靖边气田气藏特点、成因与成藏有利条件

靖边气田的成藏特点表现为:(1)气源为双向供给,二源混合;(2)储层空间以膏溶孔隙、白云石化孔隙为主,以裂缝为辅;(3)以地层和岩性圈闭为主,古构造决定了充注方向;(4)气藏流体具非均一性和负压特征;(5)地层水为有水不见水层,分隔"卧底"保存。探讨了形成这些特征的机理。同时提出促使成藏的主要地质因素是四项"合理搭配":(1)封闭海域与宽阔坪台搭配造就有利生储相带;(2)剥蚀脊与侵蚀沟搭配形成层状溶蚀水流;(3)切割与充填、溶蚀与充填搭配形成地层、岩性遮挡;(4)孔隙空间与裂隙网络搭配使得储产兼得。

Characteristics and Origin of Gas Reservoirs and the Favorable Geological Conditions in Jingbian Gasfield,Ordos Basin

This research indicates that gas reservoirs in Jingbian Gasfield,Ordos,are characteristic of:⑴ Gas is supplied by mixed gas sources from two directions;⑵ Reservoir space are dominated by anhydrite-dissolved and dolomitized pores and subordinated by fractures;⑶ Stratigraphic and lithogic traps are common and paleostuctures control the direction of hydrocarbon migration and emplacement;⑷ Fluids in gas reservoirs are of heterogencity and negative pressure feature;⑸ Formation water are compartmentally preserved without water beds.The mechanism resulting in these characteristics are discussed.The main geological factors leading to gas accumulation are owing to four"fitting match"conditions:⑴ The match of enclosed sea with wide flats brings up good source-reservoir facies belt;⑵ The match of erosion ridges with erosion grooves builds up layered dissolved currents;⑶ The match of cutting with filling,and dissolution with filling,forms stratigraphic traps and lithologic traps;⑷The match of pore space with fissures nets gets to both gas reserves and output.