近井带干化盐析和反凝析对高温气藏后期单井产能的影响——以中国南海崖城13-1高温凝析气藏为例

Influence of water vaporization and condensate bank near wellbore on well deliverability damage of high temperature gas reservoir at low pressure stage:A case study of Yacheng 13-1 high temperature gas-condensate reservoir

异常高温凝析气藏降压开采过程中近井带地层水的大量蒸发极易导致盐析产生,崖城13-1气田异常高温凝析气藏中即使不产地层水的气井到后期的凝析水产量上升速度也较快,说明这种蒸发作用是存在的。同时随压力的降低在近井带会形成反凝析饱和度的聚集,它们均会使近井带的气相渗透率降低,进而降低气井产能。研究中测试了崖城13-1气田高温下地层水蒸发情况,并利用室内实验测试了不同渗透率岩心在不同干化时间下的岩心渗透率变化,发现低渗岩心在储层高温条件下的蒸发干化对低渗储层的损害较大;在拟合地层水蒸发导致盐析前后岩心渗透率的关系的基础上、结合反凝析伤害影响分析,评价了崖城13-1凝析气藏近井带受干化盐析和反凝析影响下的产能变化。结果表明,崖城13-1气田目前低压阶段盐析对产能的最大影响为15%,平均为8.68%,反凝析最大影响为5.83%。干化盐析和反凝析综合影响下的产能下降最大可达14.51%。

Compared with the conventional gas reservoir,the evaporation of the formation water in the nearwell zone during depressurization production could easily lead to salting out,which will block the reservoir and reduce the productivity of gas well for over-temperature gas reservoir.The production of Yacheng 13-1 shows evaporation of formation water is actually real.Besides,the retrograde condensate oil will also accumulate around near well-bore formation.All of them reduce the gas permeability and gas well deliverability.Formation water evaporation test and permeability test as well as PVT test results were presented.On the basis of the change of formation permeability caused by salting out and retrograde condensation,the productivity change of Yacheng 13-1 was analyzed and evaluated.Results show that maximum gas deliverability of well decreased by salting out of water was 15%,and average value of it was 8.68%.The maximum gas deliverability decreased by oil retrograde was 5.83%.Gas well deliverability influenced by both of them could be 14.51%.