A kind of oil displacement system and oil displacement method for heterogeneous oil reservoir

Abstract

The invention provides an oil displacement system for a heterogeneous oil reservoir. The oil displacement system comprises association polymer, molecular weight of the association polymer is 1.036-40.215 million, the association polymer is obtained by polymerizing, by molar percent, acrylamide, 0.11-9.96% of hydrophobic monomer and 0-15.4% of functional monomer, and concentration of the association polymer in the oil displacement system is 400-3500mg / L. compared with the prior art, the oil displacement system has the advantages that the association polymer obtained by introducing a small amount of the hydrophobic monomer and the functional monomer on molecule main chain of polymer is adopted, and hydrophobic groups are mutually associated in a water solution to form a spatial network structure, so that viscosity of the system is improved, high resistivity coefficient and high residual resistance coefficient are established, permeability of relatively-high-permeation areas is lowered effectively, and the oil displacement system has good profile control effect; due to introduction of the functional monomer and the spatial network structure, the system has good temperature-resistant, salt-resistant, shearing-resistant and aging-resistant stability and has better effects on improving oil-water mobility ratio and injection water wave and efficiency of the heterogeneous oil reservoir, thereby better improving recovery ratio of the heterogeneous oil reservoir.

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 heterogeneous oil reservoirs. Background technique [0002] With the sharp increase in energy demand, the proportion of heterogeneous reservoirs is increasing, which has attracted great attention from domestic and foreign scholars and oil companies. Reservoir heterogeneity refers to the inhomogeneous changes in spatial distribution and internal reservoir physical properties of reservoirs under the influence of environment and force, which has a significant impact on seepage and recovery of oil and gas reservoirs. Reservoir heterogeneity is mainly divided into plane heterogeneity, intra-layer heterogeneity and inter-layer heterogeneity. On the plane, the injected water is fingered along the high-permeability zone during water injection development, resulting in a high degree of water washing i...

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Problems solved by technology

[0004] In the practical application of polymer flooding, for heterogeneous reservoirs, natural polymers are subject to seasonal and regional restrictions and high cost, relatively poor thermal stability and biological stability, and are prone to degradation. Therefore, in high-temperature and high-salt oil The application in Tibet is limited; although polyacrylamide, the most widely used synthetic polymer, 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; Affected by the formation environment (temperature, salinity, etc.), there are the following problems: 1) When it is 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 precipitation of hydrolyzed polyacrylamide accelerates; 3) High temperature and high salt 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 effect of solution viscosity on temperature and Salinity is very sensitive, and the retention viscosity of the solution is very low in high temperature and high salt environment

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

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