CN115569679B - Microfluidic chip for rapidly determining dew point bubble point - Google Patents

Abstract

The invention relates to a micro-fluidic chip for rapidly determining dew point bubble point, which consists of four groups of unit channels, displacement saturation channels and extraction pipelines which are arranged in parallel, wherein the unit channels are arranged in the horizontal direction in an order of amplification from left to right in equal proportion, and each group of unit channels comprises 5 identical channels; each channel is provided with two parts in the vertical direction, namely a top part and a conical part, and the bottom end of the conical part is provided with a capillary; the chip is provided with a displacement saturation channel along the horizontal direction, namely the central axis of the unit channel, adjacent unit channels are mutually communicated through the displacement saturation channel, two sides of the displacement saturation channel are provided with injection ends A1 and A2, the top of the chip is provided with a extraction end B1, and the top parts of the adjacent unit channels are connected with the extraction end through extraction pipelines. The invention can accurately measure the bubble point pressure of the black oil and the dew point pressure of the condensate gas reservoir, provides important theoretical basis for evaluating reserves and planning oil and gas field development and production, and has great practical significance.

Description

A microfluidic chip for rapid determination of dew point and bubble point

Technical Field

The invention relates to a microfluidic chip, in particular to a microfluidic chip for rapidly measuring dew point and bubble point, belonging to the technical field of precision detection.

Background Art

Microfluidics is a technology that specializes in the study and processing of micro-nano sized fluids. Microfluidic chips can easily construct complex flows at micro-nano sizes. More and more scholars at home and abroad have begun to use microfluidic chips to study the flow and phase change behavior of fluids in microfluidic chips.

Microfluidic chips are mainly used for two-phase displacement experiments. Some scholars have used microfluidic chips to carry out immiscible _CO2 flooding, miscible _CO2 flooding and gas-water alternating flooding, and compared the experimental results with core experiments (Fuwei, YU, et al. Experiments on imbibition mechanisms of fractured reservoirs by microfluidic chips. Petroleum Exploration and Development 48.5(2021): 1162-1172), and some scholars have used microfluidic chips to carry out three different types of surfactant flooding experiments (Yu, Fuwei, et al. Flow Dynamics of Microemulsion-Forming Surfactants and its Implications for Enhanced Oil Recovery: A Microfluidic Study. SPEInternational Conference on Oilfield Chemistry. OnePetro, 2021). However, microfluidic chips for measuring dew point and bubble point have not yet been seen.

The present invention designs a microfluidic chip for quickly measuring dew point and bubble point, which not only greatly reduces the experimental time, but also requires only a few microliters of sample. By replacing the position of the microfluidic chip, the accurate measurement of the bubble point pressure of black oil and the dew point pressure of condensate gas reservoirs can be achieved, which is of great significance for evaluating reserves and planning oil and gas field development and production.

Summary of the invention

The purpose of the present invention is to provide a microfluidic chip for quickly measuring dew point and bubble point. The microfluidic chip has micro-nanoscale pores, requires only a very small amount of sample and has a fast measurement time. By changing the relationship between the pores of the microfluidic chip and gravity, the saturation of the microfluidic chip with high-temperature and high-pressure fluid can be achieved, and the accurate measurement of the bubble point of black oil and the dew point of condensate gas can be achieved. The present invention has broad market application prospects.

In order to achieve the above technical objectives, the present invention adopts the following technical solutions.

A microfluidic chip for rapidly measuring dew point and bubble point consists of four groups of parallel unit channels, a displacement saturation channel and an extraction pipeline. The unit channels are arranged in a horizontal direction from left to right and are enlarged in equal proportions, and each group of unit channels includes five channels of the same size. Each channel has two parts in a vertical direction, namely a top part and a tapered part, the top part and the tapered part are used to accommodate samples, and a capillary is arranged at the bottom of the tapered part. The capillary is sealed and used to collect oil droplets or bubbles. The chip is provided with a displacement saturation channel along the horizontal direction, i.e., the central axis of the unit channel, and adjacent unit channels are interconnected through the displacement saturation channel. Injection ends A1 and A2 are arranged on both sides of the displacement saturation channel, and the shape and size are consistent with the fixing holes of a chip fixture. An extraction end B1 is arranged on the top of the chip, and the top parts of adjacent unit channels are connected to the extraction ends through an extraction pipeline.

The etching depths of the top part and the tapered part of the unit channel are kept consistent, and the etching depths of the tapered part and the capillary are reduced in a step-by-step manner. The volume of the capillary at the lower end of the tapered part is designed to be 0.1-0.3% of the total pore volume of the microfluidic chip.

The capillary part of the unit channel is of sealed design to prevent oil droplets or bubbles from escaping.

The design principle of the microfluidic chip of the present invention is designed based on gravity differentiation and capillary force. By adjusting the position of the microfluidic chip, accurate measurement of the black oil bubble point/condensate gas dew point can be achieved.

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

The microfluidic chip has micro-nanoscale pores and utilizes the gravity differentiation of fluids to solve the problem of incomplete saturation of high-temperature and high-pressure fluid microfluidic chips. It uses a special tip to achieve high-resolution droplet/bubble identification under gravity differentiation. The present invention can accurately measure the bubble point pressure of black oil and the dew point pressure of condensate gas reservoirs, providing an important theoretical basis for evaluating reserves and planning oil and gas field development and production, and has great practical significance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a front view of a microfluidic chip for rapidly measuring bubble point and dew point.

FIG. 2 is a design diagram of the capillary portion at the lower end of the tapered portion of the unit channel.

FIG3 is a schematic diagram of the structure of a microfluidic device for rapidly measuring bubble point and dew point.

In the figure: 1-micro displacement pump; 2-six-way valve; 3-deionized water intermediate container; 4-intermediate container; 5-sample tank; 6-reactor; 7-sapphire visual window; 8-microfluidic chip; 9-electromagnetic heater; 10-back pressure valve; 11-gas-liquid separation tube; 12-gas flow meter; 13-back pressure pump; 14-microscope; 15-image collector; 16-light source; 17, 18, 19, 20, 21, 22, 23-valves.

FIG4 is a front view of the microfluidic chip when measuring the bubble point of black oil.

FIG5 is a front view of the microfluidic chip when measuring the dew point of condensate gas.

DETAILED DESCRIPTION

The present invention is further described below with reference to the accompanying drawings and examples, so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments, and for those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, they are all protected.

See Figure 1 and Figure 2.

A microfluidic chip for rapidly measuring dew point and bubble point comprises four groups of unit channels placed in parallel, wherein the unit channels are arranged in a horizontal direction from left to right and are proportionally enlarged, and each group of unit channels comprises five channels of the same size; a total of 20 channels are etched on a microfluidic chip; a channel with a width of 60 microns is passed through the central axis position of each unit channel to connect all the unit channels with injection ends A1 and A2 on both sides; the top parts of all the unit channels are connected to a sampling end B1, and the width of the connected channels is 60 microns.

The unit channel is divided into a top part and a tapered part in the vertical direction, wherein the width of the top part of the unit channel is designed to be 250, 300, 350, and 400 microns, the length is designed to be 5000 microns, and the etching depth is 100 microns; the width of the tapered part of the unit channel is designed to be 240, 290, 340, and 390 microns, the length is designed to be 1250 microns, and the etching depth is 100 microns; such a design can ensure that the top part and the tapered part of the microfluidic chip can accommodate a large amount of gas and liquid. The capillary part at the lower end of the tapered part of the unit channel is designed to be 10 microns in width, 100 microns in length, and 10 microns in etching depth. The capillary part is a sealed design to prevent the escape of condensate oil droplets/bubbles, and the appearance of condensate oil droplets/bubbles can be intuitively detected.

See Figure 3.

The microfluidic device for rapidly measuring bubble point and dew point comprises a micro displacement pump 1, a deionized water intermediate container 3, an intermediate container 4, a sample tank 5, a reaction kettle 6, a sapphire visual window 7, a microfluidic chip 8, an electromagnetic heater 9, a back pressure valve 10, a gas-liquid separation tube 11, a gas flow meter 12, a back pressure pump 13, a microscope 14, an image collector 15 and a light source 16.

The microfluidic chip 8 is located in a reactor 6 with a sapphire visual window 7, the reactor is connected to an electromagnetic heater 9, the inlet end of the reactor is connected to a micro-displacement pump 1 through an intermediate container 4 and a sample tank 5, and the outlet end is connected to a back-pressure valve 10, the back-pressure valve is respectively connected to a gas-liquid separation tube 11 and a back-pressure pump 13, and the gas-liquid separation tube is connected to a gas flow meter 12; the confining pressure inlet of the reactor is also connected to the micro-displacement pump 1 through a deionized water intermediate container 3; a microscope 14 is arranged opposite the sapphire visual window, and the microscope is connected to an image collector 15.

See Figure 4.

When using a microfluidic chip to quickly measure the bubble point, the conical part of the unit channel is made to face vertically upwards. The specific process is as follows:

(1) A1 and A2 of the microfluidic chip 8 are used as the displacement saturation inlet, and B1 is used as the outlet controlled by the back pressure pump, and the chip is clamped in the reactor 6, and the position of the microscope 14 is adjusted so that the image in the image acquisition device 15 is clearly visible;

(2) Fill the intermediate container 4 with deionized water, fill the sample tank 5 with oil sample, and check whether there is any leak in the entire system;

(3) Since the microfluidic chip 8 is easily broken due to uneven pressure, the confining pressure and the internal pressure are established at the same time. The valves 17, 18, 20, and 21 are opened, and the microfluidic chip is established to the experimental pressure by the micro displacement pump 1 at a pump speed of 0.001 ml/min, and the back pressure pump 13 continuously applies a back pressure that is 1-2 MPa higher than the internal pressure and the confining pressure. At the same time, the electromagnetic heater 9 is used to heat the reactor to the experimental temperature;

(4) Saturate the oil sample. Close valves 18 and 21, open valves 19 and 22, and use the micro displacement pump 1 to transfer the oil sample stored in the sample tank 5 into the microfluidic chip through A1 and A2. The density of the oil sample is smaller than that of water. Due to the gravity separation effect, the oil sample floats on the upper layer of the water. During the displacement and saturation process, the water in the microfluidic chip flows out of the chip from the bottom of the microfluidic chip through B1;

(5) Observe the chip through the image acquisition device 15. When the water in the chip is completely driven out, the sample transfer is considered complete and the back pressure valve 10 is closed. Use the micro displacement pump 1 to control the inlet A2 to continuously reduce the pressure in steps of 0.3 MPa. Each pressure point is stable for 30 minutes. When bubbles are observed in the image acquisition device 15, it indicates that the bubble point of the oil sample has been reached.

See Figure 5.

When using a microfluidic chip to quickly measure dew point, the specific process is as follows:

(1) Turn the microfluidic chip 180° clockwise, use A1 and A2 of the microfluidic chip 8 as the displacement saturation inlet, and use B1 as the outlet controlled by the back pressure pump. Clamp the chip in the reactor 6, and adjust the position of the microscope 14 so that the image in the image collector 15 is clearly visible;

(2) Fill the intermediate container 4 with dry gas, fill the sample tank 5 with condensate gas sample, and check whether there are any leaks in the entire system;

(3) Since the microfluidic chip 8 is easily broken due to uneven pressure, it is necessary to establish the confining pressure and the internal pressure together. Open valves 17, 18, 20, and 21, and establish the microfluidic chip 8 to the experimental pressure by the micro displacement pump 1 at a pump speed of 0.001 ml/min, and continuously apply a back pressure 1-2 MPa higher than the internal pressure and the confining pressure by the back pressure pump 13. At the same time, use the electromagnetic heater 9 to heat the reactor 6 to the experimental temperature.

(4) Saturate the condensate gas sample, close valves 18 and 21, and open valves 19 and 22. Use the micro displacement pump 1 to transfer the condensate gas sample stored in the sample tank 5 into the microfluidic chip 8 through the pore volume of A1 and A2, each 10,000 times the volume. The pump speed is 50uL/min. The density of the condensate gas sample is greater than that of methane. Due to the gravity separation effect, the condensate gas sample sinks to the lower layer. During the displacement and saturation process, the dry gas in the microfluidic chip 8 will escape from the chip from the sampling channel B1 located at the upper part of the microfluidic chip;

(5) Close the back pressure valve 10. Use the micro displacement pump 1 to control the inlet A2 to continuously reduce the pressure in steps of 0.3 MPa. Each pressure step is stable for 30 minutes. When condensate oil droplets are observed in the image collector 15, it indicates that the dew point of the condensate gas sample has been reached.

Claims (5)

1. A microfluidic chip for rapid determination of dew point and bubble point, comprising four groups of parallel unit channels, displacement saturation channels and extraction pipelines, characterized in that the unit channels are arranged in a proportional order from left to right in the horizontal direction, and each group of unit channels includes 5 channels of the same size; each channel has two parts in the vertical direction, namely, a top part and a tapered part, the top part and the tapered part are used to accommodate samples, a capillary is arranged at the bottom of the tapered part, and the capillary is sealed for collecting oil droplets or bubbles; the chip is provided with a displacement saturation channel along the horizontal direction, i.e., the central axis of the unit channel, and adjacent unit channels are connected by a tube. The displacement saturation channels are interconnected, injection ends A1 and A2 are arranged on both sides of the displacement saturation channels, an extraction end B1 is arranged on the top of the chip, and the top parts of adjacent unit channels are connected to the extraction ends through extraction pipelines; the microfluidic chip is located in a reactor with a sapphire visual window, the reactor is connected to an electromagnetic heater, its inlet end is connected to a micro displacement pump through an intermediate container and a sample tank, and its outlet end is connected to a back pressure valve, the back pressure valve is respectively connected to a gas-liquid separation tube and a back pressure pump, and the gas-liquid separation tube is connected to a gas flow meter; the confining pressure inlet of the reactor is also connected to a micro displacement pump through a deionized water intermediate container; a microscope is arranged opposite the sapphire visual window, and the microscope is connected to an image collector. 2. A microfluidic chip for rapidly measuring dew point and bubble point as described in claim 1, characterized in that the injection ends A1 and A2 arranged on both sides of the displacement saturation channel have a shape and size consistent with the fixing holes of the chip fixture. 3. A microfluidic chip for rapid determination of dew point and bubble point as described in claim 1, characterized in that the etching depths of the top part and the tapered part of the unit channel remain consistent, the etching depths of the tapered part and the capillary are reduced in a step-by-step manner, and the volume of the capillary at the lower end of the tapered part is designed to be 0.1-0.3% of the total pore volume of the microfluidic chip. 4. A microfluidic chip for rapidly measuring dew point and bubble point as described in claim 1, 2 or 3, characterized in that the saturation of the microfluidic chip with high-temperature and high-pressure fluid is achieved by changing the relationship between the microfluidic chip pores and gravity, thereby completing the measurement of the black oil bubble point and the condensate gas dew point. 5. A microfluidic chip for rapidly measuring dew point and bubble point as described in claim 1, 2 or 3, characterized in that when the bubble point is measured using the microfluidic chip, the tapered portion of the unit channel is vertically upward.