High interfacial tension type imbibition oil washing agent for improving shale oil reservoir recovery ratio

Abstract

The invention belongs to the field of unconventional oil reservoir exploitation, and discloses a high interfacial tension type imbibition oil washing agent for improving shale oil reservoir recovery efficiency, 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 balance of water. The shale oil reservoir oil washing agent has the advantages of good wetting reversal capability, small solution particle size, low use concentration and strong infiltration capability, the oil-water interfacial tension of the solution is 4-6mN / m, the particle size is less than 60nm, the natural shale oil reservoir rock core is converted from oil wetting (the contact angle is greater than 90 degrees) to water wetting (the contact angle is 50-60 degrees), the shale oil reservoir oil washing efficiency is greater than 45%, and the shale oil reservoir oil washing agent has wide application prospects in shale oil reservoirs.

Description

Technical Field

[0001] The invention belongs to the field of unconventional oil reservoir exploitation and relates to a high interfacial tension type imbibition oil-washing agent for improving the recovery rate of shale oil reservoirs. Background Art

[0002] At present, China has entered the stage of unconventional resource exploitation, with shale oil reservoirs as an important successor resource. According to statistics from the U.S. Energy Information Administration, China's recoverable shale oil reserves amount to 32 billion barrels, and the prospects for exploration and development are broad. Shale oil reservoirs have the characteristics of low porosity, low permeability and strong reservoir heterogeneity, which makes development difficult and the degree of recovery low. At present, the development of shale oil reservoirs mainly adopts large-scale volume fracturing of horizontal wells to increase the volume of reservoir transformation, thereby increasing the contact area between the fracturing fluid and the reservoir matrix. The fracturing fluid, as a wetting phase, enters smaller pores under the action of capillary force and displaces non-wetting phase fluid into artificial fractures. Oil fields usually use surfactants as oil washing agents in combination with fracturing fluids to improve the efficiency of oil absorption and washing in tight oil reservoirs. The main factor affecting the efficiency of oil absorption and washing is capillary force. Capillary force formula Where P is capillary force, σ is interfacial tension, θ is contact angle, and r is core pore radius (generally not changed by external factors); from the capillary force formula, increasing interfacial tension and reducing contact angle can help increase capillary force, thereby improving the efficiency of oil washing by imbibition. Since shale has the characteristics of ultra-low permeability and ultra-oil wettability, conventional surfactants have unsatisfactory imbibition replacement effects due to problems such as low interfacial tension, large particle size or poor wettability.

[0003] Chinese invention patent CN114790384 "A small molecule imbibition agent and its preparation method and application" mentions a small molecule system composed of a short-chain nonionic-anionic surfactant as a tight oil reservoir imbibition washing agent. The interfacial tension between the small molecule imbibition agent solution and kerosene is 10 -1 mN / m, is a low interfacial tension type oil-absorbing agent. Chinese invention patent CN115109573 "A nano-absorbing oil-displacing agent and its preparation method" mentions that the nano-absorbing oil-displacing agent made of a mixture of surfactant, solvent and co-solvent can reduce interfacial tension and capillary force to increase recovery rate. Its lowest interfacial tension can reach 10 -3 -10 -4 mN / m, which can transform the oil-wet core into a weakly water-wet core. The above two oil-absorbing and washing agents have low interfacial tension, which is not conducive to oil-absorbing and washing in theory. Summary of the invention

[0004] In order to make up for the shortcomings of the prior art, the present invention aims to increase interfacial tension, reduce contact angle, maintain core pore radius, and increase capillary force, and proposes an application for a high interfacial tension type oil-washing agent to improve the oil-washing efficiency of shale oil reservoirs.

[0005] The purpose of the present invention is to provide a high-efficiency oil-absorbing and washing agent for improving the recovery rate of shale oil reservoirs. The oil-absorbing and washing agent comprises the following components: low-molecular alcohol ether compounds, water-soluble surfactants, inorganic salts and water. The oil-absorbing and washing agent has good rock wetting reversal ability and permeability, high capillary force, significant oil washing effect, low concentration, simple operation, can effectively improve the recovery rate of crude oil, and has broad application prospects in shale oil reservoirs.

[0006] The present invention relates to a high-efficiency permeable oil washing agent for improving the recovery rate of shale oil reservoirs. Its main component is low-molecular alcohol ether, which has good solubility and can be dissolved in formation water and crude oil. It also has good surface and interface properties and low viscosity, and can efficiently wet the rock surface to make the shale oil reservoir rock change from oil-wet to hydrophilic, and efficiently penetrate into the reservoir rock matrix, so that the capillary force direction is consistent with the direction of the injected water entering the matrix from the crack. Secondly, it is verified by experiments that the low-concentration low-molecular alcohol ether solution has a relatively high interfacial tension, and the dual effect increases the capillary force of the oil washing agent. The second component of the present invention is a water-soluble surfactant, which has good surface activity and good wettability, and can further improve the wetting ability of the solution on the rock surface. The third main component of the oil washing agent is an inorganic salt, which has the effect of preventing clay from swelling. In summary, the combined effect of multiple functions can greatly improve the recovery rate of shale oil reservoirs.

[0007] The invention provides a high interfacial tension type oil-absorbing cleaning agent for improving the recovery rate of shale oil reservoirs. The agent comprises the following components by mass percentage: 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 is water.

[0008] The low molecular 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 dodecylbenzene sulfonate, sodium dodecyl sulfonate, and calcium dodecylbenzene sulfonate;

[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 prepared by compounding three agents and then used in combination with the fracturing fluid.

[0012] The on-site usage method is as follows: prepare low molecular weight alcohol ether, water-soluble surfactant, inorganic salt and water into a concentrated solution and put it in liquid addition tank A, adjust the displacement of the proportional pump to the designed displacement, inject the solution in A into the sand mixing truck, fully mix and stir with the fracturing sand-carrying fluid, and then inject it into the well.

[0013] The beneficial effects of the present invention compared with the prior art are:

[0014] The invention relates to a high-efficiency imbibition oil-washing agent for improving the recovery rate of shale oil reservoirs. The agent comprises the following components by mass percentage: 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 ability, small solution particle size, low use concentration and strong permeability, the oil-water interfacial tension of the solution is 4-6mN / m, the particle size is less than 60nm, the core of the natural shale oil reservoir is converted from oil-wet (contact angle>90°) to water-wet (contact angle 50°-60°), the oil washing efficiency of the shale oil reservoir is>45%, and it has broad application prospects in shale oil reservoirs. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a comparison diagram of the contact angles of clean water and the imbibition oil washing agent system in shale cores, a) represents clean water, and b) represents the imbibition oil washing agent. DETAILED DESCRIPTION

[0016] The present invention is described in detail below with reference to the accompanying drawings and embodiments. In the following embodiments, the materials, reagents, etc. used were obtained from commercial sources unless otherwise specified.

[0017] Embodiment 1:

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

[0019] On-site use method: Take the preparation of 1 ton of oil-absorbing washing agent as an example. First, mix 500 kg of ethylene glycol dimethyl ether and 380 kg of water evenly, and then add 60 kg of sodium dodecylbenzene sulfonate, 50 kg of potassium chloride, and 10 kg of sodium chloride to prepare a uniform solution A. When the output displacement of the fracturing pump truck is 10 cubic meters / minute, the uniform solution A is injected into the sand mixing truck at a speed of 100 liters / minute through the liquid addition pump, and then mixed evenly with the fracturing sand-carrying fluid and then injected into the well.

[0020] Embodiment 2:

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

[0022] On-site use method: Take the preparation of 1 ton of wicking oil washing agent as an example. First, mix 600 kg of ethylene glycol tert-butyl ether and 170 kg of water evenly, then add 200 kg of sodium dodecyl sulfate and 30 kg of potassium chloride respectively to prepare uniform solution A. When the output displacement of the fracturing pump truck is 10 cubic meters / minute, the uniform solution A is injected into the sand mixing truck at a speed of 100 liters / minute through the liquid addition pump, and then mixed evenly with the fracturing sand-carrying fluid and then injected into the well.

[0023] Embodiment 3:

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

[0025] On-site use method: Take the preparation of 1 ton of oil-absorbing 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, and then add 100 kg of calcium dodecylbenzene sulfonate, 30 kg of sodium chloride, and 30 kg of potassium chloride to prepare a uniform solution A. When the output displacement of the fracturing pump truck is 10 cubic meters / minute, the uniform solution A is injected into the sand mixing truck at a speed of 100 liters / minute through the liquid addition pump, and then mixed evenly with the fracturing sand-carrying fluid and then injected into the well.

[0026] Embodiment 4:

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

[0028] On-site use method: Take the preparation of 1 ton of oil-absorbing 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, and then add 150 kg of sodium dodecylbenzene sulfonate and 60 kg of potassium chloride to prepare uniform solution A. When the output displacement of the fracturing pump truck is 10 cubic meters / minute, the uniform solution A is injected into the sand mixing truck at a speed of 100 liters / minute through the liquid addition pump, and then mixed evenly with the fracturing sand-carrying fluid and then injected into the well.

[0029] Embodiment 5:

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

[0031] On-site use method: Take the preparation of 1 ton of wicking oil 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, and then add 70 kg of calcium dodecylbenzene sulfonate and 50 kg of sodium chloride to prepare uniform solution A. When the output displacement of the fracturing pump truck is 10 cubic meters / minute, the uniform solution A is injected into the sand mixing truck at a speed of 100 liters / minute through the liquid addition pump, and then mixed evenly with the fracturing sand-carrying fluid and then injected into the well.

[0032] Embodiment 6:

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

[0034] On-site use method: Take the preparation of 1 ton of oil-absorbing 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, and 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 uniform solution A. When the output displacement of the fracturing pump truck is 10 cubic meters / minute, the uniform solution A is injected into the sand mixing truck at a speed of 100 liters / minute through the liquid addition pump, and is mixed evenly with the fracturing sand-carrying fluid before entering the well.

[0035] Embodiment 7:

[0036] The oil-water interfacial tension measurement data of the oil absorption washing agent in Examples 1 to 6 are shown in Table 1 below.

[0037] Experimental determination method: The oil-water interfacial tension of the oil absorption cleaning agent system in Examples 1 to 6 was measured using a spinning drop method full-range video interfacial tension meter. The experimental temperature was 30° C. and the experimental rotation speed was 5000 R / min.

[0038] Table 1 Oil-water interfacial tension data of oil absorption detergent

[0039]

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

[0041] Embodiment 8:

[0042] The particle size measurement data of the oil absorption cleaning agent system in Examples 1 to 6 are shown in Table 2 below.

[0043] Experimental determination method: The particle size of the solution of the oil absorption cleaning agent system in Examples 1 to 6 was measured by a particle size analyzer at room temperature and medium-high temperature, respectively. The experimental temperature was 25°C and 60°C.

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

[0045]

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

[0047] Embodiment 9:

[0048] The wettability test data of the oil absorption cleaning agent system in Examples 1 to 6 are shown in Table 3 below.

[0049] The comparison of contact angles of clean water and imbibition oil washing system in shale core is shown in the figure below. Figure 1 .

[0050] Experimental determination method: The oil-water-shale three-item contact angle of clean water and the natural shale core in the oil absorption and washing agent system in Examples 1 to 6 was measured by a contact angle meter, and the experimental temperature was 25°C.

[0051] Table 3 Contact angle measurement data of oil absorption detergent

[0052] Sample No. Shimizu 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 the natural shale core is oil-wet, and the oil-absorbing and washing agent of the present invention can effectively change the wettability of shale.

[0054] Embodiment 10:

[0055] The measured data of oil washing efficiency of the imbibition oil washing agent system on natural shale core in Examples 1 to 6 are shown in Table 4 below.

[0056] Experimental determination method: Under high temperature and vacuum conditions, the shale core was saturated with simulated oil (a mixture of crude oil and kerosene) by low-speed injection and gradient pressure increase. The oil absorption and washing efficiency of the oil absorption and washing agent systems in Examples 1 to 6 was evaluated at room temperature.

[0057] Table 4 Data on the oil washing efficiency of various imbibition oil washing agent solutions on shale core

[0058] Sample No. 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 measurement results show that the oil-absorbing cleaning agent of the present invention has good oil-cleaning performance.

[0060] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A high interfacial tension type imbibition oil washing agent for improving the recovery rate of shale oil reservoirs, characterized in that: The composition comprises the following components by mass percentage: 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.

2. The high interfacial tension type oil-absorbing cleaning agent for improving the recovery rate of shale oil reservoirs according to claim 1, characterized in that: The low molecular 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.

3. The high interfacial tension type oil-absorbing cleaning agent for improving the recovery rate of shale oil reservoirs according to claim 1, characterized in that: The water-soluble surfactant is one or two of sodium dodecylbenzene sulfonate, sodium dodecyl sulfonate and calcium dodecylbenzene sulfonate.

4. The high interfacial tension type oil-absorbing cleaning agent for improving the recovery rate of shale oil reservoirs according to claim 1, characterized in that: The inorganic salt is one or both of potassium chloride and sodium chloride.

5. The high interfacial tension type oil-absorbing and washing agent for improving the recovery rate of shale oil reservoirs according to claim 1, characterized in that: The oil-absorbing washing agent is compounded from three agents and used in combination with the fracturing fluid.

6. The high interfacial tension type oil-absorbing cleaning agent for improving the recovery rate of shale oil reservoirs according to claim 1, characterized in that: Low molecular alcohol ether, water-soluble surfactant, inorganic salt and water are prepared into concentrated solution and placed in liquid addition tank A. The displacement of the proportional pump is adjusted to the designed 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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