A system preparation method for starting remaining oil in low-permeability layers in high-permeability reservoirs

Abstract

The invention discloses a method for preparing a system for starting low permeability layer remaining oil in a high permeability oil reservoir. The method includes the following steps: determining anoil reservoir parameter of an oil reservoir, and determining ranges of the apparent viscosity and the residual resistance factor of a polymer solution according to the permeability; selecting a polyacrylamide polymer; selecting a hydrophobic associated polymer; acquiring viscosity-concentration relation curves of the polyacrylamide polymer and the hydrophobic associated polymer respectively, and determining the weights of the two polymers; accurately weighing and taking a certain amount of dry powder of the two polymers, and evenly mixing the dry powder of the two polymers for use; weighing saline water for preparing the polymer solution, and using a mechanical stirring device to stir the saline water to from vortexes at a rotation speed of 400 rpm, slowly pouring the dry powder of the polymers into the saline water, decreasing the rotation speed to 200 rpm and continuously stirring the solution till the dry powder is completely dissolved, and acquiring a polymer system. The method canenhance the adaptability of the polymer solution in the oil reservoir.

Description

technical field [0001] The invention belongs to the technical field of petroleum processing, and relates to a system preparation method for starting residual oil in a low-permeability layer in a high-permeability oil reservoir. Background technique [0002] As an improved water flooding technology, polymer is usually used in the further enhanced oil recovery technology after water flooding reservoirs with high water cut. Most of the targeted reservoirs are complex reservoir conditions with high permeability, severe heterogeneity, and high water cut, which have a huge impact on the mobility control of the polymer solution in the subsequent flooding process. As for the research and development and synthesis of polymers in the oil field at this stage, the main polymers are polyacrylamide and hydrophobic association polymers. [0003] For linear polyacrylamide, it has obvious pseudoplastic characteristics, and the viscosity of the solution decreases with the increase of shear r...

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Problems solved by technology

However, the viscosification of the entire polymer solution is also enhanced by the association, which brings serious difficulties to the injectability; the injected polymer is often affected by the viscosity in the near-wellbore zone to establish a high flow resistance, and the seepage velocity decreases. Promote the adsorption and retention of polymers in the near-wellbore area, further increase the injection pressure, and the adsorption and retention of polymers will lead to a decrease in the performance of the solution, making it difficult to enter deep reservoirs for profile control

[0007] Therefore, for the reservoir conditions that need to further improve the remaining oil recovery of medium and low permeability, it is difficult to meet the reservoir conditions whether it is commonly used polyacrylamine and hydrophobic association polymers (including branched polymers, etc.) The demand for it, and then improve the start-up of low-permeability remaining oil in the reservoir: on the one hand, polyacrylamide, after being sheared, the solution performance in porous media is weakened, and it is difficult to form an effective residual resistance coefficient; on the other hand It is a hydrophobic association polymer. The strong solution performance brings serious injection problems. It is easy to stay and block near the wellbore, and it is difficult to reach the deep part of the formation and the place where profile control is required.

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