关键词: 脱硫抑硫, 原位保留, 湮灭羟基, 低剪切工艺, 聚合物溶液黏度

Abstract: Chemical flooding has been implemented over twenty years in Shengli oilfield. Because of long time development, from 2016 to 2020, the reservoir conditions have become increasingly harsher, and the composition of the produced water has been becoming more complex, resulting in the viscosity of the injected polymer solution prepared by mother liquor mixed with freshwater and diluted by produced water has been decreasing year by year, which severely affects the effect of development by chemical flooding. To further enhance the organic integration of chemical flooding and green development, this paper systematically analyzes the causes for viscosity decrease throughout the preparation and injection of polymer solution, and the following four low and zero-shear key techniques has been developed for polymer solution through tackling key problems:(1) The biological competition inhibition technique is established to ensure the viscosity of polymer solution, in order to achieve microbial desulfurization and sulfur inhibition by use of probiotics and inhibit the generation of Fe²⁺, which creates a precedent for its large-scale application in the field of chemical flooding. (2) The technique of immediate annihilation of hydroxyl radical via in-situ reservation of polyacrylamide is invented, and a new synthetic treating agent is developed based on DLVO theory of collochemistry, in order to reduce the generation of oil-containing sludge layer that may breeds sulfate-reducing bacteria at its source. (3) The optimization method for the curing parameters of polymer solution is built, and the integrated low-shear device and process is developed for the preparation of mother liquor as well as the mixing and dilution of produced water to form the polymer solution. (4) The simulation method for the structure of large pressure difference and low-shear throttling control unit is established, and a testable and adjustable injection process of the integrated string is also developed. These low and zero shear key techniques of polymer solution have been applied to the chemical flooding project in Shengli oilfield, thus achieving the transformation from the preparation of mother liquid with freshwater to that of produced water, and saving freshwater resources. Moreover, these techniques have achieved the transformation from formaldehyde sterilization to microbial desulfurization and sulfur inhibition by probiotics, which can eliminate occupational health hazards.

Key words: desulfurization and sulfur inhibition, in-situ reservation, annihilation hydroxyl, low shear process, viscosity of polymer solution