Nanometer oil displacement material for improving crude oil recovery ratio, preparation method of nanometer oil displacement material and use method of nanometer oil displacement material in low-permeability oil reservoir

Abstract

The invention provides a nanometer oil displacement material for improving the crude oil recovery rate, a preparation method thereof and a use method of the nanometer oil displacement material in a low-permeability oil reservoir. The preparation method comprises the following steps: mixing tartaric acid, polyethylene polyamine, alkyl alcohol ether and water, carrying out a hydrothermal reaction, and freeze-drying a product obtained after the hydrothermal reaction to obtain the nano oil displacement material. Wherein the weight ratio of tartaric acid to polyethylene polyamine to alkyl alcohol ether is 1: (2-4): (3-5). The preparation method is easy to operate, the raw materials are cheap and easy to obtain, and particularly, the obtained nano oil displacement material has smaller size, higher interfacial activity and better wetting regulation and control capability, and can show a remarkable synergistic effect when being combined with CO2 displacement in a low-permeability oil reservoir.

Description

Technical Field

[0001] The present invention belongs to the field of oil displacement agents, and in particular relates to a nano oil displacement material for improving crude oil recovery, a preparation method thereof, and a method of using the nano oil displacement material in low-permeability oil reservoirs. Background Art

[0002] Nanoscale flooding materials are chemical substances produced using nanotechnology and used to enhance crude oil recovery in oil and gas fields. Their fundamental principle is to leverage the unique physical and chemical properties of nanomaterials to improve the fluidity and recoverability of crude oil. Nanoscale flooding materials typically refer to materials with at least one dimension between 1 and 100 nanometers. These materials exhibit unique properties due to their unique size effects. These properties include, but are not limited to, improved fluid flow, altered rock surface wettability, and enhanced separation efficiency between crude oil and water.

[0003] According to literature reports, some nanomaterials, such as silica, titanium oxide, and aluminum oxide, have potential applications in enhancing oil recovery. However, most nano-displacement materials suffer from large particle sizes, which can lead to blockage of nano-scale pore throats in low-permeability reservoirs. Furthermore, most nanomaterials have low surface activity. To achieve higher surface activity, they often need to be modified using surface modifiers, such as using silane coupling agents to modify nano-silica. This modification process inevitably leads to increased production costs and reduced stability of the nanomaterials. In addition to the aforementioned nanomaterials, amphiphilic Janus nanoparticles, as an asymmetric material, have also attracted much attention. However, the preparation process of Janus nanoparticles is cumbersome, and the production cost is high, limiting their application in enhancing oil recovery.

[0004] Low-permeability reservoirs are defined as those with rock permeabilities below 0.1 millidarcy. These reservoirs exhibit low porosity, poor permeability, high crude oil viscosity, and low reservoir pressure. These reservoirs are challenging to develop, with low recovery rates and require specialized techniques such as horizontal wells and hydraulic fracturing. These developments are associated with high costs, significant environmental risks, and significant water resource consumption. Therefore, the low-cost preparation of nanomaterials for oil displacement suitable for low-permeability reservoirs is a current research hotspot. Summary of the Invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a nano-oil-displacing material for improving crude oil recovery, a preparation method thereof, and a method of using the nano-oil-displacing material in low permeability oil reservoirs. The nano-oil-displacing material has a small size, high interfacial activity, and strong wettability control ability, and can be better applied to low permeability oil reservoirs to improve crude oil recovery.

[0006] To achieve the above objectives, the present invention provides a method for preparing a nano-scale oil-displacement material for enhancing crude oil recovery, comprising: mixing tartaric acid, polyethylene polyamine, an alkyl alcohol ether, and water to undergo a hydrothermal reaction, and freeze-drying the resulting product to obtain the nano-scale oil-displacement material. The weight ratio of tartaric acid, polyethylene polyamine, and alkyl alcohol ether is 1:2 to 4:3 to 5.

[0007] In some optional embodiments, the polyethylene polyamine is selected from one or a combination of two or more of diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

[0008] In some optional embodiments, the alkyl alcohol ether includes one or a combination of two or more of AEO-3, AEO-7 and AEO-9.

[0009] Furthermore, the reaction temperature of the hydrothermal reaction is 140 to 200° C.; and the reaction time of the hydrothermal reaction is 8 to 24 hours.

[0010] Furthermore, the ratio of the total weight of tartaric acid, polyethylene polyamine and alkyl alcohol ether to the weight of water is 5-20:100, that is, (weight of tartaric acid + weight of polyethylene polyamine + weight of alkyl alcohol ether) / weight of water = 5-20:100.

[0011] The present invention also provides a nano oil displacement material for improving crude oil recovery, which is prepared by the above-mentioned preparation method.

[0012] Furthermore, the particle size of the nano oil-displacing material is 3 to 10 nm.

[0013] Furthermore, the nano-displacement material makes the interfacial tension between crude oil and water below 10 -1 mN / m or less.

[0014] The present invention also provides a method for using the aforementioned nano-displacement material for enhancing crude oil recovery in low permeability reservoirs (rock permeability is less than 0.1 mD), which comprises: adding the nano-displacement material to injection water.

[0015] Furthermore, the mass concentration of the nano oil-displacing material in the injected water is 0.1-1%. The nano oil-displacing material of the present invention can be used directly after being diluted with water, or can be mixed with other surfactants (such as sodium lauryl sulfate, sodium α-olefin sulfonate, sodium lauryl polyoxyethylene ether sulfate, etc.) or polymers (such as partially hydrolyzed polyacrylamide, sodium carboxymethyl cellulose, xanthan gum, etc.) to further improve crude oil recovery.

[0016] The present invention also provides a method for using the aforementioned nano-displacement material for enhancing crude oil recovery in low-permeability oil reservoirs, which includes: using a method of alternately injecting gaseous CO2 and nanofluid in slugs, wherein the nanofluid is an aqueous solution with a mass concentration of 0.1 to 1% of the nano-displacement material.

[0017] CO2 flooding is an effective method for improving oil recovery and is widely used in oil and gas field development projects. However, when using CO2 and water as slugs alone, the reservoir heterogeneity is sensitive: high permeability layers are prone to gas channeling, which reduces sweep efficiency and affects the effectiveness of project implementation. Therefore, finding a slug fluid that has both oil displacement and anti-gas channeling functions to replace water, thereby inhibiting gas channeling and optimizing flow, improving sweep efficiency, and further reducing costs and increasing oil recovery. The alternating injection of the nanofluid and CO2 of the present invention can not only significantly inhibit CO2 gas channeling, but also significantly improve the oil recovery rate of low permeability reservoirs based on the physical and chemical properties of the nano oil displacement agent itself.

[0018] In summary, the present invention has the following beneficial effects: the present invention uses tartaric acid, polyethylene polyamine and alkyl alcohol ether as raw materials, realizes carbonization through hydrothermal reaction, and forms a high-performance oil-displacing material in situ. The particle size of the oil-displacing material is small, which can be better applied to low-permeability oil reservoirs; at the same time, the oil-displacing material is soluble in water and most common organic solvents, and has excellent interfacial activity, which can greatly reduce the interfacial tension between crude oil and water, and can also significantly inhibit CO2 gas channeling when alternately injected with CO2, thereby more effectively improving crude oil recovery. In addition, the present invention can realize the preparation of the above-mentioned oil-displacing material through a hydrothermal step. The preparation method is simple and easy to operate, and the raw materials are cheap and easy to obtain. Nano oil-displacing materials can be prepared at low cost. Compared with existing nano oil-displacing materials, the industrial application prospect is better. DETAILED DESCRIPTION

[0019] In order to have a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention is now described in detail below, but it should not be understood as limiting the scope of implementation of the present invention.

[0020] In the following examples, tartaric acid, polyethylene polyamine, and alkyl alcohol ether were purchased from Aladdin Reagent Co., Ltd.

[0021] Example 1

[0022] This embodiment provides a method for preparing a nano oil-displacing material, which comprises the following steps:

[0023] 1.0g of tartaric acid, 2.0g of triethylenetetramine, and 5.0g of AEO-9 were placed in a 100mL stainless steel autoclave lined with polytetrafluoroethylene. 75mL of deionized water was added and ultrasonicated for 2 minutes to thoroughly mix the ingredients. The sealed autoclave was heated in an oil bath at 140°C for 24 hours. After the autoclave cooled to room temperature, 10mL of the reaction product was freeze-dried to obtain a nano-oil displacement material.

[0024] Example 2

[0025] This embodiment provides a method for preparing a nano oil-displacing material, which comprises the following steps:

[0026] 1.0g of tartaric acid, 3.0g of triethylenetetramine, and 4.0g of AEO-9 were placed in a 100mL stainless steel autoclave lined with polytetrafluoroethylene. 80mL of deionized water was added and ultrasonicated for 2 minutes to thoroughly mix the ingredients. The sealed autoclave was heated in an oil bath at 200°C for 8 hours. After the autoclave cooled to room temperature, 10mL of the reaction product was freeze-dried to obtain a nano-oil displacement material.

[0027] Example 3

[0028] This embodiment provides a method for preparing a nano oil-displacing material, which comprises the following steps:

[0029] 1.0g of tartaric acid, 4.0g of triethylenetetramine, and 3.0g of AEO-9 were placed in a 100mL stainless steel autoclave lined with polytetrafluoroethylene. 50mL of deionized water was added and ultrasonicated for 2 minutes to thoroughly mix the ingredients. The sealed autoclave was heated in an oil bath at 180°C for 12 hours. After the autoclave cooled to room temperature, 10mL of the reaction product was freeze-dried to obtain a nano-oil displacement material.

[0030] Example 4

[0031] This embodiment provides a method for preparing a nano oil-displacing material, which comprises the following steps:

[0032] 1.0g of tartaric acid, 4.0g of diethylenetriamine, and 3.0g of AEO-7 were placed in a 100mL stainless steel autoclave lined with polytetrafluoroethylene. 50mL of deionized water was added and ultrasonicated for 2 minutes to thoroughly mix the ingredients. The sealed autoclave was heated in an oil bath at 180°C for 12 hours. After the autoclave cooled to room temperature, 10mL of the reaction product was freeze-dried to obtain a nano-oil displacement material.

[0033] Example 5

[0034] This embodiment provides a method for preparing a nano oil-displacing material, which comprises the following steps:

[0035] 1.0g of tartaric acid, 4.0g of tetraethylenepentamine, and 3.0g of AEO-3 were weighed and placed in a 100mL stainless steel autoclave lined with polytetrafluoroethylene. 50mL of deionized water was added and ultrasonicated for 2 minutes to thoroughly mix the ingredients. The sealed autoclave was heated in an oil bath at 180°C for 12 hours. After the autoclave cooled to room temperature, 10mL of the reaction product was freeze-dried to obtain a nano-oil displacement material.

[0036] Example 6

[0037] This embodiment provides a method for preparing a nano oil-displacing material, which comprises the following steps:

[0038] 1.0g of tartaric acid, 4.0g of triethylenetetramine, and 3.0g of AEO-9 were weighed and placed in a 100mL stainless steel autoclave lined with polytetrafluoroethylene. 100mL of deionized water was added and ultrasonicated for 2 minutes to thoroughly mix the ingredients. The sealed autoclave was heated in an oil bath at 200°C for 8 hours. After the autoclave cooled to room temperature, 10mL of the reaction product was freeze-dried to obtain a nano-oil displacement material.

[0039] Example 7

[0040] This embodiment provides a method for preparing a nano oil-displacing material, which comprises the following steps:

[0041] 1.0g of tartaric acid, 4.0g of triethylenetetramine, and 3.0g of AEO-9 were placed in a 100mL stainless steel autoclave lined with polytetrafluoroethylene. 50mL of deionized water was added and ultrasonicated for 2 minutes to thoroughly mix the ingredients. The sealed autoclave was heated in an oil bath at 140°C for 24 hours. After the autoclave cooled to room temperature, 10mL of the reaction product was freeze-dried to obtain a nano-oil displacement material.

[0042] Example 8

[0043] This embodiment provides a method for preparing a nano oil-displacing material, which comprises the following steps:

[0044] 1.0g of tartaric acid, 4.0g of triethylenetetramine, and 3.0g of AEO-9 were placed in a 100mL stainless steel autoclave lined with polytetrafluoroethylene. 50mL of deionized water was added and ultrasonicated for 2 minutes to thoroughly mix the ingredients. The sealed autoclave was heated in an oil bath at 160°C for 18 hours. After the autoclave cooled to room temperature, 10mL of the reaction product was freeze-dried to obtain a nano-oil displacement material.

[0045] Comparative Example 1

[0046] Petroleum sulfonate was purchased from Hubei Huada Fine Chemical Co., Ltd.

[0047] Performance testing:

[0048] (1) Determination of Particle Size: The oil-displacing agent in the example was prepared with water to form an oil-displacing agent solution with a mass fraction of 0.05%. The particle size of the nano-oil-displacing material was measured using a dynamic light scattering instrument. The test results are shown in Table 1.

[0049] (2) Interfacial Tension Measurement Method: The oil-displacing agents used in the Examples and Comparative Examples were prepared with mineralized water (50,000 mg / L NaCl and 5,000 mg / L CaCl2) to form an oil-displacing agent-water system having an oil-displacing agent mass fraction of 0.5%. The interfacial tension between the oil-displacing agent-water system and the oil phase (the oil phase being No. 3 aviation kerosene) was measured using a spinning drop interfacial tension meter at 60°C and 6,000 rpm. The test results are shown in Table 1.

[0050] (3) Crude oil recovery factor determination method: refer to the test method in the literature Li, Lin, Xiao-Ming Jin, Jia Chen, Zizhao Wang, Yining Wu, Mingwei Zhao and Caili Dai. “Anionic surfactant with enhanced interfacial wettability control capability for residual oil development.” Colloids and Surfaces A: Physicochemical and Engineering Aspects (2022): n.pag.

[0051] Enhanced oil recovery = crude oil recovery from the flooding system obtained in the Examples and Comparative Examples (the flooding agents in the Examples and Comparative Examples were prepared with mineralized water (50,000 mg / L NaCl and 5,000 mg / L CaCl2) to form a flooding agent-water system with a flooding agent mass fraction of 0.5%) minus the crude oil recovery from the water flooding test (a water flooding test involves direct water injection after the core is saturated with oil; the ratio of oil production to saturated oil is the water flooding test crude oil recovery). The test results are shown in Table 1.

[0052] Table 1

[0053]

[0054]

[0055] The particle size of the nano oil displacement material prepared by the present invention is less than 10nm, and the oil-water interfacial tension is less than 10 -1 mN / m, which can effectively improve the crude oil recovery rate of low permeability reservoirs.

[0056] Example 9

[0057] This embodiment provides a method for improving oil recovery by combining CO2 with nanofluid flooding, which includes the following steps:

[0058] First, 0.1 PV of CO₂ gas (pressure 15 MPa, flow rate 0.5 mL / min) was injected, followed by 0.1 PV of nanofluid (comprising 0.5 wt% of the nano-displacement material synthesized in Example 1, prepared using formation water, flow rate 0.5 mL / min). This CO₂ and nanofluid slug injection was repeated three times for a total injection volume of 0.6 PV. After the alternating cycles, 1.0 PV of mineralized water for the oil displacement agent was injected (flow rate 0.5 mL / min). The experiment was stopped when the outlet water cut was >98%, and the crude oil recovery factor (Crude oil recovery factor = the ratio of the volume of crude oil recovered from the outlet of the core experiment to the volume of crude oil initially saturated in the core) was calculated.

[0059] Comparative Example 2

[0060] This comparative example provides a method for improving oil recovery by combining CO2 flooding with water flooding, which comprises the following steps:

[0061] Inject 0.1 PV of CO2 gas (pressure 15 MPa, flow rate 0.5 mL / min), followed by 0.1 PV of formation water (flow rate 0.5 mL / min). Repeat this CO2 and oil displacement agent injection three times using a mineralized water slug, for a total injection volume of 0.6 PV. After the alternating cycles, inject 1.0 PV of formation water (flow rate 0.5 mL / min) until the outlet water cut exceeds 98%. The experiment is terminated and the crude oil recovery factor is calculated.

[0062] Comparative Example 3

[0063] This comparative example provides a method for improving oil recovery by combining CO2 with surfactant flooding, which comprises the following steps:

[0064] Inject 0.1 PV of CO2 gas (at a pressure of 15 MPa and a flow rate of 0.5 mL / min), followed by 0.1 PV of a surfactant solution (containing 0.5 wt% of the zwitterionic surfactant CAB-35, prepared in formation water) at a flow rate of 0.5 mL / min. Repeat this CO2 and surfactant solution slug injection three times for a total injection volume of 0.6 PV. After these alternating cycles, inject 1.0 PV of formation water (at a flow rate of 0.5 mL / min) until the outlet water cut exceeds 98%. The experiment is terminated and the crude oil recovery factor is calculated.

[0065] The enhanced oil recovery of the examples and comparative examples of different displacement system combinations is shown in Table 2.

[0066] Table 2

[0067]

[0068] The combination of CO2 flooding and nano-displacement agents has demonstrated significant synergistic effects in the development of low-permeability reservoirs. This synergistic enhancement mechanism is reflected in the following: the nano-displacement agent increases the contact area between CO2 and crude oil, promoting its dissolution and diffusion. Furthermore, the injection pressure of CO2 propels the nano-displacement agent deeper into low-permeability areas, expanding the swept volume and improving sweep efficiency. Low-permeability reservoirs are highly heterogeneous, and CO2 tends to penetrate along high-permeability channels. Nano-displacement agents, however, can block these channels through adsorption, diverting CO2 to micro-unswept areas with high oil saturation, expanding the swept volume and slowing gas channeling. The small size of the nano-displacement agent allows it to enter micro- and nano-pores, stripping the oil film through an "active oil-seeking" mechanism and reducing residual oil in blind pore ends. The expansion of CO2 further propels the nano-displacement agent into even smaller pores.

Claims

1. A method for preparing a nano-displacement material for enhancing crude oil recovery, wherein: include: mixing tartaric acid, polyethylene polyamine, alkyl alcohol ether and water to carry out a hydrothermal reaction, and freeze-drying the product after the hydrothermal reaction to obtain a nano oil-displacing material; The weight ratio of the tartaric acid, the polyethylene polyamine and the alkyl alcohol ether is 1:2-4:3-5.

2. The method for preparing a nano-displacement material for enhancing crude oil recovery according to claim 1, wherein: The polyethylene polyamine is selected from one or a combination of two or more of diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

3. The method for preparing the nano-displacement material for enhancing crude oil recovery according to claim 1, wherein: The alkyl alcohol ether includes one or a combination of two or more of AEO-3, AEO-7 and AEO-9.

4. The method for preparing the nano-displacement material for enhancing crude oil recovery according to claim 1, wherein: The reaction temperature of the hydrothermal reaction is 140-200°C.

5. The method for preparing the nano-displacement material for enhancing crude oil recovery according to claim 4, wherein: The reaction time of the hydrothermal reaction is 8 to 24 hours.

6. The method for preparing a nano-displacement material for enhancing crude oil recovery according to claim 1, wherein: The ratio of the total weight of the tartaric acid, the polyethylene polyamine and the alkyl alcohol ether to the weight of the water is 5 to 20:

100.

7. A nano-displacement material for enhancing crude oil recovery, wherein: The method is prepared according to any one of claims 1 to 6.

8. The nano-displacement material for enhancing crude oil recovery according to claim 7, wherein: The particle size of the nano oil-displacing material is 3 to 10 nm.

9. A method for using the nano-displacement material for enhancing crude oil recovery according to claim 7 or 8 in a low permeability oil reservoir, wherein: include: The nanometer oil-displacing material is added to the injected water, wherein the mass concentration of the nanometer oil-displacing material in the injected water is 0.1-1%.

10. A method for using the nano-displacement material for enhancing crude oil recovery according to claim 7 or 8 in a low permeability oil reservoir, wherein: include: The method adopts the method of alternately injecting gaseous CO2 and nanofluid in slugs, wherein the nanofluid is an aqueous solution with a mass concentration of the nano oil-displacing material of 0.1 to 1%.

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