Method for evaluating non-pure carbon dioxide injection capacity of exhausted gas reservoir
By constructing a binomial production capacity analysis curve and an injection capacity equation, the problem of evaluating the injection capacity of non-pure carbon dioxide multi-component gas in depleted gas reservoirs was solved, achieving a win-win effect of gas reservoir development efficiency and carbon emission reduction.
Patent Information
- Application Number
- CN202511677351.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-17
- Publication Date
- 2026-02-03
AI Technical Summary
Existing technologies make it difficult to accurately evaluate the injection capacity of non-pure carbon dioxide multi-component mixed gas in depleted gas reservoirs, increasing the uncertainty of injection and production scheme design and restricting the overall development efficiency of depleted gas reservoirs and the promotion and application of CCUS technology.
By constructing a binomial production capacity analysis curve and combining bottom hole pressure and reservoir pressure, the gas well injection capacity equation is derived, and the maximum injection volume and injection capacity of non-pure gas are calculated. This method is applicable to the injection of non-pure carbon dioxide gas into depleted gas reservoirs.
It improves the accuracy of gas injection effect prediction, simplifies the operation process, is applicable to various operating conditions and gas ratios, can effectively guide injection strategies, and improves gas reservoir development efficiency and carbon emission reduction.
Smart Images
Figure CN121451889A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of oil and gas field development, and more particularly to a method for evaluating injection capacity of non-pure carbon dioxide in depleted gas reservoirs. BACKGROUND
[0002] With the continuous growth of global energy demand, as an important unconventional gas reservoir resource, carbon dioxide injection and storage technology has become a key means of carbon emission reduction. By injecting carbon dioxide into depleted gas reservoirs, not only can residual natural gas be effectively displaced to improve resource development efficiency, but also carbon dioxide can be stored underground for a long time to help achieve the strategic goal of CCUS and promote the green and low-carbon process.
[0003] At present, the related technology is mainly focused on the injection and capacity evaluation of high-purity carbon dioxide, and the evaluation system is relatively mature and widely used. However, in the actual oil and gas reservoir development and CCUS process, the source of high-purity carbon dioxide is limited and the processing cost is high, which restricts its large-scale application. In contrast, multi-component mixed gas containing carbon dioxide is more abundant and has significantly reduced preparation costs, and components such as methane, nitrogen, and oxygen in it can synergistically improve displacement efficiency and injection-production efficiency under certain conditions. Multi-component gas injection not only reduces the technical threshold and economic burden of purification and capture, but also broadens the application range of CCUS, realizes efficient utilization of resources, and maximizes environmental benefits. However, due to the complexity of components, the existing evaluation system based on pure carbon dioxide cannot accurately reflect the behavior and efficiency of multi-component gas injection, increasing the uncertainty of injection-production scheme design and restricting the improvement of comprehensive development efficiency of depleted gas reservoirs.
[0004] Therefore, how to provide an evaluation method for the injection capacity of non-pure carbon dioxide multi-component mixed gas, which is unified, systematic and practical, to help optimize the injection-production scheme scientifically and reasonably, improve the utilization efficiency of gas reservoirs, provide technical support for the popularization and application of CCUS technology, promote the coordinated development of injection-production and carbon emission reduction technology in depleted gas reservoirs, and realize the win-win of energy utilization and environmental protection, is a problem that needs to be solved by those skilled in the art. SUMMARY
[0005] Therefore, the present application provides a method for evaluating the injection capacity of non-pure carbon dioxide in depleted gas reservoirs.
[0006] In order to achieve the above purpose, the present application adopts the following technical scheme: A method for evaluating the injection capacity of non-pure carbon dioxide in depleted gas reservoirs, comprising: Step 1: According to the original content ratio of each gas component in the reservoir, the actual daily production of each gas component is converted into the converted daily production corresponding to the gas reservoir content of 100%; Step 2: Based on the calculated daily production, combined with the bottom hole pressure and reservoir pressure, construct the binomial production capacity analysis curves for different gases, and perform linear fitting to obtain the laminar flow coefficient and turbulence coefficient. Based on the binomial production capacity equation, obtain the injection capacity equations for different gases in the gas well. Step 3: Based on the wellhead pressure and hydrostatic column pressure, derive the bottom hole injection pressure, and combine it with the reservoir pressure, substitute it into the injection capacity equation, and calculate the maximum injection amount of each gas component when injecting non-pure gas into the gas well. Step 4: Based on the proportion of each gas component in the injected gas, the maximum injection volume is calculated to obtain the injection capacity of each gas when injecting non-pure gas into the gas well.
[0007] Optionally, in step 1, based on the original content percentage of each gas component in the reservoir, the daily actual production of each gas component is converted into the converted daily production with the corresponding gas reservoir content set at 100%, as follows:
[0008] in, Daily production converted from gas components; This represents the actual daily production of the gaseous components. This represents the original content percentage of the gas components in the reservoir gas.
[0009] Optionally, in step 2, based on the converted daily production rate and combined with the bottom hole pressure and reservoir pressure, a binomial production capacity analysis curve for different gases is constructed, specifically as follows: The binomial production capacity equation is determined as follows:
[0010] in, For reservoir pressure; This refers to the bottom hole pressure. To calculate daily output; The laminar flow coefficient; The turbulence coefficient; Divide both sides of the binomial production capacity equation by... This yields the following formula:
[0011] by The vertical axis is , Plotting the x-axis yields binomial productivity analysis curves for different gases.
[0012] Optionally, in step 2, linear fitting is performed to obtain the laminar flow coefficient and turbulent flow coefficient. Based on the binomial productivity equation, the injection capacity equation for different gases in the gas well is obtained, specifically: The binomial capacity analysis curve is linearly fitted, and the ordinate of the intersection of the fitted line and the y-axis is the laminar flow coefficient. The slope of the fitted straight line is the turbulence coefficient. Based on the binomial energy production equation, the injection capacity equations for different gases are obtained as follows:
[0013] in, For reservoir pressure; Inject pressure into the bottom of the well; This represents the maximum injection volume of the gas component.
[0014] Optionally, in step 3, the bottom hole injection pressure is derived based on the wellhead pressure and hydrostatic column pressure, as follows:
[0015] in, Inject pressure into the bottom of the well; This refers to the wellhead pressure. This refers to the hydrostatic pressure. The density of the liquid; It is the acceleration due to gravity; The depth is the vertical well depth.
[0016] Optionally, in step 4, the maximum injection volume is calculated based on the proportion of each gas component in the injected gas to obtain the injection capacity of each gas when injecting non-pure gas into the gas well, as follows:
[0017] in, The ability to inject gas; This represents the maximum injection volume of the gas component; This represents the proportion of gas in the injected gas.
[0018] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a method for evaluating the injection capacity of non-pure carbon dioxide in depleted gas reservoirs. Compared with the prior art, the evaluation method of the present invention is applicable to the injection of non-pure carbon dioxide gas into depleted gas reservoirs, can accurately reflect the injection capacity, is simple to operate, and has high computational efficiency, improves the accuracy of gas injection effect prediction, is easy to apply quickly in the field, and has wide applicability and good practical value. Attached Figure Description
[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0020] Figure 1 This is a schematic diagram of the method flow provided by the present invention.
[0021] Figure 2 This is a schematic diagram of the nitrogen binomial energy production analysis curve of the present invention.
[0022] Figure 3 This is a schematic diagram of the nitrogen gas production capacity fitting analysis curve of the present invention.
[0023] Figure 4 This is a schematic diagram comparing the calculated results of the maximum injection volume of nitrogen gas under different injection pressure conditions with field data.
[0024] Figure 5 This is a schematic diagram of the binomial capacity analysis curve for methane according to the present invention.
[0025] Figure 6 This is a schematic diagram of the binomial carbon dioxide production capacity analysis curve of the present invention.
[0026] Figure 7 This is a schematic diagram of the methane gas production capacity fitting analysis curve of the present invention.
[0027] Figure 8 This is a schematic diagram of the carbon dioxide gas production capacity fitting analysis curve of the present invention. Detailed Implementation
[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0029] Example 1: Embodiment 1 of this invention discloses a method for evaluating the non-pure carbon dioxide injection capacity of depleted gas reservoirs, such as... Figure 1 As shown, it includes: A method for evaluating the non-pure carbon dioxide injection capacity of depleted gas reservoirs includes: Step 1: Based on the original content ratio of each gas component in the reservoir, convert the daily actual production of each gas component into the daily production of the corresponding gas reservoir with a content of 100%.
[0030] Based on the original content percentage of each gas component in the reservoir, the daily actual production of each gas component is converted to the corresponding daily production with a reservoir content of 100%, as follows:
[0031] in, Daily production converted from gas components; This represents the actual daily production of the gaseous components. This represents the original content percentage of the gas components in the reservoir gas.
[0032] Step 2: Based on the calculated daily production, combined with the bottom hole pressure and reservoir pressure, construct binomial production capacity analysis curves for different gases, and perform linear fitting to obtain the laminar flow coefficient and turbulence coefficient. Based on the binomial production capacity equation, obtain the injection capacity equation for different gases in the gas well.
[0033] Based on the calculated daily production, and combined with the bottom hole pressure and reservoir pressure, a binomial production capacity analysis curve for different gases is constructed, as follows: The binomial production capacity equation is determined as follows:
[0034] in, For reservoir pressure; This refers to the bottom hole pressure. To calculate daily output; The laminar flow coefficient; The turbulence coefficient; Divide both sides of the binomial production capacity equation by... This yields the following formula:
[0035] by The vertical axis is , Plotting the x-axis yields binomial productivity analysis curves for different gases.
[0036] Linear fitting was performed to obtain the laminar flow coefficient and turbulent flow coefficient. Based on the binomial productivity equation, the injection capacity equations for different gases in the gas well were obtained, specifically: The binomial capacity analysis curve is linearly fitted, and the ordinate of the intersection of the fitted line and the y-axis is the laminar flow coefficient. The slope of the fitted straight line is the turbulence coefficient. Based on the binomial energy production equation, the injection capacity equations for different gases are obtained as follows:
[0037] in, For reservoir pressure; Inject pressure into the bottom of the well; This represents the maximum injection volume of the gas component.
[0038] Step 3: Based on the wellhead pressure and hydrostatic column pressure, derive the bottom hole injection pressure, and combine it with the reservoir pressure, substitute it into the injection capacity equation, and calculate the maximum injection amount of each gas component when injecting non-pure gas into the gas well.
[0039] Based on the wellhead pressure and hydrostatic column pressure, the bottom hole injection pressure is derived as follows:
[0040] in, Inject pressure into the bottom of the well; This refers to the wellhead pressure. This refers to the hydrostatic pressure. The density of the liquid; It is the acceleration due to gravity; The depth is the vertical well depth.
[0041] Step 4: Based on the proportion of each gas component in the injected gas, the maximum injection volume is calculated to obtain the injection capacity of each gas when injecting non-pure gas into the gas well.
[0042] Based on the proportion of each gas component in the injected gas, the maximum injection volume is calculated to obtain the injection capacity of each gas when injecting non-pure gas into the gas well, as follows:
[0043] in, The ability to inject gas; This represents the maximum injection volume of the gas component; This represents the proportion of gas in the injected gas.
[0044] Example 2: Embodiment 2 of this invention discloses a specific application of a method for evaluating the non-pure carbon dioxide injection capacity of depleted gas reservoirs (single-gas injection calculation application of this invention). Taking well L2 as an example, well L2 is 3000m deep with a reservoir pressure of 17.07 MPa. The original reservoir gas is mainly methane, with impurities mainly carbon dioxide and nitrogen, of which methane accounts for 95%, carbon dioxide for 4%, and nitrogen for 1%. Currently, field nitrogen injection tests have been conducted on well L2, and the field nitrogen injection data are shown in Table 1.
[0045] Table 1. On-site nitrogen injection test data
[0046] The nitrogen production data of well L2 is shown in Table 2.
[0047] Table 2 Nitrogen On-site Production Data
[0048] The daily nitrogen production was converted using the following formula, with nitrogen accounting for 1% of the total nitrogen production:
[0049] The converted daily nitrogen gas production By combining bottom hole pressure and reservoir pressure data, nitrogen gas was obtained. The values are shown in Table 3.
[0050] Table 3 value
[0051] by The vertical axis is , Plotting the x-axis yields the binomial nitrogen production capacity analysis curve for well L2, as shown below. Figure 2 As shown.
[0052] The nitrogen binomial energy production analysis curve was linearly fitted using Origin to obtain the nitrogen gas energy production fitting analysis curve, as follows: Figure 3 As shown. Based on the fitting analysis curve, the coefficients A and B of the nitrogen injection capacity equation were obtained, and the final injection capacity equation is as follows:
[0053] Based on the nitrogen injection test data, the bottom hole injection pressures were taken as 18.36 MPa, 19.96 MPa, 22.12 MPa, 25.20 MPa, 33.96 MPa, and 45.67 MPa, respectively, and the reservoir pressure was taken as 17.07 MPa. The maximum injection volume of nitrogen gas under different injection pressure conditions was calculated, and the calculation results were compared with the field data, as shown in Table 4.
[0054] Table 4 Comparison of Calculated Results and Field Data for Maximum Nitrogen Injection Volume under Different Injection Pressures
[0055] The calculation results have a small error compared to the actual field data, such as Figure 4 As shown, this demonstrates the reliability of the method and its applicability for gas injection capacity analysis.
[0056] Example 3: Example 3 of this invention discloses a specific application of a method for evaluating the non-pure carbon dioxide injection capacity of depleted gas reservoirs (the multi-gas injection calculation application of this invention, and whether it is a multi-gas injection calculation application or a single-gas injection calculation application, the injection capacity equation of the same gas calculated is consistent. See Example 3 below, when calculating the maximum injection volume and actual gas injection capacity under different injection pressure conditions for three gases, the nitrogen injection capacity equation calculated in the single-gas injection calculation application of Example 2 is directly used). Taking well L2 as an example, well L2 is 3000m deep, the current reservoir pressure is 17.07MPa, and the original reservoir gas mainly contains methane, carbon dioxide and nitrogen, of which methane accounts for 95%, carbon dioxide accounts for 4%, and nitrogen accounts for 1%. The field production data of methane and carbon dioxide gas in well L2 are shown in Table 5.
[0057] Table 5. On-site production data of methane and carbon dioxide gas from Well L2
[0058] The daily production of methane and carbon dioxide was converted using the following formulas, with methane accounting for 95% and carbon dioxide for 4% of the total production.
[0059] The converted daily production of methane and carbon dioxide gases is shown in Table 6.
[0060]
[0061] Based on the calculated production rates obtained from Table 6, and combined with bottom hole pressure and reservoir pressure data, the production rates of methane and carbon dioxide were determined. The values are shown in Table 7.
[0062] Table 7 Methane and Carbon Dioxide value
[0063] by The vertical axis is , Plotting the x-axis yields binomial production capacity analysis curves for methane and carbon dioxide, as shown below. Figure 5 , Figure 6 As shown.
[0064] The binomial productivity analysis curves for methane and carbon dioxide were linearly fitted using Origin, resulting in gaseous productivity fitting analysis curves for methane and carbon dioxide, respectively. Figure 7 , Figure 8 As shown.
[0065] according to Figure 3, Figure 7 and Figure 8 The coefficients A and B of the injection capacity equations for nitrogen, methane, and carbon dioxide were obtained respectively. Substituting these coefficients into the injection capacity equations, the injection capacity equations for the three gases were obtained, as shown in Table 8.
[0066] Table 8 Equations for the injection capacity of three gases
[0067] The wellhead injection pressures are set at 2, 4, 6, 8, 10, and 12 MPa based on site requirements, for a well depth of 3000m. The wellhead pressures are converted to bottom-hole injection pressures (i.e., injection pressures) to calculate the maximum injection volume. The conversion method is based on the formula for trans-fluid column pressure. Take 1000 kg / m 3 , Take 9.81 m / s 2 , With a depth of 3000m, the calculated bottom hole pressures are 31.43MPa, 33.43MPa, 35.43MPa, 37.43MPa, 39.43MPa, and 41.43MPa, respectively.
[0068] Based on the bottom-hole injection pressure, reservoir pressure, and binomial injection capacity equation, the maximum injection volume of methane, carbon dioxide, and nitrogen under different injection pressure conditions was calculated. The calculation results are shown in Table 9.
[0069] Table 9 Maximum Injection Volume of Methane, Carbon Dioxide, and Nitrogen under Different Injection Pressures
[0070] According to the gas injection requirements of L2 well, the injection is 90% CO2 + 8% CH4 + 2% N2. The maximum injection volume of each component gas is calculated proportionally, and the calculation formula is as follows:
[0071] The actual injection capacity of the three gases was calculated and is shown in Table 10.
[0072] Table 10 Actual Injection Capacity of Three Gases
[0073] This invention accurately obtains the actual injection capacity of each gas component in a non-pure carbon dioxide mixture injected into a gas injection well in a gas reservoir, solving the problem that traditional methods struggle to distinguish the injection contribution of each component. Since nitrogen exists as an impurity gas in the mixture, this method is also applicable to mixed gas systems containing other impurities such as oxygen. By combining actual production data, a calculated daily production rate and a binomial production capacity equation are obtained, significantly improving the accuracy and reliability of injection capacity calculation. The method is simple to operate, applicable to various operating conditions and gas ratios, and can effectively guide injection strategies, providing solid technical support for improving gas injection efficiency and reservoir development effectiveness.
[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.
[0075] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A method for evaluating the non-pure carbon dioxide injection capacity of a depleted gas reservoir, characterized in that, include: Step 1: Based on the original content ratio of each gas component in the reservoir, convert the daily actual production of each gas component into the daily production of the corresponding gas reservoir with a content of 100%. Step 2: Based on the calculated daily production, combined with the bottom hole pressure and reservoir pressure, construct binomial production capacity analysis curves for different gases, and perform linear fitting to obtain the laminar flow coefficient and turbulence coefficient. Based on the binomial production capacity equation, obtain the injection capacity equations for different gases in the gas well. Step 3: Based on the wellhead pressure and hydrostatic column pressure, derive the bottom hole injection pressure, and combine it with the reservoir pressure, substitute it into the injection capacity equation, and calculate the maximum injection amount of each gas component when injecting non-pure gas into the gas well. Step 4: Based on the proportion of each gas component in the injected gas, the maximum injection volume is calculated to obtain the injection capacity of each gas when injecting non-pure gas into the gas well.
2. The method for evaluating the non-pure carbon dioxide injection capacity of a depleted gas reservoir according to claim 1, characterized in that, In step 1, based on the original content percentage of each gas component in the reservoir, the daily actual production of each gas component is converted into the corresponding daily production with a reservoir content of 100%, as follows: in, Daily production converted from gas components; This represents the actual daily production of the gaseous components. This represents the original content percentage of the gas components in the reservoir gas.
3. The method for evaluating the non-pure carbon dioxide injection capacity of a depleted gas reservoir according to claim 1, characterized in that, In step 2, based on the calculated daily production rate, and combining the bottom hole pressure and reservoir pressure, a binomial production capacity analysis curve for different gases is constructed, specifically as follows: The binomial production capacity equation is determined as follows: in, For reservoir pressure; This refers to the bottom hole pressure. The calculated daily output; The laminar flow coefficient; The turbulence coefficient; Divide both sides of the binomial production capacity equation by... This yields the following formula: by The vertical axis is , Plotting the x-axis yields binomial productivity analysis curves for different gases.
4. The method for evaluating the non-pure carbon dioxide injection capacity of a depleted gas reservoir according to claim 1, characterized in that, In step 2, linear fitting is performed to obtain the laminar flow coefficient and turbulent flow coefficient. Based on the binomial productivity equation, the injection capacity equations for different gases in the gas well are obtained, specifically: The binomial capacity analysis curve is linearly fitted, and the ordinate of the intersection of the fitted line and the y-axis is the laminar flow coefficient. The slope of the fitted straight line is the turbulence coefficient. Based on the binomial energy production equation, the injection capacity equations for different gases are obtained as follows: in, For reservoir pressure; Inject pressure into the bottom of the well; This represents the maximum injection volume of the gas component.
5. The method for evaluating the non-pure carbon dioxide injection capacity of a depleted gas reservoir according to claim 1, characterized in that, In step 3, the bottom hole injection pressure is derived based on the wellhead pressure and hydrostatic column pressure, as follows: in, Inject pressure into the bottom of the well; This refers to the wellhead pressure. This refers to the hydrostatic pressure. The density of the liquid; It is the acceleration due to gravity; The depth is the vertical well depth.
6. The method for evaluating the non-pure carbon dioxide injection capacity of a depleted gas reservoir according to claim 1, characterized in that, In step 4, the maximum injection volume is calculated based on the proportion of each gas component in the injected gas to obtain the injection capacity of each gas when injecting non-pure gas into the gas well, as follows: in, The ability to inject gas; This represents the maximum injection volume of the gas component; This represents the proportion of gas in the injected gas.