Method for rapidly testing interfacial tension between well entering fluid and crude oil

Abstract

The invention discloses a method for rapidly testing interfacial tension between well-entering fluid and crude oil, which comprises the following steps: heating a test tube containing a mixed solution of the well-entering fluid and the crude oil in a set proportion to reservoir temperature, uniformly stirring the mixed solution, then carrying out static demulsification for a set time, and after the static demulsification is finished, taking out the well-entering fluid and the crude oil; carrying out centrifugal treatment on the test tube so as to completely separate an oil phase and a water phase in the mixed solution; inclining the test tube by a set angle, and respectively measuring the axial length of the oil-water interface and the axial length of the oil-gas interface; according to the ratio of the axial length of the oil-water interface to the axial length of the oil-gas interface, the interfacial tensions of different well entering fluids are sequenced; the problems of high cost, low test speed, low test precision and small applicable interfacial tension range of a test instrument used in a conventional interfacial tension test method at present are effectively solved, the well entering fluid optimization efficiency is improved, the applicable range is widened, and the interfacial tension test cost is reduced.

Description

Technical Field

[0001] This disclosure relates to the field of improving oil recovery in unconventional reservoirs, specifically to the field of interfacial tension testing, and in particular to a rapid testing method for changes in interfacial tension caused by the interaction between the injection fluid (fracturing fluid, permeabilizer system) and crude oil. Background Technology

[0002] In my country, low-permeability and ultra-low-permeability oilfields account for more than half of newly discovered oil reservoirs. The main methods used to improve oil recovery are fracturing and percolation enhancement. The performance of influent fluids such as fracturing fluids and percolation agents directly affects the effectiveness of crude oil recovery from unconventional reservoirs. Furthermore, the Daqing Gulong shale oilfield has abundant exploration reserves, and fracturing and percolation are effective technologies for shale oil development. Therefore, researching testing methods for visualizing the migration process of influent fluids (fracturing fluid and percolation agent systems) on shale matrix fractures is crucial for shale oil development.

[0003] Currently, low interfacial tension wellbore fluids are one of the important directions for future wellbore fluids. Low interfacial tension helps reduce flow friction resistance, causes less damage to fracture conductivity, has a lower residue content, greatly improves the performance of wellbore fluids, and reduces pollution.

[0004] The conventional method for testing interfacial tension is the rotating drop method, which mainly determines the interfacial tension based on the shape and geometry of the drop. The test procedure is simple, but the testing instruments are expensive, the test accuracy is low, and the applicable range of interfacial tensions is small.

[0005] To address the above issues, there is an urgent need to research a rapid testing method for measuring the interfacial tension changes caused by the interaction between the well fluid and crude oil, in order to improve the efficiency and applicability of well fluid selection and reduce the cost of interfacial tension testing. Summary of the Invention

[0006] In view of this, this disclosure provides a rapid testing method for the interfacial tension between well fluid and crude oil, which solves the problems of high cost of testing instruments, low testing accuracy, and small applicable range of interfacial tension using conventional testing methods.

[0007] To achieve the above-mentioned objective, the rapid testing method for the interfacial tension between the well fluid and crude oil includes: A test tube containing a mixture of well fluid and crude oil in a set ratio is heated to the reservoir temperature. After the mixture is stirred evenly, static demulsification is performed for a set time. After the static demulsification is completed, the test tube is centrifuged to completely separate the oil phase and water phase in the mixture. The test tube was tilted at a set angle, and the axial length of the oil-water interface and the axial length of the oil-gas interface were measured respectively. The interfacial tensions of different influent fluids are ranked by the ratio of the axial length of the oil-water interface to the axial length of the oil-gas interface.

[0008] In this disclosure and possible embodiments, the set ratio is a volume ratio of the influent fluid to crude oil of 1:1.

[0009] In this disclosure and possible embodiments, the well fluid and the crude oil are each 20 mL; The test tube is a glass test tube with a capacity of 100 mL and an accuracy of 0.5 mL.

[0010] In this disclosure and possible embodiments, the reservoir temperature is 75°C.

[0011] In this disclosure and possible embodiments, the method for stirring the mixture to achieve uniformity includes: A test tube containing a mixture of well fluid and crude oil in a set ratio is heated to the reservoir temperature using a demulsification rate tester. Insert the stirring blade of the demulsification rate tester into the test tube, set the stirring speed to 1500 r / min and the stirring time to 5 min, so that the oil phase and water phase in the mixture are mixed evenly.

[0012] In this disclosure and possible embodiments, the static demulsification is performed for a set time, which is 1 hour.

[0013] In this disclosure and possible embodiments, the set angle for tilting the test tube is 5°.

[0014] In this disclosure and possible embodiments, the method for ranking the interfacial tension of different well-entry fluids by utilizing the ratio of the axial length of the oil-water interface to the axial length of the oil-gas interface includes: The greater the ratio of the axial length of the oil-water interface to the axial length of the oil-gas interface, the higher the interfacial tension of the influent fluid ranks.

[0015] The beneficial effects of this invention are as follows: This disclosure discloses a rapid testing method for interfacial tension changes caused by the interaction between well fluid and crude oil. The method involves tilting a test tube and calculating the tilt test index (TTI) based on the distance the oil-water interface moves relative to the oil-gas interface. The TTI is then used to evaluate the interfacial tension performance. This method offers high testing efficiency and accurate results, qualitatively evaluating the quality of interfacial tension in the well fluid system. Furthermore, it is not limited by the range of interfacial tension, providing theoretical support for the evaluation and use of well fluids. Simultaneously, it improves the efficiency of well fluid (fracturing fluid, permeabilizer system) selection and reduces the cost of interfacial tension testing. Attached Figure Description

[0016] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which: Figure 1a , Figure 1b , Figure 1c These are examples of demulsification in three wellbore fluid systems: System 1, System 2, and System 3, as disclosed in this embodiment. Figure 2a , Figure 2b , Figure 2c These are the states of the glass test tubes of three well fluid systems (System 1, System 2, and System 3) after being tilted by 5° according to the embodiments of this disclosure. Detailed Implementation

[0017] The present disclosure is described below based on specific embodiments; however, it is worth noting that the present disclosure is not limited to these specific embodiments. In the following detailed description of the present disclosure, certain specific details are described in detail. However, those skilled in the art will fully understand the present disclosure for the parts not described in detail.

[0018] Furthermore, unless the context explicitly requires it, the words "comprising," "including," and similar terms throughout the specification and claims should be interpreted as including rather than exclusive or exhaustive; that is, meaning "including but not limited to."

[0019] This disclosure discloses a rapid testing method for interfacial tension changes caused by the interaction between the well fluid and crude oil. The well fluid is a fluid system such as a fracturing fluid system or a percolator system. For example, the fracturing fluid system consists of drag reducers, surfactants, clay stabilizers, bactericides, and deionized water; the percolator system consists of surfactants, clay stabilizers, organic unblocking agents, and deionized water.

[0020] The core technology of this disclosed rapid testing method for interfacial tension between well fluid and crude oil includes: The well fluid and crude oil were loaded into a glass test tube at a set ratio. The glass test tube containing the mixture of well fluid and crude oil was heated to the reservoir temperature. After the mixture in the glass test tube was stirred evenly, static demulsification was performed for a set time. After static demulsification was completed, the glass test tube was centrifuged to completely separate the oil phase and water phase in the mixture. Then, the glass test tube was tilted at a certain angle, and the axial length of the oil-water interface and the axial length of the oil-gas interface were measured respectively. Finally, the interfacial tension of different well fluids was ranked according to the ratio of the axial length of the oil-water interface to the axial length of the oil-gas interface.

[0021] Based on the above-mentioned core technology, the following specific embodiments will provide a more detailed description of the rapid testing method for interfacial tension between well fluid and crude oil disclosed herein; unless otherwise specified, the materials and reagents used in the following embodiments can be obtained commercially. Example

[0022] This embodiment demonstrates a rapid test of the interfacial tension changes caused by the interaction between the well fluid (permeabilizer system) and crude oil. The specific steps are as follows: 1. First, prepare the fluid sample to be tested for well entry. The specific process is as follows: By mass percentage, the components of fluid system 1 include surfactant BHJ1 sodium dodecylbenzenesulfonate 0.3%, glycidyltrimethylammonium chloride 1%, organic unblocking agent aminosulfonic acid 5%, and deionized water; the components of fluid system 2 (permeabilizer system) include surfactant BHJ2 sodium dodecyl sulfate 0.3%, glycidyltrimethylammonium chloride 1%, organic unblocking agent aminosulfonic acid 5%, and deionized water; the components of fluid system 3 (permeabilizer system) include surfactant BHJ3 alkyl polyglycoside 0.3%, glycidyltrimethylammonium chloride 1%, organic unblocking agent aminosulfonic acid 5%, and deionized water.

[0023] 2. Using a glass test tube with a volume of 100 mL and an accuracy of 0.5 mL, add the well fluid and crude oil to the glass test tube according to a volume ratio of 1:1. Preferably, add 20 mL of crude oil to the glass test tube first, and then add 20 mL of well fluid to obtain three glass test tubes containing well fluid system 1, system 2, system 3 and crude oil mixture respectively.

[0024] 3. Heat the glass test tube containing the well fluids and crude oil mixture from systems 1, 2, and 3 (as described in step 2) to the reservoir temperature, such as 75°C. (Note: Reservoir temperatures can be obtained using conventional techniques for different reservoirs.) After heating to the reservoir temperature, thoroughly mix the mixture in the glass test tube by vigorous shaking to ensure complete mixing of the oil and water phases. After thorough mixing, place the glass test tube in a constant-temperature water bath at the reservoir temperature. Take photos of the test tube every 10 minutes to observe the demulsification process. The interval can vary; photos can be taken periodically or intermittently as needed. The specific process is as follows: (1) Set the water bath temperature of the demulsification rate tester to the reservoir temperature. After preheating the demulsification rate tester, put three glass test tubes containing the well fluid and crude oil mixture of system 1, system 2 and system 3 into the water bath of the demulsification rate tester so that the temperature of the mixture in the three glass test tubes corresponding to system 1, system 2 and system 3 is heated to the reservoir temperature. (2) After the mixture in the three glass test tubes corresponding to System 1, System 2 and System 3 reaches the reservoir temperature, insert the stirring blade of the demulsification rate tester into the glass test tube, set the stirring speed to 1500 r / min and the stirring time to 5 min, and start stirring to fully mix the oil phase and water phase in the mixture in the three glass test tubes corresponding to System 1, System 2 and System 3. (3) After stirring, keep the water bath temperature constant and start timing. Take photos of the glass test tubes every 10 minutes or other set intervals to observe the demulsification of the oil phase in systems 1, 2, and 3, as detailed below. Figure 1a , Figure 1b , Figure 1c As shown in the figure, at this time, it can be predicted from the above three figures that the interfacial tension of the fluid entering the well in system 3 is greater than that of the fluid entering the well in systems 1 and 2.

[0025] 4. However, since it is impossible to definitively determine whether an oil phase still exists in the aqueous phase, this embodiment preferably continues to use a centrifuge one hour after demulsification to completely separate the oil and aqueous phases in the glass test tube by centrifugation. For the completely separated glass test tube, to determine the distance the oil-water interface has moved relative to the oil-gas interface, the glass test tube is tilted, preferably at an angle of 5 degrees to the horizontal. Other angles are also possible, and this embodiment does not limit the tilt angle. After tilting, the distance the oil-water interface has moved relative to the oil-gas interface can be clearly shown in systems 1, 2, and 3, as shown in the following examples. Figure 2a , Figure 2b , Figure 2c As shown; then the interfacial tension ranking of the fluids entering the well in systems 1, 2 and 3 can be determined by the movement distance of the oil-water interface relative to the oil-gas interface.

[0026] 5. After tilting the test tube, combine Figure 2c As shown, the length LAir (oil-gas) of the oil-gas interface along the axial direction of the glass test tube and the length LWater (oil-water) of the oil-water interface along the axial direction of the glass test tube were measured respectively. The length LAir (oil-gas) of the oil-gas interface along the axial direction of the glass test tube represents the distance the oil-gas interface moves, and the length LWater (oil-water) of the oil-water interface along the axial direction of the glass test tube represents the distance the oil-water interface moves.

[0027] For ease of description, this disclosure presents the concept of the Tilt Test Index (TTI), which is specifically calculated using the distance the oil-water interface moves relative to the oil-gas interface.

[0028] Specifically, the tilt test index TTI is calculated using LAir (oil and gas) and LWater (oil and water), where TTI is the ratio of LWater (liquid-liquid) to LAir (gas-liquid).

[0029] According to the above definition and calculation method, as shown in Figure 2a, Figure 2b , Figure 2c As shown, in the TTI system, 1=0; TTI system 2=1.5 / 15=0.1; TTI system 3=4.0 / 15=0.27; 6. Based on the calculation results of step 5 above, and combined with the principle that the larger the ratio of the axial length of the oil-water interface to the axial length of the oil-gas interface, the higher the interfacial tension of the well fluid, the interfacial tension of the three well fluid systems from best to worst is: System 3, System 2, System 1. The ranking of the three well fluid systems from best to worst is: System 3, System 2, System 1.

[0030] Therefore, the test method of this invention can qualitatively evaluate the interfacial tension of the well fluid (fracturing fluid and permeater system) system, and there is no limitation on the range of interfacial tension. It can be seen that the test method disclosed in this invention is simple to operate, can greatly reduce the test cost, has high test efficiency, and accurate test results, providing theoretical support for the evaluation and use of well fluid (fracturing fluid and permeater system).

[0031] The embodiments described above are merely illustrative of implementation methods of this disclosure, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent disclosure. It should be noted that those skilled in the art can make various modifications, equivalent substitutions, and improvements without departing from the concept of this disclosure, and these all fall within the protection scope of this disclosure. Therefore, the protection scope of this patent disclosure should be determined by the appended claims.

Claims

1. A rapid method for testing the interfacial tension between well fluid and crude oil, characterized in that, include: A test tube containing a mixture of well fluid and crude oil in a set ratio is heated to the reservoir temperature. After the mixture is stirred evenly, static demulsification is performed for a set time. After the static demulsification is completed, the test tube is centrifuged to completely separate the oil phase and water phase in the mixture. The test tube was tilted at a set angle, and the axial length of the oil-water interface and the axial length of the oil-gas interface were measured respectively. The interfacial tensions of different influent fluids are ranked by the ratio of the axial length of the oil-water interface to the axial length of the oil-gas interface.

2. The rapid testing method for interfacial tension between well fluid and crude oil according to claim 1, characterized in that: The set ratio is a volume ratio of 1:1 between the influent fluid and crude oil.

3. The rapid testing method for interfacial tension between well fluid and crude oil according to claim 2, characterized in that: The fluid injected into the well and the crude oil are each 20 mL; The test tube is a glass test tube with a capacity of 100 mL and an accuracy of 0.5 mL.

4. The rapid testing method for interfacial tension between well fluid and crude oil according to claim 3, characterized in that: The reservoir temperature is 75°C.

5. The rapid testing method for interfacial tension between well fluid and crude oil according to claim 4, characterized in that, The method for stirring the mixture until homogeneous includes: A test tube containing a mixture of well fluid and crude oil in a set ratio is heated to the reservoir temperature using a demulsification rate tester. Insert the stirring blade of the demulsification rate tester into the test tube, set the stirring speed to 1500 r / min and the stirring time to 5 min, so that the oil phase and water phase in the mixture are mixed evenly.

6. The rapid testing method for interfacial tension between well fluid and crude oil according to claim 5, characterized in that: The process involves static demulsification for a set time, which is 1 hour.

7. The rapid testing method for interfacial tension between well fluid and crude oil according to any one of claims 1-6, characterized in that: The set angle for tilting the test tube is 5°.

8. The rapid testing method for interfacial tension between well fluid and crude oil according to claim 7, characterized in that, The method for ranking the interfacial tension of different well-entry fluids by using the ratio of the axial length of the oil-water interface to the axial length of the oil-gas interface includes: The greater the ratio of the axial length of the oil-water interface to the axial length of the oil-gas interface, the higher the interfacial tension of the influent fluid ranks.

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