Gas reservoir water invasion degree prediction method based on early production dynamics

Abstract

The invention relates to the technical field of gas reservoir dynamic analysis, in particular to a gas reservoir water invasion degree prediction method based on early production dynamics, which comprises the following steps of: dividing a gas reservoir water invasion degree grading graph, and calculating and determining gas reservoir dynamic geological reserves through a Blasingame method and linear regression according to gas reservoir production dynamics data; then, the dimensionless apparent pressure PFD and the recovery degree Rg of the closed gas reservoir are calculated, a PFD-Rg relation scatter diagram of the gas reservoir is drawn, and analysis data points in the PFD-Rg relation scatter diagram of the gas reservoir are evaluated and removed based on the basic characteristic that the energy of the stratum water body of the elastic water-drive gas reservoir is limited; based on the reserved effective analysis data points, determining a gas reservoir PFD-Rg relation curve by adopting a linear regression analysis method; and finally, comparing with a gas reservoir water invasion degree grading graph to determine the gas reservoir water invasion degree. Through the prediction method, the gas reservoir water invasion degree can be determined when the production data does not reflect the water invasion influence stage, the gas reservoir water invasion damage is weakened, and the gas reservoir recovery efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of gas reservoir dynamic analysis, and in particular to a method for predicting the water invasion degree of a gas reservoir based on early production dynamics. Background Art

[0002] Most gas reservoirs have formation water, and gas reservoir development is even more "water-scarce". When a gas reservoir produces formation water, the gas well production capacity and gas reservoir recovery rate will drop sharply, causing a significant increase in the difficulty and cost of gas reservoir development. Therefore, in order to improve the overall development efficiency of gas reservoirs, it is necessary to identify water invasion and predict the degree of water invasion in gas reservoirs based on early production dynamics before obvious water invasion damage occurs in gas reservoirs, formulate a gas reservoir water invasion prevention and control plan in advance, determine the timing of implementing water invasion prevention and control measures, and provide a basis for deploying gas reservoir water invasion control work.

[0003] At present, there are four main methods for identifying water invasion and predicting the extent of water invasion in gas reservoirs: based on the production water-gas ratio rise curve, based on the apparent geological reserves and cumulative gas production curve, based on the production indicator curve, and based on the unstable well test pressure derivative curve of the gas well. However, due to the obvious hysteresis effect of water invasion on the dynamic development of gas reservoirs, the application effect of the above commonly used methods is not good, and it is difficult to meet the demand for early warning of water invasion in gas reservoirs. Summary of the invention

[0004] The purpose of the present invention is to provide a method for predicting the degree of water invasion in gas reservoirs based on early production dynamics, so as to solve the problem that the water invasion has an obvious lag effect on the dynamics of gas reservoir development, but the application effect of the gas reservoir water invasion identification and water invasion degree prediction methods in the prior art is poor and it is difficult to meet the demand for gas reservoir water invasion early warning.

[0005] To achieve the above object, the present invention provides a method for predicting the degree of water invasion of a gas reservoir based on early production performance, the method comprising a gas reservoir water invasion degree classification diagram, the gas reservoir water invasion degree classification diagram is based on PFD~R g The classification is based on the degree of deviation from the relationship curve.

[0006] The method for predicting the degree of water invasion of gas reservoirs based on early production performance comprises the following steps:

[0007] S1: Based on the gas reservoir production dynamic data, the Blasingame method is used to calculate and determine the dynamic geological reserves of the gas reservoir through linear regression;

[0008] S2: Calculate the dimensionless apparent pressure PFD and recovery rate R of the closed gas reservoir based on the formation pressure monitoring data and production performance of the gas reservoir g , and draw the gas reservoir PFD~R g Relationship scatter plot;

[0009] S3: Based on the basic characteristic of limited formation water energy in elastic water drive gas reservoirs, the analysis data points in the scatter diagram of the PFD-Rg relationship of the gas reservoir are evaluated and invalid analysis data points are eliminated;

[0010] S4: Based on the valid analysis data points retained in step S3, a linear regression analysis method is used to calculate and determine the gas reservoir PFD~R g Relationship curve;

[0011] S5: The gas reservoir PFD~R calculated and determined in step S4 g The relationship curve is compared with the gas reservoir water invasion degree classification diagram to determine the gas reservoir water invasion degree.

[0012] Among them, in step S1, the formula for calculating and determining the dynamic geological reserves of the gas reservoir is:

[0013]

[0014] Where: X is the material balance pseudo time, Y is the normalized pseudo pressure, B is the linear regression intercept, G is the dynamic geological reserves of the gas reservoir, C is ti is the comprehensive compression coefficient of the gas reservoir in the initial state.

[0015] Among them, in step S3, the basic characteristic of the limited formation water energy of the elastic water-driven gas reservoir is that when the formation water energy weakens, the water-driven gas reservoir no longer continuously deviates from the closed gas reservoir, but gradually approaches the closed gas reservoir.

[0016] Among them, in step S3, the evaluation screening condition is: when the difference Δ=PHD-(1-Rg) starts to decrease continuously, the analysis data point will be invalid and should be eliminated.

[0017] The present invention provides a method for predicting the degree of water invasion of gas reservoirs based on early production performance, which divides the gas reservoir water invasion degree classification diagram, calculates and determines the dynamic geological reserves of the gas reservoir by linear regression based on the production performance data of the gas reservoir using the Blasingame method, and calculates the dimensionless apparent pressure PFD and the recovery degree R of the closed gas reservoir based on the gas reservoir formation pressure monitoring data and production performance. g , and draw the gas reservoir PFD~R g The relationship scatter diagram is shown in Figure 2. Based on the basic characteristics of limited formation water energy in elastic water drive gas reservoirs, the PFD~R g The data points in the relationship scatter plot are evaluated, and invalid analysis data points are eliminated. Based on the retained valid analysis data points, the linear regression analysis method is used to calculate and determine the gas reservoir PFD~R gThe relationship curve is compared with the gas reservoir water invasion degree classification diagram to determine the gas reservoir water invasion degree. Through the above prediction method, the gas reservoir water invasion degree can be determined before the production data reflects the impact of water invasion. Early gas reservoir water invasion control can save precious time and reduce the damage of gas reservoir water invasion, thereby improving the gas reservoir development effect and increasing the gas reservoir recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 This is a gas reservoir water invasion degree classification diagram provided by the present invention.

[0020] Figure 2 It is a flow chart of the steps of a method for predicting the degree of water invasion of a gas reservoir based on early production performance provided by the present invention.

[0021] Figure 3 This is a gas reservoir early production dynamic data diagram of gas reservoir A provided by the present invention.

[0022] Figure 4 It is a gas reservoir production indication curve diagram of gas reservoir A provided by the present invention.

[0023] Figure 5 It is a gas reservoir dynamic geological reserve analysis diagram based on the Blasingame method of gas reservoir A provided by the present invention.

[0024] Figure 6 It is a scatter diagram of the relationship between PFD and Rg of gas reservoir A provided by the present invention.

[0025] Figure 7 It is a gas reservoir PFD-Rg relationship curve diagram of gas reservoir A provided by the present invention.

[0026] Figure 8 This is a diagram showing the results of the gas reservoir water invasion analysis of gas reservoir A provided by the present invention.

[0027] Fig. 9 This is a dynamic data diagram of the production of gas reservoir A throughout its life cycle provided by the present invention. DETAILED DESCRIPTION

[0028] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0029] See also Figure 1 and Figure 2 The present invention provides a method for predicting the degree of water invasion of a gas reservoir based on early production performance. The method for predicting the degree of water invasion of a gas reservoir based on early production performance includes a gas reservoir water invasion degree classification diagram. The gas reservoir water invasion degree classification diagram is based on PFD~R g The classification is based on the degree of deviation from the relationship curve.

[0030] In this embodiment, compared with the closed gas reservoir, there is a water-driven gas reservoir with formation water. During the development of the gas reservoir, the intrusion of formation water will produce a certain degree of energy supplement to the gas reservoir, such as the attached Figure 1 As shown in the figure, the PFD-Rg relationship curve of the water-driven gas reservoir will gradually deviate from the relationship curve of the closed gas reservoir, and the stronger the energy of the water body connected to the gas reservoir, the greater the deviation of the PFD-Rg relationship curve, and gradually approach the relationship of the rigid water-driven gas reservoir. When the deviation is ≤5%, the gas reservoir has no obvious water invasion; when 5% < deviation ≤15%, the gas reservoir has weak water invasion; when 15% < deviation ≤30%, the gas reservoir has moderate water invasion; when 30% < deviation ≤50%, the gas reservoir has strong water invasion; when the deviation is >50%, the gas reservoir has super strong water invasion. g The definition and calculation formulas are detailed in the existing patent publication number CN116752948B, so they are not described in detail.

[0031] Furthermore, the method for predicting the degree of water invasion of a gas reservoir based on early production performance comprises the following steps:

[0032] S1: Based on the gas reservoir production dynamic data, the Blasingame method is used to calculate and determine the dynamic geological reserves of the gas reservoir through linear regression;

[0033] S2: Calculate the dimensionless apparent pressure PFD and recovery rate R of the closed gas reservoir based on the formation pressure monitoring data and production performance of the gas reservoir g , and draw the gas reservoir PFD~R g Relationship scatter plot;

[0034] S3: Based on the basic characteristic of limited formation water energy in elastic water drive gas reservoirs, the analysis data points in the scatter diagram of the PFD-Rg relationship of the gas reservoir are evaluated and invalid analysis data points are eliminated;

[0035] S4: Based on the valid analysis data points retained in step S3, a linear regression analysis method is used to calculate and determine the gas reservoir PFD~R g Relationship curve;

[0036] S5: The gas reservoir PFD~R calculated and determined in step S4 g The relationship curve is compared with the gas reservoir water invasion degree classification diagram to determine the gas reservoir water invasion degree.

[0037] In this embodiment, a gas reservoir water invasion degree classification diagram is divided, and the dynamic geological reserves of the gas reservoir are calculated and determined by linear regression using the Blasingame method based on the gas reservoir production performance data, and the dimensionless apparent pressure PFD and the recovery degree R of the closed gas reservoir are calculated based on the gas reservoir formation pressure monitoring data and production performance. g , and draw the gas reservoir PFD~R g The relationship scatter diagram is shown in Figure 2. Based on the basic characteristics of limited formation water energy in elastic water drive gas reservoirs, the PFD~R g The data points in the relationship scatter plot are evaluated, and invalid analysis data points are eliminated. Based on the retained valid analysis data points, the linear regression analysis method is used to calculate and determine the gas reservoir PFD~R g The relationship curve is compared with the gas reservoir water invasion degree classification diagram to determine the gas reservoir water invasion degree. Through the above prediction method, the gas reservoir water invasion degree can be determined before the production data reflects the impact of water invasion. Early gas reservoir water invasion control can be carried out to gain precious time and reduce the damage caused by gas reservoir water invasion, thereby improving the gas reservoir development effect and increasing the gas reservoir recovery rate.

[0038] Among them, in step S1, the formula for calculating and determining the dynamic geological reserves of the gas reservoir is:

[0039]

[0040] Where: X is the material balance pseudo time, Y is the normalized pseudo pressure, B is the linear regression intercept, G is the dynamic geological reserves of the gas reservoir, C is ti is the comprehensive compression coefficient of the gas reservoir in the initial state.

[0041] Among them, in step S3, the basic characteristic of the limited formation water energy of the elastic water-driven gas reservoir is that when the formation water energy weakens, the water-driven gas reservoir no longer continuously deviates from the closed gas reservoir, but gradually approaches the closed gas reservoir.

[0042] Among them, in step S3, the evaluation screening condition is: when the difference Δ=PHD-(1-Rg) starts to decrease continuously, the analysis data point will be invalid and should be eliminated.

[0043] See also Figures 3 to 9 , the specific embodiment is:

[0044] Take gas reservoir A as the gas reservoir to be predicted. Gas reservoir A is located in the Sichuan Basin and was officially put into production on January 22, 2010. The initial formation pressure of the gas reservoir is 54.68MPa, the formation temperature is 120℃, the gas saturation is 0.806, the average porosity is 6%, and the effective permeability is 9.5mD. The formation pressure test of the gas reservoir is shown in Appendix 1. The early production data of the gas reservoir are shown in Appendix Figure 3 The gas reservoir production indicator curve is shown in the attached Figure 4 As shown in the attached Figure 3 It can be seen that the gas reservoir is producing normally and the water production is stable. Figure 4 It can be seen that the gas reservoir production index curve has obvious linear characteristics and no upward trend, so the gas reservoir production dynamics show no obvious water invasion characteristics.

[0045] Table 1 Gas reservoir formation pressure test results

[0046] Test Date Pressure, MPa 2010 / 2 / 22 53.8425 2010 / 3 / 24 53.8119 2011 / 3 / 25 50.0238 2011 / 12 / 4 46.6791 2012 / 7 / 8 43.3401 2012 / 8 / 24 42.7411

[0047] According to the dynamic data of gas reservoir production, the Blasingame method was used to calculate the dynamic geological reserves of the gas reservoir to be 1.176 billion cubic meters through linear regression. The linear regression results are shown in the attached Figure 5 ;

[0048] According to the formation pressure monitoring data and production performance of the gas reservoir, the dimensionless apparent pressure PFD and the recovery degree R of the closed gas reservoir are calculated. g , and draw the gas reservoir PFD~R g Relationship scatter plot, here gas reservoir PFD~R g The relationship scatter plot is as attached Figure 6 As shown;

[0049] Based on the basic characteristics of limited formation water energy in elastic water drive gas reservoirs, the PFD~R g In the relationship scatter plot, the difference Δ between the analysis data points and the theoretical value of the closed gas reservoir has not started to decrease continuously, that is, all the data points are valid analysis data points;

[0050] Based on the effective analysis data points retained in the above steps, the linear regression analysis method is used to calculate and determine the gas reservoir PFD~R g Relationship curve, here gas reservoir PFD~R g The relationship curve is as follows Figure 7 As shown;

[0051] The gas reservoir PFD~R g Relationship curve, with Figure 1 Compared with the gas reservoir water invasion degree classification diagram in the gThe relationship curve falls between the offset degree of 30% and 50%, that is, the water invasion degree of the gas reservoir is strong. The analysis results of the water invasion degree of the gas reservoir are as follows: Figure 8 shown.

[0052] In this embodiment, as shown in the attached Fig. 9 As shown in the figure, the gas reservoir began to produce formation water on June 10, 2013, and was severely flooded on August 4, 2015. It was produced by draining water and producing gas until it was shut down due to flooding on July 6, 2017. The gas reservoir recovery rate was only 44%, and the gas reservoir development effect was far lower than that of the gas reservoir where water invasion control work was deployed in advance. Therefore, it is very important to predict the degree of water invasion of gas reservoirs based on early production performance and carry out water invasion control work in a timely manner to ensure the economic benefits of gas reservoir development.

[0053] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for predicting water invasion degree of gas reservoirs based on early production performance, characterized in that: It includes a gas reservoir water invasion degree classification diagram, wherein the gas reservoir water invasion degree classification diagram is based on PFD~R g The classification is based on the degree of deviation from the relationship curve.

2. The method for predicting the degree of water invasion of gas reservoirs based on early production performance according to claim 1, characterized in that: The steps include: S1: Based on the gas reservoir production dynamic data, the Blasingame method is used to calculate and determine the dynamic geological reserves of the gas reservoir through linear regression; S2: Calculate the dimensionless apparent pressure PFD and recovery rate R of the closed gas reservoir based on the formation pressure monitoring data and production performance of the gas reservoir g , and draw the gas reservoir PFD~R g Relationship scatter plot; S3: Based on the basic characteristic of limited formation water energy in elastic water drive gas reservoirs, the analysis data points in the scatter diagram of the PFD-Rg relationship of the gas reservoir are evaluated and invalid analysis data points are eliminated; S4: Based on the valid analysis data points retained in step S3, a linear regression analysis method is used to calculate and determine the gas reservoir PFD~R g Relationship curve; S5: The gas reservoir PFD~R calculated and determined in step S4 g The relationship curve is compared with the gas reservoir water invasion degree classification diagram to determine the gas reservoir water invasion degree.

3. The method for predicting the degree of water invasion of gas reservoirs based on early production performance according to claim 2, characterized in that: In step S1, the formula for calculating and determining the dynamic geological reserves of the gas reservoir is: Where: X is the material balance pseudo time, Y is the normalized pseudo pressure, B is the linear regression intercept, G is the dynamic geological reserves of the gas reservoir, C is ti is the comprehensive compression coefficient of the gas reservoir in the initial state.

4. The method for predicting the degree of water invasion of gas reservoirs based on early production performance according to claim 3, characterized in that: In step S3, the basic characteristic of the limited formation water energy of the elastic water drive gas reservoir is that when the formation water energy weakens, the water drive gas reservoir no longer continuously deviates from the closed gas reservoir, but gradually approaches the closed gas reservoir.

5. The method for predicting the degree of water invasion of gas reservoirs based on early production performance according to claim 4, characterized in that: In step S3, the evaluation screening condition is: when the difference Δ=PHD-(1-Rg) starts to decrease continuously, the analysis data point will be invalid and should be eliminated.

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