Study On Treatment Technology Of Workover Wastewater Reinjection

At present,most of China’s oil fields have entered the later stage of development,and the waterflood development mode is mainly used to maintain the formation pressure and improve the recovery rate.Henan oilfield has fully entered the later stage of development,and the workover capacity has increased accordingly,resulting in a large amount of workover sewage.Workover sewage contains water-soluble polymer and petroleum pollutants which are difficult to degrade,and the pollution sources are widely distributed,various and with multiple one-time emissions.If left untreated,it will cause both environmental pollution and waste of water resources.In order to solve this problem,the best method is reinjection of workover wastewater.However,the reinjection formation of workover wastewater must conform to the water quality standard of recommended water quality index and analysis method of detrital rock reservoir and ensure that the treatment water of workover wastewater reaches the standard before reinjection.The compatibility of treated water and permeability damage rate of core are also evaluated to ensure the scientific and feasibility of reinjection of workover wastewater treatment water.This paper first collects and analyzes the basic data through literature research and field research.Master the research status and development trend of the reinjection stratum technology of workover sewage at home and abroad,investigate the actual situation of sewage treatment technology on site,find the problems existing in the sewage treatment system,and optimize the dosing scheme:choose compound p H regulator,add proportion Na OH:Ca O is 4:1,adjust p H value around 7.5.The oxidant is potassium dichromate,and the dosage is controlled above 60mg·L^-1.The flocculant was polyaluminum chloride PAC,and the p H value was controlled in the range of 7-8,and the optimal dosage was 20mg·L^-1.The coagulant was polyacrylamide PAM,and the optimal dosage was 4mg·L^-1.Improved and optimized the sewage treatment process:p H adjustment,oxidation,sedimentation separation,flocculation and reverse osmosis membrane filtration treatment.Secondly,the water quality of workover sewage treatment water is evaluated and analyzed,and all indexes meet the standard requirements of recommended water quality indexes and analysis methods for detrital rock reservoir injection water,ensuring that the water quality of workover sewage treatment water meets the water quality requirements of reinjection formation.Finally,the compatibility of workover wastewater after treatment is studied,and the turbidity analysis method,scale ion and scale quality analysis method are used to illustrate that each workover wastewater treatment sample has good compatibility with formation water and back water injection.At the same time,the core displacement experiment was carried out on the treated workover sewage,and the damage rate of core permeability was all below 20%.According to the criteria,no damage to the permeability of the reservoir could be determined.The feasibility of reinjection formation of workover wastewater treatment is verified.Finally,it is scientific and feasible to get the reinjection strata of water from well repairing wastewater treatment in henan oilfield.It not only reduces the environmental pollution,but also realizes the recycling utilization of water resources,promotes the development of the formation technology of water reinjection for the well repairing wastewater treatment in henan oilfield,and provides reference for the construction of the sewage treatment system in the western oil region,which has far-reaching significance for the high-quality and green development of henan oilfield.