Abstract:

China has approximately 700 million tons of extra-heavy crude with a viscosity higher than 50 000 mPa·s in reservoirs thinner than 6 meters.Though low-grade, the reserves are of strategic significance.The extra-heavy crude reservoirs respond badly to conventional steam injection thermal recovery methods due to fast heat dissipation and low heat utilization efficiency.More suitable recovery technologies are badly needed to deal with the problem.After years of research and practice, hybrid thermal chemical recovery technologies were developed together with viscosity reducers tailor-made for super heavy oil.Recovery mechanisms of "viscocity reduction by steam and chemicals, formation energy enhancement and insulation by nitrogen, and swept efficiency improvement by chemicals" during the recovery processes were explored and expounded.Other achievements include the independently-developed thermal chemical numerical simulation software, optimization chart for injection and production parameters, open hole completion technologies and sand prevention tools with screen pipes for horizontal wells, integrated processes of injection and production with horizontal pump during thermal recovery, residual heat gradient utilization and of produced water recycling.The Chunfeng extra-heavy oilfield established in the Junggar Basin of Xinjiang now has an annual productivity of more than one million tons of crude and has annually produced more than 100×10⁴ tons for five years in a row.The newly developed technologies for extra-heavy oil extraction can be applied to enhance oil utilization and recovery of brown oilfields, thus of great significance to ensuring a stable or even high domestic oil production.

Key words: hybrid thermal chemical recovery, thermal recovery technology in horizontal well, enhanced oil recovery, thin-bedded reservoir, extra-heavy oil, oilfield production