Bohai Bay is one of the most important offshore oil production areas in China, and 74% of oil is heavy oil. For conventional heavy oil reservoirs, water flooding is applied normally with an inverted 9-spot flood pattern. The recovery is about 18~20% because of the heterogeneous and unconsolidated reservoirs. The current strategy for application of polymer flooding to enhance heavy oil recovery is based on the fully understanding of mechanisms and core technologies of polymer flooding in the laboratory research and field practice.

Single well pilot test and 5-spot flood pattern pilot test have been conducted in Bohai oilfield. The significant increase of oil production and reduction of water cut were observed. The limited life span of offshore platforms challenges operators to more effectively develop oil, thus it is necessary to identify the appropriate enhanced oil recovery (EOR) technology for use in a reservoir. Therefore, polymer flooding in early stage of oilfield development has been designed and conducted in Bohai oilfield. Five key technologies of polymer flooding concluded from the field practices were critical to the success of an EOR project and discussed in this paper. (1) Characteristics of polymer: polymer should tolerate high salinity and hardness of make-up brine. (2) Polymer injection technology: the technology should satisfy the requirement of offshore platform. (3) Modification of Polymer displacement under the big well spacing and multi-layer reservoir conditions. (4) Evaluation technology of polymer flooding in the early stage of oilfield development. (5) Production treatment technology of polymer flooding. This paper will focus on the impact of the five key technologies on development of offshore oilfields through introducing polymer flooding in Bohai Bay.

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