The Research On Adaptiveness And Effect Evaluation Of Cyclic Steam Stimulation Method In Dong Xin Oilfield

The heavy oil reservoir in Dong xin oilfield has the flowing characteristics including deep burial depth, thin reservoir bed, huge oil viscosity, being loose and easy to product sand, water sensitive, and comprehensive water-oil relationship which make it hard for the normal production method. The cyclic steam injection method is recommended by generalizing the experience of other similar reservoirs. Ying 27 block is chosen as a pilot zone on the basis of the zone choosing criterion of cyclic steam injection method and the reservoir & fluid conditions of Dong xin heavy oil resource. Sensitivity analysis of the following parameters including cyclic steam injection amount, injection pressure, shutting duration, thickness, well distance, injection intensity and liquid production amount are made and optimization of steam injection parameters is carried using multi-index optimization method. .The optimum results are as follows: the net thickness should be more then 12 meters, the well distance is 200 meters, injection intensity is more or less of 140 tons per meter, liquid production amount is 30 tons per day. Combing the reservoir feature and technique level, four assisting techniques such as steam injection technique, wellbore lifting technique, sand control technique and wellbore viscosity decreasing are designed. The effect and benefit evaluation models evolving single well accumulation oil production limit, single well accumulation oil-gas limit and etc. are built to rate the cyclic steam injection effect in Ying 27 block. The prediction results are as follows: on the basis of the optimum steam injection parameters and reasonable steam injection finishing condition, single oil well can product 10 cycles averagely which can product oil 2.93×104t in total, and the average daily production is 15.23t, while accumulation gas-oil rate limit is 1.56 while oil recovery can reach 45.9%; the oil company can withdraw all invested capital in the second cycle (13382t of accumulation oil, 5.31 of accumulation gas-oil rate, 20.03 t of daily oil production), meanwhile it can receive excellent benefit in other steam cycles and all the gas-oil rates in every steam cycles are much higher than 0.19 which is the cyclic gas-oil rate limit. This research of cyclic steam injection in Ying 27 block has a guide meaning to economically develop Dong xin heavy oil resource and fulfill the target of steady and increasing production, also, it will play a reference role to other similar heavy oil reservoirs.