Experimental device and method for representing thixotropy of thixotropic fluid

Abstract

The invention discloses an experimental device and method for representing thixotropy of thixotropic fluid, and belongs to the technical field of reservoir profile control experiments.The experimental device comprises a piston container, a simulation flow channel, image acquisition equipment and a computer, an inlet of the piston container is connected with a conveying pump, and an outlet of the piston container is connected with the simulation flow channel; the top of the outlet end of the piston container is provided with a standard liquid inlet pipe, the bottom is provided with a liquid outlet, and the piston container and the simulation runner are horizontally placed and located on the same horizontal line; an image acquisition device on the track can be used for observing the flowing condition of fluid in the simulation flow channel. The piston container is used for containing thixotropic fluid to be tested, the simulation flow channel is used for simulating different flow channel sizes, various data in the experiment process are recorded and analyzed through the computer, and the rheological property and thixotropic property of the thixotropic fluid are tested. By adopting the device and the method, the property of the thixotropic fluid can be quantitatively represented, the flow of the thixotropic fluid in a pipeline and a reservoir is simulated, and technical support is provided for profile control of the thixotropic fluid.

Description

Technical Field

[0001] The invention belongs to the technical field of reservoir profile control experiments, and in particular relates to an experimental device and method for characterizing the thixotropy of a thixotropic fluid. Background Art

[0002] In the process of oil production, the heterogeneity of the reservoir is a common problem. Due to the difference in permeability in different regions, the injected displacement fluid (such as water) tends to flow rapidly along the high permeability channel. The profile control technology can block these high permeability channels, forcing the injected fluid to change its flow direction and enter the low permeability area, thereby increasing the swept volume of crude oil. A thixotropic fluid is a fluid system acting on a heterogeneous reservoir. Its thixotropy is mainly manifested in that when the fluid is subjected to high pressure / high speed migration / high shear, it exhibits low viscosity, and when the fluid is in a low pressure environment / low speed flow / low shear, it exhibits high viscosity. At the same time, the thixotropic property is reversible, and its viscosity can change repeatedly within a certain range of pressure / flow rate / shear. However, the current research equipment and methods cannot accurately and quantitatively characterize this thixotropic effect. Therefore, the present invention has developed an experimental device and method that can quantitatively characterize the thixotropy of thixotropic fluids. Through indoor experimental methods, the thixotropic effect of thixotropic fluids is quantitatively characterized, and the thixotropic range and effective limit of the thixotropic agent are clarified. Summary of the invention

[0003] The purpose of the present invention is to provide an experimental device and method for characterizing the thixotropy of a thixotropic fluid, aiming to solve the technical problem in the prior art that the thixotropy of a thixotropic fluid cannot be quantitatively characterized through simulation experiments.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] An experimental device for characterizing the thixotropy of a thixotropic fluid, the experimental device comprising a piston container, a simulated flow channel for simulating different flow channel sizes, an image acquisition device and a computer, wherein the inlet side of the piston in the piston container can accommodate fluid, and distilled water is delivered to the inlet side of the piston container by a delivery pump; the outlet side of the piston in the piston container can accommodate standard liquid fluid or thixotropic fluid to be measured, the outlet of the piston container is connected to the simulated flow channel, the top of the outlet end of the piston container is provided with a liquid inlet pipe for injecting standard liquid fluid or thixotropic fluid to be measured, and the bottom is provided with a liquid discharge port, the inlet of the piston container is connected to the delivery pump, and the delivery pump is used to pump the fluid to the inlet end of the piston container and push the standard liquid fluid or thixotropic fluid to be measured on the other side of the piston through the piston; valves are provided at the inlet and outlet of the piston container and the simulated flow channel, the piston container and the simulated flow channel are placed horizontally and on the same horizontal line, the image acquisition device is arranged on a track, and is used to observe the flow of standard liquid fluid or thixotropic fluid to be measured at different positions in the simulated flow channel, and the delivery pump and the image acquisition device are both connected to the computer.

[0006] Preferably, the delivery pump is a constant speed and constant pressure pump, the inlet end of the piston container is connected to the constant speed and constant pressure pump, and the outlet of the constant speed and constant pressure pump is provided with a pump outlet valve; the outlet end of the piston container is connected to the simulated flow channel, and the inlet of the simulated flow channel is provided with a flow channel valve; the bottom of the inlet end of the piston container is provided with a rear exhaust port.

[0007] Preferably, an observation window is provided on the side of the piston container; the simulated flow channel is made of a transparent material, and a scale is provided on the side of the simulated flow channel.

[0008] Preferably, there are two piston containers, namely container No. 1 and container No. 2. The top of the outlet end of container No. 1 is provided with a liquid inlet pipe No. 1, the bottom is provided with a liquid discharge port No. 1, the lower part of the liquid inlet pipe No. 1 is provided with a liquid inlet valve No. 1, the top of the outlet end of container No. 2 is provided with a liquid inlet pipe No. 2, the bottom is provided with a liquid discharge port No. 2, the lower part of the liquid inlet pipe No. 2 is provided with a liquid inlet valve No. 2; the bottom of the inlet end of container No. 1 is provided with a rear emptying port of container No. 1, the bottom of the inlet end of container No. 2 is provided with a rear emptying port of container No. 2;

[0009] The constant speed and constant pressure pump includes a No. 1 pump and a No. 2 pump. The No. 1 pump is connected to the No. 1 container via a No. 1 pump inlet pipeline. The inlet and outlet ends of the No. 1 pump inlet pipeline are respectively provided with a No. 1 pump outlet valve and a No. 1 container pump inlet valve; the No. 2 pump is connected to the No. 2 container via a No. 2 pump inlet pipeline. The inlet and outlet ends of the No. 2 pump inlet pipeline are respectively provided with a No. 2 pump outlet valve and a No. 2 container pump inlet valve.

[0010] Preferably, there are two simulated flow channels, namely, flow channel No. 1 and flow channel No. 2, which are arranged in parallel, and the two ends of flow channel No. 1 are connected to container No. 1 and container No. 2 respectively through container No. 1 flow channel connecting valve and container No. 2 flow channel connecting valve, and the two ends of flow channel No. 2 are connected to container No. 1 and container No. 2 respectively through container No. 1 flow channel connecting valve and container No. 2 flow channel connecting valve; the flow channel No. 1 and the flow channel No. 2 are opened simultaneously to test the diversion effect of the thixotropic fluid, and the flow channel No. 1 or the flow channel No. 2 is opened alone to test the rheological properties of the thixotropic fluid;

[0011] The image acquisition device includes a first camera and a second camera, which are respectively arranged on two parallel tracks and are used to observe the flow of standard liquid fluid or thixotropic fluid to be tested at different positions in the first flow channel and the second flow channel.

[0012] Preferably, the simulated flow channel is a porous medium simulated flow channel, which is used to test the thixotropic property of the seepage process of the thixotropic fluid in the porous medium.

[0013] Preferably, the porous medium simulated flow channel is a visualized porous medium simulated flow channel, which can observe and analyze the seepage flow characteristics of the thixotropic fluid in the porous medium and the thixotropic properties in the microscopic pores.

[0014] An experimental method for characterizing the thixotropy of a thixotropic fluid comprises the following steps:

[0015] Prepare the fluid to be tested for thixotropy and standard fluids of Newtonian fluids with different viscosities (whose viscosity does not change with flow rate or pressure) according to the experimental requirements;

[0016] Assemble the above experimental device, wherein the simulated flow channel is one or more and can be adjusted according to the specific test items;

[0017] Set the flow rate of distilled water injected into the piston container by the delivery pump, and measure the injection pressure values ​​during the injection process at different flow rates; the standard liquid enters the piston container through the liquid inlet pipe and then enters the simulated flow channel;

[0018] By replacing standard fluids with different viscosities, the injection pressures of different standard fluids at different flow rates were measured to obtain the corresponding relationship between the viscosity, pressure and flow rate of the standard fluid. The fitting equation is as follows:

[0019]

[0020] Where n is the flow rate of the standard fluid; x is the viscosity of the standard fluid; y is the injection pressure of the standard fluid;

[0021] Each curve in the obtained relationship curve represents the viscosity-pressure relationship under a flow rate condition;

[0022] Clean the experimental device, replace the thixotropic fluid to be tested, set the injection speed, measure the injection pressure change of the thixotropic fluid at different flow rates, substitute the flow rate and pressure data of the thixotropic fluid into the above formula, calculate the viscosity change of the thixotropic fluid to finally obtain the thixotropic effect of the thixotropic fluid.

[0023] Furthermore, when the simulated flow channel is one,

[0024] According to the pressure change under different flow rates measured in the experiment, the pressure values ​​are respectively substituted into the above fitting equation to calculate the change of the viscosity of the thixotropic fluid with the flow rate and pressure, and the thixotropy of the thixotropic fluid to be tested is obtained;

[0025] Thixotropic index TI, dynamic thixotropic index DTI, thixotropic ring area A t , to characterize the viscosity change of the fluid at different shear rates, and to quantify the viscosity change rate and recovery ability of the thixotropic fluid under shear:

[0026]

[0027] Where, Δη: the viscosity change amplitude caused by thixotropy, which is the difference between the viscosity values ​​at the maximum flow rate and the minimum flow rate of the thixotropic fluid during the first speed increase, mPa·s;

[0028] η 0 : Viscosity of thixotropic fluid in initial static state, reference standard fluid or measured value at low speed, mPa·s;

[0029] η min ,η max : Viscosity of thixotropic fluid at minimum / maximum flow rate, mPa·s;

[0030]

[0031]

[0032] Where, Δt is the shear action time, s;

[0033] γ crit is the critical shear rate, and the flow in the simulated channel is calculated as the flow in a circular tube;

[0034] v is the average flow velocity of the thixotropic fluid in the flow channel, m / s;

[0035] R is the radius of the simulated flow channel, m;

[0036]

[0037] v max is the maximum flow rate of the thixotropic fluid during the test;

[0038] v min is the minimum flow rate of the thixotropic fluid during the test;

[0039] η 升 (v) is the viscosity change of the thixotropic fluid when the flow rate changes from low to high during the test;

[0040] η 降 (v) is the viscosity change of the thixotropic fluid when the flow rate changes from high to low during the test;

[0041] Thixotropic ring area A t Reflects the hysteresis effect of thixotropic recovery. The larger the area, the weaker the thixotropy and the weaker the fluid's recoverability.

[0042] Furthermore, when there are two simulated flow channels, the two simulated flow channels are flow channel No. 1 and flow channel No. 2, respectively, and flow channel No. 1 and flow channel No. 2 are installed in parallel between two piston containers;

[0043] Start the delivery pump and set the pressure / flow rate value so that the thixotropic fluid to be tested is injected into the piston container at a constant pressure and constant speed, turn on the image acquisition device, and record the flow state of the thixotropic fluid to be tested in the two simulated flow channels, and finally obtain the flow / seepage law of the thixotropic fluid in porous media with different flow radii / different permeabilities;

[0044] When the two simulated flow channels are circular tube simulated flow channels, the experimental data of the fluid flow in the two simulated flow channels are as follows:

[0045] Pressure of No. 1 flow channel: P a (t), MPa;

[0046] Liquid output per unit time at the outlet of No. 1 flow channel: D a (t), ml;

[0047] Flow rate of flow channel No. 1: V a (t) = D a (t) / t, ml / min;

[0048] Cumulative liquid volume at the outlet of runner No. 1: , ml;

[0049] Pressure of No.2 flow channel: P b (t), MPa;

[0050] Liquid output per unit time at the outlet of No. 2 flow channel: D b (t), ml;

[0051] Flow rate of the second flow channel: V b (t=i)=D b (t) / t, ml / min;

[0052] Cumulative liquid volume at the outlet of No. 2 flow channel: , ml;

[0053] No. 1 flow channel split ratio ;

[0054] Second channel flow rate ;

[0055] And draw a diversion curve diagram;

[0056] When the two simulated flow channels are porous medium simulated flow channels, flow channel No. 1 is a high permeability porous medium, and flow channel No. 2 is a low permeability porous medium. The profile control ability of the thixotropic fluid is characterized by the profile control efficiency coefficient ECPC as follows:

[0057] ;

[0058] In the formula, S high : Diversion rate of flow channel No. 1;

[0059] S low : Diversion rate of No.2 flow channel;

[0060] The closer the ECPC is to 1, the better the profile control effect is, and the fluid tends to flow into the low permeability reservoir.

[0061] Preferably, when there are two simulated flow channels, the two simulated flow channels are flow channel No. 1 and flow channel No. 2, respectively, and flow channel No. 1 and flow channel No. 2 are installed in parallel between two piston containers; The No. 1 flow channel is a circular tube simulation flow channel, and the No. 2 flow channel is a porous medium simulation flow channel;

[0062] Porous media usually have strong shearing effects. When a thixotropic fluid passes through a porous medium, it will be subjected to strong shearing effects, and its properties will change. The following experiment is to test the thixotropic changes of the thixotropic fluid before and after the strong shearing effects.

[0063] Start the delivery pump, turn on the image acquisition device, and test the thixotropy of the thixotropic fluid through the No. 1 flow channel;

[0064] Then, the thixotropic fluid is injected into the second flow channel at the same injection speed so as to pass through the porous medium;

[0065] The thixotropic fluid that has been sheared by the porous medium is re-injected into the No. 1 flow channel to test the thixotropy at this time;

[0066] The pressure changes during the experiment were recorded, and finally the thixotropy changes of the measured fluid before and after the shearing action of the porous medium were obtained.

[0067] The experimental data on the thixotropic changes before and after shearing were measured. The effect of porous medium shearing on thixotropic fluids was characterized by the thixotropic loss rate L and the thixotropic recovery rate R:

[0068]

[0069] TLpre: thixotropic index of thixotropic fluid before shearing;

[0070] TLpost: thixotropic index of thixotropic fluid after shearing;

[0071]

[0072] η post1 : Viscosity of the lowest flow rate during the rate-increasing test of the thixotropic fluid after shearing, mPa·s;

[0073] η post2 : Viscosity of the lowest flow rate during the speed reduction test of the thixotropic fluid after shearing, mPa·s;

[0074] η pre1 : viscosity of the lowest flow rate during the rate-increasing test of the thixotropic fluid before shearing, mPa·s;

[0075] η pre2 : viscosity of the thixotropic fluid at the lowest flow rate during the speed reduction test before shearing, mPa·s;

[0076] The thixotropic loss rate L and thixotropic recovery rate R evaluate the degree of shear damage to thixotropy and the self-repairing ability of the fluid.

[0077] Compared with the prior art, the present invention has the following beneficial effects:

[0078] The present invention uses a piston container to contain the thixotropic flow to be tested, uses a simulated flow channel to simulate different flow channel sizes, observes the fluid flow conditions at different positions in the simulated flow channel through an image acquisition device, and records and analyzes various data during the experiment through a computer to test the rheological properties and thixotropic properties of the thixotropic fluid. The present invention can quantitatively characterize the properties of the thixotropic fluid, and simulate the flow of the thixotropic fluid in the pipeline and reservoir, providing technical support for the profile control of the thixotropic fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0080] In the attached picture:

[0081] Figure 1A schematic diagram of the structure of an experimental device for characterizing the thixotropy of a thixotropic fluid provided in an embodiment of the present invention;

[0082] Figure 2 It is the viscosity-pressure standard curve of thixotropic fluid at different flow rates;

[0083] Figure 3 It is a curve diagram of viscosity change of thixotropic fluid with speed change;

[0084] Figure 4 It is the flow division curve diagram of thixotropic fluid in two parallel simulated flow channels;

[0085] Figure 5 This is the thixotropic change diagram of the thixotropic fluid before and after shearing by porous media:

[0086] Figure 6 It is a schematic diagram of the movement of the fluid in the piston container and the simulated flow channel;

[0087] In the figure:

[0088] 1- No. 1 observation window; 2- No. 2 observation window; 3- No. 1 container; 4- No. 2 container; 5- No. 1 discharge port; 6- No. 2 discharge port; 7- No. 1 liquid inlet pipe; 8- No. 2 liquid inlet pipe; 9- No. 1 liquid inlet valve; 10- No. 2 liquid inlet valve; 11- No. 1 flow channel connecting valve of No. 1 container; 12- No. 1 flow channel connecting valve of No. 2 container; 13- No. 1 flow channel connecting valve of No. 1 container; 14- No. 2 flow channel connecting valve of No. 2 container; 15- No. 1 flow channel; 16 - Flow channel No. 2; 17- scale; 18- pump inlet valve of container No. 1; 19- pump inlet valve of container No. 2; 20- pump inlet pipeline No. 1; 21- pump inlet pipeline No. 2; 22- outlet valve of pump No. 1; 23- outlet valve of pump No. 2; 24- pump No. 1; 25- pump No. 2; 26- camera No. 1; 27- camera No. 2; 28- cable; 29- track; 30- computer; 31- rear drain port of container No. 1; 32- rear drain port of container No. 2. DETAILED DESCRIPTION

[0089] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and Examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In the following detailed description of the present invention, some specific details are described in detail. However, for the parts not described in detail, those skilled in the art can also fully understand the present invention.

[0090] In addition, those skilled in the art should understand that the drawings are only provided to illustrate the purpose, features and advantages of the present invention, and the drawings are not actually drawn to scale.

[0091] At the same time, unless the context clearly requires otherwise, the words "include", "comprises" and similar words throughout the specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, the meaning is "including but not limited to".

[0092] like Figure 1 , 6 As shown, an experimental device for characterizing the thixotropy of a thixotropic fluid comprises a piston container, a simulated flow channel for simulating different flow channel sizes, an image acquisition device and a computer 30. The inlet side of the piston in the piston container can accommodate fluid, and distilled water is delivered to the inlet side of the piston container by a delivery pump; the outlet side of the piston in the piston container can accommodate a standard liquid fluid or a thixotropic fluid to be tested, the outlet of the piston container is connected to the simulated flow channel, and a liquid inlet pipe for injecting a standard liquid fluid or a thixotropic fluid to be tested is provided on the top of the outlet end of the piston container, and the fluid is sucked into the piston container by the movement of the internal piston, and a liquid discharge port is provided at the bottom of the outlet end of the piston container for discharging the fluid in the piston container; the inlet of the piston container is connected to the delivery pump, and the delivery pump is used to pump the fluid to The inlet end of the piston container pushes the standard liquid fluid or the thixotropic fluid to be tested on the other side of the piston through the piston; the inlet and outlet of the piston container and the simulated flow channel are both provided with valves for controlling the opening and closing of the flow channel; the piston container and the simulated flow channel are placed horizontally and on the same horizontal line to avoid the impact of large changes in flow state on the fluid; and the simulated flow channel is made of hydrophobic / oleophobic material or the inner wall is coated with a hydrophobic / oleophobic coating, and the material is changed according to the properties of the experimental fluid to reduce the obstruction of the flow channel material to the fluid flow; the image acquisition device is arranged on the track 29, and is used to observe the flow of the standard liquid fluid or the thixotropic fluid to be tested at different positions in the simulated flow channel. The delivery pump and the image acquisition device are respectively connected to the computer 30 through the cable 28, and the fluid flow is controlled by the computer and various data during the experiment are recorded. The fluid movement process in the piston container is as follows. Figure 6 shown.

[0093] In the specific design, there are one or more simulated flow channels. When multiple flow channels are opened, they are used to test the diversion effect of thixotropic fluids, and when a single flow channel is opened, it is used to test the rheological properties of thixotropic fluids. The size of the simulated flow channel is smaller than the outlet size of the container, which is used to ensure that the simulated flow channel is the smallest flow channel in the overall system and to ensure the accuracy of the test results. At the same time, the simulated flow channels of different lengths and diameters can be disassembled and replaced according to the test requirements. In the specific production, the inner cavity of the piston container is divided into two spaces by the piston. The fluid is pumped into the space at one end by the delivery pump to squeeze the piston movement, thereby pushing the fluid on the other side of the piston. Both ends of the piston container are detachable, which is convenient for cleaning the piston container to ensure the purity of the test fluid. Figure 1In the illustrated embodiment, the piston container has two outlet ports, and two simulated flow channels are connected between the two piston containers. When only one simulated flow channel is required for experiment, the other simulated flow channel can be closed by a valve.

[0094] As a preferred structure, the delivery pump is a constant speed and constant pressure pump, the inlet end of the piston container is connected to the constant speed and constant pressure pump, and the outlet of the constant speed and constant pressure pump is provided with a pump outlet valve; the outlet end of the piston container is connected to the simulated flow channel, and the inlet of the simulated flow channel is provided with a flow channel valve; the bottom of the inlet end of the piston container is provided with a rear exhaust port.

[0095] In a specific embodiment of the present invention, Figure 1 As shown, there are two piston containers, namely, container No. 1 3 and container No. 2 4. The top of the outlet end of container No. 1 3 is provided with a No. 1 liquid inlet pipe 7 and the bottom is provided with a No. 1 liquid discharge port 5. The lower part of the No. 1 liquid inlet pipe 7 is provided with a No. 1 liquid inlet valve 9. The top of the outlet end of container No. 2 4 is provided with a No. 2 liquid inlet pipe 8 and the bottom is provided with a No. 2 liquid discharge port 6. The lower part of the No. 2 liquid inlet pipe 8 is provided with a No. 2 liquid inlet valve 10. The bottom of the inlet end of container No. 1 3 is provided with a No. 1 container rear emptying port 31, and the bottom of the inlet end of container No. 2 4 is provided with a No. 2 container rear emptying port 32. Among them, the connection between container No. 1 and container No. 2 and the No. 1 and No. 2 flow channels is provided with chamfers to avoid a large shearing effect when the fluid flows, thereby changing the fluid properties and ensuring the accuracy of the test results. At the same time, the sides of container No. 1 3 and container No. 2 4 are provided with a No. 1 observation window 1 and a No. 2 observation window 2 respectively; the simulated flow channel is made of transparent material, and the side of the simulated flow channel is provided with a scale 17.

[0096] Among them, the constant speed and constant pressure pump includes a No. 1 pump 24 and a No. 2 pump 25. The No. 1 pump 24 is connected to the No. 1 container 3 through a No. 1 pump inlet pipeline 20, and the No. 1 pump outlet valve 22 and the No. 1 container pump inlet valve 18 are respectively provided at the inlet and outlet ends of the No. 1 pump inlet pipeline 20; the No. 2 pump 25 is connected to the No. 2 container 4 through a No. 2 pump inlet pipeline 21, and the No. 2 pump outlet valve 23 and the No. 2 container pump inlet valve 19 are respectively provided at the inlet and outlet ends of the No. 2 pump inlet pipeline 21.

[0097] At the same time, there are two simulated flow channels, namely flow channel No. 15 and flow channel No. 2 16. The flow channel No. 15 and flow channel No. 2 16 are arranged in parallel, and the two ends of the flow channel No. 15 are connected with container No. 1 3 and container No. 2 4 respectively through container No. 1 flow channel connecting valve 11 and container No. 2 flow channel connecting valve 12, and the two ends of the flow channel No. 2 16 are connected with container No. 1 3 and container No. 2 4 respectively through container No. 1 flow channel connecting valve 13 and container No. 2 flow channel connecting valve 14; the flow channel No. 1 15 and the flow channel No. 2 16 are opened at the same time to test the diversion effect of the thixotropic fluid, and the flow channel No. 15 or the flow channel No. 2 16 is opened alone to test the rheological properties of the thixotropic fluid.

[0098] The piston container and the constant speed and constant pressure pump are placed in two sets corresponding to each other, and are used to repeatedly test the thixotropic effect of the thixotropic fluid and verify the reversibility of the thixotropic effect of the tested thixotropic fluid.

[0099] In order to correspond to the two simulated flow channels, the image acquisition device includes a No. 1 camera 26 and a No. 2 camera 27. The No. 1 camera 26 and the No. 2 camera 27 are respectively arranged on two parallel tracks 29, and are respectively used to observe the flow of the standard liquid fluid or the thixotropic fluid to be tested at different positions in the No. 1 flow channel 15 and the No. 2 flow channel 16.

[0100] In another embodiment of the present invention, the simulated flow channel can be replaced with a porous medium simulated flow channel, and a porous medium (core) can be placed inside the porous medium simulated flow channel to test the thixotropic properties of the seepage process of the thixotropic fluid in the porous medium, and measure the thixotropic changes of the thixotropic fluid after shearing.

[0101] At the same time, the porous medium simulation flow channel is a visualized porous medium simulation flow channel, which is used to observe and analyze the seepage flow characteristics of thixotropic fluids in porous media and the thixotropic properties in microscopic pores. The visualized porous medium simulation flow channel can be 3D printed using a fully transparent resin.

[0102] The present invention also provides an experimental method for characterizing the thixotropy of a thixotropic fluid, comprising the following steps:

[0103] Prepare the fluid to be tested for thixotropy and standard fluids of Newtonian fluids with different viscosities according to the experimental requirements;

[0104] Assemble the above experimental device, connect the liquid inlet and outlet, and open / close the corresponding valves;

[0105] The standard liquid is pumped into the No. 1 piston container through the liquid inlet pipe by the suction movement of the No. 1 piston container, the liquid inlet is closed, and the simulated flow channel valve is opened. At this time, the liquid inlet of the No. 2 piston container is closed, the liquid discharge hole is opened, and it is in the emptying state;

[0106] Set the flow rate of distilled water injected into the piston container by the delivery pump, and measure the injection pressure value during the injection process at different flow rates; replace standard liquids with different viscosities, and measure the corresponding relationship between the viscosity-pressure-flow rate of the fluid under this flow environment (pipe diameter, material). Figure 2 Each curve represents the viscosity-pressure relationship under a flow rate condition.

[0107] According to the injection pressure of the standard liquid at different flow rates measured in the experiment, the following viscosity-pressure relationship fitting equation is obtained:

[0108]

[0109] Where n is the flow rate of the standard fluid; x is the viscosity of the standard fluid; y is the injection pressure of the standard fluid.

[0110] Clean the experimental device, replace the thixotropic fluid, set the injection speed, measure the injection pressure change of the thixotropic fluid at different flow rates, substitute the flow rate-pressure data into the above formula, calculate the viscosity change of the measured fluid, and finally obtain the thixotropic effect of the measured thixotropic fluid (viscosity change at different pressures and flow rates).

[0111] When there is only one simulated flow channel, the pressure changes at flow rates of 1, 2, 3, 4, 3, 2, and 1 ml / min are measured during the experiment. The pressure values ​​are substituted into the above fitting equation to obtain the thixotropy of the test liquid, such as Figure 3 shown.

[0112] The thixotropic index TI, dynamic thixotropic index DTI and thixotropic ring area At are used to characterize the viscosity change of the fluid at different shear rates and to quantify the viscosity change rate and recovery ability of the thixotropic fluid under shear:

[0113]

[0114] Where, Δη: the viscosity change caused by thixotropy, which is the difference between the viscosity values ​​at the maximum flow rate and the minimum flow rate during the first speed increase, mPa·s;

[0115] η 0 : Viscosity of thixotropic fluid in initial static state, reference standard fluid or measured value at low speed, mPa·s;

[0116] η min ,η max : Viscosity of thixotropic fluid at minimum / maximum flow rate, mPa·s;

[0117]

[0118]

[0119] Where, Δt is the shear action time, s;

[0120] γ crit is the critical shear rate, and the flow in the simulated channel is calculated as the flow in a circular tube;

[0121] v is the average flow velocity of the thixotropic fluid in the flow channel, m / s;

[0122] R is the radius of the simulated flow channel, m;

[0123]

[0124] v max is the maximum flow rate of the thixotropic fluid during the test;

[0125] v min is the minimum flow rate of the thixotropic fluid during the test;

[0126] η 升 (v) is the viscosity change of the thixotropic fluid when the flow rate changes from low to high during the test;

[0127] η 降 (v) is the viscosity change of the thixotropic fluid when the flow rate changes from high to low during the test;

[0128] Thixotropic ring area A t Reflects the hysteresis effect of thixotropic recovery. The larger the area, the weaker the thixotropy and the weaker the fluid's recoverability.

[0129] When there are two simulated flow channels, the two simulated flow channels are flow channel No. 1 and flow channel No. 2 respectively, and the experimental device is assembled; flow channel No. 1 and flow channel No. 2 are installed in parallel between two piston containers, the liquid inlet and outlet are connected, and the corresponding valves are opened / closed.

[0130] Start the delivery pump, turn on camera No. 1 and camera No. 2, and set the pressure / flow rate value so that the thixotropic fluid to be tested is injected into the piston container at a constant pressure and constant rate, and record the flow state of the thixotropic fluid to be tested in the two simulated flow channels, and finally obtain the flow / seepage law of the thixotropic fluid in porous media with different flow radius / different permeability.

[0131] When the two simulated flow channels are circular tube simulated flow channels, the experimental data of the fluid flow in the two simulated flow channels are as follows:

[0132] Pressure of No. 1 flow channel: P a (t), MPa;

[0133] Liquid output per unit time at the outlet of No. 1 flow channel: D a (t), ml;

[0134] Flow rate of flow channel No. 1: V a(t) = D a (t) / t, ml / min;

[0135] Cumulative liquid volume at the outlet of runner No. 1: , ml;

[0136] Pressure of No.2 flow channel: P b (t), MPa;

[0137] Liquid output per unit time at the outlet of No. 2 flow channel: D b (t), ml;

[0138] Flow rate of the second flow channel: V b (t=i)=D b (t) / t, ml / min;

[0139] Cumulative liquid volume at the outlet of No. 2 flow channel: , ml;

[0140] No. 1 flow channel split ratio ;

[0141] Second channel flow rate ;

[0142] And draw the shunt curve diagram, such as Figure 4 shown.

[0143] When the two simulated flow channels are porous medium simulated flow channels, flow channel No. 1 is a porous medium with higher permeability, and flow channel No. 2 is a porous medium with lower permeability. The profile control ability of the thixotropic fluid is characterized by the profile control efficiency coefficient ECPC as follows:

[0144] ;

[0145] In the formula, S high : Diversion rate of flow channel No. 1;

[0146] S low : Diversion rate of No.2 flow channel;

[0147] The closer the ECPC is to 1, the better the profile control effect is, and the fluid tends to flow into the low permeability reservoir.

[0148] Porous media usually have strong shearing effects. When a thixotropic fluid passes through a porous medium, it will be subjected to strong shearing effects, and its properties will change. The following experiment is to test the thixotropic changes of the thixotropic fluid before and after the strong shearing effects.

[0149] When there are two simulated flow channels, the two simulated flow channels are flow channel No. 1 and flow channel No. 2, respectively, and flow channel No. 1 and flow channel No. 2 are installed in parallel between two piston containers; Channel No. 1 is a circular tube simulation channel, and channel No. 2 is a porous medium simulation channel.

[0150] Start the delivery pump, turn on the image acquisition device, and test the thixotropy of the thixotropic fluid through the No. 1 flow channel. The specific process is the same as the operation of a simulated flow channel;

[0151] Then, the thixotropic fluid is injected into the second flow channel at the same injection speed so as to pass through the porous medium;

[0152] The thixotropic fluid that has been sheared by the porous medium is re-injected into the No. 1 flow channel to test the thixotropy at this time;

[0153] The pressure changes during the experiment were recorded, and finally the thixotropy changes of the measured fluid before and after the shearing action of the porous medium were obtained.

[0154] The experimental results show that the thixotropy changes before and after shearing are as follows: Figure 5 shown.

[0155] The effect of porous medium shear effect on thixotropic fluid is characterized by thixotropic loss rate L and thixotropic recovery rate R:

[0156]

[0157] TLpre: thixotropic index of thixotropic fluid before shearing;

[0158] TLpost: thixotropic index of thixotropic fluid after shearing;

[0159]

[0160] η post1 : Viscosity of the lowest flow rate during the rate-increasing test of the thixotropic fluid after shearing, mPa·s;

[0161] η post2 : Viscosity of the lowest flow rate during the speed reduction test of the thixotropic fluid after shearing, mPa·s;

[0162] η pre1 : viscosity of the lowest flow rate during the rate-increasing test of the thixotropic fluid before shearing, mPa·s;

[0163] η pre2 : viscosity of the thixotropic fluid at the lowest flow rate during the speed reduction test before shearing, mPa·s;

[0164] The thixotropic loss rate (L) and thixotropic recovery rate (R) evaluate the degree of damage to thixotropy caused by shear and the self-repairing ability of the fluid.

[0165] In summary, the present invention quantitatively characterizes the thixotropic effect of the thixotropic fluid, clarifies the flow / seepage law of the thixotropic fluid, and better corresponds to different flow environments in the reservoir by simulating the flow channel flow of thixotropic fluids in flow channels of different sizes and seepage channels of different permeabilities. The viscosity change of the thixotropic fluid under different pressures / flow rates can be quantitatively characterized by flow channel simulation. The seepage characteristics of the thixotropic fluid under different pressures / flow rates / shear forces can be quantitatively characterized by the seepage simulation channel, and the thixotropic changes of the fluid before and after the shearing action can be simulated, and the effective action range of the thixotropic fluid in the porous medium of the reservoir can be obtained. The flow / seepage law of the thixotropic fluid under heterogeneous conditions can be obtained by dual-channel parallel simulation, and the profile adjustment effect of the thixotropic fluid can be clarified. Accurate theoretical and technical guidance can be provided for field applications.

[0166] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. An experimental device for characterizing the thixotropy of a thixotropic fluid, characterized in that: The experimental device includes a piston container, a simulated flow channel for simulating different flow channel sizes, an image acquisition device and a computer, the inlet side of the piston in the piston container can accommodate fluid, and distilled water is delivered to the inlet side of the piston container by a delivery pump; The outlet side of the piston in the piston container can accommodate standard liquid fluid or thixotropic fluid to be measured, the outlet of the piston container is connected to the simulated flow channel, the top of the outlet end of the piston container is provided with a liquid inlet pipe for injecting standard liquid fluid or thixotropic fluid to be measured, and the bottom is provided with a liquid discharge port, the inlet of the piston container is connected to a delivery pump, and the delivery pump is used to pump the fluid to the inlet end of the piston container and push the standard liquid fluid or thixotropic fluid to be measured on the other side of the piston through the piston; valves are provided at the inlet and outlet of the piston container and the simulated flow channel, the piston container and the simulated flow channel are placed horizontally and on the same horizontal line, the image acquisition device is set on a track, and is used to observe the flow of standard liquid fluid or thixotropic fluid to be measured at different positions in the simulated flow channel, and the delivery pump and the image acquisition device are both connected to a computer.

2. The experimental device for characterizing the thixotropy of thixotropic fluid according to claim 1, characterized in that: The delivery pump is a constant speed and constant pressure pump, the inlet end of the piston container is connected to the constant speed and constant pressure pump, and the outlet of the constant speed and constant pressure pump is provided with a pump outlet valve; the outlet end of the piston container is connected to the simulated flow channel, and the inlet of the simulated flow channel is provided with a flow channel valve; the bottom of the inlet end of the piston container is provided with a rear exhaust port.

3. The experimental device for characterizing the thixotropy of thixotropic fluid according to claim 2, characterized in that: There are two piston containers, namely container No. 1 and container No.

2. The top of the outlet end of container No. 1 is provided with a liquid inlet pipe No. 1, and the bottom is provided with a liquid discharge port No.

1. The lower part of the liquid inlet pipe No. 1 is provided with a liquid inlet valve No.

1. The top of the outlet end of container No. 2 is provided with a liquid inlet pipe No. 2, and the bottom is provided with a liquid discharge port No.

2. The lower part of the liquid inlet pipe No. 2 is provided with a liquid inlet valve No.

2. The bottom of the inlet end of container No. 1 is provided with a rear emptying port of container No. 1, and the bottom of the inlet end of container No. 2 is provided with a rear emptying port of container No.

2. The constant speed and constant pressure pump includes a No. 1 pump and a No. 2 pump. The No. 1 pump is connected to the No. 1 container via a No. 1 pump inlet pipeline. The inlet and outlet ends of the No. 1 pump inlet pipeline are respectively provided with a No. 1 pump outlet valve and a No. 1 container pump inlet valve; the No. 2 pump is connected to the No. 2 container via a No. 2 pump inlet pipeline. The inlet and outlet ends of the No. 2 pump inlet pipeline are respectively provided with a No. 2 pump outlet valve and a No. 2 container pump inlet valve.

4. The experimental device for characterizing the thixotropy of thixotropic fluid according to claim 3, characterized in that: There are two simulation flow channels, namely flow channel No. 1 and flow channel No. 2, which are arranged in parallel, and the two ends of flow channel No. 1 are connected to container No. 1 and container No. 2 respectively through container No. 1 flow channel connecting valve and container No. 2 flow channel connecting valve, and the two ends of flow channel No. 2 are connected to container No. 1 and container No. 2 respectively through container No. 1 flow channel connecting valve and container No. 2 flow channel connecting valve; the flow channel No. 1 and the flow channel No. 2 are opened at the same time to test the diversion effect of the thixotropic fluid, and the flow channel No. 1 or the flow channel No. 2 is opened alone to test the rheological properties of the thixotropic fluid; The image acquisition device includes a first camera and a second camera, which are respectively arranged on two parallel tracks and are used to observe the flow of standard liquid fluid or thixotropic fluid to be tested at different positions in the first flow channel and the second flow channel.

5. The experimental device for characterizing the thixotropy of thixotropic fluid according to claim 1, characterized in that: The simulated flow channel is a porous medium simulated flow channel, which is used to test the thixotropic property of the seepage process of the thixotropic fluid in the porous medium.

6. The experimental device for characterizing the thixotropy of thixotropic fluid according to claim 5, characterized in that: The porous medium simulation flow channel is a visualized porous medium simulation flow channel, which can observe and analyze the seepage flow characteristics of thixotropic fluid in the porous medium and the thixotropic properties in microscopic pores.

7. An experimental method for characterizing the thixotropy of a thixotropic fluid, characterized in that: The following steps are involved: Prepare the fluid to be tested for thixotropy and standard fluids of Newtonian fluids with different viscosities according to the experimental requirements; Assembling the experimental device as described in any one of claims 1 to 6, wherein the number of the simulated flow channels is one or more; Set the flow rate of distilled water injected into the piston container by the delivery pump, and measure the injection pressure values ​​during the injection process at different flow rates; use the delivery pump to suck the standard liquid in the liquid inlet pipe into the piston container and then into the simulated flow channel; By replacing standard fluids with different viscosities, the injection pressures of different standard fluids at different flow rates were measured to obtain the corresponding relationship between the viscosity, pressure and flow rate of the standard fluid. The fitting equation is as follows: ; Where n is the flow rate of the standard fluid; x is the viscosity of the standard fluid; y is the injection pressure of the standard fluid; Each curve in the obtained relationship curve represents the viscosity-pressure relationship under a flow rate condition; Clean the experimental device, replace the thixotropic fluid to be tested, set the injection speed, measure the injection pressure change of the thixotropic fluid at different flow rates, substitute the flow rate and pressure data of the thixotropic fluid into the above formula, calculate the viscosity change of the thixotropic fluid to finally obtain the thixotropic effect of the thixotropic fluid.

8. An experimental method for characterizing the thixotropy of a thixotropic fluid according to claim 7, characterized in that: When there is only one simulated flow channel, according to the pressure change at different flow rates measured in the experiment, the pressure values ​​are respectively substituted into the above fitting equation to calculate the change of the viscosity of the thixotropic fluid with the flow rate and pressure, and the thixotropy of the thixotropic fluid to be tested is obtained; Thixotropic index TI, dynamic thixotropic index DTI, thixotropic ring area A t , to characterize the viscosity change of the fluid at different shear rates, and to quantify the viscosity change rate and recovery ability of the thixotropic fluid under shear: ； Where, Δη: the viscosity change caused by thixotropy, which is the difference between the viscosity values ​​at the maximum flow rate and the minimum flow rate during the first speed increase, mPa·s; η0: viscosity of the thixotropic fluid at initial resting state, mPa·s; η min ,η max : Viscosity of thixotropic fluid at minimum / maximum flow rate, mPa·s; ； ； Where, Δt is the shear action time, s; γ crit is the critical shear rate, and the flow in the simulated channel is calculated as the flow in a circular tube; v is the average flow velocity of the thixotropic fluid in the flow channel, m / s; R is the radius of the simulated flow channel, m; ； v max is the maximum flow rate of the thixotropic fluid during the test; v min is the minimum flow rate of the thixotropic fluid during the test; η 升 (v) is the viscosity change of the thixotropic fluid when the flow rate changes from low to high during the test; η 降 (v) is the viscosity change of the thixotropic fluid when the flow rate changes from high to low during the test; Thixotropic ring area A t Reflects the hysteresis effect of thixotropic recovery. The larger the area, the weaker the thixotropy and the weaker the fluid's recoverability.

9. An experimental method for characterizing the thixotropy of a thixotropic fluid according to claim 7, characterized in that: When there are two simulated flow channels, the two simulated flow channels are flow channel No. 1 and flow channel No. 2, respectively, and flow channel No. 1 and flow channel No. 2 are installed in parallel between two piston containers; Start the delivery pump and set the pressure / flow rate value so that the thixotropic fluid to be tested is injected into the piston container at a constant pressure and constant speed, turn on the image acquisition device, and record the flow state of the thixotropic fluid to be tested in the two simulated flow channels, and finally obtain the flow / seepage law of the thixotropic fluid in porous media with different flow radii / different permeabilities; When the two simulated flow channels are circular tube simulated flow channels, the experimental data of the fluid flow in the two simulated flow channels are as follows: Pressure of No. 1 flow channel: P a (t), MPa; Liquid output per unit time at the outlet of No. 1 flow channel: D a (t), ml; Flow rate of flow channel No. 1: V a (t) = D a (t) / t, ml / min; Cumulative liquid volume at the outlet of runner No. 1: , ml; Pressure of No.2 flow channel: P b (t), MPa; Liquid output per unit time at the outlet of No. 2 flow channel: D b (t), ml; Flow rate of the second flow channel: V b (t=i)=D b (t) / t, ml / min; Cumulative liquid volume at the outlet of No. 2 flow channel: , ml; No. 1 flow channel split ratio ; Second channel flow rate ; And draw a diversion curve diagram; When the two simulated flow channels are porous medium simulated flow channels, flow channel No. 1 is a high permeability porous medium, and flow channel No. 2 is a low permeability porous medium. The profile control ability of the thixotropic fluid is characterized by the profile control efficiency coefficient ECPC as follows: ； In the formula, S high : Diversion rate of flow channel No. 1; S low : Diversion rate of No.2 flow channel; The closer the ECPC is to 1, the better the profile control effect is, and the fluid tends to flow into the low permeability reservoir.

10. An experimental method for characterizing the thixotropy of a thixotropic fluid according to claim 8, characterized in that: When there are two simulated flow channels, the two simulated flow channels are flow channel No. 1 and flow channel No. 2, respectively, and flow channel No. 1 and flow channel No. 2 are installed in parallel between two piston containers; The No. 1 flow channel is a circular tube simulation flow channel, and the No. 2 flow channel is a porous medium simulation flow channel; Start the delivery pump, turn on the image acquisition device, and test the thixotropy of the thixotropic fluid through the No. 1 flow channel; Then, the thixotropic fluid is injected into the second flow channel at the same injection speed so as to pass through the porous medium; The thixotropic fluid sheared by the porous medium is re-injected into the No. 1 flow channel to test the thixotropy at this time; Record the pressure changes during the experiment, and finally obtain the thixotropy changes of the measured fluid before and after the shearing of the porous medium; The experimental data on the thixotropic changes before and after shearing were measured. The effect of porous medium shearing on thixotropic fluids was characterized by the thixotropic loss rate L and the thixotropic recovery rate R: ； TLpre: thixotropic index of thixotropic fluid before shearing; TLpost: thixotropic index of thixotropic fluid after shearing; ； η post1 : Viscosity of the lowest flow rate during the rate-increasing test of the thixotropic fluid after shearing, mPa·s; η post2 : Viscosity of the lowest flow rate during the speed reduction test of the thixotropic fluid after shearing, mPa·s; η pre1 : viscosity of the thixotropic fluid at the lowest flow rate during the rate-increasing test before shearing, mPa·s; η pre2 : viscosity of the thixotropic fluid at the lowest flow rate during the speed reduction test before shearing, mPa·s; The thixotropic loss rate L and thixotropic recovery rate R evaluate the degree of damage to thixotropy caused by shearing and the self-repairing ability of the fluid.

Images