Technologies for Reusing Resources in Abandoned Oilfield after Tertiary Oil Recovery

In traditional views, oilfield is abandoned after water flooding and chemical flooding. But the recovery is only 50%~60%，that is to say, more than 40% of the resource is still left underground. Therefore, how to utilize this part of resource economically and effectively is a key problem to be tackled. Based on the lab experiments and theoretical researches on viscosity-temperature relationship, displacement and relative permeability under high temperature, the mechanism of enhancing oil recovery through steam flooding in super-high water cut stage of water injection oilfield was analyzed. The experimental results showed that steam flooding in 200°C after polymer flooding could increase oil displacement efficiency by 14.5%. Water flooding and polymer flooding had been implemented in Sabei development area of Daqing Oilfield since it was brought into development in 1963. The recovery had reached above 70% and the water cut had exceeded 98%. There was no economic benefit to develop continually, the oilfield faced abandonment. Steam flooding test was carried out to enhance oil recovery on this basis. According to the geological characteristics and development status, special technical measures were taken based on the lab experiments and numerical simulation including high-pressure steam injection to improve heat utilization, forced fluid withdrawal to increase production rate, insulated tubing and nitrogen insulation to keep the bottom hole steam dry, and tracking analysis to adjust injection-production parameters duly. The ultimate recovery reached 81.6％ which increased 10.7% on the original basis, the field test was successful technically. Steam flooding is characterized with quick effect, high production rate and high producing degree of residual oil. This successful technology provides a direction for secondary development after polymer flooding in water flooding oilfield.