Method for determining natural commissioning of low-permeability water-bearing gas reservoir gas well

Abstract

The invention relates to a method for determining natural commissioning of a low-permeability water-bearing gas reservoir gas well, and belongs to the technical field of oil-gas field development. Comprising the following steps: screening gas wells which are naturally put into production in a research area, and determining the productivity of the screened gas wells; determining influence factors influencing the productivity of the gas well by using the logging data and the construction data; correlation analysis is conducted on the gas well productivity and the influence factors, and main evaluation indexes are determined; a grey correlation analysis method is adopted to calculate the correlation degree between each main evaluation index and the gas well productivity, and the influence weight of each main evaluation index is determined; establishing a relationship between the main evaluation index and the productivity, and determining a standard value of the main evaluation index; acquiring actual values of the main evaluation indexes, and determining discriminating parameters of natural production of the gas well in the research area; and establishing a relationship between productivity and discrimination parameters, and determining adaptive conditions of natural commissioning of the gas well. According to the method, whether the gas well has the potential of natural commissioning is judged by determining the adaptability conditions of natural commissioning of the gas well.

Description

Technical Field

[0001] The invention relates to a method for determining the natural production of a gas well in a low-permeability water-containing gas reservoir, and belongs to the technical field of oil and gas field development. Background Art

[0002] Low permeability-tight gas reservoirs are a very important natural gas resource in my country, with large reserves, mainly distributed in the Ordos, Sichuan, Songliao, Tarim and other basins. With the continuous deepening of natural gas development, the quality of the reservoirs to be developed has gradually deteriorated. Affected by the conditions of reservoir filling and preservation, the gas content of the reservoirs varies greatly, the local gas-water relationship is complex, and the reservoirs have no natural production capacity or low natural production capacity. In order to achieve efficient development, the fracturing transformation production method is often used. However, for the upper gas and lower water type reservoirs without stable interlayers between the gas-bearing layers, it is easy to communicate the gas and water layers after fracturing, and the high water content development effect of gas wells is poor. In addition, for the reservoirs in the middle and high parts with good physical properties and micro-structure development, there is differentiation between gas and water, and the gas wells have the potential for natural production. By optimizing the production method, the development investment can be reduced and the economic benefits can be improved.

[0003] At present, there are few studies on the methods for determining the natural production mode of low-permeability water-bearing gas reservoirs. For example, a document entitled "Gas-Water Distribution and Development Mode of Lithological-Structural Low-Permeability Water-Bearing Gas Reservoirs in Shiguhao Gas Area" published in Natural Gas Technology and Economy in December 2021 disclosed: Based on comprehensive geological conditions and economic benefits, in terms of natural gamma, sonic time difference, porosity and permeability, the screening criteria for natural production are smooth box-shaped natural gamma, no interlayers, sonic time difference greater than 260μs / m, porosity greater than 15%, and permeability greater than 1×10 -3 μm 2 , but the influence of gas reservoir gas content and gas reservoir structure is not considered.

[0004] The patent document with publication number CN106761718A discloses a new method for determining the production thickness limit of medium-deep oil reservoirs. This method calculates the economic limit initial production under the two production modes of natural production and fracturing production based on the total investment of a single oil well in the oil reservoir, establishes a relevant numerical model, predicts the initial production of single-layer production and multi-layer superposition production at different effective thicknesses under the two production modes, and counts the number of layers and effective thickness corresponding to the initial production above the economic limit initial production, which is the production thickness limit of the medium-deep oil reservoir. This new method for determining the production thickness limit of medium-deep oil reservoirs is easy to use and provides a reliable screening method for determining the effective production thickness limit of medium-deep oil reservoirs and improving the reserve production rate. However, it only considers the effective thickness of the oil reservoir and has certain limitations. Summary of the invention

[0005] The purpose of the present invention is to provide a method for determining the natural production of a gas well in a low-permeability water-containing gas reservoir, so as to solve the problem of how to provide a method for determining the natural production of a gas well in a low-permeability water-containing gas reservoir.

[0006] To achieve the above object, the solution of the present invention includes:

[0007] A method for determining the natural production of a gas well in a low-permeability water-containing gas reservoir according to the present invention comprises the following steps:

[0008] 1) Screen the naturally produced gas wells in the study area according to the specified conditions and determine the production capacity of the screened gas wells;

[0009] 2) Using well logging data and structural data, determine several factors that affect gas well productivity from the aspects of lithology, heterogeneity, physical properties, gas content and structure;

[0010] 3) Conduct correlation analysis on gas well productivity and several influencing factors, and use several influencing factors with a high correlation rate with gas well productivity as the main evaluation indicators;

[0011] 4) The grey correlation analysis method is used to calculate the correlation between each main evaluation index and the gas well productivity, and the influence weight of each main evaluation index on the gas well productivity is quantitatively quantified by the correlation to determine the influence weight of the main evaluation index;

[0012] 5) Establish the relationship between each main evaluation index and production capacity, take the initial production capacity of the economic limit as the constraint condition, and determine the standard value of the main evaluation index;

[0013] 6) Obtain the actual values ​​of each main evaluation index, and determine the discriminant parameters for natural production of gas wells in the study area by combining the influence weights of the main evaluation indexes and the ratios of the actual values ​​of the main evaluation indexes to the standard values;

[0014] 7) Establish the relationship between production capacity and discrimination parameters, and determine the adaptability conditions for natural production of gas wells.

[0015] The present invention uses logging data (conventional logging data) and structural data to fully consider the influence of lithology, heterogeneity, physical properties, gas content and structure on the natural production capacity of gas wells, and determines the discrimination parameters of natural production of gas wells in the study area, providing a basis for screening the production mode of gas wells in low-permeability water-containing gas reservoirs. The method is easy to operate and practical, guiding the economic and effective development of low-permeability water-containing gas reservoirs and improving the utilization rate of reserves. The present invention provides a method for determining the natural production of gas wells in low-permeability water-containing gas reservoirs, which determines the adaptability conditions of the natural production of the gas well to determine whether the gas well has the potential for natural production, that is, confirms whether the gas well is suitable for the natural production mode, and then optimizes the production mode of the gas well.

[0016] Furthermore, the specified condition is to remove gas wells whose production capacity does not meet the standard due to non-geological factors.

[0017] Furthermore, the productivity of a gas well is the average daily gas production of the gas well in the first year of production.

[0018] Furthermore, factors affecting gas well productivity include natural gamma, natural gamma toothing rate, acoustic time difference, compensated neutron, compensated density, porosity, permeability, induction resistivity, gas saturation, structural morphology and structural closure height.

[0019] Furthermore, the discriminant parameter for natural production of gas wells in the study area is Z, Among them, f i is the influence weight of the i-th main evaluation index, X i is the actual value of the i-th main evaluation index, X bi is the standard value of the ith main evaluation index.

[0020] Furthermore, according to the relationship between the production capacity and the discrimination parameter, the standard value of the discrimination parameter is determined with the initial production capacity of the economic limit as the constraint condition.

[0021] Furthermore, according to the actual calculated value of the discriminant parameter and the standard value of the discriminant parameter, the adaptability condition for natural production of the gas well is determined to be Z ≥ Z b ; Where Z is the actual calculated value of the discriminant parameter, Z b is the standard value of the discriminant parameter.

[0022] Furthermore, the constraint condition is to reach or exceed the economic limit initial production capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a flow chart of a method for determining natural production of a gas well in a low-permeability water-containing gas reservoir according to the present invention;

[0024] Figure 2 It is a schematic diagram of the relationship between the acoustic time difference as the main evaluation index and the production capacity of a naturally produced gas well of the present invention;

[0025] Figure 3 It is a schematic diagram of the relationship between the deep induction resistivity as the main evaluation index and the production capacity of a naturally produced gas well of the present invention;

[0026] Figure 4 It is a schematic diagram of the relationship between the structural height as the main evaluation index and the production capacity of the naturally produced gas well of the present invention;

[0027] Figure 5 Schematic diagram of the relationship between the toothing ratio as the main evaluation index and the production capacity of a naturally produced gas well in the present invention;

[0028] Figure 6 It is a conventional comprehensive logging diagram of Well A in the embodiment of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0030] An embodiment of a method for determining natural production of a gas well in a low-permeability water-containing gas reservoir:

[0031] A method for determining the natural production of a gas well in a low permeability water-bearing gas reservoir, such as Figure 1 As shown, the following steps are included:

[0032] 1) According to the specified conditions, the gas wells that are naturally put into production in the study area are screened to determine the production capacity of the screened gas wells; the specified conditions are to remove the gas wells whose production capacity does not meet the standard due to non-geological factors. The gas wells that are naturally put into production in the study area are screened to remove the gas wells whose production capacity does not meet the standard due to non-geological factors (remove the gas wells whose production capacity does not meet the standard due to non-geological factors), that is, from all the naturally put into production gas wells in the study area, the gas wells whose production capacity does not meet the standard due to non-geological factors are screened out, and the production capacity of the gas wells retained after screening is determined.

[0033] 2) Using conventional logging data and structural data, determine the factors affecting the production capacity of naturally produced gas wells from the aspects of lithology, heterogeneity, physical properties, gas content and structure; determine the main evaluation indicators of naturally produced wells (naturally produced gas wells) through correlation analysis, and use the grey correlation analysis method to calculate the correlation between each main evaluation indicator and the production capacity (the production capacity of the gas well). The influence weight of each main evaluation indicator on the production capacity of naturally produced wells is quantitatively quantified through the correlation to determine the influence weight of the main evaluation indicator.

[0034] Among them, the production capacity of the naturally produced wells in the established study area is the average daily gas production in the first year of gas well production. The evaluation index system of naturally produced wells is determined by comprehensively considering the lithology, heterogeneity, physical properties, gas content and structure of the gas well reservoir, which specifically includes natural gamma, natural gamma tooth rate, acoustic time difference, compensated neutron, compensated density, porosity, permeability, induction resistivity, gas saturation, structural morphology and structural closure height; a correlation analysis is conducted on the gas well production capacity and several influencing factors, and several influencing factors with a large correlation rate with the gas well production capacity are used as the main evaluation indicators, that is, the relevant data of each factor and the gas well production capacity data are obtained through conventional logging curves and gas well production, and the correlation analysis of each factor with the production capacity of naturally produced wells is conducted, and the factors with a large correlation rate are selected as the main evaluation indicators of naturally produced wells; the correlation analysis is to make a scatter plot of gas well production capacity and various production capacity influencing factors. If the points on the scatter plot are distributed regularly, such as positive correlation or negative correlation, then the factor is determined as the main evaluation indicator. If the points on the scatter plot are very scattered and irregular, that is, irrelevant, then the factor is not determined as the main evaluation indicator. The present invention screened four main evaluation indicators, namely, natural gamma-ray toothing rate, acoustic wave time difference, induction resistivity and structural height.

[0035] 3) Establish the relationship between each main evaluation index and production capacity, take the initial production capacity of the economic limit as the constraint condition, and determine the standard values ​​of the main evaluation indexes of the naturally produced wells in the study area.

[0036] A relationship chart between each main evaluation index and the production capacity of the naturally produced wells was drawn. The standard values ​​of the main evaluation indexes of the naturally produced wells in the study area were determined with the production capacity meeting the economic limit initial production capacity as the constraint condition. Among them, the economic limit initial production capacity is the lowest production capacity with economic benefits. It is economically beneficial only when the gas well production capacity exceeds the economic limit initial production capacity. Meeting the economic limit initial production capacity means that the gas well production capacity reaches or exceeds the economic limit initial production capacity.

[0037] 4) Obtain the actual values ​​of the main evaluation indicators of the naturally produced gas wells, combine the weights (influence weights) of the main evaluation indicators of the naturally produced wells and the ratios of the actual values ​​of the main evaluation indicators to the standard values, and establish the discrimination parameters for the natural production of gas wells in the study area.

[0038] The discriminant parameters for natural production of gas wells in the study area are expressed as

[0039]

[0040] Among them, f i is the weight ratio (influence weight) of the i-th main evaluation index, dimensionless (i.e. f i is the dimensionless number); X i is the actual value of the i-th main evaluation index, corresponding to the national standard unit; X biThe standard value of the i-th main evaluation indicator that meets the initial output of the economic limit corresponds to the national standard unit.

[0041] 5) According to the relationship chart between the production capacity of naturally produced gas wells in the study area and the discrimination parameters of natural production of gas wells, determine the adaptability conditions for natural production of gas wells.

[0042] According to the relationship chart between the production capacity of naturally produced gas wells in the study area and the discriminant parameters of natural production of gas wells, the standard value of the discriminant parameter for natural production of gas wells corresponding to the initial production capacity of the economic limit (the standard value of the discriminant parameter) is determined, and the adaptability condition for natural production of gas wells is further determined as follows:

[0043] Z ≥ Z b

[0044] Where Z is the actual calculated value of the discriminant parameter for natural production of gas wells in the study area (the actual calculated value of the discriminant parameter), which is dimensionless; Z b It is the standard value of the discriminant parameter corresponding to the natural production of the gas well when the production capacity meets the initial production capacity of the economic limit (the standard value of the discriminant parameter), which is dimensionless.

[0045] The present invention uses conventional logging data and structural data to determine the influencing factors of the production capacity of naturally produced gas wells from the aspects of lithology, heterogeneity, physical properties, gas content and structure, determines the main evaluation indicators of naturally produced wells through correlation analysis, uses the grey correlation analysis method to determine the influence weights of the main evaluation indicators, takes the initial production capacity of the economic limit as the constraint condition, determines the standard values ​​of the main evaluation indicators of the naturally produced wells in the study area, and combines the weights of the main evaluation indicators of the naturally produced wells and the ratio of the actual values ​​of the main evaluation indicators to the standard values ​​to establish the discrimination parameters of the natural production of gas wells in the study area. The present invention uses conventional logging data and structural data, fully considers the influence of lithology, physical properties, gas content and structure on the natural production of gas wells, establishes the discrimination parameters of the natural production of gas wells, and provides a basis for the screening of the production mode of gas wells in low-permeability water-bearing gas reservoirs. The method is easy to operate and practical, guides the economic and effective development of low-permeability water-bearing gas reservoirs, and improves the utilization rate of reserves.

[0046] Specific implementation method:

[0047] This embodiment takes a low-permeability, tight, water-bearing gas reservoir in a certain well area as an example. The production capacity of 25 naturally produced gas wells in the main stratum box 2+3 layer of the well area is 0-32,000 cubic meters / day, and the gas well production capacity varies greatly. From the analysis of conventional logging data and structural data, the factors affecting the production capacity include natural gamma, natural gamma tooth rate (tooth rate), deep induction resistivity, acoustic wave time difference, compensated neutron, compensated density, structural height, porosity, permeability, and gas saturation. These factors are analyzed for correlation with the production capacity of the gas wells. Through the correlation analysis, it is found that the four factors of acoustic wave time difference, deep induction resistivity, natural gamma tooth rate, and structural height have a greater correlation with the production capacity, corresponding to the following respectively: Figures 2 to 5 As shown. Among them, the acoustic time difference, deep induction resistivity and structural height are positively correlated with production capacity, and the natural gamma ray toothing rate is negatively correlated with production capacity. The weights (influence weights) of the acoustic time difference, deep induction resistivity, natural gamma ray toothing rate and structural height are determined by grey correlation to be 0.25, 0.32, 0.12 and 0.31 respectively.

[0048] Under the condition that the internal rate of return of single well investment is 8%, the economic limit initial production capacity of naturally produced wells is 1.0×10 4 m 3 / d. Taking the economic limit initial production capacity as the minimum standard, when the production capacity meets the economic limit initial production capacity, the acoustic time difference is greater than 260μs / m, the deep induction resistivity is greater than 8Ω·m, the natural gamma-ray toothing rate is less than 0.2, and the structural height is greater than 20m. That is, the standard values ​​of the main evaluation indicators of the naturally produced wells in the study area, the acoustic time difference, the deep induction resistivity, the toothing rate, and the structural height are 260μs / m, 8Ω·m, 0.2, and 20m, respectively.

[0049] After determining the standard values ​​of the four main evaluation indicators, the discriminant parameter Z value of the naturally produced gas wells in the study area was calculated.

[0050]

[0051] Among them, f i is the weight ratio of the i-th main evaluation index, dimensionless; X i is the actual value of the i-th main evaluation index, corresponding to the national standard unit; X bi The standard value of the ith main evaluation index to meet the initial output (capacity) of the economic limit corresponds to the national standard unit; AC is the acoustic time difference, the unit is μs / m; ILD is the deep induction resistivity, the unit is Ω·m; C is the natural gamma ray tooth rate, dimensionless; H is the structural height, the unit is m.

[0052] The Z value of the wells that have been put into natural production is calculated using the formula of the discriminant parameters of the naturally produced gas wells. Through the scatter plot of the relationship between the Z value and the production capacity, when the production capacity meets the economic limit initial production capacity, Z>1, so the adaptability condition for the natural production of the gas well is

[0053] Z ≥ Z b =1

[0054] Well A, a gas well in the well area, Figure 6As shown, the main target layer for production is Box 2, the average natural gamma curve value of the production layer is 61API, the natural gamma tooth rate is 0.15, the average acoustic time difference is 276μs / m, the average deep induction resistivity is 13.5Ω·m, the structural height is 32m, and the discriminant parameter Z value of the naturally produced gas well is calculated to be 1.46. The initial production capacity of the well after natural production is 23,000 cubic meters, and the production stability effect is good.

[0055] Through case analysis, the method for determining the natural production of gas wells in low-permeability water-containing gas reservoirs can simply and quickly determine whether the gas wells in low-permeability water-containing gas reservoirs can be put into production naturally, providing a basis for screening the production methods of gas wells in low-permeability water-containing gas reservoirs. This method is easy to operate and practical, guiding the economical and effective development of low-permeability water-containing gas reservoirs and improving the utilization rate of reserves.

[0056] The present invention adopts a quantitative method to determine whether a gas well in a low-permeability water-containing gas reservoir can be put into production naturally, thereby overcoming the blindness of the natural production of the gas well, providing a basis for the screening of the production mode of the gas well in the low-permeability water-containing gas reservoir, guiding the economical and effective development of the low-permeability water-containing gas reservoir, and improving the utilization rate of the reserves. At the same time, the method of the present invention is simple in principle, easy to operate, and has a good effect. It has been actually applied in gas fields, is easy to promote, and has a high application prospect.

Claims

1. A method for determining the natural production of a gas well in a low-permeability water-bearing gas reservoir, characterized in that: The steps include: 1) Screen the naturally produced gas wells in the study area according to the specified conditions and determine the production capacity of the screened gas wells; 2) Using well logging data and structural data, determine several factors that affect gas well productivity from the aspects of lithology, heterogeneity, physical properties, gas content and structure; 3) Conduct correlation analysis on gas well productivity and several influencing factors, and use several influencing factors with a high correlation rate with gas well productivity as the main evaluation indicators; 4) using grey correlation analysis to calculate the correlation between each main evaluation index and gas well productivity, and quantitatively quantifying the influence weight of each main evaluation index on gas well productivity through the correlation to determine the influence weight of the main evaluation index; 5) Establishing the relationship between each of the main evaluation indicators and the production capacity, taking the initial production capacity of the economic limit as the constraint condition, and determining the standard value of the main evaluation indicators; 6) Obtaining the actual value of each main evaluation index, combining the influence weight of the main evaluation index and the ratio of the actual value of the main evaluation index to the standard value, and determining the discrimination parameters for natural production of gas wells in the study area; 7) Establish the relationship between production capacity and discrimination parameters, and determine the adaptability conditions for natural production of gas wells.

2. The method for determining the natural production of a gas well in a low-permeability water-bearing gas reservoir according to claim 1, characterized in that: The specified conditions are to eliminate gas wells whose production capacity does not meet the standards due to non-geological factors.

3. The method for determining the natural production of a gas well in a low-permeability water-bearing gas reservoir according to claim 1, characterized in that: The production capacity of the gas well is the average daily gas production of the gas well in the first year of production.

4. The method for determining the natural production of a gas well in a low-permeability water-bearing gas reservoir according to claim 1, characterized in that: The factors affecting gas well productivity include natural gamma, natural gamma tooth rate, acoustic wave time difference, compensated neutron, compensated density, porosity, permeability, induction resistivity, gas saturation, structural morphology and structural closure height.

5. The method for determining the natural production of a gas well in a low-permeability water-bearing gas reservoir according to claim 1, characterized in that: The discriminant parameter for natural production of gas wells in the study area is Z, Among them, f i is the influence weight of the i-th main evaluation index, X i is the actual value of the i-th main evaluation index, X bi is the standard value of the ith main evaluation index.

6. The method for determining the natural production of a gas well in a low-permeability water-bearing gas reservoir according to claim 1, characterized in that: According to the relationship between the production capacity and the discrimination parameter, the standard value of the discrimination parameter is determined with the initial production capacity of the economic limit as a constraint condition.

7. The method for determining the natural production of a gas well in a low-permeability water-bearing gas reservoir according to claim 6, characterized in that: According to the actual calculated value of the discrimination parameter and the standard value of the discrimination parameter, the adaptability condition for natural production of the gas well is determined to be Z ≥ Z b ; Where Z is the actual calculated value of the discriminant parameter, Z b is the standard value of the discriminant parameter.

8. The method for determining the natural production of a gas well in a low-permeability water-bearing gas reservoir according to claim 1 or 6, characterized in that: The constraint condition is to reach or exceed the economic limit initial production capacity.

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