超深层多断裂碳酸盐岩气藏水侵模式及治水对策

Water-invasion patterns and ways to deal with water in ultra-deep carbonate gas reservoirs with multiple fractures

超深层天然气勘探开发潜力巨大,已经成为全球勘探开发的热点。近年川西北地区发现双鱼石构造中二叠统栖霞组气藏,成为四川盆地目前最具潜力的超深层勘探开发领域之一。该气藏高温、高压且多断裂,埋藏深度超过7000 m,开发投资成本高。2020年气藏整体投产以来,5口气井陆续产出地层水,产水井比例超过40%,效益开发面临挑战。为此,基于气藏生产动态特征,采用气藏工程方法对水体活跃性进行评价,提出气藏典型水侵模式,形成气藏差异化治水对策。研究结果表明:①气藏不同区域水体活跃性存在差异,表现出整体水体不大但局部水体活跃的特征。②气井水侵特征包括指数产水型、线性产水型及指数+线性产水型等3类,并以指数产水型为主。③结合气藏地质特征,将气井水侵模式划分为构造端部沿层推进型、单翼边水沿裂缝推进型及双翼边水沿裂缝窜进型这3种类型,并确定气藏3口产水风险井。④提出气藏治水对策:Ⅰ号条带控水为主,Ⅲ-Ⅳ号条带中部各优选排水井1口,气藏合理排水规模250 m3/d。研究结果可保障气藏的长期稳产与科学开发,同时对同类型气藏的开发具有指导意义。

Ultra-deep gas becomes a hotspot in global exploration and development for its tremendous resource potential.In recent years,gas reservoirs of the Middle Permian Qixia Formation,Shuangyushi structure,northwestern Sichuan Basin,have turned into one of the most promising domains for ultra-deep exploration and development in the basin.Accompanying with multiple fractures,the reservoirs are characterized by high temperature and pressure as well as the burial depth exceeding 7,000 m,creating high costs in their development.Since they were put into production in 2020,formation water was produced from five wells which accounted for more than 40%of the sum,leading to great challenges on reservoirs’beneficial development.Thus,water activity was evaluated through reservoir engineering approaches based on production performance.Additionally,typical water-invasion patterns were pro-posed,and some ways to deal with water were formulated.Results show that(i)there exist differences of water activity in various areas of Qixia gas reservoirs,suggesting small waterbody globally but active in part;(ii)water-invasion behaviors in gas wells can be classified into three types:exponential water production,linear water production,and exponential+linear water production,with the first one as the soul;(iii)dependent upon geological characteristics,invasion patterns are divided into three categories:water ad-vancement along strata at structural end,edge-water advancement along fractures at single flank,and edge-water advancement along fractures at double flanks.Also,three risk wells with water are identified;and(iv)the formulated ways to deal with water include con-trolling water primarily in I zone,optimizing one drainage well each in the middle III–IV zones,and setting the rational drainage rate of 250 m3/d.These findings can not only ensure long-term stable production and scientific reservoir development but provide guidance for the development of similar gas reservoirs.