Method for calculating complex mineral surface contact angle of oil and gas reservoir under action of carbon dioxide

Abstract

The invention relates to the technical field of oil development, in particular to a method for calculating a complex mineral surface contact angle of an oil and gas reservoir under the action of carbon dioxide, which comprises the following steps of: acquiring complex mineral surface component composition and geometric parameters of a target oil and gas reservoir; acquiring gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions; the complex mineral surface of the oil and gas reservoir is divided into a liquid-phase wetted surface and a gas-phase wetted surface; under the selected carbon dioxide pressure condition, the contact angle is calculated; and in combination with gas-liquid-solid interface characteristic parameters, a contact angle changing along with pressure is obtained. By researching the wettability of the carbon dioxide and different reservoir mineral surfaces, the rock characteristics of all potential storage sites can be deeply known, the storage potential and stability of the carbon dioxide in the storage sites can be evaluated, the high-quality storage sites where the carbon dioxide more stably exists are screened out, and the storage efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum development, and in particular to a method for calculating contact angles on complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide. Background Art

[0002] Ultra-low permeability reservoirs hold a significant position in my country's oil and gas resources, particularly in the Ordos Basin, where such reserves comprise a significant proportion of low-permeability resources. However, due to their poor physical properties and strong heterogeneity, development is significantly challenging. To effectively increase the recovery rate of these reservoirs, commonly used technologies include gas injection, polymer flooding, and microbial flooding. However, ultra-low permeability reservoirs face a series of challenges during waterflooding, including high injection pressures, difficulty in injecting water, and low recovery rates, limiting conventional methods. Carbon dioxide flooding, as an effective displacement method for improving recovery, is of great significance for the efficient development of ultra-low permeability reservoirs due to its wide applicability and environmentally friendly advantages.

[0003] During the development of low-permeability reservoirs, the wettability of rock mineral surfaces plays a crucial role in oil-water interaction and oil recovery efficiency. Under varying wettability conditions, the distribution of oil and water in the reservoir and its flow characteristics can significantly change, impacting ultimate recovery. During CO2 displacement recovery, changes in CO2 pressure, phase state, and mineral reactions can lead to changes in mineral surface wettability, thereby affecting oil and gas mobility in low-permeability reservoirs. Summary of the Invention

[0004] To address the problem that the wettability of complex mineral surfaces in oil and gas reservoirs under the action of oil and carbon dioxide cannot be quantitatively characterized, the present invention constructs a method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide based on the surface characteristics of complex minerals in the target oil and gas reservoirs and the characteristic parameters of the gas-liquid-solid interface, combined with the theory of complex surface wetting, and a combination of experimental research and theoretical models.

[0005] The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide comprises the following steps: Step 1: Obtain the surface component composition and geometric parameters of the complex mineral surfaces of the target oil and gas reservoir; Step 2: Obtain characteristic parameters of the gas-liquid-solid interface of different minerals under different carbon dioxide pressure conditions; Step 3: According to the surface composition and geometric parameters of the complex minerals in the oil and gas reservoir obtained in Step 1, a numerical simulation method is used to calculate the wettability of the mineral surface, and the complex mineral surfaces in the oil and gas reservoir are divided into two types: liquid-wetting surfaces and gas-wetting surfaces; Step 4: Under the selected carbon dioxide pressure conditions, the contact angle of the liquid droplet on the complex mineral surface of the oil and gas reservoir is calculated according to the actual ratio of the liquid-wetted surface to the gas-wetted surface; Step 5. Based on step 4, according to the wettability of the complex mineral surface in the oil and gas reservoir obtained in step 3, combined with the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions obtained in step 2, the contact angle of the complex mineral surface in the oil and gas reservoir that changes with pressure is obtained.

[0006] Preferably, the surface composition of complex minerals in oil and gas reservoirs includes: mineral type, mineral proportion, and mineral distribution; In the step 1, a mineral analysis and detection method is used to determine the surface component composition of complex minerals in the oil and gas reservoir.

[0007] Preferably, the geometric parameters of the complex mineral surface of the oil and gas reservoir include: mineral distribution spatial structure and roughness parameters; In the step 1, contact or optical detection methods are used to determine the geometric parameters of the complex mineral surfaces of the oil and gas reservoir.

[0008] Preferably, the specific method of step three is as follows: (1) Establish a pure component or multi-component mineral surface model based on the main minerals measured from the complex mineral surface composition of oil and gas reservoirs; (2) Based on the established pure component or multi-component mineral surface model and the measured geometric parameters of the complex mineral surface of the oil and gas reservoir, a mineral surface model with different degrees of roughness is established; (3) Using numerical simulation methods, we determined whether the surface wetting characteristics of different minerals with different roughness under different CO2 pressure conditions are liquid phase wetting or gas phase wetting; (4) The complex mineral surface of the oil and gas reservoir is divided according to the measured minerals, and the same type of minerals are divided into the same mineral area. Then, according to the distribution of components and roughness of the complex mineral surface of the oil and gas reservoir, the mineral composition and roughness of each mineral area are marked; (5) Comparing the numerical simulation results with the numerical results of the mineral composition and roughness of each mineral area, the complex mineral surfaces of the oil and gas reservoirs are marked as liquid-wetted surfaces or gas-wetted surfaces.

[0009] Preferably, the gas-liquid-solid interface characteristic parameters include the gas-solid interface tension c SG , gas-liquid interfacial tension c LG , solid-liquid interfacial tension c SL .

[0010] Preferably, the contact angle of a liquid droplet on the complex mineral surface of the oil and gas reservoir is calculated according to the actual ratio of the liquid-wetted surface to the gas-wetted surface, using the following method: The actual area of ​​the area actually covered by the measured droplet on the complex mineral surface is the total area, where the ratio of the area of ​​the liquid-wetted surface belonging to rock component i to the total area is the proportion of rock component i that exhibits liquid-wetting behavior. f li The ratio of the gas-wetting surface area of ​​rock component i to the total surface area is the proportion of rock component i that exhibits gas-wetting behavior. f gi .

[0011] Preferably, in step 4, the calculation process of the contact angle of the droplet on the complex mineral surface of the oil and gas reservoir is as follows: The following formula is used to calculate the contact angle of a liquid droplet on the complex mineral surface of an oil and gas reservoir:

[0012] Where: is the contact angle of the liquid drop on the complex mineral surface, °; f li is the proportion of rock component i that exhibits liquid wetting behavior; f gi is the proportion of rock component i that exhibits gas-phase wetting behavior; c SGi is the gas-solid interfacial tension of rock component i, mN / m; c LG is the gas-liquid interfacial tension, mN / m; c SLi is the solid-liquid interfacial tension of rock component i, mN / m; R i is the surface roughness of rock component i, um; n is the number of components.

[0013] The present invention plays a vital role in the field of carbon capture, utilization and storage. It helps to optimize carbon storage site selection and scheme design. By studying the wettability of carbon dioxide and the surfaces of different reservoir minerals, it can gain an in-depth understanding of the rock properties of each potential storage site, evaluate the storage potential and stability of carbon dioxide therein, screen out high-quality storage sites where carbon dioxide is more likely to exist stably, and improve storage efficiency.

[0014] The present invention is also of certain significance in predicting the long-term effects of carbon sequestration. During the operation of carbon capture, utilization and storage projects, the interaction between carbon dioxide and reservoir minerals changes over time, which will affect the wettability of the reservoir and thus affect the long-term stability of carbon sequestration. With the help of this calculation method, important parameters can be provided for the simulation of this dynamic process, and possible risks can be predicted in advance so that timely measures can be taken for prevention and adjustment, ensuring the long-term effectiveness of carbon sequestration, promoting the wider application of carbon capture, utilization and storage technologies, and providing strong support for the realization of global carbon emission reduction goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of the surface model of illite, chlorite and feldspar minerals in the embodiment.

[0016] Figure 2 A group of mineral surface models with different roughness levels established in the embodiment.

[0017] Figure 3 Schematic diagram of contact angle in the embodiment.

[0018] Figure 4 Schematic diagram of the relationship between carbon dioxide pressure and contact angle in the embodiment. DETAILED DESCRIPTION

[0019] The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide comprises the following steps: Step 1: Obtain the surface component composition and geometric parameters of the complex mineral surfaces of the target oil and gas reservoir; Step 2: Obtain characteristic parameters of the gas-liquid-solid interface of different minerals under different carbon dioxide pressure conditions; Step 3: Based on the surface component composition and geometric parameters of the complex mineral surfaces of the oil and gas reservoirs obtained in Step 1, the complex mineral surfaces of the oil and gas reservoirs are divided into two types: liquid-wetting surfaces and gas-wetting surfaces according to numerical calculation results; Step 4: Under the selected carbon dioxide pressure conditions, the contact angle of the liquid droplet on the complex mineral surface of the oil and gas reservoir is calculated according to the actual ratio of the liquid-wetted surface to the gas-wetted surface; Step 5. Based on step 4, according to the wettability of the complex mineral surface in the oil and gas reservoir obtained in step 3, combined with the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions obtained in step 2, the contact angle of the complex mineral surface in the oil and gas reservoir that changes with pressure is obtained.

[0020] In one embodiment, the surface composition of complex minerals in oil and gas reservoirs includes: mineral type, mineral proportion, and mineral distribution; In the step 1, a mineral analysis and detection method is used to determine the surface component composition of complex minerals in the oil and gas reservoir.

[0021] In one embodiment, the geometric parameters of the complex mineral surface of the oil and gas reservoir include: mineral distribution spatial structure and roughness parameters; In the step 1, contact or optical detection methods are used to determine the geometric parameters of the complex mineral surfaces of the oil and gas reservoir.

[0022] In one embodiment, the specific method of step three is as follows: (1) Establishing a pure component or multi-component mineral surface model based on the measured mineral surface components of complex minerals in oil and gas reservoirs; (2) Based on the established pure component or multi-component mineral surface model and the measured geometric parameters of the complex mineral surface of the oil and gas reservoir, a mineral surface model with different degrees of roughness is established; (3) Using numerical simulation methods, we determined whether the surface wetting characteristics of different minerals with different roughness under different CO2 pressure conditions are liquid phase wetting or gas phase wetting; (4) The complex mineral surface of the oil and gas reservoir is divided according to the measured minerals, and the same type of minerals are divided into the same mineral area. Then, according to the distribution of components and roughness of the complex mineral surface of the oil and gas reservoir, the mineral composition and roughness of each mineral area are marked; (5) Comparing the numerical simulation results with the numerical results of the mineral composition and roughness of each mineral area, the complex mineral surfaces of the gas reservoir are marked as liquid-wetted surfaces or gas-wetted surfaces.

[0023] Gas-liquid-solid interface characteristic parameters include gas-solid interface tension c SG , gas-liquid interfacial tension c LG , solid-liquid interfacial tension c SL .

[0024] In one embodiment, the contact angle of a liquid droplet on the complex mineral surface of the oil and gas reservoir is calculated according to the actual ratio of the liquid-wetted surface to the gas-wetted surface, as follows: The actual area of ​​the area actually covered by the measured droplet on the complex mineral surface is the total area, where the ratio of the area of ​​the liquid-wetted surface belonging to rock component i to the total area is the proportion of rock component i that exhibits liquid-wetting behavior. f li The ratio of the gas-wetting surface area of ​​rock component i to the total surface area is the proportion of rock component i that exhibits gas-wetting behavior. f gi .

[0025] In step 4, the calculation process of the contact angle of the droplet on the complex mineral surface of the oil and gas reservoir is as follows: The following formula is used to calculate the contact angle of a liquid droplet on the complex mineral surface of an oil and gas reservoir:

[0026] Where: is the contact angle of the liquid drop on the complex mineral surface, °; f li is the proportion of rock component i that exhibits liquid wetting behavior; f gi is the proportion of rock component i that exhibits gas-phase wetting behavior; c SGi is the gas-solid interfacial tension of rock component i, mN / m; c LG is the gas-liquid interfacial tension, mN / m; c SLi is the solid-liquid interfacial tension of rock component i, mN / m; R i is the surface roughness of rock component i, um; n is the number of components.

[0027] The present invention will be described below with reference to the accompanying drawings: Step 1: Cores from the Chang 6 reservoir in the Ordos Basin were processed into thin core sections. Scanning electron microscopy and energy spectrum analyzer (EDS) were used in mineral analysis and testing methods to quantitatively characterize the minerals on the surface of the rock samples. The mineral types, mineral proportions, and mineral distribution were determined (see the table below). A multifunctional profilometer (optical testing method) was used to test the spatial structure and roughness parameters of the core sections.

[0028] Step 2: Use a high temperature and high pressure interfacial tension meter to test the interfacial tension of carbon dioxide, water, and mineral systems at pressure gradients of 2.5 MPa, 5 MPa, 7.5 MPa, 10 MPa, 12.5 MPa, 15 MPa, 17.5 MPa, and 20 MPa, including: carbon dioxide-water interfacial tension c LG , mineral-water interfacial tension c SL , CO2-mineral interfacial tension c SG ; Step 3: Based on the mineral types, mineral proportions, and mineral distribution on the rock sample surface, molecular simulation modeling technology is used to establish the surface models of illite, chlorite, and feldspar minerals, such as Figure 1 As shown; According to the obtained surface spatial structure and roughness parameters of the core slice, a set of mineral surface models with different surface roughness are established in the pure component or multi-component mineral surface model, such as Figure 2 As shown; Molecular dynamics simulations were used to test the wettability of water droplets on different mineral surfaces at carbon dioxide pressure gradients of 2.5 MPa, 5 MPa, 7.5 MPa, 10 MPa, 12.5 MPa, 15 MPa, 17.5 MPa, and 20 MPa. The wetting behavior of water droplets on mineral surfaces with different roughnesses in a carbon dioxide environment was determined. For example, at 5 MPa of carbon dioxide, water droplets exhibited liquid-phase wetting on the surface of feldspar with a strip-shaped roughness of 1.5, while at 5 MPa of carbon dioxide, water droplets exhibited vapor-phase wetting on the surface of illite with a pit-shaped roughness. Core thin sections were divided into mineral regions based on the distribution of surface mineral types. Each mineral region is a pure component. Based on the surface geometric parameters of complex minerals in oil and gas reservoirs and the results of molecular dynamics simulation, the minerals in each pure component mineral region were further divided into liquid-wetted regions and gas-wetted regions. The actual area of ​​the area actually covered by the measured droplet on the complex mineral surface is the total area, where the ratio of the area of ​​the liquid-wetted surface belonging to rock component i to the total area is the proportion of rock component i that exhibits liquid-wetting behavior. f li The ratio of the gas-wetting surface area of ​​rock component i to the total surface area is the proportion of rock component i that exhibits gas-wetting behavior. f gi In this example, under the condition of carbon dioxide pressure of 5 MPa, the experimental rock sample has 27.8% feldspar liquid-wet area with an average roughness of 1.6; 3.5% feldspar gas-wet area; 18.6% illite liquid-wet area with an average roughness of 1.3; 11.3% illite gas-wet area; 16.6% chlorite liquid-wet area with an average roughness of 1.4; 10.7% chlorite gas-wet area; Step 4: Calculate the contact angle of the droplet on the complex mineral surface of the oil and gas reservoir according to the actual ratio of the liquid-phase wetted surface to the gas-phase wetted surface of the different minerals mentioned above. For the rock sample slice used in this example, the final mixed contact angle is 75.8°, and the average measured contact angle is 77.5°. Figure 3 As shown, the error is within the error range; Calculation process: Take the carbon dioxide pressure of 5Mpa as an example, cLG =50mN / m, c SG- c SL =24.5mN / m,

[0029] =(1.6×0.27+1.3×0.18+1.4×0.16)×24.5 / 45-0.03-0.11-0.1 =0.2455 but i mixed = 75.8°; Step 5: By substituting the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions, the contact angle calculation results of complex mineral surfaces that change with carbon dioxide pressure can be obtained. Figure 4 shown.

Claims

1. A method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide, characterized in that: The following steps are involved: Step 1: Obtain the surface component composition and geometric parameters of the complex mineral surfaces of the target oil and gas reservoir; Step 2: Obtain characteristic parameters of the gas-liquid-solid interface of different minerals under different carbon dioxide pressure conditions; Step 3: According to the surface composition and geometric parameters of the complex minerals in the oil and gas reservoir obtained in Step 1, a numerical simulation method is used to calculate the wettability of the mineral surface, and the complex mineral surfaces in the oil and gas reservoir are divided into two types: liquid-wetting surfaces and gas-wetting surfaces; Step 4: Under the selected carbon dioxide pressure conditions, the contact angle of the liquid droplet on the complex mineral surface of the oil and gas reservoir is calculated according to the actual ratio of the liquid-wetted surface to the gas-wetted surface; Step 5. Based on step 4, according to the wettability of the complex mineral surface in the oil and gas reservoir obtained in step 3, combined with the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions obtained in step 2, the contact angle of the complex mineral surface in the oil and gas reservoir that changes with pressure is obtained.

2. The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide as claimed in claim 1, characterized in that: The surface composition of complex minerals in the oil and gas reservoir includes: mineral type, mineral proportion, and mineral distribution; In the step 1, a mineral analysis and detection method is used to determine the surface component composition of complex minerals in the oil and gas reservoir.

3. The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide as claimed in claim 1, characterized in that: The geometric parameters of the complex mineral surface of the oil and gas reservoir include: mineral distribution spatial structure and roughness parameters; In the step 1, contact or optical detection methods are used to determine the geometric parameters of the complex mineral surfaces of the oil and gas reservoir.

4. The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide as claimed in claim 1, characterized in that: The specific method of step three is as follows: (1) Establishing a pure component or multi-component mineral surface model based on the measured mineral surface components of complex minerals in oil and gas reservoirs; (2) Based on the established pure component or multi-component mineral surface model and the measured geometric parameters of the complex mineral surface of the oil and gas reservoir, a mineral surface model with different degrees of roughness is established; (3) Using numerical simulation methods, we determined whether the surface wetting characteristics of different minerals with different roughness under different CO2 pressure conditions are liquid phase wetting or gas phase wetting; (4) The complex mineral surface of the oil and gas reservoir is divided according to the main minerals measured, and the same type of minerals are divided into the same mineral area. Then, according to the distribution of components and roughness of the complex mineral surface of the oil and gas reservoir, the mineral composition and roughness of each mineral area are marked; (5) Comparing the numerical simulation results with the numerical results of the mineral composition and roughness of each mineral area, the complex mineral surfaces of the oil and gas reservoirs are marked as liquid-wetted surfaces or gas-wetted surfaces.

5. The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide as claimed in claim 1, characterized in that: The gas-liquid-solid interface characteristic parameters include gas-solid interface tension γ SG , gas-liquid interfacial tension γ LG , solid-liquid interfacial tension γ SL .

6. The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide as claimed in claim 5, characterized in that: The contact angle of a liquid droplet on the complex mineral surface of the oil and gas reservoir is calculated according to the actual ratio of the liquid-wetted surface to the gas-wetted surface, as follows: The actual area of ​​the area actually covered by the measured droplet on the complex mineral surface is the total area, where the ratio of the area of ​​the liquid-wetted surface belonging to rock component i to the total area is the proportion of rock component i that exhibits liquid-wetting behavior. f li The ratio of the gas-wetting surface area of ​​rock component i to the total surface area is the proportion of rock component i that exhibits gas-wetting behavior. f gi .

7. The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide as claimed in claim 6, characterized in that: In step 4, the calculation process of the contact angle of the droplet on the complex mineral surface of the oil and gas reservoir is as follows: The following formula is used to calculate the contact angle of a liquid droplet on the complex mineral surface of an oil and gas reservoir: Where: is the contact angle of the liquid drop on the complex mineral surface, °; f li is the proportion of rock component i that exhibits liquid wetting behavior; f gi is the proportion of rock component i that exhibits gas-phase wetting behavior; γ SGi is the gas-solid interfacial tension of rock component i, mN / m; γ LG is the gas-liquid interfacial tension, mN / m; γ SLi is the solid-liquid interfacial tension of rock component i, mN / m; R i is the surface roughness of rock component i, um; n is the number of components.

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