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

Abstract

The application relates to a method for calculating the contact angle of the surface of complex minerals in an oil and gas reservoir under the action of carbon dioxide, and belongs to the technical field of oil development, in particular to the method for calculating the contact angle of the surface of complex minerals in an oil and gas reservoir under the action of carbon dioxide, which comprises the following steps: obtaining the surface component composition and geometric parameters of the target complex minerals in the oil and gas reservoir; obtaining the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions; dividing the surface of the complex minerals in the oil and gas reservoir into two types of liquid phase wetting surface and gas phase wetting surface; under the selected carbon dioxide pressure condition, the contact angle is calculated; and the contact angle changing with the pressure is obtained in combination with the gas-liquid-solid interface characteristic parameters. Through the study on the wettability of carbon dioxide and different reservoir mineral surfaces, the rock characteristics of each potential storage site can be deeply understood, the storage potential and stability of carbon dioxide in the site can be evaluated, the high-quality storage site where carbon dioxide is more stable can be screened out, and the storage efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil development, in particular to a method for calculating the contact angle of complex mineral surface of oil and gas reservoir under the action of carbon dioxide. BACKGROUND

[0002] The extra-low permeability reservoir occupies an important position in China's oil and gas resources, especially in Ordos Basin, and the reserves of this type account for a large proportion of low permeability resources. However, due to poor physical properties and strong heterogeneity, the development difficulty is significant. In order to effectively improve the recovery of this type of reservoir, the commonly used technologies at present include gas injection, polymer flooding and microbial flooding. However, the extra-low permeability reservoir faces a series of problems such as high water injection pressure, injection failure and low recovery in water injection development, which limits the conventional methods. Carbon dioxide flooding as an effective displacement method for enhancing oil recovery has important significance for efficient development of extra-low permeability reservoirs due to its wide application range and environmental protection advantages.

[0003] In the development process of low permeability reservoir, the wettability of rock mineral surface plays a crucial role in oil-water interaction and oil displacement efficiency. Under different wettability conditions, the oil-water distribution and flow characteristics in the reservoir will change significantly, which will affect the ultimate recovery. In the process of carbon dioxide displacement, the changes in carbon dioxide pressure, phase state and mineral reaction may lead to changes in the wettability of the mineral surface, thereby affecting the oil and gas flowability in the low permeability reservoir. SUMMARY

[0004] In view of the problem that the wettability of complex mineral surface of oil and gas reservoir under the action of carbon dioxide cannot be quantitatively characterized, the present application constructs a method for calculating the contact angle of complex mineral surface of oil and gas reservoir under the action of carbon dioxide according to the surface characteristics of complex mineral of target oil and gas reservoir and the gas-liquid-solid interface characteristic parameters, combined with the complex surface wettability theory, by using the combination of experimental research and theoretical model.

[0005] The method for calculating the contact angle of complex mineral surface of oil and gas reservoir under the action of carbon dioxide of the present application comprises the following steps:

[0006] Step one, obtaining the component composition of the complex mineral surface of the target oil and gas reservoir and the geometric parameters of the complex mineral surface of the oil and gas reservoir;

[0007] Step two, obtaining the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions;

[0008] Step three, according to the component composition of the complex mineral surface of the oil and gas reservoir and the geometric parameters of the complex mineral surface of the oil and gas reservoir obtained in step one, the wettability of the mineral surface is calculated by using numerical simulation method, and the complex mineral surface of the oil and gas reservoir is divided into two types of liquid-wetted surface and gas-wetted surface;

[0009] Step four, under the selected carbon dioxide pressure conditions, the actual proportion of liquid phase wetting surface and gas phase wetting surface is used to calculate the contact angle of the oil and gas reservoir complex mineral surface liquid drop;

[0010] Step five, based on step four, the oil and gas reservoir complex mineral surface wetting condition obtained in step three is combined with the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions obtained in step two to obtain the oil and gas reservoir complex mineral surface contact angle changing with pressure.

[0011] Preferably, the component composition of the oil and gas reservoir complex mineral surface includes: mineral type, mineral proportion, and mineral distribution;

[0012] The mineral analysis and detection method is used in step one to determine the component composition of the oil and gas reservoir complex mineral surface.

[0013] Preferably, the geometric parameters of the oil and gas reservoir complex mineral surface include: mineral distribution space structure and roughness parameters;

[0014] In step one, the contact or optical detection method is used to determine the geometric parameters of the oil and gas reservoir complex mineral surface.

[0015] Preferably, the specific method of step three is as follows:

[0016] (1) According to the main minerals measured by the component composition of the oil and gas reservoir complex mineral surface, a pure component or multi-component mineral surface model is established;

[0017] (2) According to the established pure component or multi-component mineral surface model, a mineral surface model containing different roughness is established according to the measured geometric parameters of the oil and gas reservoir complex mineral surface;

[0018] (3) Numerical simulation method is used to determine the surface wetting characteristics of different minerals under different roughness under different carbon dioxide pressure conditions, which are liquid phase wetting or gas phase wetting;

[0019] (4) The oil and gas reservoir complex mineral surface is divided according to the measured minerals, the same type of minerals is divided into the same mineral area, and then the mineral composition and roughness of each mineral area are marked according to the component distribution and roughness distribution of the oil and gas reservoir complex mineral surface;

[0020] (5) Comparing the numerical simulation results with the mineral composition and roughness numerical results of each mineral area, the oil and gas reservoir complex mineral surface is marked as liquid phase wetting surface or gas phase wetting surface.

[0021] Preferably, the gas-liquid-solid interface characteristic parameters include gas-solid interface tension gamma SG , gas-liquid interface tension gammaLG , solid-liquid interfacial tension gamma SL .

[0022] Preferably, the contact angle of the liquid droplet on the complex mineral surface of the oil and gas reservoir is calculated according to the actual proportion of the liquid phase wetting surface and the gas phase wetting surface, and the method is as follows:

[0023] According to the actual area of the complex mineral surface actually covered by the measured liquid droplet, the ratio of the area belonging to the liquid phase wetting surface of the rock component i to the total area is the proportion of the liquid phase wetting behavior on the rock component i f li , and the ratio of the area belonging to the gas phase wetting surface of the rock component i to the total area is the proportion of the gas phase wetting behavior on the rock component i f gi .

[0024] Preferably, in step four, the calculation process of the contact angle of the liquid droplet on the complex mineral surface of the oil and gas reservoir is as follows:

[0025] The contact angle of the liquid droplet on the complex mineral surface of the oil and gas reservoir is calculated by the following formula:

[0026]

[0027] In the formula: is the contact angle of the liquid droplet on the complex mineral surface, °;

[0028] f li is the proportion of the liquid phase wetting behavior on the rock component i;

[0029] f gi is the proportion of the gas phase wetting behavior on the rock component i;

[0030] gamma SGi is the gas-solid interfacial tension of the rock component i, mN / m;

[0031] gamma LG is the gas-liquid interfacial tension, mN / m;

[0032] gamma SLi is the solid-liquid interfacial tension of the rock component i, mN / m;

[0033] R i is the surface roughness of the rock component i, um;

[0034] n is the number of components.

[0035] The present application has a vital role in the field of carbon capture, utilization and storage, and the present application helps to optimize carbon storage site selection and scheme design, by studying the wettability of carbon dioxide and different reservoir minerals, the rock characteristics of each potential storage site can be understood, the storage potential and stability of carbon dioxide in the reservoir can be evaluated, and the high-quality storage site where carbon dioxide is more stable can be selected, thereby improving the storage efficiency.

[0036] The present application also has a certain significance in predicting the long-term effect of carbon storage. During the operation of the carbon capture, utilization and storage project, the interaction between carbon dioxide and reservoir minerals changes over time, which affects the wettability of the reservoir and further affects the long-term stability of carbon storage. With the aid of the calculation method, important parameters can be provided for the simulation of this dynamic process, and possible risks can be predicted in advance, so that measures can be taken in time to prevent and adjust, ensuring the long-term effectiveness of carbon storage and promoting the wider application of carbon capture, utilization and storage technology, thereby providing strong support for the realization of global carbon emission reduction targets. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 It is a schematic diagram of the surface model of illite, chlorite and feldspar minerals in the examples.

[0038] Figure 2 It is a group of mineral surface models with different roughness established in the examples.

[0039] Figure 3 It is a schematic diagram of the contact angle in the examples.

[0040] Figure 4 It is a schematic diagram of the relationship between the contact angle and the carbon dioxide pressure. DETAILED DESCRIPTION

[0041] The contact angle calculation method for complex mineral surfaces of oil and gas reservoirs under the action of carbon dioxide comprises the following steps:

[0042] Step 1: Obtain the composition and geometric parameters of the complex mineral surface of the target oil and gas reservoir.

[0043] Step 2: Obtain the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressures.

[0044] Step 3: According to the composition and geometric parameters of the complex mineral surface of the oil and gas reservoir obtained in step 1, the complex mineral surface of the oil and gas reservoir is divided into two types of liquid-wetted surface and gas-wetted surface according to the numerical calculation results.

[0045] Step four, under the selected carbon dioxide pressure conditions, the actual proportion of liquid phase wetting surface and gas phase wetting surface is used to calculate the contact angle of the oil and gas reservoir complex mineral surface liquid drop;

[0046] Step five, based on step four, the oil and gas reservoir complex mineral surface wetting condition obtained in step three is combined with the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions obtained in step two to obtain the contact angle of the oil and gas reservoir complex mineral surface varying with pressure.

[0047] In one embodiment, the component composition of the oil and gas reservoir complex mineral surface includes: mineral type, mineral proportion, and mineral distribution;

[0048] The mineral analysis and detection method is used in step one to determine the component composition of the oil and gas reservoir complex mineral surface.

[0049] In one embodiment, the geometric parameters of the oil and gas reservoir complex mineral surface include: mineral distribution space structure and roughness parameters;

[0050] In step one, the contact or optical detection method is used to determine the geometric parameters of the oil and gas reservoir complex mineral surface.

[0051] In one embodiment, the specific method of step three is as follows:

[0052] (1) According to the measured minerals of the component composition of the oil and gas reservoir complex mineral surface, a pure component or multi-component mineral surface model is established;

[0053] (2) According to the established pure component or multi-component mineral surface model, a mineral surface model containing different roughness is established according to the measured geometric parameters of the oil and gas reservoir complex mineral surface;

[0054] (3) Numerical simulation method is used to determine the surface wetting characteristics of different minerals under different roughness under different carbon dioxide pressure conditions, which are liquid phase wetting or gas phase wetting;

[0055] (4) The oil and gas reservoir complex mineral surface is divided according to the measured minerals, the same type of mineral is divided into the same mineral region, and then the mineral composition and roughness of each mineral region are marked according to the component distribution and roughness distribution of the oil and gas reservoir complex mineral surface;

[0056] (5) The gas reservoir complex mineral surface is marked as liquid phase wetting surface or gas phase wetting surface by comparing the numerical simulation results with the mineral composition and roughness numerical results of each mineral region.

[0057] The gas-liquid-solid interface characteristic parameters include gas-solid interface tension gamma SG , gas-liquid interface tensiongamma LG , solid-liquid interfacial tension gamma SL .

[0058] In one embodiment, the contact angle of a droplet on the complex mineral surface of the oil and gas reservoir is calculated according to the actual proportion of liquid-wetted surface and gas-wetted surface, as follows:

[0059] The actual area of the complex mineral surface covered by the measured droplet is the total area, wherein the ratio of the area of the liquid-wetted surface of rock component i to the total area is the proportion of the liquid-wetted behavior exhibited on the rock component i f li The ratio of the area of the gas-wetted surface of rock component i to the total area is the proportion of the gas-wetted behavior exhibited on the rock component i f gi .

[0060] In step four, the calculation process of the contact angle of a droplet on the complex mineral surface of the oil and gas reservoir is as follows:

[0061] The contact angle of a droplet on the complex mineral surface of the oil and gas reservoir is calculated using the following formula:

[0062]

[0063] In the formula: is the contact angle of a droplet on the complex mineral surface, °;

[0064] f li is the proportion of the liquid-wetted behavior exhibited on the rock component i;

[0065] f gi is the proportion of the gas-wetted behavior exhibited on the rock component i;

[0066] gamma SGi is the gas-solid interfacial tension of rock component i, mN / m;

[0067] gamma LG is the gas-liquid interfacial tension, mN / m;

[0068] gamma SLi is the solid-liquid interfacial tension of rock component i, mN / m;

[0069] R i is the surface roughness of rock component i, um;

[0070] n is the component number.

[0071] The application is described below in conjunction with the drawings:

[0072] Step one, select the Ordos Basin Chang 6 reservoir core processing as core thin section, using scanning electron microscopy and energy spectrum analyzer in the mineral analysis detection method, the surface of the rock sample is quantitatively characterized, the mineral type, mineral proportion and mineral distribution are obtained, see the table below, using multifunctional profile measuring instrument in optical detection method, the surface of the core thin section is tested for spatial structure and roughness parameters;

[0073]

[0074] Step two, using high temperature and high pressure interfacial tension instrument, according to the pressure gradient 2.5Mpa, 5Mpa, 7.5Mpa, 10Mpa, 12.5Mpa, 15Mpa, 17.5Mpa, 20Mpa, test the interfacial tension of carbon dioxide, water, mineral system, including: carbon dioxide-water interfacial tension gamma LG , mineral-water interfacial tension gamma SL , carbon dioxide-mineral interfacial tension gamma SG ;

[0075] Step three, according to the mineral type, mineral proportion and mineral distribution on the surface of the rock sample, using molecular simulation modeling technology, establish illite, chlorite and feldspar mineral surface model, as shown in Figure 1 ;

[0076] According to the obtained spatial structure and roughness parameters of the core thin section surface, a group of mineral surface models with different surface roughness are established on the pure component or multi-component mineral surface model, as shown in Figure 2 ;

[0077] Using molecular dynamics simulation method, under the condition of carbon dioxide pressure gradient of 2.5Mpa, 5Mpa, 7.5Mpa, 10Mpa, 12.5Mpa, 15Mpa, 17.5Mpa, 20Mpa, respectively test the wetting characteristics of water droplets on different mineral surfaces, get the wetting state of water droplets on different roughness mineral surfaces in carbon dioxide environment, for example: under the condition of carbon dioxide 5Mpa, water droplets on feldspar surface with strip roughness of 1.5 is liquid wetting, under the condition of carbon dioxide 5Mpa, water droplets on illite surface with pit type roughness exists gas wetting;

[0078] The core slice is divided into mineral regions according to the surface mineral type distribution, each mineral region is a pure component, and the minerals in each pure component mineral region are further divided into liquid-wetted regions and gas-wetted regions by referring to the complex mineral surface geometric parameters of the oil and gas reservoir and the results of the molecular dynamics simulation;

[0079] According to the actual area of the liquid drop actually covered on the complex mineral surface, the ratio of the area of the liquid-wetted surface of the rock component i to the total area is the proportion of the liquid-wetted behavior of the rock component i f li The ratio of the area of the gas-wetted surface of the rock component i to the total area is the proportion of the gas-wetted behavior of the rock component i f gi In this example: under the condition of a carbon dioxide pressure of 5 Mpa, the experimental rock sample has a 27.8% feldspar liquid-wetted region with an average roughness of 1.6, a 3.5% feldspar gas-wetted region, an 18.6% illite liquid-wetted region with an average roughness of 1.3, an 11.3% illite gas-wetted region, a 16.6% chlorite liquid-wetted region with an average roughness of 1.4, and a 10.7% chlorite gas-wetted region;

[0080] Step four: according to the actual proportions of the liquid-wetted surface and the gas-wetted surface of the different minerals, the contact angle of the liquid drop on the complex mineral surface of the oil and gas reservoir is calculated. For the rock sample slice used in this example, the final mixed contact angle is 75.8°, and the average value of the actual contact angle is 77.5°, as shown in Figure 3 The error is within the error range;

[0081] Calculation process: taking a carbon dioxide pressure of 5 Mpa as an example, gamma LG = 50 mN / m, gamma SG- gamma SL = 24.5 mN / m,

[0082]

[0083] = (1.6 x 0.27 + 1.3 x 0.18 + 1.4 x 0.16) x 24.5 / 45 - 0.03 - 0.11 - 0.1

[0084] = 0.2455

[0085] Then theta mixed = 75.8°;

[0086] Step five, by substituting the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions, the complex mineral surface contact angle calculation results with carbon dioxide pressure changes can be obtained as shown in Figure 4 Fig. 5.

Claims

1. A method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the influence of carbon dioxide, characterized in that, Includes the following steps: Step 1: Obtain the composition of complex minerals on the surface of the target oil and gas reservoir and the geometric parameters of complex minerals on the surface of the oil and gas reservoir; Step 2: Obtain the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions; Step 3: Based on the composition of the complex mineral surface in the oil and gas reservoir and the geometric parameters of the complex mineral surface in the oil and gas reservoir obtained in Step 1, the wetting condition of the mineral surface is calculated by numerical simulation method, and the complex mineral surface in the oil and gas reservoir is divided into two types: liquid phase wetting surface and gas phase wetting surface. Step 4: Under the selected carbon dioxide pressure conditions, calculate the droplet contact angle on the complex mineral surface of the oil and gas reservoir according to the actual ratio of the liquid phase wetting surface to the gas phase wetting surface. Step 5: Based on Step 4, according to the surface wetting of complex minerals in oil and gas reservoirs obtained in Step 3, and combined with the gas-liquid-solid interface characteristic parameters of different minerals under different carbon dioxide pressure conditions obtained in Step 2, obtain the surface contact angle of complex minerals in oil and gas reservoirs that varies with pressure. The geometric parameters of the complex mineral surface in the oil and gas reservoir include: the spatial structure of mineral distribution and roughness parameters; The gas-liquid-solid interface characteristic parameters include gas-solid interfacial tension. γ SG Gas-liquid interfacial tension γ LG and solid-liquid interfacial tension γ SL ; In step four, the calculation process for the droplet contact angle on the complex mineral surface of the oil and gas reservoir is as follows: The contact angle of droplets on the complex mineral surface of oil and gas reservoirs is calculated using the following formula: In the formula: The contact angle of a droplet on a complex mineral surface, in °; f li The proportion of rock component i exhibiting liquid phase wetting behavior; f gi The proportion of rock component i exhibiting vapor-phase wetting behavior; γ SGi Let be the gas-solid interfacial tension of rock component i, in mN / m; γ LG The gas-liquid interfacial tension is expressed in mN / m. γ SLi Let be the solid-liquid interfacial tension of rock component i, in mN / m; R i Let i be the surface roughness of rock component i, in μm; n For group numbers.

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

3. The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide as described in claim 1, characterized in that, In step one, contact or optical detection methods are used to determine the geometric parameters of complex mineral surfaces in oil and gas reservoirs.

4. The method for calculating the contact angle of complex mineral surfaces in oil and gas reservoirs under the action of carbon dioxide as described in claim 1, characterized in that, The specific method for step three is as follows: (1) Based on the minerals measured from the complex mineral surface composition of oil and gas reservoirs, establish a mineral surface model with pure or multi-component components. (2) Based on the established pure or multi-component mineral surface model, and according to the measured geometric parameters of complex mineral surfaces in oil and gas reservoirs, establish mineral surface models with different roughness. (3) Using numerical simulation, the surface wetting characteristics of different minerals under different roughnesses under different carbon dioxide pressures were determined to be either liquid phase wetting or gas phase wetting. (4) Divide the complex mineral surface of the oil and gas reservoir according to the main minerals measured. Minerals of the same type are divided into the same mineral region. Then, according to the distribution of the components and the roughness of the complex mineral surface of the oil and gas reservoir, mark the mineral composition and roughness of each mineral region. (5) By comparing the numerical simulation results with the mineral composition and roughness numerical results of each mineral region, the complex mineral surfaces of the oil and gas reservoir are marked as liquid-phase wetted surfaces or gas-phase 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 described in claim 1, characterized in that, The contact angle of droplets on the complex mineral surface of the oil and gas reservoir is calculated based on the actual ratio of the liquid phase wetting surface to the gas phase wetting surface, as follows: The total area is defined as the actual area covered by the measured droplets on the surface of the complex mineral. The ratio of the area belonging to the liquid-phase wetted surface of rock component i to the total area is the proportion of rock component i exhibiting liquid-phase wetting behavior. f li The ratio of the area of ​​the vapor-wetting surface of rock component i to the total area represents the proportion of rock component i exhibiting vapor-wetting behavior. f gi .

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