Method for analyzing effect of CO2 injection on water invasion in offshore water invasion gas reservoir

Abstract

The application discloses a kind of offshore water invasion gas reservoir injection CO2 inhibiting water invasion effect analysis method, comprising the following steps: S1: obtaining offshore water invasion gas reservoir production well gas reservoir production data and gas reservoir dynamic parameter;S2: according to the gas reservoir dynamic parameter constructs offshore water invasion gas reservoir geological model and offshore water invasion gas reservoir numerical simulation model;S3: according to the gas reservoir production data completes the history fitting and verification of the offshore water invasion gas reservoir geological model and the offshore water invasion gas reservoir numerical simulation model;S4: preferred injection well, and using the offshore water invasion gas reservoir numerical simulation model carries out injection CO2 inhibiting water invasion numerical simulation to preferred injection well, when numerical simulation, consider CO2 breakthrough and the influence of water content on CO2 inhibiting water invasion effect.This application can more reasonably analyze and obtain offshore water invasion gas reservoir injection CO2 inhibiting water invasion effect, to better optimize injection scheme, provide technical support for offshore water invasion gas reservoir development.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water invasion gas reservoir production and development in oil and gas engineering, and particularly relates to a method for analyzing the effect of CO2 injection on water invasion inhibition in offshore water invasion gas reservoirs. BACKGROUND

[0002] Offshore gas reservoir development is aimed at utilizing the natural gas resources buried under the seabed, which plays a crucial role in meeting global energy demand. However, compared with onshore gas reservoirs, offshore gas reservoir development faces more challenges, one of which is gas reservoir water invasion. Gas reservoir water invasion refers to the phenomenon of water around the seabed gas reservoir seeping into the gas reservoir. This can have a serious impact on the development of the gas reservoir. First, the presence of water will reduce the production of natural gas in the gas reservoir, as water will occupy space in the gas reservoir and drive out the gas. Second, the presence of water will increase the complexity and cost of the production process. Therefore, it is of great significance to inhibit gas reservoir water invasion. First, through effective water drive management, the production of the gas reservoir can be maximized, thereby improving the economic benefits of development. Second, effective water invasion inhibition measures can reduce the technical difficulty and cost of the production process, making development more efficient and feasible. In addition, water invasion inhibition also helps to protect the environment and avoid environmental pollution due to improper water treatment.

[0003] Due to the geographical limitations of offshore gas reservoirs, considering economic costs, conventional methods such as drainage gas recovery are difficult to carry out, and gas injection to inhibit water invasion and improve recovery is considered an effective method. Currently, CO2 injection is commonly used for enhanced oil recovery, and the CO2 injected into the formation is usually in a supercritical state, with both gaseous and liquid properties, which is good for gas displacement. However, the physical properties of supercritical CO2 also make it more prone to gas channeling, i.e., CO2 rapidly breaks through along a certain channel, greatly reducing the displacement efficiency. Existing methods for offshore gas injection to inhibit water invasion and improve recovery often only focus on the change in water cut of the gas well, ignoring the impact of CO2 breakthrough on water invasion inhibition and recovery enhancement. The data calculated and the plan developed are based on ideal conditions, and there is a large error. SUMMARY

[0004] In view of the above problems, the present application aims to provide a method for analyzing the effect of CO2 injection on water invasion inhibition in offshore water invasion gas reservoirs.

[0005] The technical solution of the present application is as follows:

[0006] A method for analyzing the effect of CO2 injection on water invasion inhibition in offshore water invasion gas reservoirs, comprising the following steps:

[0007] S1: obtaining gas reservoir production data and gas reservoir dynamic parameters of offshore water invasion gas reservoir production wells;

[0008] S2: constructing an offshore water-invasion gas reservoir geological model and an offshore water-invasion gas reservoir numerical simulation model according to the gas reservoir dynamic parameters;

[0009] S3: completing history matching and verification of the offshore water-invasion gas reservoir geological model and the offshore water-invasion gas reservoir numerical simulation model according to the gas reservoir production data;

[0010] S4: preferably selecting a gas injection well, and using the offshore water-invasion gas reservoir numerical simulation model to carry out numerical simulation of CO2 injection for inhibiting water invasion in the selected gas injection well, and in the numerical simulation, the influence of CO2 breakthrough and water cut on the effect of CO2 injection for inhibiting water invasion is considered.

[0011] Preferably, in step S1, the gas reservoir production data includes cumulative gas production, daily gas production, cumulative water production, daily water production, wellhead pressure, bottom hole pressure, water cut, well stream composition, relative permeability, rock physical properties, and initial conditions of the gas reservoir.

[0012] Preferably, in step S1, the gas reservoir dynamic parameters include gas reservoir area range, gas reservoir trap line and fault line, gas reservoir depth, gas reservoir fracture distribution, gas reservoir cave parameter, gas reservoir porosity field, gas reservoir permeability field, gas reservoir saturation field, gas reservoir net-to-gross ratio field, gas reservoir temperature field, gas reservoir pressure field, gas reservoir gas composition, gas reservoir formation water characteristics, gas reservoir rock characteristics, and gas reservoir relative permeability curve.

[0013] Preferably, in step S2, the offshore water-invasion gas reservoir geological model is constructed by using Petrel software, and the offshore water-invasion gas reservoir numerical simulation model is constructed by using CMG software.

[0014] Preferably, in step S3, the history matching and verification are completed when the matching degree of the calculation result of the numerical simulation and the gas reservoir production data is greater than a matching degree threshold.

[0015] Preferably, the matching degree threshold is 85%.

[0016] Preferably, in step S4, the gas injection well is selected according to production data, well distribution, and reservoir property distribution.

[0017] Preferably, in step S4, the selection of the gas injection well includes the following steps:

[0018] First, a gas well with water cut higher than a water cut threshold and gas production less than a gas production threshold is selected as a first selected gas injection well;

[0019] Second, a gas well located in the middle of a well group in the first selected gas injection well is selected as a second selected gas injection well based on a five-point well pattern method or a nine-point well pattern method in combination with well distribution.

[0020] Finally, according to the reservoir physical property distribution, the heterogeneity type of the formation is determined, and the gas injection well is selected in combination with the gas well horizon;

[0021] When the formation is a positive rhythm, the gas well with the upper perforation position in the gas injection well two is selected as the final preferred gas injection well;

[0022] When the formation is a reverse rhythm, the gas well with the lower perforation position in the gas injection well two is selected as the final preferred gas injection well;

[0023] When the formation is a composite rhythm, when there is only the preferred gas injection well one, the gas injection well one is taken as the final preferred gas injection well; when there is the preferred gas injection well two, the gas injection well two is taken as the final preferred gas injection well.

[0024] As preferred, in step S4, when CO2 breakthrough is considered, the CO2 breakthrough time and the mole fraction after breakthrough are considered.

[0025] The beneficial effects of the present application are:

[0026] The present application can improve the accuracy of analyzing the effect of CO2 injection on water invasion by considering the important mechanism of CO2 breakthrough in the analysis process of numerical simulation results, thereby better optimizing the gas injection scheme and providing technical support for the development of offshore water invasion gas reservoirs. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0028] Figure 1 A 2D offshore water invasion gas reservoir geological model schematic diagram of an embodiment of offshore water invasion gas reservoir is shown;

[0029] Figure 2 A 3D offshore water invasion gas reservoir geological model schematic diagram of an embodiment of offshore water invasion gas reservoir is shown;

[0030] Figure 3 A numerical simulation model schematic diagram of an embodiment of offshore water invasion gas reservoir is shown;

[0031] Figure 4 A production well water cut result schematic diagram of an embodiment is shown;

[0032] Figure 5 A CO2 breakthrough time and breakthrough mole fraction result schematic diagram of an embodiment is shown. DETAILED DESCRIPTION

[0033] The application will be further described below in conjunction with the accompanying drawings and examples. It should be noted that the examples in the present application and the technical features in the examples can be combined with each other without conflict. It should be noted that all the technical and scientific terms used in the present application have the same meaning as generally understood by the ordinary skilled person in the technical field to which the present application belongs, unless otherwise specified. The present application discloses that the "including" or "containing" and similar words mean that the elements or objects before the words cover the elements or objects listed after the words and their equivalents, and do not exclude other elements or objects.

[0034] The application provides an analysis method for inhibiting water invasion effect by injecting CO2 into a marine water invasion gas reservoir, comprising the following steps:

[0035] S1: obtaining gas reservoir production data and gas reservoir dynamic parameters of a production well of a marine water invasion gas reservoir.

[0036] In a specific embodiment, the gas reservoir production data comprises cumulative gas production, daily gas production, cumulative water production, daily water production, wellhead pressure, bottom hole pressure, water cut, well stream composition, relative permeability, rock physical properties and initial conditions of the gas reservoir.

[0037] In a specific embodiment, the gas reservoir dynamic parameters comprise gas reservoir area range, gas reservoir trap line and fault line, gas reservoir depth, gas reservoir fracture distribution, gas reservoir cave parameter, gas reservoir porosity field, gas reservoir permeability field, gas reservoir saturation field, gas reservoir net / gross ratio field, gas reservoir temperature field, gas reservoir pressure field, gas reservoir gas composition, gas reservoir formation water characteristics, gas reservoir rock characteristics and gas reservoir relative permeability curve.

[0038] S2: constructing a marine water invasion gas reservoir geological model and a marine water invasion gas reservoir numerical simulation model according to the gas reservoir dynamic parameters.

[0039] In a specific embodiment, the marine water invasion gas reservoir geological model is constructed by using Petrel software, and the marine water invasion gas reservoir numerical simulation model is constructed by using CMG software.

[0040] In the above embodiment, Petrel software is used for geological modeling and subsequent numerical simulation in the field of domestic and foreign petroleum geology. As a mature commercial software, the modeling precision is high, the functions are complete, and the precision of the model of the present application can be improved. CMG software is a commonly used numerical simulator in the field of domestic and foreign petroleum geology, which has high calculation speed and high calculation precision, and can consider the water-rock chemical reaction after injecting CO2, so that the simulation result is closer to the actual situation.

[0041] It should be noted that the two software above are only preferred software of the present application, and other software capable of establishing a geological model and a numerical simulation model in the prior art can also be applicable to the present application.

[0042] S3: completing the history matching and verification of the offshore water-invasion gas reservoir geological model and the offshore water-invasion gas reservoir numerical simulation model according to the gas reservoir production data.

[0043] In the present application, the offshore water-invasion gas reservoir geological model and the offshore water-invasion gas reservoir numerical simulation model established by the present application can be made more in line with actual working conditions through history matching and verification, thereby improving the accuracy of subsequent numerical simulation results. In the history matching process, the permeability and relative permeability of the model are mainly adjusted, and the bottom hole pressure and water cut are fitted by the constant gas production rate.

[0044] In a specific embodiment, the history matching and verification are completed when the matching degree of the calculation result of the numerical simulation and the gas reservoir production data is greater than a matching degree threshold. Optionally, the matching degree threshold is 85%.

[0045] S4: preferably selecting a gas injection well, and carrying out numerical simulation of CO2 injection for water invasion prevention in the preferred gas injection well by using the offshore water-invasion gas reservoir numerical simulation model, and considering the influence of CO2 breakthrough and water cut on the effect of CO2 injection for water invasion prevention in the numerical simulation.

[0046] In a specific embodiment, the gas injection well is preferably selected according to the production data, well distribution and reservoir property distribution; and the preferred selection of the gas injection well comprises the following steps:

[0047] First, a gas well with a water cut higher than a water cut threshold and a gas production rate lower than a gas production rate threshold is selected as a preferred gas injection well one;

[0048] Second, a gas well located in the middle of a well group in the gas injection well one is selected as a preferred gas injection well two based on a five-point well pattern method or a nine-point well pattern method in combination with well distribution;

[0049] Finally, the heterogeneity type of the formation is determined according to the reservoir property distribution, and a gas injection well is selected in combination with the layer position of the gas well;

[0050] When the formation is a positive rhythm, a gas well with a perforation position higher up is selected as a final preferred gas injection well in the gas injection well two;

[0051] When the formation is an inverse rhythm, a gas well with a perforation position lower down is selected as a final preferred gas injection well in the gas injection well two;

[0052] When the formation is a composite rhythm, when there is only the preferred gas injection well one, the gas injection well one is taken as the final preferred gas injection well; and when there is the preferred gas injection well two, the gas injection well two is taken as the final preferred gas injection well.

[0053] In the above embodiment, the injection well can be quickly selected by the production data, the well distribution and the reservoir property distribution, and the workload of predicting the preferred well position by numerical simulation is reduced.

[0054] In the above embodiment, the gas well with the water cut higher than the water cut threshold and the gas production lower than the gas production threshold is selected as the gas well with high water cut and low gas production. In a specific embodiment, the water cut threshold is 70%, and the gas production threshold is 50,000 cubic meters per day.

[0055] In a specific embodiment, the CO2 breakthrough time and the mole fraction after the breakthrough are considered when the CO2 breakthrough is considered. The CO2 breakthrough time refers to the time when the proportion of CO2 in the produced gas exceeds 30%. In this embodiment, the analysis result of the present application is closer to the actual working condition by considering the CO2 breakthrough, so that the production plan is more accurate.

[0056] Taking a certain offshore water-intrusion gas reservoir as an example, the analysis method for analyzing the effect of CO2 injection on water intrusion inhibition in the offshore water-intrusion gas reservoir is used to analyze the effect of CO2 injection on water intrusion inhibition and enhanced oil recovery in the offshore water-intrusion gas reservoir. In this embodiment, the established geological model of the offshore water-intrusion gas reservoir is as shown in Figure 1 and Figure 2 The established numerical simulation model of the offshore water-intrusion gas reservoir is as shown in Figure 3 .

[0057] The working system is set as follows: the injection rate of the injection well is 100,000 cubic meters per day, the injected fluid is pure CO2, and the production rates of the production wells are 50,000 cubic meters per day and 100,000 cubic meters per day, respectively. The calculated water cut of the production well is as shown in Figure 4 , and the CO2 breakthrough time and the mole fraction are as shown in Figure 5 .

[0058] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent change and modification of the above embodiment according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A method for analyzing the effect of CO2 injection on inhibiting water intrusion in offshore water-invaded gas reservoirs, characterized in that: The following steps are involved: S1: Obtain gas reservoir production data and gas reservoir dynamic parameters of production wells in offshore water-invaded gas reservoirs; S2: constructing an offshore water-invasion gas reservoir geological model and an offshore water-invasion gas reservoir numerical simulation model according to the gas reservoir dynamic parameters; S3: completing history fitting and verification of the offshore water-invasion gas reservoir geological model and the offshore water-invasion gas reservoir numerical simulation model based on the gas reservoir production data; S4: Selecting gas injection wells based on production data, well location distribution, and reservoir physical property distribution, and using the offshore water-invasion gas reservoir numerical simulation model to perform numerical simulation of CO2 injection to inhibit water intrusion on the selected gas injection wells. During the numerical simulation, the effects of CO2 breakthrough and water content on the CO2 water intrusion inhibition effect are considered; The preferred gas injection well includes the following steps: First, a gas well with a water cut higher than a water cut threshold and a gas production lower than a gas production threshold is selected as the preferred gas injection well 1; Secondly, based on the five-point well pattern method or the nine-point well pattern method, the gas well located in the middle of the well group is selected as the preferred gas injection well 2 in combination with the well location distribution; Finally, the heterogeneity type of the formation is determined based on the distribution of reservoir physical properties, and the gas injection wells are selected in combination with the gas well positions; When considering CO2 breakthrough, the CO2 breakthrough time and mole fraction after breakthrough are considered.

2. The method for analyzing the effect of CO2 injection on inhibiting water intrusion in offshore water-invaded gas reservoirs according to claim 1, characterized in that: In step S1, the gas reservoir production data includes cumulative gas production, daily gas production, cumulative water production, daily water production, wellhead pressure, bottom hole pressure, water content, well flow composition, relative permeability, rock physical properties and gas reservoir initial conditions.

3. The method for analyzing the effect of CO2 injection on inhibiting water intrusion in offshore water-invaded gas reservoirs according to claim 1, characterized in that: In step S1, the gas reservoir dynamic parameters include the gas reservoir area range, gas reservoir closure line and fault line, gas reservoir depth, gas reservoir fracture distribution, gas reservoir cave parameters, gas reservoir porosity field, gas reservoir permeability field, gas reservoir saturation field, gas reservoir net-to-gross ratio field, gas reservoir temperature field, gas reservoir pressure field, gas reservoir gas composition, gas reservoir formation water characteristics, gas reservoir rock characteristics and gas reservoir relative permeability curve.

4. The method for analyzing the effect of CO2 injection on inhibiting water intrusion in offshore water-invaded gas reservoirs according to claim 1, characterized in that: In step S2, the geological model of the offshore water-invading gas reservoir is constructed using Petrel software, and the numerical simulation model of the offshore water-invading gas reservoir is constructed using CMG software.

5. The method for analyzing the effect of CO2 injection on inhibiting water intrusion in offshore water-invaded gas reservoirs according to claim 1, characterized in that: In step S3, when the degree of matching between the calculation result of the numerical simulation and the gas reservoir production data is greater than a matching degree threshold, the history matching and verification are completed.

6. The method for analyzing the effect of CO2 injection on inhibiting water intrusion in offshore water-invaded gas reservoirs according to claim 5, characterized in that: The matching degree threshold is 85%.

7. The method for analyzing the effect of CO2 injection on inhibiting water intrusion in offshore water-invaded gas reservoirs according to claim 1, characterized in that: In step S4, the gas injection well preferably further comprises the following steps: When the formation has a positive rhythm, a gas well with an upper perforation position is selected from the second gas injection well as the final preferred gas injection well; When the formation has an anti-rhythm, the gas well with the lower perforation position is selected as the final preferred gas injection well among the second gas injection wells; When the formation has a complex rhythm, when there is only one preferred gas injection well, the first gas injection well is used as the final preferred gas injection well; when there is a second preferred gas injection well, the second gas injection well is used as the final preferred gas injection well.

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