Condensate recovery calculation method for condensate gas microfluidic experiment

Abstract

The present application belongs to the technical field of oil and gas reservoir development, and relates to a condensate oil recovery calculation method for condensate gas micro-fluid control experiment. The method comprises the following steps: (1) measuring the length, width and etching depth of the etching area of the micro-fluid control chip, and calculating the pore volume of the micro-fluid control chip and the corresponding gas storage volume; (2) vacuumizing the micro-fluid control chip, saturating the chip with condensate gas, and calculating the total amount of condensate oil in the micro-fluid control chip in the initial state; (3) keeping the inlet pressure of the micro-fluid control chip unchanged, and performing pressure reduction depletion experiment on the outlet end according to the preset pressure step, and stopping when the pressure is reduced to the target pressure point below the dew point pressure; (4) calculating the total amount of condensate oil in the chip, including the amount of condensed condensate oil and the amount of condensed condensate oil that is not condensed in the chip; and (5) calculating the condensate oil recovery. The present application establishes a condensate oil recovery calculation method for condensate gas micro-fluid control experiment, and the calculation result is accurate and reliable, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas reservoir development technology, specifically relating to a method for calculating condensate oil recovery rate in condensate gas microfluidic experiments. Background Technology

[0002] Condensate gas reservoirs are a special type of gas reservoir with high economic value. Under original formation conditions, condensate gas reservoirs are a single gas phase. However, during the development process, as the gas is continuously extracted, the formation pressure continues to decrease. When the pressure is lower than the dew point of the condensate gas reservoir, condensate oil will precipitate due to reverse condensation, forming a gas-liquid two-phase system, which affects the development effect of the condensate gas reservoir.

[0003] In recent years, with the continuous development of technology, the rise of microfluidic experimental research in the field of oil and gas field development cannot be ignored. Microfluidic models can easily realize the visualization of fluid flow in micro- and nano-scale spaces. Some scholars have carried out microscopic condensate gas visualization experiments and studied the microscopic gas-liquid two-phase phase change characteristics of condensate gas. Their results are concentrated on the analysis of condensate oil occurrence, but no quantitative method for condensate oil recovery has been established (Zhu Weiyao, Liu Xuewei, Hu Yongle, Luo Kai, Shan Wenwen. Study on the microscopic seepage mechanism of condensate gas-liquid phase change [J]. Natural Gas Geoscience, 2006(03):292-295). "A method for testing the saturation of condensate oil in low-permeability condensate gas reservoirs by gas injection and reverse evaporation" (CN112285201A) uses sound waves to test the saturation of condensate oil in the core, which has a certain deviation from the actual condensate oil saturation and cannot be visualized. Since the sample volume involved in microfluidic technology is at the microliter level, the volume is too small, and conventional gas gathering measurement cannot determine the produced volume. Summary of the Invention

[0004] The purpose of this invention is to provide a method for calculating condensate oil recovery in condensate gas microfluidic experiments. This method is reliable in principle. It calculates the amount of condensate oil precipitated in the experimental image through image processing, and at the same time, it combines conventional condensate gas constant volume exhaustion experiments to obtain the amount of condensate oil that has not precipitated in the gas phase, thereby obtaining the total amount of condensate oil remaining in the microfluidic chip, and thus determining the final condensate oil recovery rate. This invention establishes a method for calculating condensate oil recovery rate in condensate gas microfluidic experiments and has broad application prospects.

[0005] To achieve the above technical objectives, the present invention adopts the following technical solution.

[0006] First, the length and width of the etched area on the microfluidic chip were measured to determine the etching depth. Image processing software was used to calculate the number of pixels in the image where the microfluidic chip was not saturated with any fluid; this was defined as the porosity. Next, the number of pixels in the microscopic decay experiment photographs of condensate gas at pressures below the condensate gas dew point pressure were calculated, and the condensate oil saturation was calculated using image processing software. Then, combined with the decay gas-oil ratio parameters obtained from the constant-volume decay experiment, the condensate oil content in the gas phase was calculated. After determining the actual amount of condensate oil remaining within the microfluidic chip, the condensate oil recovery rate was calculated.

[0007] A method for calculating condensate oil recovery in a condensate gas microfluidic experiment includes the following steps:

[0008] (1) The length and width of the etched area of ​​the microfluidic chip are accurately measured using vernier calipers to obtain the etched area A. Based on the etch depth h and the porosity of the microfluidic chip surface, the etch depth h and porosity of the microfluidic chip surface are determined. (Image pixels of the microfluidic chip that are not saturated with any fluid), calculate the pore volume V of the microfluidic chip using equation (1). P The gas storage volume V corresponding to the microfluidic chip is calculated using equation (2). g :

[0009]

[0010]

[0011] In the formula:

[0012] V P — Microfluidic chip pore volume, cm 3 ;

[0013] V g —Gas storage volume corresponding to the microfluidic chip, in cm 3 ;

[0014] A – Area of ​​the etched region, cm² 2 ;

[0015] h — etching depth, μm;

[0016] — Microfluidic chip surface porosity, %;

[0017] S g — Condensate gas saturation, %;

[0018] (2) Evacuate the microfluidic chip and saturate it with condensate gas. At this point, the microfluidic chip is in its initial state, and the condensate gas saturation is S. g =1, According to the condensate gas sampling report, the initial gas-oil ratio (GOR) was found to be... 初1. Condensate volume factor B under initial conditions g初 Calculate the total amount of condensate oil V of the microfluidic chip in the initial state. O初 :

[0019]

[0020]

[0021] In the formula:

[0022] V g初 —In the initial state (S) g =1) Gas storage volume corresponding to the microfluidic chip, cm 3 ;

[0023] V sc初 —Volume of condensate gas under initial conditions and at standard ground conditions, in cm³ 3 ;

[0024] B g初 —The volume coefficient of condensate gas in the initial state is dimensionless;

[0025] GOR 初 —Initial gas-oil ratio, m 3 / m 3 ;

[0026] V o初 —The total amount of condensate oil in the microfluidic chip under initial conditions, in ml;

[0027] (3) Keep the inlet pressure of the microfluidic chip constant, and perform a pressure reduction and exhaustion experiment at the outlet according to the preset pressure step. Stop when the pressure drops to the target pressure point P below the dew point pressure.

[0028] (4) Calculate the total amount of condensate oil in the microfluidic chip, including the amount of condensate oil precipitated in the microfluidic chip and the amount of condensate oil that did not precipitate from the condensate gas in the microfluidic chip. The process is as follows:

[0029] 1) Calculate the amount of condensate oil precipitated within the microfluidic chip:

[0030] The image of the microfluidic chip, where condensate oil has precipitated below the dew point pressure, is imported into image processing software. A reasonable grayscale range is selected, with the high grayscale values ​​representing condensate gas. The percentage of pixels corresponding to the current condensate gas is calculated. The percentage of condensate oil content is obtained by subtracting the percentage of pixels corresponding to the current condensate gas from the porosity. This yields the condensate oil saturation S precipitated within the microfluidic chip. o Condensate gas saturation S g The amount of condensate oil V precipitated within the microfluidic chip is calculated using equation (5). po1 :

[0031] V po1 =V p ×S o (5)

[0032] In the formula:

[0033] V po1 —Amount of condensate oil precipitated within the microfluidic chip, in ml;

[0034] V P — Microfluidic chip pore volume, cm 3 ;

[0035] S o —Saturation of condensate oil precipitated within the microfluidic chip, %;

[0036] V po1 Converted to the amount of condensate oil precipitated within the microfluidic chip under standard ground conditions, V o1 :

[0037]

[0038] In the formula:

[0039] V o1 —Amount of condensate oil precipitated within the microfluidic chip under standard ground conditions, in ml;

[0040] c—Condensate oil volume correction factor, dimensionless;

[0041] 2) Calculate the amount of condensate oil that did not precipitate from the condensate gas in the microfluidic chip:

[0042] Condensate gas constant-volume depletion experiment (according to industry standard "Methods for Fluid Property Analysis of Oil and Gas Reservoirs" GB-T26981—2020) was conducted to obtain condensate gas and condensate oil at the target pressure point P. The depletion gas-oil ratio (GOR) and condensate oil content (σ) were determined. The composition of condensate gas was measured using gas chromatography, and the condensate gas density (ρ) under standard surface conditions was obtained. g 1. Condensate gas density ρ under formation conditions gf The composition of the condensate oil was determined using oil chromatography, and the density ρ of the condensate oil was obtained. c The condensate gas volume factor B is calculated using equation (7). g (“Method and Apparatus for Determining the Volume Factor of Natural Gas in Condensate Gas Reservoirs”, CN 113536201 A):

[0043]

[0044] In the formula:

[0045] B g — Condensate volume coefficient, dimensionless;

[0046] ρg —Density of condensate gas under standard ground conditions, g / cm³ 3 ;

[0047] ρ gf —Density of condensate gas under formation conditions, g / cm³ 3 ;

[0048] ρ c —Density of condensate oil, g / cm³ 3 ;

[0049] σ — Condensate oil content, cm 3 / cm 3 ;

[0050] The current gas saturation S within the microfluidic chip g Substitute into equation (2) to calculate the gas storage volume V corresponding to the microfluidic chip. g Then, according to equation (8), the volume V of the condensate gas in the microfluidic chip under standard ground conditions is calculated. sc :

[0051]

[0052] In the formula:

[0053] B g — Condensate volume coefficient, dimensionless;

[0054] V sc —Volume of condensate gas in a microfluidic chip under standard ground conditions, in cm³ 3 ;

[0055] The amount of condensate oil V that did not precipitate from the condensate gas in the microfluidic chip was calculated using equation (9). o2 :

[0056]

[0057] In the formula:

[0058] V o2 —Amount of condensate oil that did not precipitate from the condensate gas in the microfluidic chip, in ml;

[0059] GOR – Exhaustion Gas-Fuel Ratio, m 3 / m 3 ;

[0060] (5) Calculate the total amount of condensed oil V in the microfluidic chip. o总 Then, based on the total amount of condensate oil V of the microfluidic chip in the initial state... O初 The condensate oil recovery rate E of the condensate gas microfluidic experiment was calculated as follows:

[0061] Vo总 =V o1 +V o2 (10)

[0062]

[0063] In the formula:

[0064] E – Condensate oil recovery rate, %.

[0065] Furthermore, the process of determining the condensate oil volume correction factor c is as follows: A certain volume of condensate oil sample in standard condition is taken from the collector at the outlet end of the microfluidic chip and transferred into a PVT container. The condensate oil sample in the PVT container is pressurized to the formation pressure at the formation temperature. After thorough stirring and stabilization, the volume of condensate oil under formation conditions is measured. The ratio of the volume under formation conditions to the volume under standard conditions is the condensate oil volume correction factor c.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] The amount of condensate oil remaining within a microfluidic chip is calculated, including the amount of condensate oil in images captured by a microscope during a microscopic decay experiment of condensate gas within the microfluidic chip and the amount of condensate oil that has not precipitated in the gas phase. After measuring the pore volume of the microfluidic chip, the condensate oil recovery rate at any given time can be calculated. This invention achieves accurate measurement of condensate oil recovery rate in condensate gas microfluidic experiments, with a simple calculation process and accurate and reliable results. Attached Figure Description

[0068] Figure 1 To calculate the interfacial gap of a microfluidic chip using image processing software.

[0069] Figure 2 To calculate the condensate oil saturation of a microfluidic chip using image processing software. Detailed Implementation

[0070] The present invention will be further described below with reference to the accompanying drawings and examples to enable those skilled in the art to understand the invention. However, it should be understood that the present invention is not limited to the specific embodiments described herein, and all variations within the spirit and scope of the invention as defined and determined by the appended claims are protected by those skilled in the art.

[0071] Example

[0072] A method for calculating the recovery rate of condensate gas in a microfluidic experiment is presented. By combining microscopic depletion experiments with conventional volumetric depletion experiments, the recovery rate of condensate oil within a microfluidic chip can be deduced. The specific process is as follows:

[0073] (1) The length and width of the etched area of ​​the microfluidic chip are accurately measured using vernier calipers. Then, the pore volume of the microfluidic chip is calculated based on the etching depth and porosity of the microfluidic chip. In this embodiment, the length of the etched pore structure of the microfluidic chip is 5.8 mm, the width is 3.9 mm, and the etching depth is 10 μm.

[0074] (2) Figure 1 As shown, image processing software is used to calculate the number of image pixels in a microfluidic chip that are not saturated with any fluid, which is defined as the surface porosity. The surface porosity of the microfluidic chip is calculated by the software. The saturation rate is 22.75%. After saturating the chip with condensate gas, the saturation rate of the condensate gas is 1. The gas storage volume V corresponding to the microfluidic chip in the initial state is calculated according to formulas (1) and (2). g初 It is 0.051cm 3 .

[0075] (3) The initial condensate gas-oil ratio (GOR) was obtained from the condensate gas sampling report. 初 and volume factor B g初 1453m respectively 3 / m 3 and 1.054×10 -3 The total amount of condensate V of the microfluidic chip in the initial state before condensate oil precipitation is calculated according to formulas (3) and (4). o初 It is 0.033316ml.

[0076] (4) After the chip is fully saturated, a voltage reduction and attenuation experiment is started according to the preset pressure step size. For example... Figure 2 As shown, the experimental image of the microfluidic chip with condensate oil precipitated below the dew point pressure was imported into image processing software. A reasonable grayscale range was selected, and the software calculated that the pixel percentage corresponding to condensate gas was 14.38%. By subtracting the current percentage of condensate gas from the porosity, the percentage of condensate oil was obtained as 8.37%, thus calculating the condensate oil saturation S. o The saturation of condensate gas was 36.79%, and the saturation of condensate gas was S. g It is 63.21%.

[0077] (5) According to the condensate oil saturation S in formula (5) o The percentage is 36.79% and the microfluidic chip pore volume V. P It is 0.051cm 3 The amount of oil V extracted within the image from the microfluidic chip can then be calculated. po1 It is 0.0188ml.

[0078] (6) Based on the coefficient c = 0.73 in formula (6) and the amount of oil precipitated in the microfluidic chip V po1The volume of condensate oil precipitated within the microfluidic chip under standard ground conditions was 0.0188 ml, yielding V. o1 It is 0.0258ml.

[0079] (7) Based on the conventional fixed-volume exhaustion experiment, the gas-oil ratio (GOR) at the experimental point was determined to be 5538.341 m³. 3 / m 3 The condensate gas composition was measured using a gas chromatograph to obtain the condensate gas density under standard ground conditions. The condensate oil composition was measured using an oil chromatograph to obtain the condensate oil density. The condensate oil content was measured, and the condensate gas volume factor B at the selected experimental point was calculated according to formula (7). g It is 1.227×10 -3 .

[0080] (8) Condensate gas saturation S g The condensate volume V inside the microfluidic chip at the experimental point pressure is 63.21%. Based on formula (2), the condensate volume V is calculated. g It is 0.03223cm 3 Combined with the calculated condensate gas volume factor B g It is 1.227×10 -3 The volume V of condensate gas under standard ground conditions is calculated according to equation (8). sc It is 26.27cm 3 .

[0081] (9) According to formula (9) and the conventional volumetric exhaustion test, the gas-oil ratio GOR is 5538.341m. 3 / m 3 The condensate gas volume under standard ground conditions is 26.27 cm³. 3 The amount of condensate oil that did not precipitate in the gas phase, V, was obtained. o2 It is 0.0047 ml.

[0082] (10) According to formula (10), the total amount of condensate oil V inside the chip is obtained. o总 It is 0.0305ml.

[0083] (11) According to formula (11), the condensate oil recovery rate E is calculated to be 8.45%.

Claims

1. A method for calculating condensate oil recovery in a condensate gas microfluidic experiment, comprising the following steps: (1) Measure the length and width of the etched area of ​​the microfluidic chip to obtain the etched area A. Based on the etch depth h and the porosity of the microfluidic chip surface, Calculate the pore volume of a microfluidic chip The gas storage volume corresponding to the microfluidic chip : (1) (2) In the formula: — Microfluidic chip pore volume, cm 3 ; —Gas storage volume corresponding to the microfluidic chip, in cm 3 ; A —Area of ​​the etched area, cm 2 ; h — etching depth, μm; — Microfluidic chip surface porosity, % — Condensate gas saturation, %; (2) Evacuate the microfluidic chip and saturate it with condensate gas. At this time, the microfluidic chip is in its initial state and the condensate gas saturation is [value missing]. =1, = Calculate the total amount of condensate oil in the microfluidic chip under the initial state. : ； In the formula: —The initial gas storage volume corresponding to the microfluidic chip, in cm 3 ; —Volume of condensate gas under initial conditions and at standard ground conditions, in cm³ 3 ; B g初 —The volume coefficient of condensate gas in the initial state is dimensionless; GOR 初 —Initial gas-oil ratio, m 3 / m 3 ; —The total amount of condensate oil in the microfluidic chip under initial conditions, in ml; (3) Keep the inlet pressure of the microfluidic chip constant, and perform a pressure reduction and exhaustion experiment at the outlet according to the preset pressure step. Stop when the pressure drops to the target pressure point P below the dew point pressure. (4) Calculate the total amount of condensate oil in the microfluidic chip, including the amount of condensate oil precipitated in the microfluidic chip and the amount of condensate oil that did not precipitate from the condensate gas in the microfluidic chip. The process is as follows: 1) Calculate the amount of condensate oil precipitated within the microfluidic chip: The image of the microfluidic chip, where condensate oil has precipitated below the dew point pressure, is imported into image processing software. The percentage of pixels corresponding to the current condensate gas is calculated. The percentage of condensate oil content is obtained by subtracting the percentage of pixels corresponding to the current condensate gas from the porosity, thus yielding the condensate oil saturation precipitated within the microfluidic chip. S o Condensate gas saturation S g Calculate the amount of condensate oil precipitated within the microfluidic chip. : （5） In the formula: —Amount of condensate oil precipitated within the microfluidic chip, in ml; — Microfluidic chip pore volume, cm 3 ; —Saturation of condensate oil precipitated within the microfluidic chip, % Will Converted to the amount of condensate oil precipitated within the microfluidic chip under standard ground conditions : （6） In the formula: —Amount of condensate oil precipitated within the microfluidic chip under standard ground conditions, in ml; — Condensate oil volume correction factor, dimensionless; 2) Calculate the amount of condensate oil that did not precipitate from the condensate gas in the microfluidic chip: A constant-volume exhaustion experiment was conducted on condensate gas to obtain the condensate gas and condensate oil at the target pressure point P. The exhaustion gas-to-oil ratio (GOR) and condensate oil content were then determined. The composition of condensate gas and condensate oil was determined using a chromatograph, and the volume factor of condensate gas was calculated. B g : （7） In the formula: B g — Condensate volume coefficient, dimensionless; ρ g —Density of condensate gas under standard ground conditions, g / cm³ 3 ; ρ gf —Density of condensate gas under formation conditions, g / cm³ 3 ; ρ c —Density of condensate oil, g / cm³ 3 ; — Condensate oil content, cm 3 / cm 3 ; The gas saturation level inside the current microfluidic chip S g Substitute into equation (2) to calculate the gas storage volume corresponding to the microfluidic chip. The volume of condensate gas in the microfluidic chip under standard ground conditions is calculated using the following formula. V sc : （8） In the formula: B g — Condensate volume coefficient, dimensionless; V sc —Volume of condensate gas in a microfluidic chip under standard ground conditions, in cm³ 3 ; The amount of condensate oil that did not precipitate from the condensate gas in the microfluidic chip was calculated. : （9） In the formula: —Amount of condensate oil that did not precipitate from the condensate gas in the microfluidic chip, in ml; GOR – Exhaustion Gas-Fuel Ratio, m 3 / m 3 ; (5) Calculate the total amount of condensate oil in the microfluidic chip Then, based on the total amount of condensate oil in the microfluidic chip under the initial state... The condensate oil recovery rate was calculated using a microfluidic experiment on condensate gas. E : （10） （11） In the formula: E — Condensate oil recovery rate,%.

2. The method for calculating condensate oil recovery in a condensate gas microfluidic experiment as described in claim 1, characterized in that, In step (2), the initial gas-oil ratio GOR is... 初 1. Condensate volume coefficient under initial conditions B g初 This was found in the condensate gas sample preparation report.

3. The method for calculating condensate oil recovery in a condensate gas microfluidic experiment as described in claim 1, characterized in that, In step (4), the determination process of the condensate oil volume correction coefficient is as follows: A certain volume of condensate oil sample in standard condition is taken from the collector at the outlet end of the microfluidic chip and transferred into the PVT container. The condensate oil sample in the PVT container is pressurized to the formation pressure at the formation temperature. After thorough stirring and stabilization, the volume of condensate oil under formation conditions is measured. The ratio of the volume under formation conditions to the volume under standard conditions is the condensate oil volume correction coefficient. c .

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