A method of oil displacement

Abstract

The application provides an oil displacement method, which comprises the following steps: firstly, injecting a drag-reducing and injection-increasing agent into a low-permeability oil reservoir, modifying the surface of rocks by the drag-reducing and injection-increasing agent, modifying the surface of rocks into a hydrophobic and oleophobic double-scarcity state, reducing injection pressure, and playing a role of reducing pressure and increasing injection; and then injecting an oil displacement agent, and realizing efficient displacement of deep residual oil and remaining oil in the oil reservoir by the low flow resistance and strong oil washing capacity of the oil displacement agent.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, and particularly relates to an oil displacement method. Background Technology

[0002] Low-permeability reservoirs are widely distributed and abundant in my country, and have become an important part of the country's oil and gas resources. Most low-permeability reservoirs are primarily developed using waterflooding. However, due to the poor physical properties, small pore throats, high flow resistance, and strong heterogeneity of low-permeability reservoirs, problems such as high injection pressure, low injection rate, and poor oil displacement effect arise, resulting in a prominent contradiction of "inability to inject and inability to recover," and low waterflooding recovery rates.

[0003] Chemical flooding is a key area of ​​research focus for enhanced oil recovery. Injecting chemical flooding agents to improve oil recovery primarily addresses two interfacial issues: the liquid-solid interface and the liquid-liquid interface. Based on capillary number theory, ultra-low interfacial tension flooding agents are typically injected to enhance reservoir recovery, mainly considering the liquid-liquid interface. This involves utilizing the high interfacial activity of surfactants to reduce the oil-water interfacial tension, thereby achieving good oil displacement. However, low-permeability reservoirs have small pore throat radii and significant capillary action, resulting in high seepage resistance and injection pressure during injection development. Furthermore, the adsorption and retention of surfactants on the reservoir rock surface lead to severe losses, significantly hindering the surfactant's oil displacement effect in deep reservoirs, resulting in poor performance in actual field tests. How to reduce the injection pressure of injection wells and maximize the efficient oil washing effect of flooding agents in deep reservoirs remains unresolved. Summary of the Invention

[0004] This invention provides an oil displacement method, which includes the following steps:

[0005] 1) Inject drag-reducing and injection-enhancing agents to modify the rock surface into a hydrophobic and oleophobic state, thereby reducing the injection pressure;

[0006] 2) Inject oil displacement agents to displace residual and remaining oil in the deep reservoir.

[0007] The oil displacement method provided by this invention can be implemented by alternating multiple injections of drag-reducing and injection-enhancing agents and oil displacement agents, depending on the actual reservoir conditions.

[0008] In one specific embodiment, the injection concentration of the drag-reducing and injection-enhancing agent is 0.13% to 0.55%.

[0009] In one specific embodiment, the injection concentration of the oil displacement agent is 0.05% to 0.35%.

[0010] In one specific embodiment, the drag-reducing and injection-enhancing agent includes a main agent, an auxiliary agent, and an adjuvant.

[0011] In one specific embodiment, the drag-reducing and injection-enhancing agent is 100% by mass, and the drag-reducing and injection-enhancing agent comprises 0.1% to 0.35% main agent, 0.02% to 0.1% excipient, 0.01% to 0.1% auxiliary agent, and the balance being water.

[0012] In one specific embodiment, the main component of the drag-reducing and injection-enhancing agent is a semisiloxane organic compound; and / or

[0013] The excipient is an inorganic nano-oxide material; and / or

[0014] The additives are silane-based organic compounds;

[0015] Preferably, the main agent is one of cage-type hexahedral semisiloxane, cage-type octahedral semisiloxane, and cage-type dodecahedral semisiloxane;

[0016] Preferably, the excipient is at least one of nano-silica, nano-alumina, and nano-ferric oxide;

[0017] Preferably, the particle size of the excipient is 20 to 40 nm;

[0018] Preferably, the median particle size of the excipient is 29 to 31 nm;

[0019] Preferably, the auxiliary agent is at least one selected from dimethyldichlorosilane, propyltrimethylsilane, and vinyltrimethoxysilane.

[0020] In one specific embodiment, the oil displacement agent is an aqueous solution of a surfactant;

[0021] Preferably, the surfactant is an alkyl sulfonate and / or an alkylbenzene sulfonate;

[0022] Preferably, the alkyl sulfonate is a dodecyl sulfonate (e.g., sodium dodecyl sulfonate);

[0023] Preferably, the alkylbenzene sulfonate is a tetradecylbenzene sulfonate (e.g., sodium tetradecylbenzene sulfonate).

[0024] In one specific embodiment, the interfacial tension between the drag-reducing and injection-enhancing agent and the crude oil, and the interfacial tension between the oil displacement agent and the crude oil, are independently not higher than 10. -2 mN / m.

[0025] In one specific embodiment, the viscosity of the oil displacement agent is not higher than 3 mPa·s.

[0026] In one specific embodiment, the injection volume of the drag-reducing and injection-enhancing agent can be selected according to the actual target reservoir conditions;

[0027] Preferably, the injection volume of the drag-reducing and injection-enhancing agent is 0.1 to 0.5 PV.

[0028] The oil displacement method provided by this invention is applied in reservoir oil displacement, particularly in low-permeability reservoir oil displacement. The beneficial effects of this invention are:

[0029] This invention addresses the problems of difficult injection of oil displacement agents and poor oil displacement effects in existing oil displacement methods for low-permeability reservoirs, and provides an oil displacement method. By organically combining drag-reducing and injection-enhancing agents with oil displacement agents, a synergistic effect is achieved, solving the "injectable but not extractable" problem faced by enhanced oil recovery in low-permeability reservoirs. Laboratory core oil displacement experiments using the oil displacement method provided by this invention showed a 43% reduction in injection pressure and a 13.89% increase in oil displacement efficiency during the chemical flooding stage. Attached Figure Description

[0030] Figure 1 This is a flowchart of an oil displacement simulation experimental setup.

[0031] Figure 2 The dynamic curves of interfacial tension between the drag-reducing and injection-enhancing agents and crude oil in Examples 1 to 3 are shown.

[0032] Figure 3 The dynamic curves of interfacial tension between the oil displacement agent and crude oil in Examples 1 to 3 are shown. Detailed Implementation

[0033] The present invention will be further described below with reference to the embodiments. However, the embodiments of the present invention are merely illustrative examples and should not be construed as limiting the present invention under any circumstances.

[0034] The water used was simulated formation water from a low-permeability oilfield, with a salinity of 5200 mg / L;

[0035] The crude oil used was degassed crude oil from the oil field, with a viscosity of 10.5 mPa·s and a reservoir temperature of 55℃;

[0036] The core used was an artificial columnar core, and the core parameters were as follows: 50mD.

[0037] Example 1

[0038] 1) Preparation of drag-reducing and injection-enhancing agent: Mix 0.2g cage-type hexahedral semisiloxane, 0.05g nano-silica with a particle size range of 22 to 37nm and a median particle size of 30.5nm, 0.05g dimethyldichlorosilane and 99.7g water evenly to obtain drag-reducing and injection-enhancing agent;

[0039] 2) Preparation of oil displacement agent: Mix 0.2g sodium tetradecylbenzenesulfonate with 99.8g water evenly to obtain the oil displacement agent;

[0040] 3) Using the oil displacement method provided in this embodiment, utilizing... Figure 1 The apparatus shown was used to conduct an oil displacement simulation experiment: water was driven to the residual oil state, drag-reducing and injection-enhancing agent in 0.3PV 1) was injected first, and then oil displacement agent in 2) was injected to drive the oil until the water content of the produced fluid was greater than 95%.

[0041] Example 2

[0042] 1) Preparation of drag-reducing and injection-enhancing agent: Mix 0.1g cage-type octahedral semisiloxane, 0.02g nano-alumina with a particle size range of 23 to 36nm and a median particle size of 29.5nm, 0.01g propyltrimethylsilane and 99.87g water evenly to obtain drag-reducing and injection-enhancing agent;

[0043] 2) Preparation of oil displacement agent: Mix 0.05g sodium dodecyl sulfonate with 99.95g water evenly to obtain the oil displacement agent;

[0044] 3) Using the oil displacement method provided in this embodiment, utilizing... Figure 1 The apparatus shown was used to conduct an oil displacement simulation experiment: water was driven to the residual oil state, drag-reducing and injection-enhancing agent in 0.5PV 1) was injected first, and then oil displacement agent in 2) was injected to drive the oil until the water content of the produced fluid was greater than 95%.

[0045] Example 3

[0046] 1) Preparation of drag-reducing and injection-enhancing agent: Mix 0.35g cage-type dodecahedral semisiloxane, 0.1g nano-iron oxide with a particle size range of 20 to 39nm and a median particle size of 30.4nm, 0.1g vinyltrimethoxysilane and 99.45g water evenly to obtain drag-reducing and injection-enhancing agent;

[0047] 2) Preparation of oil displacement agent: Mix 0.35g sodium tetradecylbenzenesulfonate with 99.65g water evenly to obtain the oil displacement agent;

[0048] 3) Using the oil displacement method provided in this embodiment, utilizing... Figure 1 The apparatus shown was used to conduct an oil displacement simulation experiment: water was driven to the residual oil state, drag-reducing and injection-enhancing agent in 0.1PV 1) was injected first, and then oil displacement agent in 2) was injected to drive the oil until the water content of the produced fluid was greater than 95%.

[0049] Example 4

[0050] 1) Preparation of drag-reducing and injection-enhancing agent: Same as in Example 1;

[0051] 2) Preparation of the oil displacement agent: Same as in Example 1;

[0052] 3) Using the oil displacement method provided in this embodiment, utilizing... Figure 1The apparatus shown was used to conduct an oil displacement simulation experiment: water was pumped to the residual oil state, drag-reducing and injection-enhancing agent in 0.3PV 1) was injected first, followed by oil displacement agent in 2) to drive the oil until the water content of the produced fluid was greater than 95%, drag-reducing and injection-enhancing agent in 0.3PV 1) was injected again, followed by oil displacement agent in 2) to drive the oil until the water content of the produced fluid was greater than 95%.

[0053] Comparative Example 1

[0054] 1) Preparation of oil displacement agent: Mix 0.2g sodium tetradecylbenzenesulfonate with 99.8g water evenly to obtain the oil displacement agent;

[0055] 2) Using the oil displacement method provided in this comparative example, utilizing... Figure 1 The apparatus shown was used to conduct an oil displacement simulation experiment: water was used to drive the oil to a residual oil state, and the oil displacement agent in 1) was injected to drive the oil until the water content of the produced fluid was greater than 95%.

[0056] Comparative Example 2

[0057] 1) Preparation of drag-reducing and injection-enhancing agent: Mix 0.2g cage-type hexahedral semisiloxane, 0.05g nano-silica with a particle size range of 22 to 37nm and a median particle size of 30.5nm, 0.05g dimethyldichlorosilane and 99.7g water evenly to obtain drag-reducing and injection-enhancing agent;

[0058] 2) Using the oil displacement method provided in this comparative example, utilizing... Figure 1 The apparatus shown was used to conduct an oil displacement simulation experiment: water flooding was carried out until the residual oil state was reached, drag-reducing and injection-enhancing agent in 0.3PV 1) was injected, and water flooding continued until the water cut of the produced fluid was greater than 95%.

[0059] Experimental Evaluation

[0060] 1. Evaluation of the ability of drag-reducing and injection-enhancing agents to modify and modify rock surfaces

[0061] Bailey sandstone cores and artificial sandstone cores saturated with oil were respectively immersed in the drag-reducing and injection-enhancing agents prepared in Examples 1 to 3 and deionized water for 24 hours. After immersion, the contact angles of the aqueous and oil phases were measured using a contact angle measuring instrument at room temperature and pressure. The specific experimental conditions and results are shown in Table 1.

[0062] Table 1. Contact angles and surface properties of different core sections with aqueous and oil phases after treatment with different soaking agents.

[0063]

[0064] (Continued from Table 1)

[0065]

[0066] 2. Evaluation of interfacial tension between drag-reducing and injection-enhancing agents and crude oil, and viscosity of the oil displacement agent.

[0067] During the core flooding experiment using the oil displacement methods provided in Examples 1 to 3, the dynamic interfacial tension curves between the drag-reducing and injection-enhancing agent and crude oil, as well as the dynamic interfacial tension curves between the oil displacement agent and crude oil, were obtained as follows: Figure 2 , Figure 3 As shown.

[0068] The viscosity of the oil displacement agents in Examples 1 to 3 was determined using a Brookfield viscometer.

[0069] The specific data of the interfacial tension between the drag-reducing and injection-enhancing agent and crude oil, the interfacial tension between the oil displacement agent and crude oil, and the viscosity of the oil displacement agent in Examples 1 to 3 are shown in Table 2.

[0070] Table 2. Interfacial tension between crude oil and different formulations of drag-reducing and injection-enhancing agents and oil displacement agents, and viscosity of different oil displacement agents.

[0071]

[0072] 3. Evaluation of the oil displacement effect of oil displacement methods

[0073] The oil displacement efficiency, injection pressure, and other relevant data of the oil displacement methods provided in Examples 1 to 4 and Comparative Examples 1 to 2 in the core oil displacement simulation experiment are shown in Table 3.

[0074] Table 3. Evaluation of the oil displacement effect of oil displacement methods

[0075]

[0076] Based on the above data, it can be seen that the oil displacement method provided in this application organically combines drag-reducing and injection-enhancing agents with oil displacement agents, producing a synergistic effect. This effectively reduces injection pressure and significantly improves oil displacement efficiency, overcoming the "injectable but unrecoverable" problem faced by low-permeability reservoirs in enhancing oil recovery. In application, using the oil displacement method provided in this application, combined with alternating injection of drag-reducing and injection-enhancing agents, has greater potential to improve oil displacement efficiency. The injection volume and timing of each sluice block can be adjusted according to the actual reservoir conditions.

[0077] While the present invention has been described with reference to specific embodiments, those skilled in the art will understand that various changes can be made without departing from the true spirit and scope of the invention. Furthermore, numerous modifications can be made to the subject, spirit, and scope of the invention to suit specific situations, materials, material compositions, and methods. All such modifications are included within the scope of the claims of the present invention.

Claims

1. An oil displacement method, comprising the following steps: 1) Inject drag-reducing and injection-enhancing agents to modify the rock surface into a hydrophobic and oleophobic state, thereby reducing the injection pressure; 2) Inject oil displacement agents to displace residual and remaining oil in the deeper parts of the reservoir; The injection concentration of the drag-reducing and enhancing agent is 0.13% to 0.55%; The injection concentration of the oil displacement agent is 0.05% to 0.35%; The drag-reducing and injection-enhancing agent includes a main agent, an auxiliary agent, and an adjuvant. The drag-reducing and injection-enhancing agent is 100% by mass, comprising 0.1% to 0.35% main agent, 0.02% to 0.1% excipient, 0.01% to 0.1% auxiliary agent, and the balance being water; In the drag-reducing and injection-enhancing agent, the main component is a semi-siloxane organic compound; The excipient is an inorganic nano-oxide material; The additives are silane-based organic compounds; The oil displacement agent is an aqueous solution of a surfactant; The surfactant is an alkyl sulfonate and / or an alkylbenzene sulfonate.

2. The oil displacement method according to claim 1, characterized in that, The main agent is one of cage-type hexahedral semisiloxane, cage-type octahedral semisiloxane, and cage-type dodecahedral semisiloxane.

3. The oil displacement method according to claim 1, characterized in that, The excipient is at least one of nano-silica, nano-alumina, and nano-ferric oxide.

4. The oil displacement method according to claim 1, characterized in that, The excipient has a particle size of 20 to 40 nm, with a median particle size of 29 to 31 nm.

5. The oil displacement method according to claim 1, characterized in that, The auxiliary agent is at least one of dimethyldichlorosilane, propyltrimethylsilane, and vinyltrimethoxysilane.

6. The oil displacement method according to claim 1, characterized in that, The alkyl sulfonate is dodecyl sulfonate; the alkyl benzene sulfonate is tetradecyl benzene sulfonate.

7. The oil displacement method according to any one of claims 1 to 6, characterized in that, The interfacial tension between the drag-reducing and injection-enhancing agent and crude oil, and the interfacial tension between the oil displacement agent and crude oil, are each independently no higher than 10. -2 mN / m.

8. The oil displacement method according to any one of claims 1 to 6, characterized in that, The viscosity of the oil displacement agent is not higher than 3 mPa•s.

9. The application of the oil displacement method according to any one of claims 1 to 8 in reservoir oil displacement.

10. The application according to claim 9, characterized in that, The application is the use of the oil displacement method in low-permeability reservoirs.

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