石油与天然气地质 ›› 1993, Vol. 14 ›› Issue (3): 169-180.doi: 10.11743/ogg19930301

• 论文 •    下一篇

超致密砂岩含气问题

王金琪   

  1. 地质矿产部西南石油地质局 成都610081
  • 收稿日期:1993-01-28 修回日期:1993-04-05 出版日期:1993-09-25 发布日期:2012-01-16

PROBLEMS RELATING TO GAS-BEARING IN SUPER-TIGHT SANDSTONE

Wang Jinqi   

  1. Southwest Bureau of Petroleum Geology, MGMR, Chengdu
  • Received:1993-01-28 Revised:1993-04-05 Online:1993-09-25 Published:2012-01-16

PDF (PC)

726

被引次数

111

摘要：

作者探讨了砂岩孔隙度非常低情况下气藏形成的若干问题。突出了晚期相对活动构造对孔渗条件起死回生的决定性意义。阐明低级别砂岩孔隙结构、毛管作用以及油气活动方式。研究了气在砂岩基质孔隙中活动的“似极限”和有效性、超致密砂岩演化史、普遍超高压、次生气藏等新问题。强调早期聚集和晚期改造的相辅作用。

关键词: 超致密砂岩, 构造裂缝, 次生气藏, 晚期成藏, 四川盆地, 上三叠统

Abstract:

The co-existence of both Upper Triassic organic-rich sediments and super-tight sand-stone is a very typical petroleum geological condition in Western Sichuan Basin.The oil-generating peak period in the end of Middle Jurassic was just the time when original porosity of the sandstone reduced and secondary porosity increased gradually.Favourable condition,combined with various traps formed earlier,formed the first upsurge of lateral migration and accumulation.After continuous subsidence of more than 100 million years of the basin,the rocks were already getting super-tight (average Φ<7%),hydrocarbon generating was slow down and turned to craking,and superpressure formed in sedimenta-ry rocks,thus resulting in the sluggishness of natural gas.Himalayan tectonic movement resulted in many new structural traps,and fractures connected pore spaces in the super-tight sandstone.This let to the second upsurge of both horizental and lateral migration and accumulation.The porosity of supertight sandstone tended to be“pseudo-limit”of gas migration,this made things more complicated for gas accumulation and recovery:1.Linear gas-pool groups distributed along fracture system;2.Layer-like reservoirs formed by felty sand-stone with fracture system could be good anticlina gas pools with edge water drive,but the gas production would vary remarkably in different wells.However,this type of gas poolsare still the main targets for gas prospecting in West Sichuan.3.Porosity lower than the“pseudo-limit” (Φ≈2.5%,throat T≈10nm)is not valuable,but the gas would flow out from fracture belt suddenly into the wellbore and even make blowout sometime,then the production will decline rapidly.4.Gas fields with certain reserve might form in local places where better porosity of sandstone equivalent to the tight sandstone class (8%—15%)at the shallow formations or favourable facies and petrogenetics.The production is high when fissure developed in the sandstone;otherwise,it is low.This is another target for gas exploration.