阅读说明：本技术 一种用于二氧化碳流变性的测试装置和方法 (Testing device and method for rheological property of carbon dioxide ) 是由 贺甲元 王海波 李小龙 周彤 李凤霞 刘长印 于 2020-04-08 设计创作，主要内容包括：本发明提出了一种用于二氧化碳流变性的测试装置和方法,该测试装置包括气源；能与气源连通的相态改变系统,相态改变系统用于接收气源供给的二氧化碳并改变二氧化碳的体系温度和压力；能与相态改变系统连通的旋转流变仪,旋转流变仪能测试二氧化碳的流变性能并能实时观察体系相态；用于记录旋转流变仪采集到的试验数据的数据处理系统,该测试装置可以评价二氧化碳的流变性能,同时,该装置结构简单,操作便利,测量数据精准度高,为进一步研究流变规律以及二氧化碳压裂设计和施工提供理论依据。(The invention provides a testing device and a method for rheological property of carbon dioxide, wherein the testing device comprises an air source; the phase state changing system is communicated with the gas source and is used for receiving the carbon dioxide supplied by the gas source and changing the system temperature and pressure of the carbon dioxide; the rotational rheometer can be communicated with the phase state changing system, and can test the rheological property of the carbon dioxide and observe the phase state of the system in real time; a data processing system for recording the experimental data that rotatory rheometer gathered, this testing arrangement can evaluate the rheology performance of carbon dioxide, and simultaneously, the device simple structure, the operation is convenient, and the measured data precision is high, provides the theoretical foundation for further research rheology law and carbon dioxide fracturing design and construction.)

1. A device for testing the rheology of carbon dioxide, comprising:

an air source is arranged on the air-conditioning system,

a phase change system communicable with the gas source, the phase change system for receiving carbon dioxide supplied from the gas source and changing a system temperature and pressure of the carbon dioxide,

the rotational rheometer can be communicated with the phase state changing system, can test the rheological property of the carbon dioxide and can observe the phase state of the system in real time,

and the data processing system is used for recording the test data acquired by the rotational rheometer.

2. The apparatus of claim 1, wherein the rotational rheometer includes a measurement cup with a visual window in a wall of the measurement cup.

3. The testing device of claim 2, wherein a rotor is disposed in the interior cavity of the measuring cup, the rotor being magnetically driven.

4. A testing apparatus according to claim 2 or 3, wherein the phase change system comprises an intermediate container, a piston is arranged in an inner cavity of the intermediate container to divide the inner cavity of the intermediate container into an upper space and a lower space, the upper space is communicated with the booster pump, and the lower space is communicated with both the gas source and the rotational rheometer.

5. The test device as claimed in claim 4, wherein a circulation duct is provided on an outer wall of the intermediate container in a winding manner, the circulation duct is communicated with the refrigerator, and an insulation layer is provided on an outer side of the circulation duct.

6. The testing device of claim 5, wherein the refrigerator is further connectable to the measuring cup to cool the measuring cup, and wherein the data processing system further comprises an industrial personal computer to control the refrigerator and the additional pump.

7. A method for testing the rheology of carbon dioxide using a testing device according to any one of claims 1 to 6, comprising:

step one, selectively putting tackifier into a measuring cup according to needs,

and step two, vacuumizing the intermediate container, the measuring cup and a pipeline connecting the intermediate container and the measuring cup, wherein the vacuum state is determined to be reached when the numerical value of the vacuum pump reaches-0.09 MPa.

Step three, pre-cooling the intermediate container and the measuring cup,

injecting carbon dioxide into the intermediate container, cooling and pressurizing the carbon dioxide to liquefy the carbon dioxide gas,

step five, injecting the carbon dioxide in the intermediate container into a measuring cup,

step six, setting the shear rate of the rotational rheometer so that the rotor begins to select to cause shear to the liquid carbon dioxide,

and step seven, picking up test data.

8. The test method according to claim 7, wherein in step five, the piston of the intermediate container is actuated at a constant rate to actuate the injection of carbon dioxide into the measuring cup.

9. The method of claim 7, wherein in step six, the temperature change of the carbon dioxide in the measuring cup is used to test the rheology of the carbon dioxide at different temperatures over time.

10. The test method according to claim 7, wherein in step seven, the viscosity of the fluid fluctuates at the beginning of the test, and the reading is performed after the value is stabilized.

Technical Field

The invention relates to the technical field of unconventional oil and gas yield increasing transformation, in particular to a device and a method for testing rheological property of carbon dioxide.

Background

Shale oil is a novel unconventional resource, and has huge reserve scale and take-over potential. Shale oil reservoirs are generally compact, have poor seepage capability and are difficult to realize energy supplement in an injection-production well pattern mode, most shale oil is produced in an exhaustion mode, but the exhaustion production mode has fast energy reduction and low recovery rate, so the recovery rate can be increased only by energy supplement and displacement efficiency increase. CO2 stored energy fracturing can provide enhanced recovery in both fracturing and production. The CO2 fracturing fluid has low viscosity, is easy to enter micro cracks during fracturing, and is beneficial to forming complex cracks; CO2 has no water phase, no residue and ultra-low interfacial tension, has no harm to stratum, the energy storage function is beneficial to back flow and production after pressing, and CO2 has no function of crude oil, can play a role in mixing phases, reduces interfacial tension and seepage resistance, improves recovery ratio, and has better adaptability to water-sensitive and compact reservoirs.

The rheological property of the liquid carbon dioxide fracturing fluid directly influences the sand carrying property and the fluid loss property of the liquid carbon dioxide fracturing fluid, so that the measurement work of the rheological property of the liquid carbon dioxide fracturing fluid is particularly important. The conventional testing equipment cannot maintain the low-temperature and high-pressure condition for a long time, so that the liquid carbon dioxide rheological property testing work cannot be carried out.

Therefore, it is necessary to invent a testing device and method for the rheological property of carbon dioxide to be better suitable for the measurement of the rheological property of carbon dioxide.

Disclosure of Invention

In view of some or all of the above technical problems in the prior art, the present invention provides a device and a method for testing the rheology of carbon dioxide. The test unit can evaluate the rheological properties of carbon dioxide. Meanwhile, the device is simple in structure, convenient to operate and high in measured data accuracy, and theoretical basis is provided for further research on rheological laws and carbon dioxide fracturing design and construction.

According to a first aspect of the present invention, there is provided a testing apparatus for the rheology of carbon dioxide, comprising:

an air source is arranged on the air-conditioning system,

a phase change system capable of communicating with the gas source, the phase change system for receiving carbon dioxide supplied by the gas source and changing the system temperature and pressure of the carbon dioxide,

a rotary rheometer capable of being communicated with the phase change system, wherein the rotary rheometer can test the rheological property of the carbon dioxide and observe the phase state of the system in real time,

and the data processing system is used for recording the test data acquired by the rotational rheometer.

In one embodiment, the rotational rheometer includes a measurement cup with a window in a wall of the measurement cup.

In one embodiment, a rotor is disposed in the interior cavity of the measuring cup, the rotor being magnetically driven.

In one embodiment, the phase change system includes an intermediate container having an inner chamber with a piston disposed therein to divide the inner chamber into an upper space and a lower space, the upper space being in communication with the booster pump and the lower space being in communication with both the gas source and the rotational rheometer.

In one embodiment, a circulation duct is provided on an outer wall of the intermediate container in a winding manner, the circulation duct is communicated with the refrigerator, and an insulation layer is provided on an outer side of the circulation duct.

In one embodiment, the refrigerator is further connectable to the measuring cup for cooling the measuring cup, and the data processing system further comprises an industrial control computer for controlling the refrigerator and for adding a pump.

According to another aspect of the present invention, there is provided a method for testing rheological property of carbon dioxide by using the above-mentioned testing apparatus, comprising:

step one, selectively putting tackifier into a measuring cup according to needs,

and step two, vacuumizing the intermediate container, the measuring cup and a pipeline connecting the intermediate container and the measuring cup, wherein the vacuum state is determined to be reached when the numerical value of the vacuum pump reaches-0.09 MPa.

Step three, pre-cooling the intermediate container and the measuring cup,

injecting carbon dioxide into the intermediate container, cooling and pressurizing the carbon dioxide to liquefy the carbon dioxide gas,

step five, injecting the carbon dioxide in the intermediate container into a measuring cup,

step six, setting the shear rate of the rotational rheometer so that the rotor begins to select to cause shear to the liquid carbon dioxide,

and step seven, picking up test data.

In one embodiment, in step five, the piston of the intermediate container is actuated at a constant rate to actuate the injection of carbon dioxide into the measuring cup.

In one embodiment, in step four, the piston of the intermediate container is actuated at a constant rate to actuate the injection of carbon dioxide into the measuring cup.

In one embodiment, the temperature change of the carbon dioxide within the measuring cup over time is used to test the rheology of the carbon dioxide at different temperatures.

In one embodiment, in step seven, the viscosity of the fluid fluctuates just at the beginning of the test and the reading is taken after the value has stabilized.

Compared with the prior art, the device has the advantage that the rheological property of the carbon dioxide can be evaluated by the testing device. Meanwhile, the device is simple in structure, convenient to operate and high in measured data accuracy, and theoretical basis is provided for further research on rheological laws and carbon dioxide fracturing design and construction.

Drawings

Preferred embodiments of the present invention will be described in detail below with reference to the attached drawing figures, wherein:

FIG. 1 shows a test apparatus according to one embodiment of the invention;

FIG. 2 is a graph of viscosity of liquid carbon dioxide at 10MPa as a function of temperature;

FIG. 3 is a graph of the viscosity of liquid carbon dioxide at 0 ℃ as a function of pressure.

The figures are not drawn to scale.

Detailed Description

The invention will be further explained with reference to the drawings.

Fig. 1 shows a test apparatus for rheology of carbon dioxide according to the invention. As shown in fig. 1, the test apparatus includes a gas source 1, a phase change system, a rotational rheometer 12, and a data processing system 16. Wherein a gas source 1 is used to provide the required gaseous carbon dioxide. A phase change system for receiving carbon dioxide supplied from the gas source 1 and changing the system temperature and pressure of the carbon dioxide. A rotational rheometer 12 for receiving liquid carbon dioxide supplied by the phase change system for testing the rheology of the liquid carbon dioxide. At the same time, the rotational rheometer 12 is also configured to allow real-time observation of the system phase. The data processing system 16 is used to record the test data collected by the rotational rheometer 12.

In particular, the rotational rheometer 12 includes a measuring cup. The wall of the measuring cup is provided with a visual window for observing the condition of the inner cavity. Preferably, the main body part of the measuring cup is made of stainless steel material, and the working strength of the measuring cup can reach 35 MPa. The visible window is inlaid with sapphire. The dissolution of the liquid carbon dioxide and the preset additive can be directly observed through the transparent visual window.

A rotor is arranged in the measuring cup, which rotor is driven magnetically. During use, the rotating speed of the rotor is controlled through the magnetic field, and shearing is caused to the liquid carbon dioxide in the measuring cup. The rotor may be driven by a motor or the like through a lid of the measuring cup. Compared with an electric driving mode, the rotor in the magnetic driving mode can be completely sealed in the measuring cup, a connecting port and the like do not need to be formed in the measuring cup, the measuring cup can be better sealed, heat exchange between a liquid carbon dioxide system and the outside is avoided, and test precision is guaranteed. In addition, the rotating speed of the rotor can be changed by changing the magnitude of the magnetic field, so that the test parameters can be conveniently set.

The phase change system comprises an intermediate vessel 7. A piston (not shown in the drawings) is provided in the inner chamber of the intermediate container 7 to divide the inner chamber of the intermediate container 7 into an upper space and a lower space. The upper space is communicated with a booster pump 4 to compress the carbon dioxide arranged in the lower space and provide pressure for the liquefaction of the carbon dioxide. The lower space is in communication with the gas source 1 for receiving carbon dioxide from the gas source 1. The lower space is also in communication with the measuring cup of the rotational rheometer 12 for supplying the liquid carbon dioxide required for the test.

A circulation duct 9 is provided in a winding manner on the outer wall of the intermediate container 7. The circulation conduit 9 is communicated with the refrigerator 3 to convey cooling liquid into the circulation conduit 9 through the refrigerator 3 to cool the carbon dioxide therein. An insulating layer 8 is arranged on the outer side of the circulation duct 9 for avoiding excessive heat exchange and ensuring effective energy utilization.

In addition, the refrigerator 3 can also be connected to the measuring cup for performing operations such as precooling of the measuring cup. The connection between the refrigerator 3 and the measuring cup may refer to the connection between the refrigerator 3 and the intermediate container 7. That is, the outer wall of the measuring cup may also be wound with a circulation duct for receiving cooling and for performing a pre-cooling operation for the measuring cup.

The data processing system 16 includes an industrial personal computer in addition to functions of acquisition control processing software for acquiring data and calculating. The industrial personal computer can control the refrigerator 3 to perform cooling processing on the intermediate container and the measuring cup. The industrial personal computer can also control the booster pump 4 to perform the compression operation on the carbon dioxide. The acquisition control processing software can directly convert the test parameters into viscosity data according to a formula shear viscosity which is shear stress/shear rate.

In addition, a cylinder valve 2 is provided at the opening of the gas source 1 for opening or closing the passage to the intermediate container 7. Between the intermediate container 7 and the measuring cup there is a filling valve 10 for closing or opening the passage. A mass flow meter 11 is also provided between the intermediate container 7 and the measuring cup downstream of the filling valve 10 for detecting the amount of carbon dioxide. The measuring cup is also communicated with a vacuum pump 15. A vacuum valve 14 is arranged between the vacuum pump 15 and the measuring cup. Meanwhile, an emptying valve 13 is arranged on a pipeline for communicating the measuring cup with the outside so as to perform emptying operation. Of course, a pressure gauge 5 for detecting pressure and a temperature gauge 6 for detecting temperature are provided on both the intermediate container 7 and the measuring cup.

The method of testing the rheological properties of carbon dioxide is discussed in detail below in conjunction with FIG. 1.

For the first time, the connection of the pipeline is checked and the data processing system 16 is turned on. The tackifier is preset in the measuring cup according to the choice. That is, the addition ratio of the tackifier is determined according to a specific experimental design, and the viscosity of the pure liquid carbon dioxide is measured without adding the tackifier. It is further preferred that the total amount of tackifier and liquid carbon dioxide in the experimental design is just enough to fill the measuring cup.

Then, the purge valve 13 and the cylinder valve 2 are closed. At the same time, the injection valve 10 and the vacuum valve 14 are opened. The vacuum pump 15 is switched on and the interior of the intermediate container 7 and the measuring cup is evacuated. At the same time, the vacuum pump 15 also vacuums the lines connecting the gas source 1 with the intermediate container 7, and connecting the measuring cup and the vacuum pump 15. It should be noted that when the reading of the pressure gauge of the vacuum pump is-0.09 MPa, the vacuum state in the line is considered to be achieved. After the vacuum requirement is met, the vacuum pump 14, the injection valve 10 and the vacuum valve 14 are closed.

After that, the refrigerator 3 is opened to pre-cool the intermediate container 7 and the measuring cup. The pre-cooling time was about 1h, based on the intermediate container and the measuring cup reaching the specified temperature.

And then, after the temperature in the intermediate container 7 and the measuring cup is cooled to a set value, opening the gas cylinder valve 2 to introduce carbon dioxide into the lower space of the intermediate container 7. The booster pump 4 is then turned on to pressurize the upper space of the intermediate container 7, forcing the piston of the intermediate container 7 to move down and apply pressure to the carbon dioxide in the lower space, eventually causing it to liquefy. It should be noted that the amount of carbon dioxide introduced into the intermediate container 7 through the gas source 1 should be higher than a value specified by a design of the experiment, and is generally 2 to 3 times, and it is further preferable that the amount of carbon dioxide actually introduced should be 2 times of the design value. The arrangement mode gives consideration to the feasibility and the economic benefit of the test.

After a proper amount of carbon dioxide is introduced, the cylinder valve 2 is closed. Thereafter, the booster pump 4 and the injection valve 10 are opened, the booster pump 4 pushes the piston at a constant rate, liquid carbon dioxide is pushed into the measuring cup, and the mass of the inflowing liquid carbon dioxide is measured by the mass flow meter 11. For example, the injection speed of the liquid carbon dioxide can be 10mL/min, so as to ensure the phase stability of the carbon dioxide and avoid the influence of the phase change on the test result. It should be noted that if the rheological properties of pure liquid carbon dioxide are to be tested (i.e. it is not necessary to carry out the operation of injecting the viscosifier in step one), the measuring cup is filled. And the rheological property of the liquid carbon dioxide system containing the tackifier is tested, and the specific numerical value is based on the specific test design.

The fill valve 10 is closed and the rheometer shear rate is set so that the rotor begins to rotate causing shear to the liquid carbon dioxide. When the viscosity of pure liquid carbon dioxide is tested, the viscosity of the pure liquid carbon dioxide is Newtonian fluid, and the viscosity of the Newtonian fluid does not change along with the shear rate and only relates to the temperature and the pressure of the fluid. Therefore, in the experiment, only the viscosity value under a certain shear rate in the corresponding state needs to be tested, namely the viscosity of the pure carbon dioxide in the state. The shear rate can be easily set by the testing device to meet the requirements of the test, according to the requirements of different tests, for example, the shear rate of the rotor to carbon dioxide is set to 170s^-1When the viscosity of the liquid carbon dioxide and tackifier mixed system was measured, the shear rate was set to 170s^-1。

With the addition of the tackifier, the experimental data (shear rate, shear stress, time) were taken up after the liquid phase of the peroxide was thoroughly mixed with the tackifier (visual good mixing, no delamination). At the beginning of the test, the viscosity of the fluid has obvious fluctuation, and after the value is stable, the reading is the viscosity value under the temperature and pressure condition. After the experiment, the rotational rheometer 12 is closed, the atmospheric valve 13 is opened, and the pipeline connection is disconnected.

The testing device can realize the integrated work of liquefying carbon dioxide and directly measuring the rheological property of the carbon dioxide; in the test operation process, the CO2 to be detected can be in the totally-enclosed measuring cup by the device, so that the heat exchange between the system and the outside is avoided, and the accuracy of measurement is ensured; the addition amounts of the tackifier and the liquid carbon dioxide can be accurately controlled, and the method is used for improving the test precision; the actual phase state of CO2 and the dissolution condition of the tackifier in the test process can be directly observed through a visual window of the measuring cup, so that the operation is convenient; the data processing system 16 can directly obtain the viscosity parameters and draw a CO2 rheological curve, so that the complicated calculation work is reduced. In addition, in the test using the test apparatus, after carbon dioxide is injected into the measuring cup, the temperature of the carbon dioxide in the measuring cup and the like change with the passage of time, and thus the viscosity at different temperatures can be measured at a constant shear rate. It is also monitored and obtained that a change in phase at the time the carbon dioxide reaches a temperature threshold causes data, such as liquid carbon dioxide, to change to a supercritical state. Therefore, the test result of the test device is very high and is more practical. Of course, under the condition of a certain temperature, the measuring cup of the application can easily realize the change of the shear rate, and can conveniently observe the change of the viscosity, and know whether the carbon dioxide has the change of the liquid property, and the like, for example, the Newtonian fluid is converted into the non-Newtonian fluid.

In addition, the viscosity of liquid carbon dioxide as a function of temperature at 10MPa and the viscosity of liquid carbon dioxide as a function of pressure at 0 ℃ are shown in FIGS. 2 and 3, respectively. According to the result chart, the test device can achieve a good test effect and obtain an accurate test result.

The above is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily make changes or variations within the technical scope of the present invention disclosed, and such changes or variations should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.