interpretation model of each classification of the water-straight combined injection-production well pattern is established; the tracer production curve fitting and solving are carried out through the tracer production curve interpretation model of the water-straight combined injection-production well pattern, the fracture quantitative parameters between different injection wells and different fracturing sections of the horizontal well are obtained, and the quantitative interpretation of the fracture network of the water-straight combined injection-production well pattern is completed. The present application reduces the error caused by the artificial input parameters in the previous simulation method, thereby effectively guaranteeing the field practicability, accuracy and operability.

Description

Technical Field

[0001] This invention pertains to oil and gas field development and relates to a quantitative interpretation method for multi-point tracing technology curves in a combined water injection and production well network. Background Technology

[0002] Tight oil reservoirs are widely distributed in my country and have gradually become the main battleground for oil and gas field exploration and development. Due to the characteristics of tight oil reservoirs, such as low permeability, poor reservoir space, high cement content, and poor sorting, horizontal wells and large-scale hydraulic fracturing are often used to establish artificial fracture networks for effective development. Water injection is then used to replenish formation energy to ensure continuous and normal production of oil wells. With large-scale hydraulic fracturing, the artificial fractures around horizontal wells have become increasingly complex and varied.

[0003] Accurately characterizing the connectivity structure in tight oil-water integrated injection-production well networks and establishing a simple, effective, and comprehensive simplified model that reflects the tight oil reservoir's water-water integrated injection-production well network is key to improving injection-production efficiency. Inspired by inter-well tracers in vertical wells (vertical well injection-production well networks are often centered around water injection wells, requiring only the injection of tracers into the central water injection well), for areas developed by water-water integrated injection-production well networks, different water-soluble tracers can be added to different water injection wells around horizontal wells within the region. Each water-soluble tracer enters the formation with the injected water and circulates within the underground well network. Samples are taken from each horizontal well to analyze the production of different tracers, which can be used to analyze information such as the water inflow direction of the horizontal wells in the region (well network control can be disregarded).

[0004] This invention aims to establish a simplified mathematical model for multi-point tracing of water-direct injection-production well networks in tight oil reservoirs based on the above-mentioned ideas, to achieve quantitative interpretation of complex tracer curves, and to use the interpretation results to solve complex fracture network information, thereby deepening the understanding of complex fracture networks in tight oil reservoirs. This is of great significance for providing theoretical basis data for the formulation of technical measures such as improving water drive and water injection development in this type of reservoir, and thus improving development efficiency. Summary of the Invention

[0005] This invention addresses the problem that existing methods for interpreting tracer curves between vertical wells cannot explain tracer methods in combined water-water injection and production well networks. It proposes a quantitative interpretation method for multi-point tracer curves in combined water-water injection and production well networks.

[0006] The technical solution of this invention is as follows: (I) A method for quantitative interpretation of curves in a multi-point tracing technology for a combined water injection and production well network, the method being as follows: Classify the flow of tracers in a combined water injection and production well network into equivalent categories; The equivalent classification results are classified separately; Establish interpretation models for tracer production curves of water-direct injection-production well networks of various categories; By fitting and solving the tracer production curve of the water-injection and horizontal well network interpretation model, quantitative parameters of fractures between different injection wells and different fracturing sections of horizontal wells are obtained, thus completing the quantitative interpretation of the fracture network of the water-injection and horizontal well network.

[0007] (II) A method for quantitative interpretation of curves in a multi-point tracing technology for a combined water injection and production well network, the method being as follows: S1: The flow of tracer in the water-direction integrated injection-production well network is divided into the flow of tracer in the fracture network between horizontal and vertical wells and the flow of tracer in the wellbore of horizontal wells; the flow of tracer in the wellbore of horizontal wells is equivalent to the tracer flow at a constant concentration boundary and the one-dimensional steady flow. S2: Ignore tracer flow in the horizontal wellbore; The flow of tracers in the fracture network between horizontal and vertical wells is divided into single-fracture mode and multi-fracture mode. S3: Establish an interpretation model for the tracer production curve of the water-direct injection-production well network; including an interpretation model for the tracer production curve of the water-direct injection-production well network in single fracture mode and an interpretation model for the tracer production curve of the water-direct injection-production well network in multi fracture mode. S4: By fitting and solving the tracer production curve of the water-direction injection-production well network using the tracer production curve interpretation model, quantitative parameters of fractures between different injection wells and different fracturing sections of horizontal wells are obtained. The quantitative parameters of fractures are used to complete the quantitative interpretation of the fracturing network of the water-direction injection-production well network.

[0008] The interpretation model for the tracer production curve of the single fracture mode water-direct injection-production well network is as follows: In the formula: c j (t) is the interpretation model of tracer production curve of water-direct injection-production well network under single fracture mode; c j0 The initial mass concentration of the tracer injected into injection well j, in mg / L; f j The injection water distribution coefficient is dimensionless. V j Let m be the injection volume of the water injection well. 3 ; D ji Let be the equivalent diameter, in meters, of the fracture strip between injection well j and horizontal well i. α ji Hydrodynamic dispersion, in meters (m); t is the time from the start of tracer injection, d; Q j Let m be the average daily water injection rate of injection well j. 3 / d; l ji The equivalent length, in meters, from injection well j to the i-th fracturing section of the horizontal well; x i Let m be the distance from the fracturing section i of the horizontal well to the horizontal wellhead. D l Let m be the hydrodynamic dispersion coefficient. 2 / d; u2 is the flow velocity at the outlet of the horizontal well, in m / d; t0 is the time, in seconds, for the tracer to penetrate from the formation into the horizontal wellbore. N j The number of fractured sections in a horizontal well is dimensionless.

[0009] The interpretation model for the tracer production curve of the multi-fracture mode water-direct injection-production well network is as follows: In the formula: c j '(t) represents the explanatory model for the tracer production curve of the multi-fracture mode water-direct injection-production well network; R ji The flow resistance of different fracturing sections in injection wells and horizontal wells is given in mPa·s / m. 3 .

[0010] The goal of fitting and solving the problem is to minimize the overall fitting error of the tracer production curve; the objective function F is: In the formula: F is the objective function; C i (t) represents the tracer concentration value (mg / L) of injection well i at time t calculated by the method of this invention; C i * (t) represents the tracer concentration value of injection well i at time t, obtained by field measurement in the mine, in mg / L; n represents the actual number of days (d) that tracers in injection well i are monitored in the production well.

[0011] Among them, the quantitative parameters of the fracture include the equivalent diameter D of the fracture band between injection well j and horizontal well i. ji Equivalent length l of different fracturing sections in water injection wells and horizontal wells ji The flow resistance R of different fracturing sections in water injection wells and horizontal wells ji, .

[0012] Among them, the PSO algorithm is used when fitting the tracer production curve of the water-direction combined injection and production well network tracer production curve interpretation model.

[0013] The technical advantages of this invention are as follows: This invention simplifies the complex fracture network in tight oil-water integrated injection-production well networks into two modes: single fracture and multi-fracture. Corresponding tracer production curve interpretation models are established for the connectivity characteristics of the two different fracture modes, avoiding the shortcomings of previous models that conflated inter-well tracers in vertical wells and inter-well tracers in integrated water-water injection-production well networks. This makes the model more targeted to actual field conditions. The established curve fitting and solution methods can achieve the equivalent diameter D of the fracture. ji Equivalent length l ji Flow resistance R ji Quantitative characterization of well connectivity parameters; with the goal of minimizing the overall fitting error of the tracer production curve interpretation model of the water-direction injection-production well network, the PSO algorithm is used to fit and solve the tracer production curve interpretation model of the water-direction injection-production well network. This method is simpler to operate and has higher computational accuracy, reducing the errors caused by the need for manual parameter input in previous simulation methods. As a result, the practicality, accuracy and operability of the mine are effectively guaranteed. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the well location distribution of the water-direct injection-production well network in Experiment Example 1 of the present invention.

[0015] Figure 2 The tracer production curves are shown for the four water injection wells in Experiment Example 1 of this invention.

[0016] Figure 3 The measured and fitted curves of tracer concentration in injection well 1-1 are shown in this embodiment of the invention.

[0017] Figure 4 The measured and fitted curves of tracer concentration in injection wells 1-2 in this embodiment of the invention are shown.

[0018] Figure 5 The measured and fitted curves of tracer concentration in injection wells 1-3 in this embodiment of the invention are shown.

[0019] Figure 6 The measured and fitted curves of tracer concentration in injection wells 1-4 in this embodiment of the invention are shown. Detailed Implementation

[0020] Multi-point tracing technology was used to monitor the water-direct injection-production well network in a tight reservoir. The well location map is as follows: Figure 1 As shown.

[0021] Four different tracers were added to injection wells 1-1, 1-2, 1-3, and 1-4, respectively. Samples were taken from the horizontal production wells to test the concentrations of the different tracers, and tracer production curves were plotted based on the test results. The tracer production curves for the four injection wells are shown below. Figure 2As shown.

[0022] from Figure 2 It can be seen that injection well 1-1 is a single fracture mode, and the tracer production curve interpretation model of the single fracture mode water-direction injection-production well network is used for interpretation; injection wells 1-2, 1-3 and 1-4 are multi-fracture modes, and the tracer production curve interpretation model of the multi-fracture mode water-direction injection-production well network is used for interpretation.

[0023] The explanatory model for the tracer production curve of the single fracture mode water-direct injection-production well network is as follows: For injection well 1-1, the above-mentioned single fracture mode water-direction combined injection-production well network tracer production curve interpretation model is used for interpretation.

[0024] The interpretation model for tracer production curves in multi-fracture mode combined injection and production well network is as follows: For injection wells 1-2, 1-3, and 1-4, the tracer production curve interpretation model of the multi-fracture mode water-direction combined injection-production well network mentioned above was used for interpretation.

[0025] By fitting and solving the tracer production curve of the combined water injection and production well network using an interpretation model, the equivalent diameter D of the fracture band between injection well j and horizontal well i was obtained. ji Equivalent length l of different fracturing sections in water injection wells and horizontal wells ji The flow resistance R of different fracturing sections in water injection wells and horizontal wells ji， The results are shown in Tables 1-4: Table 1. Data obtained from fitting injection well 1-1 <![CDATA[flow resistance R ji > 0.71 0.72 0.86 0.52 0.44 <![CDATA[equivalent diameter D ji > 0.30 0.34 0.26 0.28 0.29 <![CDATA[equivalent length l ji > 173.41 124.40 194.92 237.86 329.42 Table 2. Data obtained from fitting injection wells 1-2 <![CDATA[Flow resistance R ji > 0.10 0.50 0.41 0.61 0.11 <![CDATA[equivalent diameter D ji > 0.33 0.18 0.14 0.15 0.43 <![CDATA[equivalent length l ji > 182.72 171.33 286.46 227.91 126.52 Table 3 shows the data obtained from fitting injection wells 1-3. <![CDATA[flow resistance R ji > 0.77 0.92 0.72 0.71 0.57 <![CDATA[equivalent diameter D ji > 0.47 0.33 0.47 0.30 0.33 <![CDATA[equivalent length l ji > 150 180.94 100 200.00 300.01 Table 4. Data obtained from fitting injection wells 1-4 <![CDATA[flow resistance R ji > 0.94 0.98 0.89 0.90 0.84 <![CDATA[equivalent diameter D ji > 0.41 0.45 0.65 0.55 0.53 <![CDATA[equivalent length l ji > 100 100 100 115 112 .

[0026] Model validation: Among them, when the tracer production curve interpretation model of the water-direct injection-production well network fits the tracer production curve using the PSO algorithm, the objective is to minimize the overall fitting error of the tracer production curve; the objective function F is:

[0027] Figures 3-6 This is a comparison chart of the measured tracer concentration curves of the four injection wells in Experiment Example 1 of this invention and the fitted curve of this invention. Error analysis was performed on the fitting results of this invention, and the results are shown in Table 5. It can be seen that the absolute errors of the tracer concentration output by this invention compared to the sum of the concentrations in injection wells 1-1, 1-2, 1-3, and 1-4 are 1.05, 2.27, 0.16, and 0.06 mg / L, respectively, and the relative errors are 28.77%, 34.34%, 6.96%, and 2.58%, respectively. The average relative error of the four wells is less than 25%, and the fitting results meet the requirements of field engineering.

[0028] Table 5 Error Analysis

Claims

1. A method for quantitative interpretation of curves in a multi-point tracing technology for combined water injection and production well networks, characterized in that: The method is as follows: S1: The flow of tracer in the water-direction integrated injection-production well network is divided into the flow of tracer in the fracture network between horizontal and vertical wells and the flow of tracer in the wellbore of horizontal wells; the flow of tracer in the wellbore of horizontal wells is equivalent to the tracer flow at a constant concentration boundary and the one-dimensional steady flow. S2: Ignore tracer flow in the horizontal wellbore; The flow of tracers in the fracture network between horizontal and vertical wells is divided into single-fracture mode and multi-fracture mode. S3: Establish an interpretation model for the tracer production curve of the water-direct injection-production well network; including an interpretation model for the tracer production curve of the water-direct injection-production well network in single fracture mode and an interpretation model for the tracer production curve of the water-direct injection-production well network in multi fracture mode. S4: By fitting and solving the tracer production curve of the water-injection-production well network through the interpretation model of the tracer production curve, quantitative parameters of fractures between different injection wells and different fracturing sections of horizontal wells are obtained. The quantitative interpretation of the fracturing network of the water-injection-production well network is completed through the quantitative parameters of fractures. The interpretation model for the tracer production curve of the single fracture mode water-direct injection-production well network is as follows: ； In the formula: c j (t) is the interpretation model of tracer production curve of water-direct injection-production well network under single fracture mode; c j0 The initial mass concentration of the tracer injected into injection well j, in mg / L; f j The injection water distribution coefficient is dimensionless. V j Let m be the injection volume of the water injection well. 3 ; D ji Let be the equivalent diameter, in meters, of the fracture strip between injection well j and horizontal well i. α ji Hydrodynamic dispersion, in meters (m); t is the time from the start of tracer injection, d; Q j Let m be the average daily water injection rate of injection well j. 3 / d; l ji Let J be the equivalent length from injection well j to the i-th fracturing section of the horizontal well, in meters. x i Let i be the distance from the horizontal well fracturing section i to the horizontal wellhead, in meters. D l Let m be the hydrodynamic dispersion coefficient. 2 / d; u2 is the flow velocity at the outlet of the horizontal well, in m / d; t0 is the time, in seconds, for the tracer to penetrate from the formation into the horizontal wellbore. N j The number of fractured sections in a horizontal well is dimensionless. The interpretation model for the tracer production curve of the multi-fracture mode water-direct injection-production well network is as follows: ； In the formula: c j ’ (t) is the interpretation model for tracer production curves of the multi-fracture mode water-direct injection-production well network; R ji The flow resistance is given in mPa·s / m³ for different fracturing sections of injection wells and horizontal wells.

2. The method for quantitative interpretation of curves using multi-point tracing technology for combined water injection and production well networks according to claim 1, characterized in that: The fitting and solution process aims to minimize the overall fitting error of the tracer production curve; the objective function F is: ； In the formula: F is the objective function; C i (t) represents the tracer concentration value calculated for injection well i at time t, in mg / L; C i * (t) represents the tracer concentration value of injection well i at time t, obtained by field measurement in the mine, in mg / L; n represents the actual number of days (d) that tracers in injection well i are monitored in the production well.

3. The method for quantitative interpretation of curves using multi-point tracing technology for combined water injection and production well networks according to claim 2, characterized in that: The quantitative parameters of the fracture include the equivalent diameter D of the fracture band between injection well j and horizontal well i. ji Equivalent length l of different fracturing sections in water injection wells and horizontal wells ji The flow resistance R of different fracturing sections in water injection wells and horizontal wells ji, .

4. The method for quantitative interpretation of curves using multi-point tracing technology for combined water injection and production well networks according to claim 3, characterized in that: The PSO algorithm is used when fitting the tracer production curve of the water-direction combined injection-production well network tracer production curve interpretation model.

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