Techniques of Reinjecting 100% of Produced Water in Daqing Oil Field

Abstract In the history of over 40 years of development, Daqing Oilfield has witnessed three phases of development: basic well pattern, infill well pattern, and tertiary oil recovery. To cope with that, three sets of systems including general produced water re-injection, produced water fine treatment re-injection, and polymer flooding produced water re-injection have been set up catering to the varied requirements in injection water quality of different well patterns. Among them, general water re-injection system feeds the basic well pattern and primary infill well pattern; fine treatment water re-injection system serves secondary and tertiary infill well pattern as well as marginal low-permeability oilfields; and polymer water reinjection system is dedicated mainly to polymer flooding blocks. Aiming to satisfy the requirements of the oily produced water treatment and oilfield water re-injection development, and based on the specifications of the original produced liquid and output water, Daqing Oilfield water treatment system is divided into four subsystems, they are: general produced water treatment, produced water fine treatment, polymer flooding produced water treatment, and clear fresh water treatment. Original liquid to the produced water treatment subsystem comes from water flooding and dehydration stations, part of the treated water is re-injected to the basic well pattern and the primary infill well pattern, the remaining portion goes through fine treatment before being re-injected into the secondary and the tertiary infill well patterns. Original produced liquid to the polymer flooding produced water treatment subsystem originates from polymer flooding and dehydration stations, and all of which is re-injected to the basic well pattern and the primary infill well patterns after being treated. As for the marginal low permeability oilfields, due to their low permeability, the original liquid coming from dehydration stations is treated straight in the fine treatment station before being totally re-injected, in locations where the produced water quantity can not satisfy the injection demand, underground water and surface water will be treated to reach quality required by the low permeability reservoir injection process. The key process of the water re-injection technology is to treat the produced liquid into standards required by reinjection. This thesis is to introduce the produced water treatment technologies used in Daqing.