复式盖层、走滑断裂带控储控藏作用——以塔里木盆地满西—古城地区下奥陶统白云岩勘探为例

Compound Cap Rocks and Slide Faults Controlling Mechanism on Reservoir and Reserves:An Example on Lower Ordovician Dolostones Exploration in Manxi-Gucheng Area,Tarim Basin

位于塔里木盆地古城地区的古城6井在下奥陶统白云岩中获得工业气流;该井气藏发育在致密灰岩之下,代表非常规储盖组合与油气成藏类型,其储层与天然气运聚机理研究对于勘探有利区带优选非常重要。通过对古城6井下奥陶统气藏储盖组合与油气运聚分析,提出古城6井下奥陶统白云岩储层形成于同生期白云岩化作用叠加埋藏期热液改造作用、气源通道为走滑断裂的认识,并建立了复式盖层与走滑断裂控储控藏模式:储层形成期热液流体沿走滑断裂侵入,遇复式盖层遮挡横向运移改造储层,成藏期天然气沿走滑断裂充注,受复式盖层遮挡成藏。通过对上奥陶统泥岩厚度统计、中奥陶统致密灰岩分布与走滑断裂带分布研究,认为满西低凸起与古城低凸起是中上奥陶统复式盖层与深大走滑断裂发育的有利区域;依据目的层埋深,提出满西低凸起北部与古城低凸起南部是下奥陶统白云岩勘探的有利区带。

Well Gucheng 6,which lies in the Gueheng region,obtained industrial gas flow at Lower Ordovi- clan dolostones in 2012,and represented a kind of unconventional reservoir-cap combination and gas accu- mulation type with great importance on gas exploration. Since reservoirs are mainly controlled by pene-con- temptuous dolomitization and hydrothermal alternations,and gases accumulate along slide faults,the reser- voir-cap rock combination characteristics and hydrocarbon accumulations in Gucheng 6 were studied. Based on the research of reservoir formation and gas accumulation in well Gucheng 6,double cap rocks and slide faults controlling reservoir and reserves model is suggested, i. e. , hydrothermal fluids upwells along slide faults, then transports horizontally beneath cap rocks completing reservoir constructive reformation at early stage, gas inputs along slide faults and accumulates under cap rocks in gas discharging process. According to the distribution study on the Upper Ordovician mudstone, the Middle Ordovician compact limestones and the slide faults,it is redeemed that Manxi-Gucheng area is advantaged distribution district of combined cap rocks and slide faults,and that northern Manxi Uplift and southern Gucheng Uplift are the most practical area for the Lower Ordovician dolostones explorations.