Thickened oil CO2 huff and puff gas injection amount correction method

Abstract

The invention relates to the technical field of oil reservoir development, in particular to a thickened oil CO2 huff and puff gas injection amount correction method which comprises the steps that a foam liquid film image and sand filling pipe pressure data are collected; correcting the pressure of different areas in the sand filling pipe by using the pressure visualization information; calculating the average radius of all bubbles; calculating the bubble density by using the average radius; calculating a gas compression coefficient by using a non-linear relationship between the bubble density and the gas volume; calculating an effective gas volume by using a gas compression coefficient; calculating the gas injection substance mass by using the effective gas volume; the gas injection amount is calculated and corrected through the gas injection matter amount. The method solves the problem of large error of gas injection amount calculation based on an ideal gas state equation in the prior art.

Description

Technical Field

[0001] This invention relates to the field of reservoir development technology, and in particular to a method for correcting CO2 huff and puff injection volume in heavy oil. Background Technology

[0002] The accuracy of CO2 injection directly determines the reservoir development effect; insufficient gas injection will result in crude oil not being effectively viscosity-reduced and driven, with limited recovery rate improvement; excessive injection may cause gas channeling, reduce sweep efficiency, and significantly increase operating costs and carbon emission risks; precise control of gas injection is the key to ensuring oil displacement efficiency and achieving economic feasibility and low-carbon development.

[0003] Traditional CO2 injection volume design methods are mostly based on the ideal gas equation of state, ignoring the reservoir's heterogeneous pressure gradient and the actual compressibility characteristics under CO2 pressure, resulting in large errors in the injection volume calculation; therefore, a method is needed to correct the CO2 injection volume. Summary of the Invention

[0004] To address the shortcomings of existing methods, this invention solves the problem of large errors in calculating the injection volume based on the ideal gas equation of state.

[0005] The technical solution adopted in this invention is: a method for correcting the CO2 huff and puff volume of heavy oil, comprising the following steps: Step 1: Acquire images of the foam liquid film and pressure data of the sand-filled pipe; In a preferred embodiment of the present invention, the foam liquid film image is acquired by a device consisting of a camera, a PDMS chip and an LED light group.

[0006] Step 2: Using pressure visualization information, correct the pressure in different areas of the sand-filled pipe; calculate the average radius of all bubbles; calculate the bubble density using the average radius; calculate the gas compressibility coefficient using the nonlinear relationship between bubble density and gas volume; calculate the effective gas volume using the gas compressibility coefficient; calculate the injection mass using the effective gas volume; calculate the corrected injection volume using the injection mass. In a preferred embodiment of the present invention, the formula for pressure correction is: (2) in, This is the pressure correction factor; This represents the average pressure value for each region.

[0007] In a preferred embodiment of the present invention, the formula for the average radius of the bubble is: (3) in, For the first i The radius of each bubble.

[0008] In a preferred embodiment of the present invention, the formula for bubble density is: (4) Where, n A This indicates the number of bubbles per unit area. This represents the average radius of all bubbles.

[0009] In a preferred embodiment of the present invention, the formula for the effective gas volume is: (5) Among them, gas compressibility coefficient , f () is a quadratic function in one variable.

[0010] In a preferred embodiment of the present invention, the formula for the mass of the injected gas is: (6) in, R This is the universal gas constant. T The temperature is the thermodynamic temperature of the system.

[0011] In a preferred embodiment of the present invention, the formula for correcting the gas injection volume is: (8) Among them, P in To inject pressure; This represents the total mass of the injected gas in all regions.

[0012] In a preferred embodiment of the present invention, the membership degree of the bubbles is scored.

[0013] As a preferred embodiment of the present invention, a heavy oil CO2 huff and puff injection volume correction system includes: a memory for storing instructions executable by a processor; and a processor for executing the instructions to implement a heavy oil CO2 huff and puff injection volume correction method.

[0014] The beneficial effects of this invention are: 1. This invention combines dynamic correction and nonlinear fitting to significantly improve the accuracy of gas injection volume calculation; 2. Improving the precision of gas injection can reduce unnecessary CO2 injection, lower development costs, and thus improve reservoir recovery; 3. Construct a bubble membership scoring system to verify the accuracy of the corrected gas injection volume. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method for correcting the CO2 huff and puff volume of heavy oil according to the present invention; Figure 2 This is a schematic diagram of the device of the present invention; Figure 3 This is a bubble image distribution diagram of the present invention; Figure 4 This is a diagram showing the overall distribution density of bubbles in this invention; Figure 5 This is a diagram showing the area distribution of the bubbles in this invention. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments. The drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0017] like Figure 1 As shown, a method for correcting the CO2 huff and puff injection volume of heavy oil includes the following steps: Step 1: Acquire images of the foam liquid film and pressure data of the sand-filled pipe; like Figure 2 After passing through the live oil piston container, CO2 flows through the pipeline into the sand-filled pipe and then into the BPR (back pressure regulator). The BPR is used to regulate the pressure and generate foam liquid films under different operating conditions. The foam liquid film images are collected by a device consisting of a camera, a PDMS chip, and an LED light group. The PDMS chip is placed in the PDMS observation chamber. The foam liquid is recovered through a waste liquid collection device. Three pressure measuring points are set on the pipeline and the sand-filled pipe to collect pressure data. Pressure measuring point 1 is the injection pressure in the sand-filled pipe; pressure measuring point 2 captures the pressure gradient change in the sand-filled pipe to locate the seepage bottleneck; pressure measuring point 3 is the outlet pressure of the sand-filled pipe. BPR supports continuous pressure regulation and, in conjunction with a constant speed and constant pressure pump, enables simulation of well shut-in pressure gradient. Quartz sand was filled into the sand-filled pipe in layers. After each layer was compacted, it was saturated with water, the permeability was measured, and then heavy oil was injected. Live oil preparation involves adding heavy oil to a compression container, injecting CO2 to 7 MPa, stirring for 2 hours, and preparing live oil. The live oil is then injected into the sand-filled pipe through a constant pressure pump until the inlet pressure stabilizes at 20 MPa, the outlet BPR is set to 15 MPa, and the well is left to simmer for 1 hour. Heavy oil and CO2 were injected into the sand-packed pipe to simulate the reservoir environment; the BPR reduced the outlet pressure to 10 MPa at a rate of 0.1 MPa / min, while the camera and pressure sensor were activated to record the pressure distribution and bubble dynamics.

[0018] Step 2: Process the pressure data and use the numerical simulation algorithm (finite difference method) and graphics drawing software (Image) in the host computer to generate a visual image of the pressure gradient, which intuitively shows the distribution of pressure in the system. The pressure visualization image is based on the pressure values ​​of three measurement points. The interpolation algorithm generates a continuous pressure distribution curve, which transforms the data into an intuitive pressure field map, clearly showing the pressure change trend from high to low. The pressure gradient calculation directly depends on the pressure difference between adjacent pressure measurement points and the distance between the two points. The pressure gradient of each segment is quantified by the pressure difference and distance. The pressure change trend presented by the pressure visualization can also help verify the rationality of the pressure gradient calculation results.

[0019] Step 3: Visualizing the pressure gradient. The pressure gradient is calculated using methods such as numerical differentiation to obtain the rate of pressure change at different locations; pressure visualization information is then obtained based on the rate of pressure change. Through threshold segmentation and morphological processing, such as Figure 3 As shown, the average radius and density of the bubbles are extracted, the gas compressibility coefficient is calculated, and the effective gas volume is corrected. At the same time, the sand-filled pipe is divided into multiple regions, the average pressure of each region is calculated, the corrected pressure is obtained, and the ideal gas equation is corrected. The bubble images inside the cavity are continuously captured by a camera, and the bubble distribution is statistically analyzed and the density parameter is extracted using image software. Figure 3 'a' represents the bubble distribution extraction map; the outlines of all bubbles are extracted from the image. Figure 3 b is the bubble-liquid film marking diagram, which is based on Figure 3 The bubble outline is used to mark the liquid film between the bubbles; Figure 3 c represents the liquid film labeling extraction diagram; Figure 3 The liquid film marked in b was extracted to obtain the bubble liquid film density distribution map; The rate of change of pressure reflects local changes, while the gradient field characterizes the overall trend. The rate of change of pressure in each direction is a component of the gradient field, which is the vector sum of these components. The formula for the gradient field is: (1) in, For pressure x Partial derivatives in direction; For pressure y Partial derivatives in direction; Based on the pressure visualization information, the pressure in different areas within the sand-filled pipe is corrected; firstly, the reservoir model is divided into sections based on unit area. j In a small region, considering both pressure and foamed oil conditions, the average pressure value of each region was determined through numerical simulation. To account for the impact of pressure gradient changes on the CO2 state, a pressure correction coefficient is introduced. The corrected pressure value is: (2) Where, 0 < <1.

[0020] Step 4: Calculate the volume correction for bubble compression to obtain the corrected injection volume for each region; The overall distribution characteristics of bubbles are quantified. After observing the foam liquid film image, independent bubbles are identified based on the closed boundary, and the liquid film thickness between adjacent bubbles is also identified. A preset threshold for liquid film thickness is set; if the thickness exceeds the preset threshold, the bubble is not considered a liquid film. The bubble distribution is statistically analyzed using image software to obtain the distribution pattern, and the effective radius is calculated using the area formula. The average radius of all bubbles (independent bubbles + adjacent bubbles) is then calculated as follows: (3) in, For the first i The radius of each bubble; The bubble density is: (4) Where, n A This indicates the number of bubbles per unit area. This represents the average radius of all bubbles. Indicates bubble density; Bubble density was established through experiments. With gas volume The correspondence was established; experiments were conducted under different pressure conditions to measure the corresponding bubble density and actual gas volume; and a quadratic function relationship between the two was fitted. f =ax 2 +bx+c; The gas compressibility coefficient is obtained through reverse calculation. ; Subsequently, based on the measured bubble density, a function is used to... f Determine the gas compressibility factor and calculate the effective gas volume in a certain region. The formula is: (5) The formula for the amount of gas injected in a certain area is: (6) in, R This is the universal gas constant. T The temperature is the thermodynamic temperature of the system.

[0021] The formula for calculating the total mass of injected gas in all regions is: (7) The formula for calculating the corrected gas injection volume is: (8) Among them, P inThis refers to the injection pressure; specifically, the pressure value at measurement point 1.

[0022] Table 1 shows the statistical information for bubble statistics:

[0023] Construct membership degree scoring indices for different indicators; score the membership degree of bubbles to evaluate the accuracy of the modified gas injection volume model of this invention; for example, according to expert scoring, when S>= a set threshold of 90, it indicates that the gas injection volume model is reliable; the membership degree scoring formula is: S= (9) Various scattered indicators are integrated into a comprehensive score, as shown in Table 2, and quantitative comparison is achieved.

[0024] Table 2 Detailed List of Membership Degree Scoring Indicators

[0025] like Figure 4 The left image is processed to obtain the bubble extraction image on the right, from which the overall distribution density of the bubbles can be seen; Figure 5 A histogram uses bubble area as the horizontal axis and bubble number as the vertical axis to show the distribution pattern of bubble area.

[0026] The method of this invention, through pressure zoning correction and volume correction, has a calculation error of <10%; the traditional method has an error of >40%. In heavy oil CO2 huff and puff experiments, after optimizing the gas injection volume according to the method of this invention, the efficiency is improved by 10%-20% compared with the traditional method.

[0027] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for correcting the CO2 huff and puff injection volume of heavy oil, characterized in that, Includes the following steps: Step 1: Acquire images of the foam liquid film and pressure data of the sand-filled pipe; Step 2: Use pressure visualization information to correct the pressure in different areas of the sand-filled pipe; calculate the average radius of all bubbles; calculate the bubble density using the average radius; The gas compressibility coefficient is calculated using the nonlinear relationship between bubble density and gas volume. Calculate the effective gas volume using the gas compressibility coefficient; calculate the mass of the injected gas using the effective gas volume; calculate the corrected injection volume using the mass of the injected gas.

2. The method for correcting the CO2 huff and puff volume of heavy oil according to claim 1, characterized in that, The formula for pressure correction is: in, This is the pressure correction factor; This represents the average pressure value for each region.

3. The method for correcting the CO2 huff and puff volume of heavy oil according to claim 1, characterized in that, The formula for the average radius of a bubble is: in, For the first i The radius of each bubble.

4. The method for correcting the CO2 huff and puff volume of heavy oil according to claim 3, characterized in that, The formula for bubble density is: Where, n A This indicates the number of bubbles per unit area. This represents the average radius of all bubbles.

5. The method for correcting the CO2 huff and puff volume of heavy oil according to claim 1, characterized in that, The formula for effective gas volume is: Among them, gas compressibility coefficient , f () is a quadratic function in one variable.

6. The method for correcting the CO2 huff and puff injection volume of heavy oil according to any one of claims 2 and 5, characterized in that, The formula for the mass of the injected gas is: in, R This is the universal gas constant. T The temperature is the thermodynamic temperature of the system.

7. The method for correcting the CO2 huff and puff volume of heavy oil according to claim 6, characterized in that, The formula for correcting the gas injection volume is: Among them, P in To inject pressure; This represents the total mass of the injected gas in all regions.

8. The method for correcting the CO2 huff and puff injection volume of heavy oil according to claim 1, characterized in that, Score the membership degree of the bubbles.

9. The method for correcting the CO2 huff and puff volume of heavy oil according to claim 1, characterized in that, The foam liquid film image was acquired using a device consisting of a camera, a PDMS chip, and an LED light assembly.

10. A heavy oil CO2 huff and puff gas injection volume correction system, characterized in that, include: Memory is used to store instructions that can be executed by the processor; A processor for executing instructions to implement the heavy oil CO2 huff and puff injection volume correction method as described in any one of claims 1-9.

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