Method for evaluating exploitation potential of shale gas well with inter-well communication

Abstract

The invention discloses a mining potential evaluation method for a shale gas well with inter-well communication, and belongs to the technical field of oil and gas field development gas reservoir remaining reserve evaluation. The mining potential evaluation method comprises the following steps that S1, the final recoverable reserve of the gas well is comprehensively predicted through an adjacent well comparison method and a production dynamic analogy method; s2, calculating the recovery percentage of the gas well under the current formation pressure; s3, the shale gas well with the actually-measured pressure recovery formation pressure is obtained, and the relation between different recovery degrees and the formation pressure is obtained; s4, according to the flow pressure test results of the different test points, the change rule of the bottom hole flow pressure at different production time is obtained; s5, the gas well production pressure difference is calculated; s6, according to the production pressure difference obtained through calculation of the actual measurement well, the relation of the daily gas production rates under different production pressure differences is obtained; and S7, the theoretical daily gas production rate of the current well to be evaluated is calculated and compared with the actual daily gas production rate, the mining potential condition of the well to be evaluated is evaluated, and the problem that in the prior art, mining potential evaluation of the shale gas wells communicated between the wells is not accurate is solved.

Description

Technical Field

[0001] The invention relates to the technical field of research on application methods for evaluating remaining reserves of gas reservoirs in oil and gas field development, and in particular to a method for evaluating the exploitation potential of shale gas wells with inter-well communication. Background Art

[0002] Shale gas reservoirs have the characteristics of low porosity, low permeability, and high adsorption. Generally, they cannot be directly produced by natural fluid migration. Artificial transformation measures such as fracturing are required to improve the migration efficiency of shale gas from the gas reservoir to the bottom of the well. Shale gas wells usually adopt the well layout method of cluster horizontal wells, and the well spacing is generally 200~400 meters. During the fracturing process, it is possible to communicate with the surrounding pores and natural fractures, resulting in well connectivity. Well connectivity will cause the well-controlled reserves of the gas well to change with the production of itself and the connected wells, making it more difficult to evaluate the mining potential. At present, the evaluation methods for the mining potential of shale gas wells are mainly to evaluate the size of their remaining reserves. There are mainly analytical model method, numerical model method, material balance method, modern production decline method, empirical production decline method, etc. The first two methods involve many physical parameters, require large data volumes, complex models, and large calculation amount; material balance method, modern production decline method, and empirical production decline method are simple in form and small in calculation amount, but the calculation results are too affected by data fluctuations and cannot consider the existence of well connectivity.

[0003] At present, the unstable production analysis method commonly used in shale gas wells has high prediction accuracy, but it requires 25 parameters such as formation pressure, fracture half-length, matrix and fracture permeability, gas saturation, and compression coefficient. These parameters are usually difficult to obtain accurately and are not universal. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and provide a method for evaluating the exploitation potential of shale gas wells with inter-well connectivity. The present invention uses the current cumulative gas production to calculate the ultimate recoverable reserves (EUR) recovery degree, combines dynamic monitoring data, and fits the relationship curve between formation pressure and recovery degree and the relationship curve between bottom hole flow pressure and production time. The current production pressure difference of the gas well is obtained through the two curves, and the current theoretical daily gas production of the gas well is obtained through the relationship between the production pressure difference and the daily gas production. The difference between the theoretical and actual daily gas production is compared and calculated to evaluate the exploitation potential of the shale gas well.

[0005] The present invention is achieved through the following technical solutions: A method for evaluating the production potential of shale gas wells with inter-well connectivity comprises the following steps: S1. Comprehensively predict the ultimate recoverable reserves of gas wells by using the adjacent well comparison method and production performance analogy method EUR ; S2. Calculate the recovery degree of the gas well under the current formation pressure according to the result of step S1. R ; S3. Obtain a shale gas well with measured pressure recovery formation pressure, draw a relationship diagram between the pressure recovery formation pressure and the shale gas well recovery degree under this pressure, and use linear relationship fitting to obtain different recovery degrees. R and formation pressure P N relationship; S4. Obtain the bottom hole flow pressure according to the flow pressure test results at different measuring points P wf , draw the relationship between the bottom hole flow pressure and the production time of the shale gas well when the test flow pressure is tested, and use the power relationship to fit to get different production times t Bottom hole pressure P wf Laws of change; S5. According to steps S3 and S4, calculate the gas well production pressure difference △ P ; S6. According to the production pressure difference calculated by the actual well logging, the relationship between the production pressure difference and the daily gas production during the test is plotted, and the linear relationship is used for fitting to obtain the different production pressure differences △ P Daily gas production q relationship; S7. Calculate the theoretical daily gas production of the well to be evaluated according to steps S1-S6 q 理论 , and the actual daily gas production q 实际 Make comparisons and evaluate the production potential of the wells to be evaluated.

[0006] Further, in step S2, the recovery degree of the gas well under the current formation pressure R Satisfying the relationship (I): R=G p / EUR 10000 (Ⅰ), In the formula, R is the extraction degree, %; G p is the current cumulative gas production, 10 4 m 3 ; EUR is the ultimate recoverable reserves, 10 8 m 3 .

[0007] Further, in step S3, different recovery degrees R and formation pressure P N The satisfying formula (II) relationship: P N =-0.4538× R +36.478 (Ⅱ), In the formula, P N is the current formation pressure, MPa; R is the degree of recovery, %.

[0008] Further, in step S4, different production times t Bottom hole pressure P wf Satisfying the relationship (III): P wf =151.21× t -0.46 (III), In the formula, P wf is the bottom hole flowing pressure, MPa; t The number of days of production during testing, days.

[0009] Further, in step S5, the gas well production pressure difference Δ P Satisfies the following relationship (IV): △ P = P N - P wf (IV), In the formula, △ P is the production pressure difference, MPa; P N is the current formation pressure; P wf is the bottom hole flowing pressure, MPa.

[0010] Further, in step S6, different production pressure difference △ P and daily gas production q Satisfies the following relationship (V): q =0.737×△ P (V), In the formula, q is the daily gas production, ten thousand cubic meters per day; P is the production pressure difference, MPa.

[0011] Furthermore, in step S7, the theoretical daily gas production of the well to be evaluated is calculated through steps S1-S6. q 理论 , and the actual daily gas production q 实际 For comparative evaluation: likeq 理论 ×0.6≥ q 实际 , then the well has great exploitation potential; like q 理论 ×0.6< q 实际 < q 理论 , then the mining potential of the well is generally like q 理论 ≤ q 实际 , then the recovery potential of the well is small.

[0012] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. In the present invention, a new method for calculating the theoretical daily gas production of shale gas wells with inter-well connectivity is obtained by utilizing the relationship between formation pressure, bottom hole flow pressure, production degree, and production time. The relative error of the theoretical daily gas production calculated by the new method is 3.9%, while the error of the Duong production decline model is 10.7%. The new method has higher accuracy.

[0013] Second, in the present invention, the required parameters are clear, and the calculation process of the theoretical daily gas production of shale gas wells is simple. The theoretical daily gas production can be calculated through only 3 parameters and 6 steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the formation pressure-production degree fitting curve diagram in Example 2.

[0015] Figure 2 This is a fitting curve diagram of bottom hole flowing pressure-production time in Example 2.

[0016] Figure 3 This is a fitting curve diagram of daily gas production-production pressure difference in Example 2. DETAILED DESCRIPTION

[0017] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0018] Example 1 A method for evaluating the exploitation potential of shale gas wells with inter-well connectivity, which relates to the technical field of research on application methods for evaluating remaining reserves of gas reservoirs in oil and gas field development, comprises the following steps: S1. Comprehensively predict the ultimate recoverable reserves of gas wells by using the adjacent well comparison method and production performance analogy method EUR ; S2. Calculate the recovery degree of the gas well under the current formation pressure according to the result of step S1. R ; S3. Obtain a shale gas well with measured pressure recovery formation pressure, draw a relationship diagram between the pressure recovery formation pressure and the shale gas well recovery degree under this pressure, and use linear relationship fitting to obtain different recovery degrees. R and formation pressure P N relationship; S4. Obtain the bottom hole flow pressure according to the flow pressure test results at different measuring points P wf , draw the relationship between the bottom hole flow pressure and the production time of the shale gas well when the test flow pressure is tested, and use the power relationship to fit to get different production times t Bottom hole pressure P wf Laws of change; S5. According to steps S3 and S4, calculate the gas well production pressure difference △ P ; S6. According to the production pressure difference calculated by the actual well logging, the relationship between the production pressure difference and the daily gas production during the test is plotted, and the linear relationship is used for fitting to obtain the different production pressure differences △ P Daily gas production q relationship; S7. Calculate the theoretical daily gas production of the well to be evaluated according to steps S1-S6 q 理论 , and the actual daily gas production q 实际 Make comparisons and evaluate the production potential of the wells to be evaluated.

[0019] Example 2 To facilitate the public to understand the present solution, this embodiment takes a known well as an example, where the known well is a shale gas well that is connected to an adjacent well, to further illustrate the present solution.

[0020] A method for evaluating the production potential of shale gas wells with inter-well connectivity comprises the following steps: Step 1: The final recoverable reserves of the gas well are predicted by using the adjacent well comparison method and production performance analogy method. EUR .

[0021] Step 2: According to the result of step 1, calculate the recovery degree of the gas well under the current formation pressure R , the degree of extraction R Satisfies the following relationship (I): R=G p / EUR 10000 (Ⅰ), In the formula, R is the extraction degree, %;G p is the current cumulative gas production, 10 4 m 3 ; EUR is the ultimate recoverable reserves, 10 8 m 3 .

[0022] Step 3: Obtain shale gas wells with measured pressure recovery formation pressure, draw a relationship diagram between the pressure recovery formation pressure and the degree of shale gas well production under this pressure, and refer to Figure 1 , linear relationship was used for fitting, and different recovery degrees were obtained. R and formation pressure P N Satisfying the relationship in formula (II): P N =-0.4538× R +36.478 (Ⅱ), In the formula, P N is the current formation pressure, MPa; R is the degree of recovery, %.

[0023] According to formula (II), the current theoretical formation pressure can be calculated: P N .

[0024] Step 4: Obtain bottom hole flow pressure based on flow pressure test results at different measuring points P wf , draw a graph of the relationship between the bottom hole flowing pressure and the production time of the shale gas well when the test flowing pressure is tested, refer to Figure 2 , using the power relationship to fit, we can get different production times t Bottom hole pressure P wf The bottom hole pressure can be calculated by P wf value.

[0025] According to this method, different production time t Bottom hole pressure P wf Satisfying the relationship (III): P wf =151.21× t -0.46 (III), In the formula, P wf is the bottom hole flowing pressure, MPa; t The number of days of production during testing, days.

[0026] Step 5: According to step 3 and step 4, calculate the gas well production pressure difference △ P . Gas well production pressure difference △ P Satisfies the following relationship (IV): △ P = P N - P wf (IV), In the formula, △ P is the production pressure difference, MPa; P N is the current formation pressure; P wf is the bottom hole flowing pressure, MPa.

[0027] Step 6: According to the production pressure difference calculated by the actual well logging, the relationship between the production pressure difference and the daily gas production during the test is plotted. Figure 3 , linear relationship was used for fitting, and different production pressure differences were obtained. P Daily gas production q Satisfies the following relationship (V): q =0.737×△ P (V), In the formula, q is the daily gas production, ten thousand cubic meters per day; P is the production pressure difference, MPa.

[0028] Step 7: According to steps 1 to 6, calculate the theoretical daily gas production of the well to be evaluated. q 理论 , and the actual daily gas production q 实际 Compare and evaluate the mining potential of the well to be evaluated. The judgment method is as follows: like q 理论 ×0.6≥ q 实际 , then the well has great exploitation potential; like q 理论 ×0.6< q 实际 < q 理论 , then the recovery potential of the well is average; like q 理论 ≤ q 实际 , then the recovery potential of the well is small.

[0029] According to steps 1 to 6, the parameters and calculation results required for this scheme are shown in Table 1 below.

[0030] Table 1 In this embodiment, the calculation q 理论 ×0.6 is 33,400 cubic meters per day. The actual daily gas production of the gas well is 21,000 cubic meters per day. After comparison, it can be judged that the gas well has great potential for exploitation. This is consistent with the prediction result of the unstable production analysis method for the well, which shows that the method described in the present invention is reliable.

[0031] By drawing the double logarithmic curves of time and normalized production of the Duong model and this method to fit the actual well data, the error between the theoretical daily gas production calculated by this method and the actual well daily gas production is about 3.9%, which is more accurate than the result obtained by the Duong production decline model and the result is more reliable.

[0032] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for evaluating the production potential of shale gas wells with inter-well connectivity, characterized in that: The steps include: S1. Comprehensively predict the ultimate recoverable reserves of gas wells by using the adjacent well comparison method and production performance analogy method EUR ; S2. Calculate the recovery degree of the gas well under the current formation pressure according to the result of step S1. R ; S3. Obtain a shale gas well with measured pressure recovery formation pressure, draw a relationship diagram between the pressure recovery formation pressure and the shale gas well recovery degree under this pressure, and use linear relationship fitting to obtain different recovery degrees. R and formation pressure P N relationship; S4. Obtain the bottom hole flow pressure according to the flow pressure test results at different measuring points P wf , draw the relationship between the bottom hole flow pressure and the production time of the shale gas well when the test flow pressure is tested, and use the power relationship to fit to get different production times t Bottom hole pressure P wf Laws of change; S5. According to steps S3 and S4, calculate the gas well production pressure difference △ P ; S6. According to the production pressure difference calculated by the actual well logging, the relationship between the production pressure difference and the daily gas production during the test is plotted, and the linear relationship is used for fitting to obtain the different production pressure differences △ P Daily gas production q relationship; S7. Calculate the theoretical daily gas production of the well to be evaluated according to steps S1-S6 q 理论 , and the actual daily gas production q 实际 Make comparisons and evaluate the production potential of the wells to be evaluated.

2. The method for evaluating the production potential of shale gas wells with inter-well connectivity according to claim 1, characterized in that: In step S2, the recovery degree of the gas well under the current formation pressure R Satisfying the relationship (I): R=G p / EUR ·10000 （Ⅰ）， In the formula, R is the extraction degree, %; G p is the current cumulative gas production, 10 4 m 3 ; EUR is the ultimate recoverable reserves, 10 8 m 3 .

3. The method for evaluating the production potential of shale gas wells with inter-well connectivity according to claim 1, characterized in that: In step S3, different extraction levels R and formation pressure P N Satisfying the relationship in formula (II): P N =-0.4538× R +36.478 （Ⅱ）， In the formula, P N is the current formation pressure, MPa; R is the degree of recovery, %.

4. The method for evaluating the production potential of shale gas wells with inter-well connectivity according to claim 1, characterized in that: In step S4, different production times t Bottom hole pressure P wf Satisfying the relationship (III): P wf =151.21× t -0.46 （Ⅲ）， In the formula, P wf is the bottom hole flowing pressure, MPa; t The number of days of production during testing, days.

5. The method for evaluating the production potential of shale gas wells with inter-well connectivity according to claim 1, characterized in that: In step S5, the gas well production pressure difference Δ P Satisfies the following relationship (IV): △ P = P N - P wf （Ⅳ）， In the formula, △ P is the production pressure difference, MPa; P N is the current formation pressure; P wf is the bottom hole flowing pressure, MPa.

6. The method for evaluating the production potential of shale gas wells with inter-well connectivity according to claim 1, characterized in that: In step S6, different production pressure difference △ P and daily gas production q Satisfies the following relationship (V): q =0.737×△ P （Ⅴ）， In the formula, q is the daily gas production, ten thousand cubic meters per day; △ P is the production pressure difference, MPa.

7. The method for evaluating the production potential of shale gas wells with inter-well connectivity according to claim 1, characterized in that: In step S7, the theoretical daily gas production of the well to be evaluated is calculated through steps S1-S6. q 理论 , and the actual daily gas production q 实际 For comparative evaluation: like q 理论 ×0.6≥ q 实际 , then the well has great exploitation potential; like q 理论 ×0.6< q 实际 < q 理论 , then the recovery potential of the well is average; like q 理论 ≤ q 实际 , then the recovery potential of the well is small.

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