Method for in-situ determination of process of cleaning oil-based rock debris by microemulsion on molecular scale

Abstract

The invention discloses a method for in-situ determination of a process of cleaning oil-based rock debris by microemulsion on a molecular scale. The method comprises the following steps: obtaining base oil on the surface of the oil-based rock debris through Soxhi; base oil is adsorbed to the surface of the dual-polarization interferometer chip through a spin coating method, and the surface of oil-based rock debris is simulated; preparing a middle-phase microemulsion from a surfactant, a cosurfactant, saline water and an oil phase; a dual-polarization interferometer is used for measuring a change curve of the adsorption quality of the surface of the chip along with time when different micro-emulsions flow through the chip, and in-situ online simulation of the process of cleaning the oil-based rock debris by the micro-emulsions on the molecular scale is realized. According to the method, the DPI can be utilized to realize in-situ online simulation of the process of cleaning the oil-based rock debris by the microemulsion on a micro-level, and theoretical support is provided for the work of cleaning the oil-based rock debris by the microemulsion.

Description

Technical Field

[0001] The invention belongs to the technical field of dual polarization interference, and in particular relates to a method for in-situ measuring a process of cleaning oil-based rock cuttings with a microemulsion on a molecular scale. Background Art

[0002] Dual polarization interferometry (DPI) technology is a new type of nonlinear optical interface detection technology developed in recent years. It mainly draws on the concept of evanescent waves in biological detectors, based on traditional optical interference theory, and uses specific sensor chips to monitor the changes of the molecules above them in real time. It has the characteristics of real-time dynamic, in-situ label-free, high resolution, and high sensitivity, and can detect mass changes of 0.1ng / mm 2 and a tiny change of 0.1nm in thickness. Due to its advantages of high detection sensitivity, real-time dynamic in-situ, and diversified information, it is currently used in surface / interface detection research in many fields such as proteins, drug molecules, and enhanced oil recovery.

[0003] In the process of shale gas extraction, due to the high clay content of the shale layer, when it swells with water, it is easy to cause drilling accidents such as collapse and congestion. Oil-based drilling fluid is widely used to protect oil and gas layers, maintain hydrostatic pressure, stabilize the well wall, and clean the bottom of the well. However, a large amount of oil-based cuttings will inevitably be produced during the drilling stage of oil-based drilling fluid. The random discharge of untreated oil-based cuttings will cause serious environmental pollution and have serious effects on human health. Therefore, oil-based cuttings have been included in China's HW08 "National List of Hazardous Wastes (2021 Edition)", and the treatment of oil-based cuttings has received increasing attention from countries around the world. At present, the commonly used technologies for the treatment of oil-based cuttings mainly include thermal desorption, solvent extraction, and chemical cleaning. In some places, the cost of transporting oil-based cuttings to centralized processing stations is too high. Chemical cleaning has the advantages of high efficiency, simple cleaning equipment, and the possibility of use at the well site, so it has received more and more attention. Microemulsion cleaning is one of the most studied chemical cleaning methods, but there is still a lack of sufficient understanding of the microscopic process by which it achieves the cleaning effect. This is mainly because traditional macroscopic experiments cannot explore the microscopic desorption behavior of base oil on the rock surface during the cleaning process. Therefore, it is crucial to establish a method that can simulate the microemulsion cleaning process in situ at the microscopic level. Summary of the invention

[0004] The purpose of the present invention is to provide a method for in-situ measuring the process of microemulsion cleaning oil-based rock cuttings at the molecular scale. First, an oil / microemulsion / rock three-phase simulation system is constructed, and then a dual polarization interferometer is used to simulate the process of microemulsion cleaning oil-based rock cuttings in situ online at the molecular scale.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for in-situ measuring a process of cleaning oil-based rock cuttings with a microemulsion at a molecular scale, comprising:

[0007] Get the base oil on the surface of oil-based cuttings;

[0008] Adsorbing the base oil onto the surface of a dual-polarization interferometer chip to simulate the surface of oil-based rock cuttings;

[0009] A middle phase microemulsion is prepared by using a surfactant, a co-surfactant, a saline solution and an oil phase;

[0010] The variation curve of the adsorption mass on the chip surface with time when the configured middle phase microemulsion flows through the chip is measured by dual polarization interferometer, and the process of microemulsion cleaning oil-based cuttings is characterized on the molecular scale.

[0011] Furthermore, the step of obtaining the base oil on the surface of the oil-based cuttings comprises:

[0012] Soxhlet extraction was used to obtain the base oil on the surface of oil-based cuttings.

[0013] Furthermore, the base oil on the surface of the oil-based rock cuttings is obtained by Soxhlet extraction, and the solvent used is petroleum ether with a boiling range of 60-90°C.

[0014] Furthermore, the method of obtaining the base oil on the surface of the oil-based rock cuttings by Soxhlet extraction comprises:

[0015] Weigh a certain amount of oil-based rock cuttings and place them in a Soxhlet extractor;

[0016] Heat petroleum ether with a boiling range of 60-90°C and reflux the reaction to extract the oil-based rock cuttings for 12 hours;

[0017] The petroleum ether was removed by rotary evaporation to obtain the base oil.

[0018] Furthermore, the base oil is adsorbed onto the surface of a dual polarization interferometer chip to simulate the surface of oil-based rock cuttings, comprising:

[0019] Adsorbing the base oil onto the surface of a dual polarization interferometer chip by a spin coating method;

[0020] The spin coating time is 50s-90s, and the rotation speed is 800-1600rpm.

[0021] Furthermore, the dual polarization interferometer chip adopts a commercial hydrophobic C18 dual polarization interferometer chip.

[0022] Furthermore, the co-surfactant is any one of n-butanol, n-pentanol and n-octanol.

[0023] Furthermore, the oil phase of the microemulsion is selected from any one of 5# white oil and diesel. The beneficial effects of the present invention are:

[0024] The present invention provides a method for in-situ online simulation of the process of microemulsion cleaning oil-based rock cuttings at a molecular scale, wherein the base oil on the surface of the oil-based rock cuttings is obtained by extraction and then spin-coated onto the surface of a DPI commercial chip. The middle phase microemulsion is composed of a surfactant, a co-surfactant, brine and an oil phase. The present invention utilizes DPI to achieve in-situ online simulation of the process of microemulsion cleaning oil-based rock cuttings at a microscopic level, providing theoretical support for the work of microemulsion cleaning oil-based rock cuttings. In addition, by adopting the method of the present invention, the elution amount of base oil on the chip surface by different microemulsions can be compared, thereby achieving rapid screening of microemulsion formulas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The DPI test results when the oil phase in the microemulsion of Example 1 of the present invention is white oil;

[0026] Figure 2 The DPI test results when the oil phase in the microemulsion of Example 2 of the present invention is diesel;

[0027] Figure 3 The DPI test results of comparative example 1 of the present invention using saline are shown below;

[0028] Figure 4 The DPI test results of comparative example 2 of the present invention are carried out using an aqueous solution of sodium sulfate of fatty alcohol polyoxyethylene ether. DETAILED DESCRIPTION

[0029] The present invention is further described below. The following examples are only used to more clearly illustrate the technical solution of the present invention, and are not intended to limit the protection scope of the present invention.

[0030] The present invention provides a method for in-situ measuring a process of cleaning oil-based rock cuttings with a microemulsion at a molecular scale, comprising:

[0031] The base oil on the surface of oil-based rock cuttings was obtained by Soxhlet extraction;

[0032] The obtained base oil was adsorbed onto the surface of the dual-polarization interferometer chip by spin coating to simulate the surface of oil-based rock cuttings;

[0033] A middle phase microemulsion is prepared by using a surfactant, a co-surfactant, a saline solution and an oil phase;

[0034] The variation curve of the adsorption mass on the chip surface with time when the middle phase microemulsion flows through the chip is measured by dual polarization interferometer, so as to realize the in-situ online simulation of the microemulsion cleaning process of oil-based cuttings at the molecular scale.

[0035] In the present invention, the solvent used when the base oil on the surface of the oil-based rock cuttings is obtained by Soxhlet extraction is petroleum ether (boiling range 60-90° C.).

[0036] In the present invention, the dual polarization interferometer chip is a commercial hydrophobic C18 dual polarization interferometer chip.

[0037] In the present invention, the spin coating time is 50-90s and the rotation speed is 00-1600rpm.

[0038] In the present invention, the oil phase in the microemulsion is selected from any one of 5# white oil and diesel.

[0039] In the present invention, the co-surfactant is usually n-butanol, n-pentanol and n-octanol.

[0040] It should be noted that the present invention uses DPI to quickly evaluate the process of cleaning oil-based rock cuttings with a middle phase microemulsion. As for the formulation of the middle phase microemulsion using surfactants, co-surfactants, brine and oil phase, it is not within the scope of the present invention. Those skilled in the art should know that the middle phase microemulsion can be prepared by mixing surfactants, co-surfactants, brine and oil phase in a certain ratio. After the concentration of each component is changed, different middle phase microemulsions will be obtained, and their cleaning effects will be different. The present invention only studies the cleaning process, not the cleaning effects of different formulations.

[0041] Example 1

[0042] S1. Obtaining the base oil on the surface of oil-based cuttings:

[0043] Weigh 30 g of oil-based rock chips and place them in a Soxhlet extractor. Heat petroleum ether (boiling range 60-90° C.) to reflux and extract the oil-based rock chips for 12 hours; remove the petroleum ether by rotary evaporation to obtain the base oil.

[0044] S2. Spin-coat base oil on the surface of the DPI chip:

[0045] The commercial hydrophobic C18 chip of DPI was fixed on the KW-4A desktop coating machine; the coating machine was turned on, 100 μL of base oil was dripped onto the chip surface at a speed of 1000 rpm, and the coating was performed for 60 seconds.

[0046] S3. Prepare microemulsion:

[0047] Prepare a 2wt% sodium chloride saline solution, add 20g of saline into a colorimetric tube; add 10wt% sodium sulfate of fatty alcohol polyoxyethylene ether, 5% n-pentanol and 5mL 5# white oil in sequence and shake well; take the middle phase microemulsion for experiment.

[0048] S4. Conduct DPI experiment:

[0049] The DPI test results when the oil phase in the microemulsion is white oil are shown in Figure 1DPI is performed using the Analight Nano200 dual polarization interferometer from the British Farfield Group. Figure 1 As shown, the initial adsorption of base oil on the chip is 0.200ng / mm 2 When the microemulsion passes through the base oil surface, the unit adsorption amount on the chip surface will first increase and then decrease. This shows that the microemulsion does not directly elute the base oil, but first quickly adsorbs to the base oil surface, then desorbs, and finally elutes the base oil from the chip. Finally, the adsorption amount of the base oil on the chip surface is reduced to 0.186ng / mm 2 .

[0050] Example 2

[0051] The basic implementation of this embodiment is the same as that of Embodiment 1, except that the oil phase used in preparing the microemulsion in this embodiment is diesel.

[0052] The DPI test results when the oil phase in the microemulsion is diesel are shown in Figure 2 .like Figure 2 As shown, the experimental results at this time are consistent with Figure 1 Similarly, when the microemulsion passes through the base oil surface, the unit adsorption amount on the chip surface also increases first and then decreases. Finally, the adsorption amount of the base oil on the chip surface can be reduced to 0.161ng / mm 2 The elution amount is greater than the microemulsion formed by 5# white oil.

[0053] Comparative Example 1

[0054] The basic implementation of this example is the same as that of Example 1, except that this example does not use microemulsion, but directly uses 2 wt% sodium chloride saline solution to perform the DPI experiment. The results of the direct saline experiment are shown in Figure 3 .like Figure 3 As shown, although the brine is first adsorbed and then desorbed on the surface of the base oil, it cannot elute the base oil.

[0055] Comparative Example 2

[0056] The basic implementation of this example is the same as that of Example 1, except that this example does not use microemulsion, but directly uses 10 wt% fatty alcohol polyoxyethylene ether sodium sulfate aqueous solution to perform the DPI experiment. The results of the direct experiment with fatty alcohol polyoxyethylene ether sodium sulfate aqueous solution are shown in Figure 4 .like Figure 4 As shown, the aqueous solution of sodium fatty alcohol polyoxyethylene ether sulfate cannot elute the base oil.

[0057] Example 3

[0058] In order to further illustrate the technical effect of the present invention, the present invention also provides the results of cleaning oil-based cuttings in actual applications of the above embodiments and comparative examples.

[0059] The prepared cleaning solution (microemulsion / other solution) was mixed with the oil-based cuttings at a mass ratio of 5:1, stirred at room temperature for 60 minutes and then centrifuged, the lower solid phase was removed, rinsed with pure water and dried; the dried oil-based cuttings were extracted with tetrachloroethylene and their oil content was measured using an infrared oil meter. The experimental results are shown in Table 1. It can be seen from Table 1 that the microemulsion can smoothly elute the base oil from the surface of the cuttings, but the salt water and fatty alcohol polyoxyethylene ether sodium sulfate aqueous solution cannot, which is consistent with the experimental results of DPI.

[0060] Table 1 Experimental results of cleaning oil-based cuttings with different cleaning fluids

[0061]

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for in-situ determination of the process of cleaning oil-based cuttings with microemulsion at the molecular scale, characterized in that: include: Get the base oil on the surface of oil-based cuttings; Adsorbing the base oil onto the surface of a dual-polarization interferometer chip to simulate the surface of oil-based rock cuttings; A middle phase microemulsion is prepared by using a surfactant, a co-surfactant, a saline solution and an oil phase; The variation curve of the adsorption mass on the chip surface with time when the configured middle phase microemulsion flows through the chip is measured by dual polarization interferometer, and the process of microemulsion cleaning oil-based cuttings is characterized on the molecular scale.

2. A method for in-situ determination of the process of cleaning oil-based cuttings with microemulsion at the molecular scale according to claim 1, characterized in that: The method of obtaining the base oil on the surface of the oil-based rock cuttings comprises: Soxhlet extraction was used to obtain the base oil on the surface of oil-based cuttings.

3. A method for in-situ determination of the process of cleaning oil-based cuttings with microemulsion at the molecular scale according to claim 2, characterized in that: The base oil on the surface of the oil-based rock cuttings is obtained by the Soxhlet extraction method, and the solvent used is petroleum ether with a boiling range of 60-90°C.

4. A method for in-situ determination of the process of cleaning oil-based cuttings with microemulsion at the molecular scale according to claim 3, characterized in that: The method of obtaining the base oil on the surface of oil-based rock cuttings by Soxhlet extraction comprises: Weigh a certain amount of oil-based rock cuttings and place them in a Soxhlet extractor; Heat petroleum ether with a boiling range of 60-90°C and reflux the reaction to extract the oil-based rock cuttings for 12 hours; The petroleum ether was removed by rotary evaporation to obtain the base oil.

5. The method for in-situ determination of the process of cleaning oil-based cuttings with microemulsion at the molecular scale according to claim 1, characterized in that: The base oil is adsorbed onto the surface of a dual polarization interferometer chip to simulate the surface of oil-based rock cuttings, including: Adsorbing the base oil onto the surface of a dual polarization interferometer chip by a spin coating method; The spin coating time is 50 s-90s, and the rotation speed is 800-1600 rpm.

6. A method for in-situ determination of a process of cleaning oil-based cuttings with a microemulsion at a molecular scale according to claim 5, characterized in that: The dual polarization interferometer chip adopts a commercial hydrophobic C18 dual polarization interferometer chip.

7. The method for in-situ determination of the process of cleaning oil-based cuttings with microemulsion at the molecular scale according to claim 1, characterized in that: The co-surfactant is any one of n-butanol, n-pentanol and n-octanol.

8. A method for in-situ determination of a process of cleaning oil-based cuttings with a microemulsion at a molecular scale according to claim 7, characterized in that: The oil phase of the microemulsion is selected from any one of 5# white oil and diesel.

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