Quantitative splitting method for drainage and mining water source of coal-bed gas well based on hydrogen and oxygen isotopes of produced water

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Through the quantitative splitting method based on the hydrogen and oxygen isotopes of the output water, the static water volume and dynamic water volume in the coalbed methane well were identified and divided, and the complexity of water source caused by interlayer interference in the coalbed methane mining was solved, and the development of coalbed methane was improved. Efficiency and accuracy.

CN119288395APending Publication Date: 2025-01-10XIAN MEIHANG APPL OF SATELLITE DATA

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Patent Information

Application Number: CN202411666634.0
Authority / Receiving Office: CN · China
Patent Type: Applications(China)
Current Assignee / Owner
Filing Date: 2024-11-21
Publication Date: 2025-01-10

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Technical Problem

Interlayer interference in coalbed methane multi-layer mining leads to complex and changeable water discharge and mining sources, lacking effective quantitative splitting methods, affecting the reservoir pressure reduction and gas production effects.

Method used

Based on the quantitative splitting method of the output water hydroxide isotope, the output water samples are collected systematically, laboratory isotope testing, D drift index and cluster analysis are constructed, and the static water volume, dynamic water volume and mixing types are identified, and the quantitative splitting method is constructed. , combined with gas and water production profile tests, achieve accurate division of water sources.

Benefits of technology

The diagnosis of water production and production efficiency of coalbed methane wells has been achieved, providing a quantitative basis for economical and efficient coalbed methane mining in multiple coalbed methane areas, and improving the efficiency and accuracy of coalbed methane development.

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Abstract

The invention relates to the technical field of commingling production interference of coal-bed gas wells, and discloses a coal-bed gas well drainage and production water source quantitative splitting method based on hydrogen and oxygen isotopes of produced water, which comprises the following steps: a system collects a water sample produced by a regional coal-bed gas well and tests the stable hydrogen and oxygen isotope composition of the water sample; and performing delta 2H and delta 18O stable isotope composition characteristic analysis. And constructing a D drift index and a calculation method thereof, and carrying out quantitative characterization on the D drift degree of the produced water. And analyzing the correlation between the hydrogen and oxygen isotope composition and the gas production efficiency and the water yield. Clustering analysis is carried out on water samples produced by the coal-bed gas well, three types of static water volume, dynamic water volume and mixing are identified, isotope composition characteristic values of the static water volume and the dynamic water volume are determined, a splitting result has clear correlation with the gas production level, and a quantitative basis is provided for diagnosis of water production and production efficiency of the coal-bed gas well. And a reference basis is provided for economic and efficient commingling production of coal bed gas in a multi-coal-bed region.

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Description

Technical Field

[0001] The invention relates to the technical field of coalbed methane well co-production interference, and in particular to a method for quantitatively splitting a coalbed methane well drainage water source based on hydrogen and oxygen isotopes of produced water. Background Art

[0002] The efficient development of coalbed methane is of great significance for increasing the supply capacity of oil and gas, alleviating the contradiction between oil and gas supply and demand, and achieving clean, low-carbon and sustainable development of fossil energy. Coalbed methane resources are mostly found in multiple sets of main mining coal seams in coal-bearing basins. The implementation of multi-layer coalbed methane production is an objective way to improve the efficiency of coalbed methane development. However, due to the differences in inter-layer geological characteristics and reservoir conditions, multi-layer coalbed methane production often faces more serious inter-layer interference problems, which restricts the efficient output of coalbed methane and even causes the failure of coalbed methane development projects.

[0003] Coalbed methane development is a process in which gas and water fluids are produced together. Interlayer interference has a direct reflection on the quantity and material characteristics of gas and water output. The geochemical composition of water produced from coalbed methane wells contains rich drainage information, which is of great reference significance for splitting drainage water sources and production layer contributions, indicating the degree of interlayer interference, and diagnosing the efficiency of coalbed methane production. The combined production of multiple coal seams is prone to communicate different water dynamic systems, resulting in complex and changeable drainage water sources. Differences in drainage water sources directly affect reservoir depressurization and gas production effects. Effective splitting of drainage water sources is an important basis for diagnosing the production status of gas wells and implementing dynamic adjustments to subsequent development plans.

[0004] Among the many properties of produced water, the stable hydrogen and oxygen isotope composition carries geological information such as the origin, evolution, and migration of groundwater, and is an important basis for splitting the source of produced water. Previous studies have been conducted on the hydrogen and oxygen isotope composition of produced water from coalbed methane wells, expounding its distribution and variation characteristics, analyzing the main controlling factors from the two perspectives of geology and engineering, and initially forming a basic method and principle for splitting the drainage water source and diagnosing the production capacity characteristics of coalbed methane wells based on hydrogen and oxygen isotopes. However, previous studies were mostly limited to the qualitative analysis of drainage water sources, and no quantitative splitting method for water source composition has been formed. Summary of the invention

[0005] The purpose of the present invention is to provide a method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water, so as to solve the problems raised in the above-mentioned background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water, the method comprising the following steps:

[0007] S1. The system collects water samples produced from coalbed methane wells;

[0008] S2. The laboratory conducts geochemical testing of hydrogen and oxygen stable isotopes;

[0009] S3. Carry out δ 2 H, δ 18 O stable isotope composition characteristics analysis;

[0010] S4. Construct a D drift index to quantitatively characterize the degree of D drift of produced water;

[0011] S5. Perform cluster analysis on the produced water samples to identify three types: static water volume, dynamic water volume and mixed water volume, and determine the isotopic composition characteristic values of static water volume and dynamic water volume;

[0012] S6. Split the static water volume and dynamic water volume of the second category according to the distribution characteristics of the two types of data, and construct a quantitative splitting method for the produced water source of coalbed methane wells based on the hydrogen and oxygen isotope composition of the produced water;

[0013] S7. Testing and processing of gas and water production profiles of coalbed methane wells.

[0014] Optionally, the S4 further includes:

[0015] 1) The main explanations for the drift of isotope D in produced water from coalbed methane wells are as follows:

[0016] The hydrogen content in coal is higher than the oxygen content, which causes the hydrogen isotope exchange reaction to be more intense than the oxygen isotope exchange reaction;

[0017] 2) Coal measures are prone to produce H2S gas under reducing conditions and microbial action, among which D is relatively enriched. After dissolving in water, it undergoes isotope exchange reaction with water molecules:

[0018] HDS+H2O=H2S+HDO

[0019] 3) Hydrocarbon exchange reaction: Coal contains various hydrocarbon-containing hydrogen compounds such as hydrocarbons, and the coal-bearing strata are in a reducing environment. The hydrogen isotopes in the water can undergo a "hydrocarbon exchange" reaction with the hydrogen isotopes in the coal, thereby forming a D drift:

[0020] H2O+D(coal series)=HDO+H(coal series)

[0021] 4) Coalbed methane can be dissolved in groundwater in large quantities under high temperature conditions, and when sulfate is present, CH4 can promote its reduction to generate H2S and cause the above reaction. This causes isotope exchange in the H2S-H2O or CH4-H2O system, making the hydrogen isotope in the water heavier.

[0022] The D drift characteristic of the produced water from coalbed methane wells is the result of the interaction between the special material composition of the coal series and groundwater under specific conditions. It can reflect the characteristics of the coalbed water itself and help reduce pressure after production.

[0023] The D drift index is defined as the vertical distance between the hydrogen and oxygen isotope data point and the atmospheric precipitation line. The larger the distance, the stronger the D drift.

[0024] Let the equation of the line be y=kx+b;

[0025] The distance formula from point (x0, y0) to the straight line is:

[0026]

[0027] According to the above formula, the distance d from each isotope data point to the atmospheric precipitation line is calculated as the D drift index to quantitatively characterize the degree of D drift.

[0028] Optionally, the S5 further includes:

[0029] S51, based on hydrogen and oxygen isotope values and D drift index, Q-type cluster analysis of samples was performed;

[0030] S52. Data with abnormal D drift, obviously lighter hydrogen isotope composition, and insufficient coalbed water characteristics were eliminated from this analysis;

[0031] S53. The third category is regarded as the static reserve type of coal seam water, and the first category is regarded as the dynamic water volume type connecting shallow groundwater.

[0032] Optionally, the S6 further includes:

[0033] S61, firstly, linear fitting is performed on the first type and the third type of data respectively to obtain a straight line equation;

[0034] S62. Take the coordinates of the midpoints of each straight line as the isotopic composition characteristic values of the two types of water sources, static water volume and dynamic water volume;

[0035] S63, calculating the straight-line distance between the second type of data point and the above two characteristic values, the closer the distance, the greater the contribution, and the contribution degree of the two types of water sources can be obtained based on the relative proportion of the two;

[0036] S64. Split the static water volume and dynamic water volume of the mixed type, determine the mixing ratio of various water sources in the produced water, and form a quantitative splitting method for the dynamic water volume and static water volume source composition of the produced water.

[0037] Optionally, the S7 further includes:

[0038] S71. Quantitative chart showing the relationship between the response of the quantitative test instrument and the gas-water flow rate in a simulated coalbed methane well;

[0039] S72, placing the test instrument in the coalbed methane well, and obtaining the response of the quantitative test instrument in the measured gas-producing layer;

[0040] S73. In combination with the quantitative chart made in step S71, obtain the quantitative data corresponding to the response of the quantitative test instrument under the measured gas-producing layer.

[0041] Compared with the prior art, the present invention provides a method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water, which has the following beneficial effects:

[0042] This method for quantitative splitting of coalbed methane well drainage water sources based on produced water hydrogen and oxygen isotopes systematically collects produced water samples from regional coalbed methane wells and tests their stable hydrogen and oxygen isotope compositions. 2 H, δ 18 O stable isotope composition characteristics analysis. Construct D drift index and its calculation method to quantitatively characterize the D drift degree of produced water. Analyze the correlation between hydrogen and oxygen isotope composition and gas production efficiency and water production. Cluster analysis of produced water samples from coalbed methane wells was carried out to identify three types of static water volume, dynamic water volume and mixed water volume, and determine the isotope composition characteristic values of static water volume and dynamic water volume. The splitting results have a clear correlation with the gas production level, providing a quantitative basis for the diagnosis of water production and production efficiency of coalbed methane wells, and providing a reference basis for the economic and efficient joint production of coalbed methane in multi-coal seam areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of a flow chart in an embodiment of the present invention;

[0044] Figure 2 This is a distribution diagram of hydrogen and oxygen isotope composition of water produced from coalbed methane wells in the region in the embodiment of the present invention;

[0045] Figure 3 is a relationship diagram between the isotopic composition of regional produced water and the production capacity characteristic parameters in the embodiment of the present invention;

[0046] Figure 4 It is a Q-type clustering tree diagram of produced water samples from regional coalbed methane wells in an embodiment of the present invention;

[0047] Figure 5 It is a splitting diagram of static water volume and dynamic water volume of produced water in a region based on hydrogen and oxygen isotope composition in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] like Figure 1-Figure 5As shown, the present invention provides a technical solution: a method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water, the method comprising the following steps:

[0050] S1. The system collects water samples produced from coalbed methane wells;

[0051] The system collects the produced water samples of coalbed methane wells, including: the system collects the production data of typical coalbed methane wells in the region, including but not limited to the drainage and production layer, the buried depth of the production layer, the thickness of the production layer, the daily gas production, and the daily water production information;

[0052] Typical coalbed methane wells include single coalbed and multi-coalbed combined production wells. When the system collects water samples produced by coalbed methane wells, it is necessary to collect surface water samples from surrounding rivers for comparative analysis.

[0053] S2. The laboratory conducts geochemical testing of hydrogen and oxygen stable isotopes;

[0054] S3. Carry out δ 2 H, δ 18 O stable isotope composition characteristics analysis;

[0055] Standardize the hydrogen and oxygen isotope parameters and analyze and sort out δ 2 H, δ 18 O test results and standard deviation, make δ 2 H, δ 18 O composition distribution diagram;

[0056] Isotope exchange reactions involved in groundwater include:

[0057] Hydrogen isotope exchange reaction: H2 16 O+D(coal series)=HD 16 O+H(coal series)

[0058] Oxygen isotope exchange reaction: H2 16 O+ 18 O (coal series) = H2 18 O+ 16 O (coal series);

[0059] Based on the stable isotope test results, the hydrogen and oxygen isotope parameters are first standardized;

[0060] Calculate the data mean μ:

[0061]

[0062] Calculate the standard deviation σ of this feature:

[0063]

[0064] Each parameter value is converted to a standard distribution value using the following formula:

[0065]

[0066] Insert the atmospheric precipitation line equation and analyze the distribution characteristics of water samples from coalbed methane wells in this area along the atmospheric precipitation line.

[0067] S4. Construct a D drift index to quantitatively characterize the degree of D drift of produced water;

[0068] 1) The main explanations for the drift of isotope D in produced water from coalbed methane wells are as follows:

[0069] The hydrogen content in coal is higher than the oxygen content, which causes the hydrogen isotope exchange reaction to be more intense than the oxygen isotope exchange reaction;

[0070] 2) Coal measures are prone to produce H2S gas under reducing conditions and microbial action, among which D is relatively enriched. After dissolving in water, it undergoes isotope exchange reaction with water molecules:

[0071] HDS+H2O=H2S+HDO

[0072] 3) Hydrocarbon exchange reaction: Coal contains various hydrocarbon-containing hydrogen compounds such as hydrocarbons, and the coal-bearing strata are in a reducing environment. The hydrogen isotopes in the water can undergo a "hydrocarbon exchange" reaction with the hydrogen isotopes in the coal, thereby forming a D drift:

[0073] H2O+D(coal series)=HDO+H(coal series)

[0074] 4) Coalbed methane can be dissolved in groundwater in large quantities under high temperature conditions, and when sulfate is present, CH4 can promote its reduction to generate H2S and cause the above reaction. This causes isotope exchange in the H2S-H2O or CH4-H2O system, making the hydrogen isotope in the water heavier.

[0075] The D drift characteristic of the produced water from coalbed methane wells is the result of the interaction between the special material composition of the coal series and groundwater under specific conditions. It can reflect the characteristics of the coalbed water itself and help reduce pressure after production.

[0076] The D drift index is defined as the vertical distance between the hydrogen and oxygen isotope data point and the atmospheric precipitation line. The larger the distance, the stronger the D drift.

[0077] Let the equation of the line be y=kx+b;

[0078] The distance formula from point (x0, y0) to the straight line is:

[0079]

[0080] According to the above formula, the distance d from each isotope data point to the atmospheric precipitation line is calculated as the D drift index to quantitatively characterize the degree of D drift.

[0081] S5. Perform cluster analysis on the produced water samples to identify three types: static water volume, dynamic water volume and mixed water volume, and determine the isotopic composition characteristic values of static water volume and dynamic water volume;

[0082] S51, based on hydrogen and oxygen isotope values and D drift index, Q-type cluster analysis of samples was performed;

[0083] S52. Data with abnormal D drift, obviously lighter hydrogen isotope composition, and insufficient coalbed water characteristics were eliminated from this analysis;

[0084] S53. The third category is regarded as the static reserve type of coal seam water, and the first category is regarded as the dynamic water volume type connecting shallow groundwater.

[0085] S6. The static water volume and dynamic water volume of the second category are split according to the distribution characteristics of the two types of data, and a quantitative splitting method for the produced water source of coalbed methane wells based on the hydrogen and oxygen isotope composition of the produced water is constructed.

[0086] S61, firstly, linear fitting is performed on the first type and the third type of data respectively to obtain a straight line equation;

[0087] S62. Take the coordinates of the midpoints of each straight line as the isotopic composition characteristic values of the two types of water sources, static water volume and dynamic water volume;

[0088] S63, calculating the straight-line distance between the second type of data point and the above two characteristic values, the closer the distance, the greater the contribution, and the contribution degree of the two types of water sources can be obtained based on the relative proportion of the two;

[0089] S64. Split the static water volume and dynamic water volume of the mixed type, determine the mixing ratio of various water sources in the produced water, and form a quantitative splitting method for the dynamic water volume and static water volume source composition of the produced water.

[0090] S7, gas and water production profile testing and processing of coalbed methane wells;

[0091] S71. Quantitative chart showing the relationship between the response of the quantitative test instrument and the gas-water flow rate in a simulated coalbed methane well;

[0092] S72, placing the test instrument in the coalbed methane well, and obtaining the response of the quantitative test instrument in the measured gas-producing layer;

[0093] S73. In combination with the quantitative chart made in step S71, obtain the quantitative data corresponding to the response of the quantitative test instrument under the measured gas-producing layer.

[0094] As an application of this embodiment:

[0095] By calibrating the response curves of the piezoresistive flowmeter and the water content meter under different gas production and water production conditions in the laboratory, a quantitative calibration chart of gas production and water production is produced, and the instrument response value of the gas-producing layer is obtained using the piezoresistive flowmeter sensor and the water content sensor. The quantitative charts of water production and gas production under the instrument response value of the piezoresistive flowmeter and the capacitive water content meter are fitted respectively, and the two fitting curves are intersected. The gas production and water production corresponding to the intersection point of the two fitting curves are the water production and gas production under the measurement conditions. The measurement efficiency is high and the measurement data is accurate.

[0096] The above generally describes the present invention in detail, but it is obvious to a person skilled in the art that some modifications or improvements can be made to the present invention. Therefore, modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water, characterized in that: The method comprises the following steps: S1. The system collects water samples produced from coalbed methane wells; S2. The laboratory conducts geochemical testing of hydrogen and oxygen stable isotopes; S3. Carry out δ 2 H, δ 18 O stable isotope composition characteristics analysis; S4. Construct a D drift index to quantitatively characterize the degree of D drift of produced water; S5. Perform cluster analysis on the produced water samples to identify three types: static water volume, dynamic water volume and mixed water volume, and determine the isotopic composition characteristic values of static water volume and dynamic water volume; S6. Split the static water volume and dynamic water volume of the second category according to the distribution characteristics of the two types of data; S7. Testing and processing of gas and water production profiles of coalbed methane wells.

2. The method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water according to claim 1, characterized in that: The system collects water samples produced by coalbed methane wells, including: the system collects production data of typical coalbed methane wells in the region, and the collected data are not limited to drainage and production layer positions, production layer burial depths, production layer thicknesses, daily gas production, and daily water production information.

3. The method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water according to claim 2, characterized in that: The typical coalbed methane wells include single-coal-seam and multi-coal-seam combined production wells; when the system collects water samples produced by coalbed methane wells, it is necessary to collect surface water samples from surrounding rivers for comparative analysis.

4. The method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water according to claim 1, characterized in that: The S3 further comprises: Standardize the hydrogen and oxygen isotope parameters and analyze and sort out δ 2 H, δ 18 O test results and standard deviation, make δ 2 H, δ 18 O composition distribution diagram; Insert the atmospheric precipitation line equation and analyze the distribution characteristics of water samples from coalbed methane wells in this area along the atmospheric precipitation line.

5. The method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water according to claim 1, characterized in that: The S4 further comprises: The D drift index is defined as the vertical distance between the hydrogen and oxygen isotope data point and the atmospheric precipitation line. The larger the distance, the stronger the D drift. Let the equation of the line be y=kx+b; The distance formula from point (x0, y0) to the straight line is: According to the above formula, the distance d from each isotope data point to the atmospheric precipitation line is calculated as the D drift index to quantitatively characterize the degree of D drift.

6. The method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water according to claim 1, characterized in that: The S5 further comprises: S51, based on hydrogen and oxygen isotope values and D drift index, Q-type cluster analysis of samples was performed; S52. Data with abnormal D drift, obviously lighter hydrogen isotope composition, and insufficient coalbed water characteristics were eliminated from this analysis; S53. The third category is regarded as the static reserve type of coal seam water, and the first category is regarded as the dynamic water volume type connecting shallow groundwater.

7. The method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water according to claim 1, characterized in that: The S6 further comprises: S61, firstly, linear fitting is performed on the first type and the third type of data respectively to obtain a straight line equation; S62. Take the coordinates of the midpoints of each straight line as the isotopic composition characteristic values of the two types of water sources, static water volume and dynamic water volume; S63, calculating the straight-line distance between the second type of data point and the above two characteristic values, the closer the distance, the greater the contribution, and the contribution degree of the two types of water sources can be obtained based on the relative proportion of the two; S64. Split the static water volume and dynamic water volume of the mixed type, determine the mixing ratio of various water sources in the produced water, and form a quantitative splitting method for the dynamic water volume and static water volume source composition of the produced water.

8. The method for quantitatively splitting the water source of coalbed methane wells based on hydrogen and oxygen isotopes of produced water according to claim 1, characterized in that: The S7 further comprises: S71. Quantitative chart showing the relationship between the response of the quantitative test instrument and the gas-water flow rate in a simulated coalbed methane well; S72, placing the test instrument in the coalbed methane well, and obtaining the response of the quantitative test instrument in the measured gas-producing layer; S73. In combination with the quantitative chart made in step S71, obtain the quantitative data corresponding to the response of the quantitative test instrument under the measured gas-producing layer.