Optimization design method for working gas volume of gas reservoir type gas storage

Abstract

The invention belongs to the technical field of natural gas underground, and particularly provides a gas reservoir type gas storage working gas volume optimization design method, which comprises the following steps: determining a gas well seepage radius r and a single well control area Szc by adopting seepage theoretical calculation, numerical simulation II and a well control storage capacity conversion method; the method comprises the following steps: researching the proportional relation between the capacity of a built reservoir and dynamic reserves in the reservoir building process, determining the effective reservoir capacity GKR and the effective area S of the gas reservoir, designing the number n of wells required to be deployed for reservoir building, analyzing the matching between the daily total gas production capacity of the gas reservoir and the designed daily gas production quantity according to peak regulation requirements, optimizing the working gas quantity of the gas reservoir, and finally realizing the benefit building of the gas reservoir.

Description

Technical Field

[0001] The invention belongs to the technical field of underground natural gas storage, and in particular relates to a method for optimizing the design of working gas volume of a gas reservoir type gas storage facility. Background Art

[0002] Gas storage generally refers to a closed underground storage space that injects natural gas during the off-season and quickly extracts it during the peak season, so as to achieve the purpose of quickly adjusting the supply of natural gas on demand. To achieve efficient regulation of gas storage, it is necessary to ensure that the design indicators of the gas storage are optimized.

[0003] At present, the evaluation methods for gas storage design indicators are based on evaluating the storage capacity of the construction area, designing a certain working gas volume, and optimizing the number of injection and production wells according to the different peak-to-valley ratios of the gas storage peak regulation. This method does not take into account the seepage control range of the injection and production wells, and the designed working gas volume and number of injection and production wells are too small, the storage capacity utilization ratio is too low, the cushioning cost is high, the investment ratio is high, and the economic benefits are low.

[0004] A Chinese patent document with publication number CN114943190A and publication date August 26, 2022 discloses a method and device for determining the working gas volume of an underground gas storage, the method comprising: splitting the underground gas storage into multiple gas storage units centered on a gas production well; calculating the gas production well-controlled gas storage formation range according to the pseudo-pressure value corresponding to the bottom hole pressure resistance value of each gas production well, the underground gas storage operation parameters, and the pseudo-pressure value corresponding to the target lower limit pressure of the underground gas storage, and obtaining the formation radius controlled by each gas production well in each gas storage unit; determining the increased working gas volume of the underground gas storage according to the formation radius controlled by each gas production well in each gas storage unit and the target lower limit pressure of the underground gas storage. By independently determining the formation radius controlled by each gas production well in units of gas storage units, the increased working gas volume of the underground gas storage is obtained. Compared with the prior art, there is no need to solve the problem of pressure imbalance, the data measurement is accurate, and the working gas volume of the underground gas storage increased by reducing the lower limit pressure can be accurately determined. This document does not take into account the demand for natural gas peak-shaving, the changes in formation pressure and gas production capacity during the gas reservoir peak-shaving process, and the matching between the overall total gas production capacity of the gas reservoir and the designed daily gas production. The designed working gas volume is too large, and the actual operation of the gas reservoir cannot produce the corresponding working gas volume. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems in the prior art of not considering the difference between the built storage capacity and the dynamic reserves of the gas reservoir, not considering the seepage control range of the injection and production gas wells and the peak-shaving demand of natural gas, not considering the changes in formation pressure and gas production capacity during the peak-shaving process of the gas reservoir, not analyzing the matching between the overall total gas production capacity of the gas reservoir and the designed daily gas production, and there is a deviation in the designed working gas volume.

[0006] To this end, the present invention provides a method for optimizing the working gas volume of a gas reservoir type gas storage, comprising the following steps:

[0007] 1) Using the gas reservoir pressure drop method and the flowing material balance method, determine the dynamic reserves G of the reservoir construction area in the gas reservoir g Combined with numerical simulation, the proportional relationship between the storage capacity and dynamic reserves is established to determine the storage capacity G KR and effective storage area S;

[0008] 2) Use the seepage theory calculation, numerical simulation and well control storage capacity conversion method to determine the gas well seepage radius r and single well control area S zc and the number of wells n required to be deployed in the reservoir construction area;

[0009] 3) According to the external transmission wellhead pressure P cq , using the gas well productivity equation and the wellbore flow equation, establish the relationship between different formation pressures P and single well gas production capacity q cq curve;

[0010] 4) According to step 3), a relationship curve between the total gas production capacity of n wells in the reservoir construction area and the formation pressure P is established;

[0011] 5) According to the natural gas market demand, a natural gas peak-shaving normalization model is established, and the upper limit pressure of the gas storage operation is set as the original formation pressure P of the gas reservoir. 原始 Given the working gas volume W, establish the daily gas production volume Q of the gas storage i Curves changing over time;

[0012] 6) Based on the daily gas production Q of the gas storage i and the storage capacity, and the pressure drop method is used to obtain the daily formation pressure P of the gas storage. i ;

[0013] 7) According to different formation pressures P and single well gas production capacity q cq Curve, gas storage daily formation pressure P i Get the total gas production capacity Q of the gas storage cqi Curves changing over time;

[0014] 8) The daily gas production of the gas storage is Q i The total gas production capacity Q of the gas storage cqi Compare and determine whether they match; when the daily gas production of the gas storage is Q i The total gas production capacity Q of the gas storage cqi If there is no match, repeat steps 5) to 8) until a match is found. The total gas extraction capacity of the gas storage after matching is Q cqi The final working gas volume of the gas storage facility.

[0015] Preferably, the number of wells required for the reservoir construction area in step 2) is n=S / Szc .

[0016] Preferably, the specific method of step 3) is: under different formation pressures P, using the gas well productivity equation, given different daily gas production q, calculate the gas well bottom flow pressure P wf , draw the inflow curve; according to the external wellhead pressure, use the wellbore flow equation to calculate the gas well bottom flow pressure P corresponding to different daily gas production q wf , draw the outflow curve; intersect the inflow curve and the outflow curve to obtain the different formation pressures P and the single well gas production capacity q cq curve.

[0017] Preferably, the gas well productivity equation is:

[0018] Preferably, the wellbore flow equation

[0019]

[0020] Preferably, in step 4), the total gas production capacity Q of n wells in the reservoir construction area is cq =∑q cq .

[0021] Preferably, the step 5) establishes a specific normalized natural gas peak-shaving model according to the natural gas market demand.

[0022] Preferably, during the matching, the total gas production capacity Q of the gas storage per day during the specified production period is cqi Are greater than or less than the daily gas production Q of the gas storage i , the match fails.

[0023] Preferably, when the matching is performed, the gas storage production capacity Q nli Curve and daily gas production Q of gas storage i The curves are tangent, and the tangent point is Q cqi =Q i , and Q in the non-tangent region cqi >Q i , the match is successful.

[0024] Preferably, the prescribed production period is 120 days.

[0025] Beneficial effects of the present invention:

[0026] The method for optimizing the working gas volume of a gas reservoir type gas storage provided by the present invention adopts the seepage theory calculation, numerical simulation and well control storage capacity conversion method to determine the seepage radius r of the gas well and the well control area S of a single well. zc ; The relationship between the storage capacity and dynamic reserves during the construction process was studied to determine the effective storage capacity G of the gas reservoir. KRAnd the effective area S, design the number of wells n required for reservoir construction, analyze the matching between the total daily gas production capacity of the gas storage and the designed daily gas production according to the peak-shaving demand, optimize the working gas volume of the gas storage, and finally realize the efficient construction of the gas storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be further described in detail below with reference to the accompanying drawings.

[0028] Figure 1 It is a comparison chart of the reservoir capacity utilization effect of high and low permeability homogeneous reservoirs (numerical simulation);

[0029] Figure 2 is the plot of throat-controlled pore volume and movable fluid saturation for different samples;

[0030] Figure 3 This is the result diagram of the mathematical method of unsteady seepage;

[0031] Figure 4 is the result diagram of the numerical simulation method;

[0032] Figure 5 This is the result diagram of the well-controlled storage capacity conversion method;

[0033] Figure 6 This is the normalized model diagram of natural gas peak load regulation;

[0034] Figure 7 The pressure drop method is used to establish the relationship curve between reservoir capacity and formation pressure;

[0035] Figure 8 It is the inflow and outflow curve to evaluate the gas production capacity of the gas well;

[0036] Fig. 9 This is the curve of different formation pressures and single well gas production capacity under the condition of 6.4MPa gas wellhead pressure;

[0037] Fig.10 It is to establish a gas storage peak-shaving model based on the natural gas market demand;

[0038] Fig.11 The daily gas production curve of the gas storage is determined according to the gas storage peak regulation model;

[0039] Fig.12 According to the daily formation pressure P of the gas storage i , determine the formation pressure drop curve for calculating the gas storage reservoir;

[0040] Fig.13 It is the decline curve of the overall gas production capacity of the gas storage facility;

[0041] Fig.14 It is the comparison curve between the designed daily gas production and the daily gas production capacity of the gas storage facility;

[0042] Fig.15 It is the comparison curve between the three designed daily gas production and daily gas production capacity;

[0043] Fig.16 It is the curve of formation pressure drop after three designed gas reservoir gas production. DETAILED DESCRIPTION

[0044] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0045] Embodiment 1:

[0046] A method for optimizing the working gas volume of a gas reservoir type gas storage facility comprises the following steps:

[0047] 1) Using the gas reservoir pressure drop method and the flowing material balance method, determine the dynamic reserves G of the reservoir construction area in the gas reservoir g Combined with numerical simulation, the proportional relationship between the storage capacity and dynamic reserves is established to determine the storage capacity G KR and effective storage area S;

[0048] In actual operation, the gas reservoir pressure drop method and the flowing material balance method are both existing methods, the purpose of which is to determine the dynamic reserves G in the reservoir construction area. g ; Numerical simulation - choose according to the actual situation, and establish the proportional relationship between the storage capacity and dynamic reserves. Figure 1 This is a comparison chart of the storage capacity utilization effect of high and low permeability homogeneous reservoirs formed after numerical simulation. Figure 2 The pore volume and movable fluid saturation were controlled for different sample throats formed using the flowing material balance method.

[0049] 2) Use the seepage theory calculation, numerical simulation and well control storage capacity conversion method to determine the gas well seepage radius r and single well control area S zc and the number of wells n required to be deployed in the reservoir construction area;

[0050] Specific Figure 3 It is a curve diagram of permeability and dynamic radius of gas storage obtained by using the unstable seepage mathematical method in seepage theory calculation; Figure 4 is the well control area S of a single well determined by numerical simulation 2 zc ; Figure 5 It is the discharge area and volumetric reserve map determined by the well-controlled storage capacity conversion method;

[0051] 3) According to the external transmission wellhead pressure P cq , using the gas well productivity equation and the wellbore flow equation, establish the relationship between different formation pressures P and single well gas production capacity q cq curve;

[0052] 4) According to step 3), a relationship curve between the total gas production capacity of n wells in the reservoir construction area and the formation pressure P is established;

[0053] 5) According to the natural gas market demand, a natural gas peak-shaving normalization model is established, and the upper limit pressure of the gas storage operation is set as the original formation pressure P of the gas reservoir. 原始 Given the working gas volume W, establish the daily gas production volume Q of the gas storage i Curves changing over time;

[0054] Specifically, according to the natural gas market demand, a natural gas peak-shaving normalization model can be established. The unevenness of winter peak-shaving gas production in different months can be analyzed according to the natural gas market demand. Taking the winter peak as the benchmark, a winter peak-shaving normalization model can be established (see Figure 6 ).

[0055] 6) Based on the daily gas production Q of the gas storage i and the storage capacity, and the pressure drop method is used to obtain the daily formation pressure P of the gas storage. i ;

[0056] 7) According to different formation pressures P and single well gas production capacity q cq Curve, gas storage daily formation pressure P i Get the total gas production capacity Q of the gas storage cqi Curves changing over time;

[0057] 8) Compare the daily gas production of the gas storage facility Qi with the total gas production capacity of the gas storage facility Q cqi Compare and determine whether they match; when the daily gas production of the gas storage is Q i The total gas production capacity Q of the gas storage cqi If there is no match, repeat steps 5) to 8) until a match is found. The total gas extraction capacity of the gas storage after matching is Q cqi The final working gas volume of the gas storage facility.

[0058] The method for optimizing the working gas volume of a gas reservoir type gas storage provided by the present invention adopts the seepage theory calculation, numerical simulation and well control storage capacity conversion method to determine the seepage radius r of the gas well and the well control area S of a single well. zc ; The relationship between the storage capacity and dynamic reserves during the construction process was studied to determine the effective storage capacity G of the gas reservoir. KR And the effective area S, design the number of wells n required for reservoir construction, analyze the matching between the total daily gas production capacity of the gas storage and the designed daily gas production according to the peak-shaving demand, optimize the working gas volume of the gas storage, and finally realize the efficient construction of the gas storage.

[0059] Preferably, the number of wells required for the reservoir construction area in step 2) is n=S / S zc .

[0060] Preferably, the specific method of step 3) is: under different formation pressures P, using the gas well productivity equation, given different daily gas production q, calculate the gas well bottom flow pressure P wf , draw the inflow curve; according to the external wellhead pressure, use the wellbore flow equation to calculate the gas well bottom flow pressure P corresponding to different daily gas production q wf , draw the outflow curve; intersect the inflow curve and the outflow curve to obtain the different formation pressures P and the single well gas production capacity q cq curve.

[0061] Preferably, the gas well productivity equation is: Among them, P e is the average formation pressure, MPa; P wf is the bottom flow pressure of the gas well, MPa; q is the daily gas production, 10 4 m 3 / d; e is the total gas production days; a and b are the coefficients of the gas well productivity equation.

[0062] Preferably, the wellbore flow equation

[0063] Among them, P wf is the bottom hole flowing pressure of the gas well, MPa; P wh is the wellhead pressure, MPa; f is the friction coefficient; q is the different daily gas production, m 3 / d; is the average temperature of the gas in the column, K; is the average deviation coefficient of wellbore gas, dimensionless; D is the inner diameter of the oil pipe, mm; s is the equation index; e is the total gas production days.

[0064] Preferably, in step 4), the total gas production capacity Q of n wells in the reservoir construction area is cq =∑q cq .

[0065] Preferably, the step 5) establishes a specific normalized natural gas peak-shaving model according to the natural gas market demand.

[0066] Preferably, during the matching, the total gas production capacity Q of the gas storage per day during the specified production period is cqi Are greater than or less than the daily gas production Q of the gas storage i , the match fails.

[0067] Compare the total gas production capacity of the gas storage facility every day Q cqi The daily gas production Q of the gas storage i , need to ensure Q nli ≥Q i , if the total gas production capacity of the gas storage facility is Q cqi Both are greater than the daily gas production Q of the gas storagei , it means that the peak-shaving capacity of the gas storage is not fully utilized; if there is Q i Greater than Q cqi , it means that the design working gas volume parameters of the gas storage are unreasonable, and both need to adjust the working gas volume.

[0068] Preferably, when the matching is performed, the gas storage production capacity Q nli Curve and daily gas production Q of gas storage i The curves are tangent, and the tangent point is Q cqi =Q i , and Q in the non-tangent region cqi >Q i , the match is successful.

[0069] Preferably, the prescribed production period is 120 days.

[0070] By repeatedly adjusting the working gas volume W and repeating steps 5) to 8), the gas storage production capacity Q nli Curve and daily gas production Q i The curves are tangent, and the tangent point is Q cqi =Q i At this time, the designed daily gas production is equal to the production capacity. For other untangent areas, Q cqi >Q i , and finally determine the working gas volume of the gas storage.

[0071] Embodiment 2:

[0072] Based on Example 1, a method for optimizing the working gas volume of a gas reservoir type gas storage facility includes the following steps:

[0073] 1) Based on the reconstruction of a gas reservoir into a gas storage, the gas reservoir pressure drop method and the flow material balance method were used to determine the effective area of ​​the storage to be 18.2 km 2 The dynamic reserves in the reservoir construction area are 56.8×10 8 m 3 , according to the ratio of the built storage capacity to the dynamic reserves of 0.8 times ( Figure 2 ), the storage capacity of the reservoir is determined to be 4.55 billion cubic meters, and the relationship curve between the storage capacity and the formation pressure P is established (see Figure 7 );

[0074] 2) Using seepage theory calculation, numerical simulation and well control storage capacity conversion method, it is determined that the gas well seepage radius is 350m, the injection and production well spacing is 600m×700m, and the well control area of ​​a single well is 0.42km 2 and the number of wells required to be deployed in the reservoir construction area is 42;

[0075] 3) Under different formation pressures of 27.7, 25.0, 20.0, 15.0, 10.0, and 50 MPa, the gas well productivity equation is used to calculate the bottom hole flowing pressure P of the gas well given different daily gas production q. wf , draw the inflow curve; according to the external transmission wellhead pressure of 6.4MPa, use the wellbore pipe flow equation to calculate the gas well bottom flow pressure P corresponding to different daily gas production q wf , draw the outflow curve (see Figure 8 ) ; Intersect the inflow curve and the outflow curve to obtain the relationship between different formation pressures P and single well gas production capacity q cq Curve (see Fig. 9 ).

[0076] 4) According to step 3), 42 injection and production wells are built in the reservoir construction area, and the total gas production capacity Q is obtained. cq Relationship curve with formation pressure P: Q cq = -2.924 × P 2 +325.37×P-2152.9;

[0077] 5) According to the natural gas market demand, establish a natural gas peak load normalization model (see Fig.10 ), the upper limit pressure of the gas storage operation is set to the original formation pressure of the gas reservoir 27.7MPa, the working gas volume is given to be 2.2 billion cubic meters, and the daily gas production Q of the gas storage is established according to the natural gas peak regulation normalization model i Curves of change over time (see Fig.11 );

[0078] 6) Based on the daily gas production Q of the gas storage i and the library capacity G KR The daily formation pressure P of the gas storage can be obtained by using the pressure drop method. i ; According to the daily gas production Q of the gas storage i , combined with the relationship between the storage capacity and the formation pressure P, calculate the formation pressure Pi-1 of the gas storage reservoir for the next day, and get the daily formation pressure P of the gas storage reservoir i (See Fig.12 );

[0079] 7) According to different formation pressures P and single well gas production capacity q cq Curve, combined with step 6) daily formation pressure P of the gas storage i , we can get the total gas production capacity Q of n wells in the gas storage reservoir cqi Curves of change over time; (see Fig.13 );

[0080] 8) The daily gas production of the gas storage is Q i The total gas production capacity Q of the gas storage cqi For comparison, Q cqi ≥Q iThe designed gas storage facility has a daily production period of 120 days. i Much smaller than Q cqi , it means that the peak-shaving capacity of the gas storage is not fully utilized ( Fig.14 ); by continuously adjusting the working gas volume, repeating steps 5) to 8), the gas storage production capacity Q cqi Curve and daily gas production Q i The curves gradually approach each other, and finally after three calculations, the gas storage production capacity Q nli Curve and daily gas production Q i The curves are tangent, and the tangent point is Q cqi =Q i ,(See Fig.15 and Fig.16 ) The working gas volume of the gas storage facility is determined to be 2.66 billion cubic meters, and the lower limit operating pressure is 11.5 MPa.

[0081] At present, the present invention has been applied in the design of gas storage construction schemes. The method is simple and practical and meets the requirements of engineering design. The method provides a reliable index optimization design method for gas storage construction at home and abroad. The existing index design methods for gas storage are all based on the number of wells optimized based on storage capacity, and the evaluation of working gas volume is relatively small. This application can be applied to the design of gas storage construction at home and abroad, with advanced technology and broad market application prospects.

[0082] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A method for optimizing the working gas volume of a gas reservoir type gas storage, characterized in that: The steps include: 1) Using the gas reservoir pressure drop method and the flowing material balance method, determine the dynamic reserves G of the reservoir construction area in the gas reservoir g Combined with numerical simulation, the proportional relationship between the storage capacity and dynamic reserves is established to determine the storage capacity G KR and effective storage area S; 2) Use the seepage theory calculation, numerical simulation and well control storage capacity conversion method to determine the gas well seepage radius r and single well control area S zc and the number of wells n required to be deployed in the reservoir construction area; 3) According to the external transmission wellhead pressure P cq , using the gas well productivity equation and the wellbore flow equation, establish the relationship between different formation pressures P and single well gas production capacity q cq curve; 4) According to step 3), a relationship curve between the total gas production capacity of n wells in the reservoir construction area and the formation pressure P is established; 5) According to the natural gas market demand, a natural gas peak-shaving normalization model is established, and the upper limit pressure of the gas storage operation is set as the original formation pressure P of the gas reservoir. 原始 Given the working gas volume W, establish the daily gas production volume Q of the gas storage i Curves changing over time; 6) Based on the daily gas production Q of the gas storage i and the storage capacity, and the pressure drop method is used to obtain the daily formation pressure P of the gas storage. i ; 7) According to different formation pressures P and single well gas production capacity q cq Curve, gas storage daily formation pressure P i Get the total gas production capacity Q of the gas storage cqi Curves changing over time; 8) The daily gas production of the gas storage is Q i The total gas production capacity Q of the gas storage cqi Compare and determine whether they match; when the daily gas production of the gas storage is Q i The total gas production capacity Q of the gas storage cqi If there is no match, repeat steps 5) to 8) until a match is found. The total gas extraction capacity of the gas storage after matching is Q cqi The final working gas volume of the gas storage facility.

2. The method for optimizing the working gas volume of a gas reservoir type gas storage facility according to claim 1, characterized in that: Step 2) The number of wells required to be deployed in the reservoir construction area n=S / S zc .

3. The method for optimizing the working gas volume of a gas reservoir type gas storage facility according to claim 1, characterized in that: The specific method of step 3) is: under different formation pressures P, the gas well productivity equation is used to calculate the bottom flow pressure P of the gas well given different daily gas production q. wf , draw the inflow curve; According to the wellhead pressure, the wellbore flow equation is used to calculate the bottom flow pressure P of the gas well corresponding to different daily gas production q. wf , draw the outflow curve; Intersecting the inflow curve and the outflow curve, we can get the relationship between different formation pressures P and the single well gas production capacity q cq curve.

4. The method for optimizing the working gas volume of a gas reservoir type gas storage facility according to claim 3, characterized in that: The gas well productivity equation is:

5. The method for optimizing the working gas volume of a gas reservoir type gas storage facility according to claim 3, characterized in that: The wellbore flow equation 6. The method for optimizing the working gas volume of a gas reservoir type gas storage facility according to claim 1, characterized in that: Step 4) The total gas production capacity Q of n wells in the reservoir construction area cq =∑q cq .

7. The method for optimizing the working gas volume of a gas reservoir type gas storage facility according to claim 1, characterized in that: The step 5) establishes a natural gas peak-shaving normalization model according to the natural gas market demand.

8. The method for optimizing the working gas volume of a gas reservoir type gas storage facility according to claim 1, characterized in that: When the matching is performed, the total gas production capacity of the gas storage facility per day during the specified production period is Q cqi Are greater than or less than the daily gas production Q of the gas storage i , the match fails.

9. The method for optimizing the working gas volume of a gas reservoir type gas storage facility according to claim 1, characterized in that: When the above matching is performed, the gas storage production capacity Q nli Curve and daily gas production Q of gas storage i The curves are tangent, and the tangent point is Q cqi =Q i , and Q in the non-tangent region cqi >Q i , the match is successful.

10. The method for optimizing the working gas volume of a gas reservoir type gas storage facility according to claim 8, characterized in that: The stipulated production period is 120 days.

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