Oil saturation distribution measurement method suitable for open system

Abstract

The invention relates to an oil saturation distribution measuring method suitable for an open system, which comprises the following steps: dyeing non-wetting phase oil, keeping wetting phase water colorless, and when the dyed oil is injected into a visual seepage model of saturated water, measuring the oil saturation distribution of the open system. An oil phase greatly absorbs a spectrum which does not correspond to the color of the oil phase, a linear relation exists between the light intensity attenuation of the spectrum and the corresponding oil quantity, and a quantitative relation between the light intensity attenuation and the corresponding oil quantity is established through dynamic calibration, so that a calibration coefficient is obtained and used for calculating the oil saturation distribution in the medium. According to the fluid saturation measuring method provided by the invention, the saturation and the optical signal have a good linear relationship, and the measuring precision is high.

Description

Technical Field

[0001] This invention relates to fluid saturation distribution measurement technology in oil and gas reservoir exploration and development research, specifically a method for measuring oil saturation distribution applicable to open systems. Background Technology

[0002] Fluid saturation distribution measurement is a crucial task in evaluating hydrocarbon accumulation and development effectiveness. In recent decades, although techniques such as computed tomography (CT), magnetic resonance imaging (MRI), and gamma / X-ray attenuation methods have been successfully applied to test fluid saturation distribution in porous media, these methods have long testing cycles, making it difficult to meet the need for continuous monitoring of saturation changes. Optical methods can measure saturation instantaneously. The papers "Visualization by light transmission of oil and water contents in transient two-phase flow fields" and "Amodified light transmission visualization method for DNAPL saturation measurements in 2-D models" respectively published methods for calculating oil saturation using transmitted light hue and intensity. However, the different absorption rates of the RGB components of light by the medium lead to poor linearity between oil content and hue or intensity. The paper "Multispectral Two-Dimensional Visualized Seepage Model Fluid Saturation Testing Device and Method" discloses a method that dyes oil and water phases with different colors and measures the saturation distribution through selective absorption of light. The paper "A Semi-Sealed Two-Dimensional Seepage Model and its Fabrication Method" provides an open experimental system in which the saturated water in the model is connected to the ambient water, and has been widely used. However, when the dyed water phase in the model exchanges with the ambient water, it will change the color of the ambient water, thus causing measurement errors. Therefore, this method is not suitable for open systems. Summary of the Invention

[0003] The purpose of this invention is to provide a method for measuring oil saturation distribution in open systems. This method addresses the problem of measurement errors in existing fluid saturation distribution measurement methods.

[0004] The technical solution adopted by this invention to solve its technical problem is as follows: This method for measuring the oil saturation distribution in open systems involves dyeing the non-wetting phase oil while keeping the wetting phase water colorless. When the dyed oil is injected into a visualized flow model of saturated water, the oil phase absorbs a large amount of light that does not correspond to its own color. There is a linear relationship between the attenuation of the spectral intensity and the corresponding oil content. Through dynamic calibration, a quantitative relationship between the attenuation of the spectral intensity and the corresponding oil content is established to obtain a calibration coefficient, which is used to calculate the oil saturation distribution in this type of medium. The formula for calculating the calibration coefficient is:

[0005] In the formula: Q To inject traffic, t Vp represents the filling time, and Vp represents the aperture volume corresponding to the pixel in the optical path. ΔI This represents the logarithmic difference in light intensity.

[0006] The method for creating the visualized seepage model in the above scheme is as follows: Place the lower glass plate flat on the test bench, put a rubber pad around the glass plate to form an open groove, fill the open groove with glass beads until the open groove is full, cover the open groove with the upper glass plate, and use C-clamps to fix and clamp the upper and lower glass plates from the top, bottom, left and right sides respectively.

[0007] The oil saturation distribution measurement method applicable to open systems described above utilizes an oil saturation distribution measurement device. This device includes an injection module, a visual seepage model, a transparent water tank, and a measurement module. The injection module comprises a micro-pump, an injection line, and valves. The measurement module includes a uniform surface light source, a high-resolution digital camera, and a computer. The visual seepage model is placed inside the transparent water tank. The micro-pump and valves are connected to the visual seepage model via the injection line. The injection line passes through a rubber pad at the bottom of the visual seepage model and is inserted into it. A uniform surface light source is positioned behind the transparent water tank, and a high-resolution digital camera is positioned in front of the transparent water tank. The high-resolution digital camera is connected to the computer, which contains an imaging module.

[0008] The above-mentioned method for measuring oil saturation distribution in open systems specifically includes the following steps: Step 1: Dye the oil phase red, while keeping the aqueous phase colorless; accurately measure the total pore volume of the visualized seepage model; Step 2: Immerse the visualized seepage model in the water in the transparent tank, and saturate the visualized seepage model using the water phase displacement pressure and capillary force. Step 3: Baseline Image Acquisition: Turn on the imaging module and the planar uniform light source, inject oil using a micro-pump until the oil just reaches the injection line inlet, capture and save a baseline image, and record the initial light intensity. I Bw ; Step 4: Dynamic calibration experiment: Inject dyed red oil into the visualized seepage model after saturation with water through the injection pipeline at a constant low flow rate, and take a photo at fixed intervals; when taking photos, keep the lighting and camera position different from those in step 3; Step 5: Determine the calibration coefficients C Process the series of filling images and calculate the cumulative area occupied by the oil phase in each filling image. ΔI , plot cumulative ΔI The distribution diagram between the cumulative injected oil volume and the calibration coefficient was obtained by fitting the data. C ; Step 6: Calculate the oil saturation distribution of different pixels:

[0009] In the formula: S o This represents the oil saturation level.

[0010] The calibration coefficients are obtained in the above scheme as follows: When oil is dyed red, blue or green light is significantly absorbed by the oil phase as it passes through, resulting in a decrease in intensity. I B The attenuation is only related to the number of pores in the optical path occupied by oil. k o related:

[0011] in I Bw The blue light intensity is visualized in a seepage model of light passing through saturated water. α o The absorption coefficient of red kerosene for blue light. d The pore diameter; From formula (1): ; Define the logarithmic difference of light intensity ΔI for: ; oil saturation S o for: ; in k This represents the total number of apertures in the optical path. Based on equations (2), (3), and (4), we obtain: ; make C=1 / α o dk , CIf is a constant representing the physical properties of a pixel, then: ; Therefore, oil saturation and ΔI There is a linear relationship between them; The total oil volume of all pixels is: ; On the other hand, the amount of oil injected that allows for visualized seepage: ; Combining equations (7) and (8), we get:

[0012] Obtaining calibration constants C Then, the oil saturation distribution of the visualization seepage model is calculated using equation (6). Beneficial effects

[0013] 1. This invention can measure not only the saturation distribution of transparent fluids in open systems, but also the saturation distribution of fluids in conventional closed systems.

[0014] 2. The fluid saturation measurement method provided by this invention is simple, easy to implement, and convenient to carry out.

[0015] 3. This invention can obtain a model oil saturation distribution map, which can be used to evaluate the enrichment degree in reservoir formation and the displacement effect during development.

[0016] 4. The fluid saturation measurement method provided by this invention has a good linear relationship between saturation and optical signal, and the measurement accuracy is high. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the oil saturation distribution measuring device in this invention.

[0018] Figure 2 Analyze the location of each pixel.

[0019] Figure 3 The image shows a grayscale diagram of a saturated oil-water two-phase fluid in the transport region, where A. kerosene injection volume is 0.5 ml, B. kerosene injection volume is 2.0 ml, C. kerosene injection volume is 4.0 ml, and D. kerosene injection volume is 6.0 ml.

[0020] Figure 4 This is a diagram showing the RGB component distribution of pixels along line segment AB.

[0021] Figure 5 This is a diagram showing the distribution of oil filling volume and optical signal intensity.

[0022] Figure 6 This is a graph showing the oil saturation distribution in the model after 30 minutes of charging.

[0023] In the image: 1. Uniform surface light source, 2. Micro-pump, 3. Injection pipeline, 4. Valve, 5. Transparent water tank, 6. Visualized seepage model, 7. C-clamp, 8. Computer, 9. High-definition digital camera. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings: This method for measuring oil saturation distribution in open systems only requires staining the non-wetting oil phase, while the wetting water phase remains colorless. When the stained oil is injected into a visualized flow model of saturated water, the oil phase absorbs a large amount of light that does not correspond to its own color. There is a linear relationship between the light intensity attenuation of the large amount of light and the corresponding oil quantity. Through dynamic calibration, a quantitative relationship between the light intensity attenuation and the corresponding oil quantity is established, and a calibration coefficient is obtained to calculate the oil saturation distribution in this type of medium.

[0025] When the oil is dyed red, blue light is significantly absorbed by the oil phase as it passes through, reducing its intensity. I B The attenuation is only related to the number of pores in the optical path occupied by oil. k o related: When oil is dyed red, blue or green light is significantly absorbed by the oil phase as it passes through, resulting in a decrease in intensity. I B The attenuation is only related to the number of pores in the optical path occupied by oil. k o related: ; in I Bw The blue light intensity is visualized in a seepage model of light passing through saturated water. α o The absorption coefficient of red kerosene for blue light. d The pore diameter; From formula (1): ; Define the logarithmic difference of light intensity ΔI for: ; oil saturation S o for: ; in k This represents the total number of apertures in the optical path. Based on equations (2), (3), and (4), we obtain: ; make C=1 / α o dk , C If is a constant representing the physical properties of a pixel, then: ; Therefore, oil saturation and ΔI There is a linear relationship between them; The total oil volume of all pixels is: ; On the other hand, the amount of oil injected that allows for visualized seepage: ; Combining equations (7) and (8), we get: ; Obtaining calibration constants C Then, the oil saturation distribution of the visualization seepage model is calculated using equation (6).

[0026] This method for measuring oil saturation distribution in open systems utilizes an oil saturation distribution measurement device. The device includes an injection module, a visual flow model 6, a transparent water tank 5, and a measurement module. The injection module includes a micro-pump 2, an injection line 3, and a valve 4. The measurement module includes a uniform surface light source 1, a high-resolution digital camera (HD digital camera 9), and a computer 8. The visual flow model 6 is placed inside the transparent water tank 5. The micro-pump 2 and valve 4 are connected to the visual flow model 6 via the injection line 4. The injection line passes through a rubber pad from the bottom of the visual flow model and is inserted into it. The uniform surface light source 1 is positioned behind the transparent water tank 5, and the high-resolution digital camera is positioned in front of the transparent water tank 5. The high-resolution digital camera is connected to the computer 8, which contains an imaging module.

[0027] The following is a dynamically calibrated method for measuring oil saturation suitable for open systems: Preparation: The oil phase is dyed red, while the aqueous phase remains colorless; the total pore volume of the model is accurately measured using methods such as weighing.

[0028] Visualized seepage model construction: Place the lower glass plate flat on the test bench, surround the glass plate with a narrow rubber pad to form an open groove, fill the open groove with glass beads until it is full, cover with the upper glass cover plate, and use C-clamps to fix and clamp the two glass plates on the top, bottom, left and right sides respectively.

[0029] Visualized seepage model saturation: The visualized seepage model is immersed in water in a transparent water tank, and the displacement pressure and capillary force of the transparent water tank are used to saturate the visualized seepage model. System connection: such as Figure 1The connection device is shown. The injection line passes through the rubber pad from below the model and is inserted into the model. The oil saturation distribution measurement device is now connected.

[0030] Baseline Image Acquisition: The imaging module and a uniform planar light source are activated. A micro-pump dispenses oil until it just reaches the injection line inlet. A baseline image is captured and saved, and the initial light intensity is recorded. I Bw .

[0031] Dynamic calibration experiment: Red dye was injected into the saturated water model at a constant low flow rate through the injection line, and photographs were taken every 5 minutes. During photography, the lighting and camera position were kept different from those in step 5.

[0032] Determine calibration coefficients C Process the series of filling images and calculate the cumulative area occupied by the oil phase in each filling image. ΔI . , plotting the cumulative ΔI The distribution diagram between the cumulative injected oil volume and the calibration coefficients were obtained by fitting the data.

[0033] The oil saturation distribution of different pixels is calculated using formula (6). Example

[0034] The internal dimensions of the two-dimensional visualization model (visualized seepage model) in this embodiment (i.e., the size of the sand body within the model's covered area) are 200mm × 300mm × 3mm, with a width of 200mm, a height of 300mm, and a glass plate spacing of 2mm. The interior is uniformly filled with 40-mesh transparent glass microspheres, and the perimeter is filled with 100-mesh glass microspheres. The porosity of both the 40-mesh and 100-mesh glass microsphere packs was measured to be 36.5% using a weighing method.

[0035] The steps of this method for measuring oil saturation in open systems include: Preparation: Use pure water to simulate formation water as the wetting phase; dye kerosene red with oil red dye as the non-wetting phase.

[0036] Model making: Place the lower glass plate flat on the test table, surround the glass plate with a narrow rubber pad, fill the rectangular area (open groove) with 40-mesh glass microbeads in the center with a width × height of 200mm × 300mm, and fill the surrounding area with 100-mesh glass microbeads, cover with the upper glass cover plate, and use C-clamps to fix and clamp the two glass plates on the top, bottom, left and right sides respectively.

[0037] The model was immersed in water in a transparent tank until it was fully saturated with water.

[0038] System connection: Connect the equipment as shown in the attached diagram. Insert the injection line into the model from below, through the rubber pad.

[0039] Baseline Image Acquisition: The model is fully saturated with colorless water. The imaging module and a uniform planar light source are activated. Oil is pumped in until it just reaches the injection line inlet. A baseline image is captured and saved, and the initial light intensity is recorded. I Bw .

[0040] Dynamic calibration experiment: Red dye was injected into the saturated water model through the injection line at a flow rate of 0.5 ml / min, and a photograph was taken every five minutes. Figure 3 To ensure that the model's position in the photo does not change with each shot, the digital camera uses manual focus mode.

[0041] Calibration coefficient calculation: Figure 2 It's a photograph of the filling process. The RGB component diagram of the light rays is drawn along line segment AB marked in the image. Figure 4 As can be seen, when the oil is dyed red, the intensity of blue or green light decreases significantly when white light passes through the oil phase, while the intensity of red light remains essentially unchanged. The cumulative intensity of the oil phase coverage area at different times is calculated using formula (3). ΔI Draw a cumulative injection oil volume and cumulative distribution map ( Figure 5 Considering Vp = 5.24 × 10 -5 cm 3 The calibration coefficient C was found to be 0.764.

[0042] The photo was filled at 30 minutes, and the oil saturation of each pixel was calculated using formula (6) to obtain the oil saturation distribution map at that time. Figure 6 ).

Claims

1. A method for measuring oil saturation distribution in open systems, characterized in that: The unwetting phase oil is stained, while the wetting phase water remains colorless. When the stained oil is injected into a visualized flow model saturated with water, the oil phase significantly absorbs a spectrum that does not correspond to its own color. A linear relationship exists between the attenuation of this spectral intensity and the corresponding oil content. Through dynamic calibration, a quantitative relationship between the intensity attenuation and the corresponding oil content is established, yielding a calibration coefficient used to calculate the oil saturation distribution in this type of medium. The formula for calculating the calibration coefficient is: ； In the formula: Q To inject traffic, t Vp represents the filling time, and Vp represents the aperture volume corresponding to the pixel in the optical path. ΔI This represents the logarithmic difference in light intensity.

2. The method for measuring oil saturation distribution in open systems according to claim 1, characterized in that: The method for making the visualized seepage model is as follows: Place the lower glass plate flat on the test bench, put a rubber pad around the glass plate to form an open groove, fill the open groove with glass beads until the open groove is full, cover the open groove with the upper glass plate, and use C-clamps to fix and clamp the upper and lower glass plates from the top, bottom, left and right sides respectively.

3. The method for measuring oil saturation distribution in open systems according to claim 2, characterized in that: The method for measuring oil saturation distribution in open systems utilizes an oil saturation distribution measuring device. This device includes an injection module, a visual seepage model, a transparent water tank, and a measurement module. The injection module comprises a micro-pump, an injection line, and a valve. The measurement module includes a uniform surface light source, a high-resolution digital camera, and a computer. The visual seepage model is placed inside the transparent water tank. The micro-pump and valve are connected to the visual seepage model via the injection line. The injection line passes through a rubber pad at the bottom of the visual seepage model and is inserted into it. A uniform surface light source is positioned behind the transparent water tank, and a high-resolution digital camera is positioned in front of the transparent water tank. The high-resolution digital camera is connected to the computer, which contains an imaging module.

4. The method for measuring oil saturation distribution in open systems according to claim 3, characterized in that... Specifically, the steps include the following: Step 1: Dye the oil phase red, while keeping the aqueous phase colorless; accurately measure the total pore volume of the visualized seepage model; Step 2: Immerse the visualized seepage model in the water in the transparent tank, and saturate the visualized seepage model using the water phase displacement pressure and capillary force. Step 3: Baseline Image Acquisition: Turn on the imaging module and the planar uniform light source, inject oil using a micro-pump until the oil just reaches the injection line inlet, capture and save a baseline image, and record the initial light intensity. I Bw ; Step 4: Dynamic calibration experiment: Inject dyed red oil into the visualized seepage model after saturation with water through the injection pipeline at a constant low flow rate, and take a photo at fixed intervals; when taking photos, keep the lighting and camera position different from those in step 3; Step 5: Determine the calibration coefficients C Process the series of filling images and calculate the cumulative area occupied by the oil phase in each filling image. ΔI , plot cumulative ΔI The distribution diagram between the cumulative injected oil volume and the calibration coefficient was obtained by fitting the data. C ; Step 6: Calculate the oil saturation distribution of different pixels: ； In the formula: S o This represents the oil saturation level.

5. The method for measuring oil saturation distribution in open systems according to claim 4, characterized in that: The method for obtaining the calibration coefficients is as follows: When oil is dyed red, blue or green light is significantly absorbed by the oil phase as it passes through, resulting in a decrease in intensity. I B The attenuation is only related to the number of pores in the optical path occupied by oil. k o related: ； in I Bw The blue light intensity is visualized in a seepage model of light passing through saturated water. α o The absorption coefficient of red kerosene for blue light. d The pore diameter; From formula (1): ； Define the logarithmic difference of light intensity ΔI for: ； oil saturation S o for: ； in k This represents the total number of apertures in the optical path. Based on equations (2), (3), and (4), we obtain: ； make C=1 / α o dk , C If is a constant representing the physical properties of a pixel, then: ； Therefore, oil saturation and ΔI There is a linear relationship between them; The total oil volume of all pixels is: ； On the other hand, the amount of oil injected that allows for visualized seepage: ； Combining equations (7) and (8), we get: ； Obtaining calibration constants C Then, the oil saturation distribution of the visualization seepage model is calculated using equation (6).

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