稠油油田空气辅助蒸汽驱现场试验

Field test on air-assisted steam flooding of heavy oil field

为考察稠油油田空气辅助蒸汽驱的开采效果,开展了稠油油田空气辅助蒸汽驱现场试验研究工作。在齐40块蒸汽驱试验区选择原油濒临枯竭的、油藏已经发生严重蒸汽窜流和超覆的、亟待改变开发方式的5个井组进行现场试验,结果表明:5个试验井组平均单井组日产油由14.8 t/d升至16.1 t/d,油汽比由0.14升至0.17;油层纵向动用程度明显提高,分析认为是注入的空气在纵向和平面上首先向蒸汽驱优势方向波及,与残余原油发生低温氧化反应使孔隙中沥青质沉积增加,降低油层渗透率,迫使蒸汽转向,扩大蒸汽波及范围。研究认为:空气辅助蒸汽驱宜采用连续式空气/蒸汽注入方式;汽气比接近1∶40可取得较高采收率;70 m井距注入的空气与地下原油发生低温氧化反应,油藏温度有所提高,产出氧气含量可降到安全范围内。现场试验取得成功,利用空气辅助蒸汽驱改善稠油油田蒸汽驱开发效果具有可行性。所选试验井组存在的问题在普通稠油蒸汽驱井组生产后期具有普遍性,因此本文试验方法和相关技术参数可为类似井组开展空气辅助蒸汽驱试验提供参考。

Field test and research was carried out on air-assisted steam flooding of heavy oil field to investigate its production effects. Five well groups whose development mode was in urgent need to be transformed due to the depleting crude oil and the serious steam channeling and overlapping in oil reservoirs were selected from the steam flooding test area of Qi 40 Block. And then field test was carried out on these five well groups. It is shown that the average daily oil production per well group of 5 test well groups is increased from 14.8 t/d to 16.1 t/d and the oil/steam ratio is increased from 0.14 to 0.17. The vertical producing degree of oil layers is increased significantly. It is indicated from the analysis that the injected air firstly sweeps in the predominant direction of steam flooding vertically and areally and low-temperature oxidation reaction happens between the injected air and the residual crude oil, increasing the bituminous sediments in pores. And consequently, the permeability of oil layers is decreased to force the steam to divert, so that the sweeping area of steam is enlarged. It is revealed that continuous air/steam injection is the suitable mode for air-assisted steam flooding;the recovery factor is higher when the steam/air ratio is close to 1:40;and if the well spacing is 70 m, the reservoir temperature will rise slightly and the content of produced oxygen can drop to the safety range after low-temperature oxidation reaction happens between the underground crude oil and the injected air. The success of field test demonstrates the feasibility of air-assisted steam flooding to improve the production of heavy oil fields. The problems of the selected test well groups are common in the late production stage of well groups in ordinary heavy oil reservoirs developed by steam flooding, so the test method and the related technical parameters in this paper can be used as the reference for the air-assisted steam flooding of similar well groups.