High interfacial tension type imbibition oil displacement agent for improving recovery of shale oil reservoir

Abstract

The present application belongs to the field of unconventional reservoir exploitation, and discloses a high interfacial tension type imbibition oil washing agent for improving shale oil reservoir recovery, which comprises the following components in percentage by mass: 0.1-0.6% of low-molecular alcohol ether, 0.01-0.3% of water-soluble surfactant, 0.02-0.07% of inorganic salt, and the rest of water. The agent has good wetting reversal capacity, small solution particle size, low use concentration, strong penetration capacity, oil-water interfacial tension of 4-6 mN / m, particle size of <60 nm, and can convert the natural shale oil reservoir core from oil-wet (contact angle > 90°) to water-wet (contact angle 50°-60°), with the shale oil reservoir oil washing efficiency of >45%, and has a broad application prospect in shale oil reservoirs.

Description

Technical Field

[0001] This invention belongs to the field of unconventional oil reservoir development and relates to a high interfacial tension type of percolation and washing agent for improving the recovery rate of shale oil reservoirs. Background Technology

[0002] Currently, China has entered the stage of unconventional resource exploitation, with shale oil reservoirs serving as an important alternative resource. According to statistics from the U.S. Energy Information Administration, China's recoverable shale oil reserves reach 32 billion barrels, indicating broad exploration and development prospects. Shale oil reservoirs are characterized by low porosity, low permeability, and strong heterogeneity, resulting in significant development difficulties and low recovery rates. Currently, shale oil reservoir development primarily employs large-scale volumetric fracturing with horizontal wells to increase the reservoir stimulation volume, thereby increasing the contact area between the fracturing fluid and the reservoir matrix. The fracturing fluid, acting as the wetting phase, enters smaller pores under capillary force, displacing the non-wetting phase fluid into the artificial fractures. Oilfields typically use surfactants as washers in conjunction with fracturing fluids to improve the percolation and washing efficiency of tight oil reservoirs. The main factor affecting percolation and washing efficiency is capillary force. (Capillary force formula) Where P is the capillary force, σ is the interfacial tension, θ is the contact angle, and r is the core pore radius (generally unaffected by external factors). From the capillary force formula, increasing the interfacial tension and decreasing the contact angle helps increase the capillary force, thereby improving the efficiency of oil washing. Due to the ultra-low permeability and ultra-oil wettability of shale, conventional surfactants have unsatisfactory permeation and replacement effects due to problems such as low interfacial tension, large particle size, or poor wettability.

[0003] Chinese invention patent CN114790384, "A Small Molecule Permeabilizer and Its Preparation Method and Application," mentions a small molecule system formulated with short-chain nonionic-anionic surfactants as a permeabilizing and washing agent for tight oil reservoirs. The interfacial tension between the small molecule permeabilizer solution and kerosene is 10. -1 mN / m is a low interfacial tension type of permeation oil displacement agent. Chinese invention patent CN115109573, "A Nano-Permeation Oil Displacement Agent and Its Preparation Method," mentions a nano-permeation oil displacement agent composed of surfactants, solvents, and co-solvents, which can reduce interfacial tension and capillary force to improve oil recovery. Its interfacial tension can be as low as 10. -3 -10 -4 mN / m can transform oleophilic cores into weakly hydrophilic cores. The two percolation washing agents mentioned above have low interfacial tension, which theoretically is unfavorable for percolation washing. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention proposes a high-interfacial-tension type percolation washing agent to improve the percolation washing efficiency of shale oil reservoirs, with the goals of increasing interfacial tension, reducing contact angle, maintaining core pore radius, and increasing capillary force.

[0005] The purpose of this invention is to provide a highly efficient permeation washing agent for enhancing oil recovery in shale oil reservoirs. This permeation washing agent comprises the following components: low-molecular-weight alcohol ether compounds, water-soluble surfactants, inorganic salts, and water. This permeation washing agent exhibits excellent rock wetting reversal ability and permeability, high capillary force, significant oil washing effect, low concentration, and simple operation, effectively improving crude oil recovery and showing broad application prospects in shale oil reservoirs.

[0006] This invention relates to a highly efficient permeation washing agent for enhancing oil recovery in shale oil reservoirs. Its main component is a low-molecular-weight alcohol ether, which has good solubility, dissolving in formation water and crude oil. It also possesses good interfacial properties and low viscosity, effectively wetting the rock surface and transforming the shale oil reservoir rock from oil-wet to hydrophilic, allowing for efficient penetration into the reservoir matrix. This ensures that the capillary force direction aligns with the direction of injected water entering the matrix through fractures. Furthermore, experiments have verified that low-concentration low-molecular-weight alcohol ether solutions exhibit relatively high interfacial tension, further enhancing the capillary force of the washing agent. The second component of this invention is a water-soluble surfactant, which possesses good surface activity and wettability, further improving the solution's wetting ability on the rock surface. A third main component of this washing agent is an inorganic salt, which helps prevent clay swelling. In summary, the combined effect of these multiple functions significantly improves the oil recovery rate of shale oil reservoirs.

[0007] This invention provides a high interfacial tension type percolation washing agent to improve the recovery rate of shale oil reservoirs. The agent comprises, by mass percentage: 0.1–0.6% low molecular weight alcohol ether, 0.01–0.3% water-soluble surfactant, 0.02–0.07% inorganic salt, and the remainder being water.

[0008] The low molecular weight alcohol ether is one or two of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol tert-butyl ether, or diethylene glycol butyl ether;

[0009] The water-soluble surfactant is one or two of sodium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate, and calcium dodecylbenzenesulfonate;

[0010] The inorganic salt is one or both of potassium chloride and sodium chloride;

[0011] The oil-absorbing washing agent of the present invention is a compound of three agents used in combination with fracturing fluid.

[0012] The on-site application method is as follows: Prepare a concentrated solution by mixing low molecular weight alcohol ether, water-soluble surfactant, inorganic salt, and water, and put it into liquid filling tank A. Adjust the discharge rate of the proportional pump to the design discharge rate, inject the solution in A into the sand mixing truck, and inject it into the well after fully mixing and stirring with the fracturing sand carrying fluid.

[0013] The advantages of this invention compared to the prior art are:

[0014] This invention relates to a highly efficient permeation and washing agent for enhancing oil recovery in shale oil reservoirs. The agent comprises, by mass percentage: 0.1–0.6% low-molecular-weight alcohol ethers, 0.01–0.3% water-soluble surfactants, 0.02–0.07% inorganic salts, with the remainder being water. It exhibits excellent wetting reversal ability, small solution particle size, low concentration, and strong permeability. The oil-water interfacial tension of the solution is 4–6 mN / m, and the particle size is <60 nm. It transforms the oil-wet (contact angle >90°) state of natural shale oil reservoir cores into a water-wet (contact angle 50°–60°) state, achieving a washing efficiency >45% in shale oil reservoirs, and has broad application prospects in shale oil reservoirs. Attached Figure Description

[0015] Figure 1 This is a comparison diagram of the contact angles of water and permeation washing agent systems in shale cores. a) represents water, and b) represents permeation washing agent. Detailed Implementation

[0016] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0017] Example 1:

[0018] A shale oil reservoir percolation washing agent comprises, by mass percentage, the following components: 0.5% ethylene glycol dimethyl ether, 0.06% sodium dodecylbenzene sulfonate, 0.05% potassium chloride, 0.01% sodium chloride, and 99.38% water.

[0019] Field application method: Taking the preparation of 1 ton of percolating washing agent as an example. First, mix 500 kg of ethylene glycol dimethyl ether with 380 kg of water until homogeneous. Then, add 60 kg of sodium dodecylbenzene sulfonate, 50 kg of potassium chloride, and 10 kg of sodium chloride to prepare a homogeneous solution A. When the fracturing pump truck outputs a flow rate of 10 cubic meters per minute, inject homogeneous solution A into the sand mixing truck at a rate of 100 liters per minute using a liquid injection pump. After mixing evenly with the fracturing sand-carrying fluid, it is then introduced into the well.

[0020] Example 2:

[0021] A self-permeable oil washing agent for tight oil reservoirs comprises, by mass percentage: 0.6% ethylene glycol tert-butyl ether, 0.2% sodium dodecyl sulfonate, 0.03% potassium chloride, and 99.17% water.

[0022] Field application method: Taking the preparation of 1 ton of percolating washing agent as an example. First, mix 600 kg of ethylene glycol tert-butyl ether with 170 kg of water until homogeneous. Then, add 200 kg of sodium dodecyl sulfonate and 30 kg of potassium chloride to prepare a homogeneous solution A. When the fracturing pump truck outputs a flow rate of 10 cubic meters per minute, inject homogeneous solution A into the sand mixing truck at a rate of 100 liters per minute through the liquid injection pump. After mixing evenly with the fracturing sand-carrying fluid, it is then injected into the well.

[0023] Example 3:

[0024] A self-permeable oil washing agent for tight oil reservoirs comprises, by mass percentage: 0.23% ethylene glycol dimethyl ether, 0.3% ethylene glycol tert-butyl ether, 0.1% calcium dodecylbenzenesulfonate, 0.03% sodium chloride, 0.03% potassium chloride, and 99.31% water.

[0025] Field application method: Taking the preparation of 1 ton of percolating washing agent as an example. First, mix 230 kg of ethylene glycol dimethyl ether, 300 kg of ethylene glycol tert-butyl ether, and 310 kg of water evenly. Then, add 100 kg of calcium dodecylbenzenesulfonate, 30 kg of sodium chloride, and 30 kg of potassium chloride to prepare a homogeneous solution A. When the fracturing pump truck outputs a flow rate of 10 cubic meters per minute, inject homogeneous solution A into the sand mixing truck at a rate of 100 liters per minute using a liquid injection pump. After mixing evenly with the fracturing sand-carrying fluid, it is then injected into the well.

[0026] Example 4:

[0027] A self-permeable oil washing agent for tight oil reservoirs comprises, by mass percentage, the following components: 0.33% ethylene glycol dimethyl ether, 0.14% diethylene glycol butyl ether, 0.15% sodium dodecylbenzenesulfonate, 0.06% potassium chloride, and 99.32% water.

[0028] Field application method: Taking the preparation of 1 ton of percolating washing agent as an example. First, mix 330 kg of ethylene glycol dimethyl ether, 140 kg of diethylene glycol butyl ether, and 320 kg of water evenly. Then, add 150 kg of sodium dodecylbenzene sulfonate and 60 kg of potassium chloride to prepare a homogeneous solution A. When the fracturing pump truck outputs a displacement of 10 cubic meters per minute, inject homogeneous solution A into the sand mixing truck at a rate of 100 liters per minute using a liquid injection pump. After mixing evenly with the fracturing sand-carrying fluid, it is then injected into the well.

[0029] Example 5:

[0030] A self-permeable oil washing agent for tight oil reservoirs comprises, by mass percentage, the following components: 0.24% diethylene glycol dimethyl ether, 0.31% ethylene glycol butyl ether, 0.07% calcium dodecylbenzenesulfonate, 0.05% sodium chloride, and 99.33% mineralized water.

[0031] Field application method: Taking the preparation of 1 ton of percolating and washing agent as an example. First, mix 240 kg of diethylene glycol dimethyl ether, 310 kg of ethylene glycol butyl ether, and 330 kg of water evenly. Then, add 70 kg of calcium dodecylbenzenesulfonate and 50 kg of sodium chloride to prepare a homogeneous solution A. When the fracturing pump truck outputs a flow rate of 10 cubic meters per minute, inject homogeneous solution A into the sand mixing truck at a rate of 100 liters per minute using a liquid injection pump. After mixing evenly with the fracturing sand-carrying fluid, it is then injected into the well.

[0032] Example 6:

[0033] A self-permeable oil washing agent for tight oil reservoirs comprises, by mass percentage, the following components: 0.21% diethylene glycol butyl ether, 0.36% ethylene glycol tert-butyl ether, 0.13% sodium dodecyl sulfonate, 0.12% calcium dodecylbenzene sulfonate, 0.03% potassium chloride, 0.01% sodium chloride, and 99.14% water.

[0034] Field application method: Taking the preparation of 1 ton of percolating washing agent as an example. First, mix 210 kg of diethylene glycol butyl ether, 360 kg of ethylene glycol tert-butyl ether, and 140 kg of water evenly. Then, add 130 kg of sodium dodecyl sulfonate, 120 kg of calcium dodecylbenzene sulfonate, 30 kg of potassium chloride, and 10 kg of sodium chloride to prepare a homogeneous solution A. When the fracturing pump truck outputs a displacement of 10 cubic meters per minute, inject homogeneous solution A into the sand mixing truck at a rate of 100 liters per minute using a liquid injection pump. After mixing evenly with the fracturing sand-carrying fluid, it is then injected into the well.

[0035] Example 7:

[0036] The data on the interfacial tension of the oil-water interface in the oil-absorbing washing agents in Examples 1 to 6 are shown in Table 1 below.

[0037] Experimental measurement method: The oil-water interfacial tension of the oil-absorbing washing agent system in Examples 1 to 6 was measured using a full-range video interfacial tensiometer with a rotary drop method. The experimental temperature was 30℃ and the experimental rotation speed was 5000 R / min.

[0038] Table 1. Oil-water interfacial tension data for penetrant washing agents

[0039]

[0040] The test results show that the oil-absorbing and washing agent of the present invention has good interfacial activity.

[0041] Example 8:

[0042] The particle size determination data of the oil-absorbing washing agent systems in Examples 1 to 6 are shown in Table 2 below.

[0043] Experimental determination method: The particle size of the oil-absorbing washing agent system in Examples 1 to 6 was determined by a particle size analyzer at room temperature and medium and high temperature, respectively. The experimental temperatures were 25℃ and 60℃.

[0044] Table 2 Particle size data of the penetrating washing oil solution

[0045]

[0046] The test results show that the particle size of the oil-absorbing washing agent of the present invention is small at room temperature, and the particle size of each solution does not change significantly after the temperature is increased, indicating that it has good temperature resistance.

[0047] Example 9:

[0048] The wettability test data of the oil-absorbing washing agent systems in Examples 1 to 6 are shown in Table 3 below.

[0049] The comparison diagram of contact angles between water-based and infiltration-based oil washing systems in shale cores is shown below. Figure 1 .

[0050] Experimental measurement method: The contact angles of oil, water and shale in natural shale cores in water and the oil washing agent systems in Examples 1 to 6 were measured using a contact angle meter at an experimental temperature of 25℃.

[0051] Table 3. Data on the contact angle measurement of the penetrating washing oil.

[0052] Sample number Clear water Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Contact angle 107.18° 53.23° 59.61° 55.21° 50.02° 52.69° 56.47°

[0053] The test results show that natural shale cores are oily and wet, and the oil-absorbing agent of this invention can effectively change the wettability of shale.

[0054] Example 10:

[0055] The data on the oil washing efficiency of the permeation washing agent system in Examples 1-6 on natural shale cores are shown in Table 4 below.

[0056] Experimental determination method: Under high temperature and vacuum conditions, saturated simulated oil (a mixture of crude oil and kerosene) was produced on shale cores using a low-speed injection and gradient pressurization method. The percolation and washing efficiency of the percolation washing agent systems in Examples 1-6 was evaluated at room temperature.

[0057] Table 4. Data on the oil washing efficiency of various permeation washing agent solutions for shale cores.

[0058] Sample number Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Oil washing efficiency (%) 48.36 46.34 45.32 49.46 46.24 46.03

[0059] The test results show that the oil-absorbing and washing agent of the present invention has good oil-washing performance.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A high interfacial tension type permeation washing agent for improving the recovery rate of shale oil reservoirs, characterized in that, By mass percentage, it includes the following components: 0.1-0.6% low molecular weight alcohol ethers, 0.01-0.3% water-soluble surfactants, 0.02-0.07% inorganic salts, and the remainder is water; The low molecular weight alcohol ether is one or two of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and ethylene glycol tert-butyl ether; The water-soluble surfactant is one or two of sodium dodecylbenzenesulfonate, sodium dodecylbenzenesulfonate, and calcium dodecylbenzenesulfonate; The inorganic salt is one or both of potassium chloride and sodium chloride.

2. The high interfacial tension type permeation and washing agent for improving shale oil reservoir recovery according to claim 1, characterized in that, The aforementioned oil-washing agent is a compound of three agents used in conjunction with fracturing fluid.

3. The high interfacial tension type permeation and washing agent for improving shale oil reservoir recovery according to claim 1, characterized in that, A concentrated solution is prepared by mixing low molecular weight alcohol ethers, water-soluble surfactants, inorganic salts, and water, and then placed in liquid filling tank A. The displacement of the proportional pump is adjusted to the design displacement, and the solution in A is injected into the sand mixing truck. After being fully mixed and stirred with the fracturing sand-carrying fluid, it is injected into the well.

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