塔河缝洞型超稠油油藏二氧化碳驱实验研究

CO_2 Flooding Experiment of Super-Heavy Oil Reservoir in Tahe Oilfield

塔河油田YQ区块是典型的碳酸盐岩缝洞型超稠油油藏,其溶洞分布的随机性和裂缝尺度的多样性使常规开采方式无法取得理想的效果。由于CO_2特殊的物理和化学性质,使注CO_2成为一种新型开采缝洞型超稠油油藏方法。结合YQ区块油藏特点制作了缝洞岩心模型,开展了不同注入压力和注入量的CO_2驱油物理模拟实验,并对气窜后原油和产出气进行气相色谱分析。实验结果表明:注气压力过高或过低都会导致原油采收率降低;注气压力为53 MPa,注气量为6.5倍孔隙体积时最为经济合理;气窜后CO_2对该区块超稠油抽提作用主要是抽提组分C_(20)—C_(31)。依据气油比和原油采收率曲线图,建议现场注气时,当油井气油比超过2 700时关闭该油井。

Block YQ is considered as a typical carbonate super-heavy oil reservoir in Tahe Oilfield and conventional development mode cannot achieve efficient production performance due to the random distribution of caves and diversity of fracture scales. CO_2 flooding is considered as a new recovery mode for fracture-cave super-heavy oil reservoir due to its special physical and chemical properties. A fracture-cave core model considering the reservoir properties in Block YQ is prepared,the CO_2 flooding simulations with different injection pressures and rates are carried out to analyze thechromatography of produced oil and gas after gas breakthrough. Experimental result shows that both too high and too low CO_2 injection pressureswill result in the reduction of oil recovery factor. The most economic scenario is gained when CO_2 injection pressure is 53 MPa and CO_2 injection rate is 6. 5 porevolumes. The CO_2 extraction of heavy oil in this block after breakthrough is dominated by C_(20-31) extraction. According to the CO_2-oil ratio and oil recovery degree histories,production well shut-in is recommended in case of CO_2-oil ratio exceeding 2700.