High permeability reservoir oil displacement system and oil displacement method

Abstract

The invention provides a high permeability reservoir oil displacement system. The system comprises an association polymer. The association polymer has molecular weight of 1.987 to 40.215 million. The association polymer is prepared from acrylamide, 0.11%-9.96% by mole of a hydrophobic monomer and 0-14.79% by mole of a functional monomer through polymerization. The oil displacement system has an association polymer concentration of 400-3500 mg/L. Compared with the existing oil displacement system, the high permeability reservoir oil displacement system utilizes the association polymer obtained by introducing a small amount of the hydrophobic monomer and functional monomer to the polymer molecular chain, and the hydrophobic groups are associated in an aqueous solution to form a space network structure so that system viscosity is improved and a real high-resistance coefficient and a high residual resistance coefficient are built. Through use of the functional monomer and the space network structure, the system has good temperature, salt and shear resistance and aging stability, improves oil-water mobility of high permeability reservoir, improves injection water wave and efficiency and well improves high permeability reservoir recovery efficiency.

Description

technical field [0001] The invention belongs to the technical field of petroleum exploitation, and in particular relates to an oil displacement system and an oil displacement method for high permeability reservoirs. Background technique [0002] For high-permeability (permeability ≥ 500mD) reservoirs, due to the large size of pore throats and fractures in the reservoir, and the large difference in viscosity between oil and water, long-term water flooding development will gradually form high-permeability channels or large pores in the reservoir, making the formation pressure field, The streamline field forms a fixed position, and the dominant channel of water flow is formed between the oil and water wells, resulting in a rapid rise in water flooding water content, low recovery, and difficulty in increasing the swept volume of water flooding. It is difficult to greatly increase the oil recovery of the reservoir by relying on conventional water injection technology; The above c...

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Problems solved by technology

Natural polymers are limited by seasons and regions and have high cost, relatively poor thermal and biological stability, and are prone to degradation, so their application in high-temperature and high-salt reservoirs is limited; the most widely used synthetic polymers are polymers. Although acrylamide can increase the viscosity of aqueous solution to a certain extent, it is easy to mechanically degrade the long chain of molecules due to strong shear during construction; it is easily affected by the formation environment (temperature, salinity, etc.), and there are the following problems : 1) When applied under the condition of high temperature and high salinity, the hydrolysis of polyacrylamide is serious when the temperature is high; 2) when the formation temperature exceeds 75°C, as the formation temperature rises, the formation of hydrolyzed polyacrylamide precipitation accelerates; 3 ) High temperature and high salt can easily cause hydrolyzed polyacrylamide to precipitate from the aqueous solution, and the higher the degree of hydrolysis, the more significant this phenomenon is; 4) The viscosity of the solution is very sensitive to temperature and salinity, and the retained viscosity of the solution is very high in a high temperature and high salt environment. Low

In view of the above problems, ordinary polyacrylamide can only adjust the molecular weight and hydrolysis degree and the adjustment range is limited, and it is difficult to further overcome it on the basis of its existing molecular structure. Therefore, it cannot meet the high-efficiency development needs of high-permeability oil fields.

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