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Oil displacement system and method for low permeability reservoir

A technology of oil displacement and system, which is applied in the field of oil displacement system of low permeability reservoirs, can solve the problems of residue clogging formation, poor viscoelasticity, application limitations, etc., and achieve the effects of cost saving, high viscosity and elasticity

Active Publication Date: 2017-06-20
SICHUAN GUANGYA POLYMER CHEM
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Problems solved by technology

The molecular weight of natural polymers is not easy to control, and after decomposition, it is easy to generate a large number of residues to block the formation, which is not suitable for the use of low-permeability reservoirs, and it is subject to seasonal and regional restrictions and high cost. The thermal stability and biological stability are relatively poor, and it is easy to occur Therefore, its application in high-temperature and high-salt oil reservoirs is limited; polyacrylamide, as a mature synthetic polymer, can increase the viscosity of aqueous solution to a certain extent, but it is easy to be damaged due to the strong shearing action of blast holes during construction. Break the long molecular chain, resulting in the irreversible loss of the viscosity of the displacement fluid; it is easily affected by the formation environment (temperature, salinity), and there are the following problems: 1) When it is applied under the condition of high temperature and high salinity, when the temperature is high The hydrolysis of polyacrylamide is severe; 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 hydrolyze 4) The viscosity of the solution is very sensitive to temperature and salinity, and the retention viscosity of the solution is very low in a high-temperature and high-salt environment
Therefore, the application of polyacrylamide in slightly harsh reservoir conditions is greatly limited
The important thing is that in low-permeability reservoirs, the molecular weight of the polymer should not be too high. Polyacrylamide can reduce the molecular weight to match the low-permeability formation relatively easily. The cost is bound to increase, and if high molecular weight polymer is used for oil flooding, the molecular coil size may be larger than the pore throat size of low-permeability reservoirs, which is easy to block the formation and cause injection difficulties; and because the adjustable parameters for determining the molecular coil size are relatively simple , poor matching with the pore throats of low-permeability reservoirs, and the established resistance coefficient and residual resistance coefficient are small, which cannot effectively expand the swept volume and seal the dominant channel of water flooding
When adding surfactants and alkalis to prepare binary (ternary) systems, the viscosity and viscoelasticity of most surfactants and alkalis will be reduced to varying degrees (negative synergistic effect); and at low concentrations and low viscosities Weak structure, poor viscoelasticity, reduced mobility control ability
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 based on its existing molecular structure. Therefore, it cannot meet the high-efficiency development needs of low-permeability oil fields.

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[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

[0020] The invention provides an oil displacement system for low-permeability oil reservoirs, including an association polymer; the molecular weight of the association polymer is 1.014 to 9.975 million; in molar percentage, the association polymer is composed of acrylamide , 0.09% to 10.2% of hydrophobic monomers and 0 to 15.4% of functional monomers are polymerized; the concentration of the associated polymer in the oil displacement system is 200 to 3500 mg / L; the hydrophobic...

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Abstract

The invention provides an oil displacement system for a low permeability reservoir. The oil displacement system comprises an associative polymer having molecular weight of 1014000 to 9975000. The associative polymer comprises, by mole, acrylamide, 0.09-10.2% of a hydrophobic monomer and 0-15.4% of a functional monomer. In the oil displacement system, a concentration of the associative polymer is in a range of 200 to 3500 mg / L. Compared with the prior art, a small amount of the hydrophobic monomer and functional monomer are introduced into the polymer molecular chain so that the associative polymer is obtained and the hydrophobic groups are combined into a space network structure in the aqueous solution so that the viscosity of the system is greatly improved, a high resistance coefficient is built and a high residual resistance coefficient is built. Through introduction of the functional monomer into the space network structure, the system has good resistance to a temperature, a salt and shearing and good aging stability, improves an oil-water mobility ratio of low permeability reservoir, improves injection water wave and efficiency and improves the recovery of low permeability 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 low-permeability reservoirs. Background technique [0002] With the development of petroleum exploration and development, the proportion of low-permeability oilfields in newly proven reserves is increasing. Low-permeability oil reservoirs account for more than half of the oil and gas fields discovered in my country, and their production capacity construction accounts for more than 70% of the total. Low-permeability oil and gas fields have become the main battlefield for oil and gas development and construction. Due to the small size of pore throats and fractures in low-permeability reservoirs, prominent capillary phenomenon, and high resistance to oil and gas flow, it is difficult to develop and low recovery. Therefore, how to better develop them is an inevitable trend of current research. ....

Claims

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Application Information

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IPC IPC(8): C09K8/588C09K8/584E21B43/22
CPCC09K8/584C09K8/588E21B43/16
Inventor 郭拥军张新民胡俊曹苗刘洋
Owner SICHUAN GUANGYA POLYMER CHEM
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