Advances in Polymer Flooding and Alkaline/Surfactant/Polymer Processes as Developed and Applied in the People's Republic of China

Abstract

Paper includes discussion and reply published in May 2006 JPT. Distinguished Author Series articles are general, descriptive representations that summarize the state of the art in an area of technology by describing recent developments for readers who are not specialists in the topics discussed. Written by individuals recognized as experts in the area, these articles provide key references to more definitive work and present specific details only to illustrate the technology. Purpose: to inform the general readership of recent advances in various areas of petroleum engineering. Abstract Polymer flooding (PF) and alkaline/surfactant/polymer (ASP) flooding have been applied throughout the world for more than 20 years. However, few large-scale successes with these processes have been reported, except in China. To date, the PF process has been applied successfully in several major Chinese oil fields such as Daqing and Shengli. PF alone contributed approximately 250,000 BOPD of production in 2004 from these two fields. Incremental oil recoveries of up to 14% of the original oil in place (OOIP) have been obtained in good-quality reservoirs. Profile modifications by use of polymers and a crosslinker to form colloidal-dispersion gels (CDGs) also have been implemented successfully in large-scale production operations in China. Results show that the CDG process is more cost-effective than the PF process. Several ASP floods also have been pilot tested in various Chinese oil fields. Incremental recoveries of up to 25% OOIP have been reported, although commercial-scale applications have not been implemented. Plans to implement three large-scale projects have been made for 2006 in the Daqing oil field. This paper discusses the progress made in these processes in China over the last 20 years, including field results, new concepts, and economics. Introduction The PF concept in the U.S. has been to use a small slug at low polymer concentrations. The amount of polymer used is measured with a combination unit calculated by multiplying the concentration in parts per million (ppm) by the slug size in pore volume (Vp). The 1976 U.S. Natl. Petroleum Council (NPC) study used 125 ppm·Vp. The amount of polymer used in the 1984 NPC study was increased to 240 ppm·Vp, but it was still much less than that used in China. NPC projected incremental recoveries were in the range of 6 to 8% OOIP in successful projects, approximately 50% of that obtained in good-quality reservoirs in the Daqing oil field. Seven PF pilot tests were conducted in the Daqing oil field from 1972 through 1998. Continued research and field testing led to fieldwide expansion in 1996. There were 31 commercial-scale PF projects in Daqing in 2004, with 2,427 injection wells and 2,916 production wells. Currently, PF is implemented in a total area of 67,759 acres, as shown in Fig. 1. Oil production from PF has been maintained since 1999. The production reached 73.5 million bbl in 2004, approximately 23% of the total field production.