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A composite flooding system for low-permeability oil reservoir and its preparation and application methods

A compound flooding, low-permeability technology, which is applied in the field of compound flooding technology and chemistry in oilfields, can solve the problems of poor injectability and selectivity of water swelling, limiting oil displacement effect of oil displacement agent, and oil displacement agent fingering into oil wells, etc. , to improve the sweeping ability and oil washing ability, strengthen the fluidity control ability, and facilitate on-site construction.

Active Publication Date: 2022-08-05
PETROCHINA CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, in polymer and polymer-based composite flooding systems, the polymer is greatly affected by the shear of the injection equipment, the shear of the porous medium of the formation, and the physical and chemical properties of the formation, resulting in a significant decrease in the viscosity of the polymer and a weakened mobility control ability.
Especially in the subsequent water flooding stage, the injection pressure drops rapidly, and the oil displacement agent is prone to fingering into the oil well, which greatly limits the oil displacement effect of the oil displacement agent, reduces the use value of the oil displacement agent, and is difficult to obtain long-term effective Development effect
The injectability and selectivity of water swelling are poor; the formation adaptability of polymer microspheres is poor, the cost is high, and the monomer acrylamide is used as the raw material for preparation, which has high toxicity and poor environmental protection
Foam control and displacement systems have been widely used in oilfields, but for low-permeability reservoirs, how to solve their injectivity and long-term effectiveness is the technical bottleneck for their popularization and application in low-permeability reservoirs

Method used

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  • A composite flooding system for low-permeability oil reservoir and its preparation and application methods
  • A composite flooding system for low-permeability oil reservoir and its preparation and application methods

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Experimental program
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Embodiment 1

[0032] In order to solve the problem of the application of the above-mentioned adjusting and flooding agent in low-permeability oil reservoirs, and fully consider improving the oil-washing efficiency and sweeping volume of the oil-displacing agent to achieve improved crude oil recovery, the present invention provides a compound for low-permeability oil reservoirs. The oil displacement system is composed of the following components by mass percentage:

[0033] Nanographite 0.05%~0.35%;

[0034] Dispersant 0.05%~0.15%;

[0035] Zwitterionic surfactant 0.15%~0.35%;

[0036] The remainder is water.

[0037] The composite flooding system is a water-based dispersed, environmentally friendly, non-toxic, long-term stability, soft texture, can effectively reduce the oil-water interfacial tension, and has self-lubricating properties of modified nano-graphite emulsion heterogeneous flooding system. The system can not only improve the oil-washing efficiency of the oil-displacing agent,...

Embodiment 2

[0039] On the basis of Example 1, further, the initial particle size of the nanographite particles is 20 nm to 60 nm.

[0040] Further, the dispersing agent is one of sodium methylene bis-naphthalene sulfonate, sodium methylene bis-methyl naphthalene sulfonate, sodium benzyl naphthalene sulfonate, polycarboxylate Tersperse 2500 or a mixture thereof. The dispersant is preferably sodium methylene bisnaphthalene sulfonate, which has the structure shown in formula (1); the suspension stability of the graphite nanoparticles can be improved by adding a dispersant:

[0041]

[0042] Further, the zwitterionic surfactant is one of erucamidopropyl betaine, oleic acid amidopropyl betaine, cocamidopropyl betaine, and sulfopropyl betaine. The zwitterionic surfactant is preferably sulfopropyl betaine, which has the structure shown in formula (2):

[0043]

[0044] In the formula, R is an alkyl group having 7 to 17 carbon atoms, preferably 13. By adding zwitterionic surfactant, the a...

Embodiment 3

[0046] Further, the preparation method of the composite flooding system for low-permeability oil reservoirs includes the following steps:

[0047] At room temperature (20±5℃), firstly add nano-graphite particles to the solution water, stir for 10 minutes with ultrasonic to disperse uniformly; then add dispersant, stir for 20 minutes with ultrasonic to fully disperse, and finally add zwitterionic surface active agent, stirring for 5 minutes, thereby obtaining a modified nano-graphite heterogeneous composite oil flooding system for low-permeability oil reservoirs.

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Abstract

The invention provides a composite oil displacement system for low-permeability oil reservoirs and a preparation and application method thereof. The system consists of the following components by mass percentage: 0.05%-0.35% of nano-graphite; 0.05%-0.15% of dispersant ; Zwitterionic surfactant 0.15% to 0.35%; the balance is water. The system has the ability to significantly reduce the oil-water interfacial tension and improve the oil washing efficiency. The particle aggregation effect of the modified nano-graphite emulsion can realize the dual functions of deep formation regulation and expansion of the swept volume. Injection into the oil layer by means of staged plug injection can maximize the oil displacement effect of the heterogeneous composite flooding system.

Description

technical field [0001] The invention belongs to the technical chemistry field of oilfield composite flooding, and particularly relates to a composite flooding system for low-permeability oil reservoirs and a preparation and application method thereof. technical background [0002] Low-permeability oil reservoirs are widely distributed in China. The newly discovered low-permeability oil and gas fields account for more than half of the newly discovered oil and gas reservoirs, while the average recovery factor is only 21.6%. Therefore, studying how to improve the recovery factor is the key to exploiting low-permeability oil and gas fields. In view of the generally poor physical properties of low-permeability oilfields, the development of natural or artificial fractures, the low water absorption capacity of water injection wells, the poor water injection effect, and the low natural productivity, conventional oil displacement measures cannot meet the needs of low-permeability rese...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C09K8/584C09K8/504C09K8/506E21B43/22
CPCC09K8/584C09K8/5045C09K8/506E21B43/16C09K2208/18
Inventor 曹荣荣郑力军杨海恩何治武吴天江张荣易萍任建科朱家杰张涛
Owner PETROCHINA CO LTD