Method for calculating reasonable well pattern density of tight sandstone gas reservoir

Abstract

The invention relates to the field of oil-gas field development engineering, and particularly discloses a method for calculating the reasonable well pattern density of a tight sandstone gas reservoir, which comprises the following steps of: firstly, calculating the optimal economic well pattern density and the economic limit well pattern density of a target gas reservoir, and then calculating the reasonable well pattern density of the target gas reservoir by adopting a principle of adding a trisection difference method, namely under the condition that the original basic conditions are not changed. And calculating the reasonable well pattern density by using the obtained optimal economic well pattern density and limit well pattern density. The optimal economic well pattern density is the well pattern density when the profit is maximum, the limit well pattern density is the well pattern density when the profit is zero, and the reasonable well pattern density of the gas field is between the optimal economic well pattern density and the limit well pattern density and is close to the reasonable well pattern density as much as possible. And the method has very important significance for ensuring the continuous and stable natural gas yield of the current low-permeability tight sandstone gas reservoir.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development engineering, specifically to a method for calculating the reasonable well pattern density of tight sandstone gas reservoirs. Background Technology

[0002] The proven reserves of low-permeability tight sandstone gas reservoirs in my country have now exceeded 10,000 × 10⁸ m³. 3 These gas reservoirs are mainly concentrated in the western Sichuan Basin and the Shaanxi-Gansu-Ningxia Basin. The Changqing Sulige gas field is a representative example of a low-permeability tight gas reservoir with extremely complex geological conditions. The geological conditions of tight gas reservoirs in western Sichuan are even more complex, characterized by heterogeneity, low porosity and permeability, high water saturation, and abnormally high pressure. In development, these gas fields all face challenges such as difficulty in utilizing reserves, low extraction rates, poor production stability, and difficulties in improving overall production efficiency. Although my country's natural gas development has, after many years of development, acquired the basic technologies required for conventional gas field development and accumulated much valuable experience, it is still far from meeting the needs of developing low-permeability gas reservoirs with complex geological conditions and high extraction difficulty. Therefore, developing technologies and theories suitable for these complex low-permeability gas reservoirs is of great practical significance for the efficient development of these reservoirs.

[0003] Among them, selecting a reasonable well density is the core content of the development design of low-permeability tight sandstone gas reservoirs. If the well density is too small, due to the poor continuity of the reservoir and the strong planar heterogeneity, the well network will not be able to control the reserves sufficiently, making it difficult to fully utilize the reserves and resulting in a low final recovery rate of the gas reservoir. However, if the well density is too large, the interference between wells will become more serious. Although the recovery rate can be further improved, the economic benefits are difficult to guarantee.

[0004] Therefore, developing a scientific and reasonable method for calculating well density that can achieve low reserve loss, high final recovery rate, high gas production rate and good development effect, as well as good economic benefits, is of great significance for ensuring the continuous and stable production of natural gas in current low-permeability tight sandstone gas reservoirs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for calculating the optimal well density in tight sandstone gas reservoirs, addressing the problems existing in the prior art. This calculation method employs the "addition of three differences" principle, meaning that under unchanged basic conditions, the optimal economic well density and the limiting well density are used to calculate the optimal well density. This method achieves minimal reserve loss, high final recovery rate, high gas production rate, and good development results, while also yielding good economic benefits. It is of great significance for ensuring the continuous and stable production of natural gas from current low-permeability tight sandstone gas reservoirs.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for calculating the optimal well pattern density for tight sandstone gas reservoirs includes the following steps:

[0008] Calculate the optimal economic well density for the target gas reservoir;

[0009] Calculate the economically limiting well density of the target gas reservoir;

[0010] The following formula is used to calculate a reasonable well pattern density:

[0011]

[0012] In the formula:

[0013] SPC represents a reasonable well pattern density. a Optimal economic well density for the target gas reservoir; SPC min The economically limited well network density for the target gas reservoir.

[0014] This application provides a method for calculating the reasonable well pattern density of tight sandstone gas reservoirs. First, the optimal economic well pattern density and the economic limit well pattern density of the target gas reservoir are calculated. Then, the "addition of three differences" principle is used, that is, under the condition that the original basic conditions remain unchanged, the reasonable well pattern density is calculated using the already obtained optimal economic well pattern density and limit well pattern density. The optimal economic well pattern density is the well pattern density when profitability is maximized, and the limit well pattern density is the well pattern density when profitability is zero. The reasonable well pattern density of the gas field should be between the optimal economic well pattern density and the limit well pattern density, and as close as possible to the reasonable well pattern density. This is of great significance for ensuring the continuous and stable production of natural gas from current low-permeability tight sandstone gas reservoirs.

[0015] The optimal well density for a gas field should fall between the optimal economic well density and the limiting well density, and be as close as possible to the optimal well density. The optimal well density can be calculated using the "adding three-part difference method". The calculated SPCmin (economic limiting well density) is the well density when the economic benefit is 0, and SPCa (optimal economic well density) is the well density when the economic benefit is maximized, but the gas field production is lower than SPCmin (economic limiting well density). In practical applications, the intermediate value is not simply taken. Instead, the point that is one-third away from SPCa (optimal economic well density) plus the difference between SPCmin (economic limiting well density) and SPCa (optimal economic well density) is selected as the optimal well density. In this way, the calculated SPC (optimal well spacing) is closer to SPCa (optimal economic well density) and can achieve a good production.

[0016] This invention uses the core porosity obtained under actual formation temperature and pressure as the basic parameter. Since the volume coefficient of natural gas is different under different temperatures and pressures, a volume coefficient is introduced to convert the volume of natural gas under formation conditions to the volume of natural gas under surface conditions, which is more accurate.

[0017] Furthermore, considering factors such as capital investment and output benefits, the optimal economic well density for a gas reservoir is the well density at which the economic benefits are maximized.

[0018] Furthermore, when the invested capital and output benefits are the same, that is, when the total profit of gas field development is 0, the corresponding well density is the economic limit well density.

[0019] Furthermore, the optimal economic well density for the target gas reservoir is calculated using the following formula:

[0020]

[0021] In the formula:

[0022] SPC a For optimal economic well density, wells / km 2 G a m represents the abundance of the target natural gas reservoir. 3 / km 2 P represents the unit price of natural gas, in yuan / m³. 3 I represents the total investment in single-well drilling and oilfield construction, 10 4 Yuan / well; E R f represents the natural gas recovery rate; t represents the evaluation period (in years); and O represents the average gas production operating cost (in yuan / m³). 3 R is the loan interest rate, f; a is the commodity rate, f; T a For the tax rate, f; L R For a reasonable profit, yuan / m 3 .

[0023] Furthermore, the economically limiting well density of the target gas reservoir is calculated using the following formula:

[0024]

[0025] Where: SPC min The economically limited well density, in wells per km 2 G a m represents the abundance of the target natural gas reservoir. 3 / km 2 P represents the unit price of natural gas, in yuan / m³. 3 I represents the total investment in single-well drilling and oilfield construction, 10 4 Yuan / well; E Rf represents the natural gas recovery rate; t represents the evaluation period (in years); and O represents the average gas production operating cost (in yuan / m³). 3 R is the loan interest rate, f; a is the commodity rate, f; T a Let f be the tax rate.

[0026] Furthermore, the abundance of the target natural gas reservoir is calculated using the following formula:

[0027]

[0028] In the formula:

[0029] G a m represents the abundance of the target natural gas reservoir. 3 / km 2 H represents the average thickness of the target gas reservoir, in meters; φ represents the average porosity of the core sample from the target gas reservoir, dimensionless; B g This is the volume factor for natural gas.

[0030] Furthermore, the volume factor of natural gas is calculated using the following formula:

[0031]

[0032] In the formula: B g V is the volume factor of natural gas, dimensionless; V is the volume of natural gas under formation conditions, in meters. 3 V sc Let m be the volume of natural gas under surface conditions. 3 .

[0033] Furthermore, the average porosity φ of the target gas reservoir core samples was measured using the following method:

[0034] S1: Obtain standard core samples and gas samples from the target gas reservoir, and then blend them according to the composition of the gas samples respectively;

[0035] S2: Using a compound gas to displace standard core samples, the average porosity φ of the target gas reservoir core samples under formation temperature and pressure conditions was measured.

[0036] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0037] This application provides a method for calculating the reasonable well pattern density of tight sandstone gas reservoirs. The optimal economic well pattern density is the well pattern density when profitability is maximized, and the limiting well pattern density is the well pattern density when profitability is zero. The reasonable well pattern density of a gas field should be between the optimal economic well pattern density and the limiting well pattern density, and as close as possible to the reasonable well pattern density. This application first calculates the optimal economic well pattern density and the economic limiting well pattern density of the target gas reservoir. Then, it adopts the "addition of three differences" principle, that is, under the condition that the original basic conditions remain unchanged, it uses the obtained optimal economic well pattern density and the limiting well pattern density to calculate the reasonable well pattern density. This is of great significance for ensuring the continuous and stable production of natural gas in the current low-permeability tight sandstone gas reservoirs. Attached Figure Description

[0038] Figure 1 This is a diagram illustrating the process of calculating the optimal well pattern density for a tight sandstone gas reservoir, as shown in the example. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings.

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0041] The present invention will be further described below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and technical features described in this application can be combined with each other. It should also be pointed out that, unless otherwise indicated, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terms "comprising" or "including" and similar words used in this invention refer to elements or objects preceding the word that encompass the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0042] Example

[0043] In a specific embodiment, taking the tight sandstone gas reservoir wells of the Zhongjiang Gas Field as an example, the method for calculating the reasonable well pattern density of tight sandstone gas reservoirs described in this invention is used to calculate the reasonable well pattern density. The method specifically includes the following steps:

[0044] (1) Obtain standard core samples and gas samples from the target gas reservoir, and reconstitute them according to the composition of the gas samples. The ionic composition of formation water and the composition of gas are shown in Table 1.

[0045] Table 1. Composition analysis of gas samples

[0046]

[0047]

[0048] (2) Using compound gas to displace standard core samples, the average porosity φ of the core samples under formation temperature and pressure conditions was measured. The matrix porosity of rock samples in this area ranges from 0.9% to 15.3%.

[0049] (3) Combined with the geological and economic parameters of the Zhongjiang gas field reservoir (Table 2).

[0050] Table 2. Economic Limit Parameters of Zhongjiang Gas Field

[0051]

[0052] (4) The optimal economic well pattern density for the target gas reservoir is calculated as follows:

[0053]

[0054] In the formula: SPCa is the optimal economic well density, in wells / km2; Ga is the reserve abundance of the target natural gas reservoir, m3 / km2; P is the unit price of natural gas, yuan / m3; I is the total investment in single-well drilling and oilfield construction, 104 yuan / well; ER is the natural gas recovery rate, f; t is the evaluation period, years; O is the average gas production operation cost, yuan / m3; R is the loan interest rate, f; a is the commodity rate, f; Ta is the tax rate, f; LR is the reasonable profit, yuan / m3.

[0055] The economically limiting well pattern density calculation method for the target gas reservoir is as follows:

[0056]

[0057] In the formula: SPCmin is the economic limit well network density, in wells / km2; Ga is the reserve abundance of the target natural gas reservoir, m3 / km2; P is the unit price of natural gas, yuan / m3; I is the total investment in single-well drilling and oilfield construction, 104 yuan / well; ER is the natural gas recovery rate, f; t is the evaluation period, years; O is the average gas production operation cost, yuan / m3; R is the loan interest rate, f; a is the commodity rate, f; Ta is the tax rate, f.

[0058] The method for determining the reasonable well density of a target gas reservoir is as follows: the optimal economic well density is the well density at which profitability is maximized, and the limiting well density is the well density at which profitability is zero. Therefore, the reasonable well density of a gas field should be between the optimal economic well density and the limiting well density, and as close as possible to the reasonable well density. The reasonable well density can be calculated using the "addition of three differences" principle, that is, under the condition that the original basic conditions remain unchanged, the reasonable well density is calculated using the already obtained optimal economic well density and the limiting well density.

[0059]

[0060] The calculated optimal economic well density, limit well density, and reasonable well density are shown in Table 3 below.

[0061] Table 3. Economic Limits and Reasonable Well Spacing of the Shaximiao Formation Gas Reservoir in Zhongjiang Gas Field

[0062]

[0063] This embodiment provides a method for calculating the reasonable well pattern density of tight sandstone gas reservoirs, including the following steps: S1: Obtain standard core samples and gas samples from the target gas reservoir, and blend them according to the composition of the gas samples; S2: Displace the standard core samples with the blended gas, and measure the average porosity φ of the core samples under formation temperature and pressure conditions; S3: Measure the volume factor B of the blended natural gas under the target reservoir temperature and pressure conditions. g S4: Calculate the abundance of natural gas reserves in the target tight gas reservoir based on parameters such as average porosity, reservoir thickness, and natural gas volume factor; S5: Calculate the optimal economic well density (SPC) for the target gas reservoir. a Considering factors such as capital investment and output benefits, the well density that maximizes economic benefits is the optimal economic well density (SPC) for a gas reservoir. a S6: Calculate the economic limit well density (SPC) of the target gas reservoir. min When the invested capital and the output benefits are the same, that is, when the total profit of gas field development is 0, the corresponding well density is the economic limit well density (SPC). min S7: The reasonable well density can be determined using the "addition of three differences" principle, utilizing the already obtained optimal economic well density and limiting well density. This invention can calculate the reasonable well density of tight sandstone gas reservoirs considering the optimal economic well density and the economic limiting well density. The optimal economic well density is the well density when profitability is maximized, and the limiting well density is the well density when profitability is zero. Therefore, the reasonable well density of a gas field should be between the optimal economic well density and the limiting well density, and as close as possible to the reasonable well density. The reasonable well density can be calculated using the "addition of three differences" principle, that is, under the condition that the original basic conditions remain unchanged, the reasonable well density is calculated using the already obtained optimal economic well density and limiting well density. Selecting a reasonable well density is the core content of the development design of low-permeability tight sandstone gas reservoirs. A scientifically reasonable well density should achieve both low reserve loss, high final recovery rate, high gas production rate and good development effect, and good economic benefits.

[0064] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for calculating the optimal well pattern density in tight sandstone gas reservoirs, characterized in that, Includes the following steps: Calculate the optimal economic well density for the target gas reservoir; Calculate the economically limiting well density of the target gas reservoir; The following formula is used to calculate a reasonable well pattern density: In the formula: SPC represents a reasonable well pattern density. a Optimal economic well density for the target gas reservoir; SPC min The economically limited well network density for the target gas reservoir.

2. The method for calculating the reasonable well pattern density of tight sandstone gas reservoirs according to claim 1, characterized in that, The optimal economic well density for the target gas reservoir is calculated using the following formula: In the formula: SPC a For optimal economic well density; G a P represents the abundance of the target natural gas reservoir; I represents the price per unit of natural gas; E represents the total investment in drilling and construction of a single well; and E represents the total investment in the reservoir. R t is the natural gas recovery rate; t is the evaluation period; O is the average gas production operating cost; R is the loan interest rate; a is the commodity rate; T a For tax rate; L R For reasonable profit.

3. The method for calculating the reasonable well pattern density of tight sandstone gas reservoirs according to claim 1, characterized in that, The economically limiting well density of the target gas reservoir is calculated using the following formula: Where: SPC min For the economically limited well density; G a P represents the abundance of the target natural gas reservoir; I represents the price per unit of natural gas; E represents the total investment in drilling and construction of a single well; and E represents the total investment in the reservoir. R t is the natural gas recovery rate; t is the evaluation period; O is the average gas production operating cost; R is the loan interest rate; a is the commodity rate; T a For tax rates.

4. The method for calculating the reasonable well pattern density of tight sandstone gas reservoirs according to claim 2 or 3, characterized in that, The abundance of the target natural gas reservoir is calculated using the following formula: In the formula: G a H represents the abundance of the target natural gas reservoir; H represents the average thickness of the target gas reservoir reservoir; φ represents the average porosity of the core sample from the target gas reservoir; B represents the average porosity of the core sample from the target gas reservoir. g This is the volume factor for natural gas.

5. The method for calculating the reasonable well pattern density of tight sandstone gas reservoirs according to claim 4, characterized in that, The volume factor of natural gas is calculated using the following formula: In the formula: B g V is the volume factor of natural gas; V is the volume of natural gas under formation conditions; V sc This represents the volume of natural gas under surface conditions.

6. The method for calculating the reasonable well pattern density of tight sandstone gas reservoirs according to claim 4, characterized in that, The average porosity φ of the core sample from the target gas reservoir was measured using the following method: S1: Obtain standard core samples and gas samples from the target gas reservoir, and then blend them according to the composition of the gas samples respectively; S2: Using a compound gas to displace standard core samples, the average porosity φ of the target gas reservoir core samples under formation temperature and pressure conditions was measured.

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