BK气藏反凝析污染评价及解除方法实验

Laboratory study on the evaluation and removal of retrograde condensate damage in the Baka Gas Reservoir,Tuha Basin

凝析气藏反凝析污染严重影响气井产能,正确评价反凝析污染程度,寻找合适的解除反凝析污染方法,对提高凝析气藏采收率具有重要意义。根据石油天然气行业标准SY/T 5542—2009油气藏流体物性分析方法,以及BK气藏现场PVT资料,采用地面分离器气和分离器油配制了两种不同凝析油含量的凝析气样品,并在PVT仪中进行高压物性分析实验。分别将配置的两种不同凝析油含量的凝析气样进行气源与岩心联合衰竭模拟近井区凝析油污染,岩心单独衰竭模拟远井区凝析油污染,共进行了4组长岩心实验,通过测定气测渗透率定量比较了两种不同凝析气的反凝析污染程度,同时还开展了5组解除反凝析污染实验:注入0.1烃类孔隙体积(HCPV)干气、注0.05 HCPV甲醇+0.05 HCPV干气、注0.1HCPV氮气、提高温度15℃、提高温度30℃。实验结果显示:上述5种方案均在一定程度上缓解了反凝析污染,而对于BK凝析气藏而言,则推荐采用注干气和甲醇+注干气这两种方案来解除反凝析污染。

Retrograde condensation damage may significantly reduce condensate gas well productivity. Accurate evaluation of retrograde damage degree and proper methods to remove such damage may help enhance recovery rates of condensate gas reservoirs. According to SY/T5542-2009 ＂Test Method for Reservoir Fluid Physical Properties＂ and the field PVT data obtained in the Baka Gas Reservoir, Tuha Basin, the oil and gas obtained from the separator at ground were utilized to make two kinds of condensate gas sam- ples with different condensate oil contents. The two samples were measured in a PVT analyzer to determine their physical properties under high pressures. Four groups of tests were performed on long cores to monitor the near and far wellbore depletion by different experimental methods, and then the condensation damage degree was compared quantitatively for the two different samples with dif- ferent condensate oil contents. In addition, five experiments were conducted for the removal of contamination induced by retrograde condensation, through injecting 0.1 HCPV （Hydrocarbon Pore Volume） dry gas, 0.05 HCPV dry gas ＋ 0.05 HCPV methanol, and 0.1 HCPV nitrogen respectively, raising temperature by 15℃ and by 30℃. Research results show that the contamination induced by retrograde condensation can be removed to certain extent in all the above five tests. Therefore, for such condensate gas reservoir as the Baka Gas Reservoir, the two schemes of injecting dry gas and injecting methanol 9 dry gas are recommended to remove contamination induced by retrograde condensation.