准噶尔盆地陆梁地区复式油气成藏系统初探

准噶尔盆地陆梁油田的发现表明盆地腹部具有复式油气成藏系统特征,形成多源、多藏和多期次的混源现象。该区可划分为玛湖凹陷—环玛湖东斜坡油气成藏子系统、盆1井西凹陷—石南油田油气成藏子系统及盆1井西凹陷—陆梁油田油气成藏子系统。前者中,烃源灶为玛湖凹陷的风城组,成藏时期分别为晚三叠世及中侏罗世末期,成藏通道为不整合面及扇状砂体,主要形成扇体和古潜山油气藏。盆1井西凹陷—石南油田油气成藏子系统中,烃源灶主要为盆1井西凹陷的风城组,成藏时期分别为早白垩世及古近纪末期,成藏通道主要为断层及不整合面,具有阶梯状成藏特征。盆1井西凹陷—陆梁油田油气成藏子系统中,烃源灶主要为盆1井西凹陷的乌尔禾组,成藏时期分别为中侏罗世末期—早白垩世及古近纪末期,成藏通道主要为断层、不整合面及连通砂体,具有环状成藏特征。各子系统形成的原油特征也有着较大差异。各成藏子系统的分布基本受盆地的构造形态及烃源灶控制,即:玛湖凹陷—环玛湖东斜坡油气成藏子系统相对比较独立,盆1井西凹陷—陆梁油田油气成藏子系统是盆1井西凹陷—石南油田油气成藏子系统的延续与发展。断层和不整合面构成的空间输导网络为各子系统的成藏创造了有利条件。

CHARACTERISTICS OF MULTIPLE HYDROCARBON ACCUMULATION SYSTEMS IN LULIANG AREA, THE JUNGGAR BASIN

The investigations in Luliang area, the Junggar Basin showed the characteristics of the multiple hydrocarbon accumulation systems. Three hydrocarbon accumulation subsystems in the area could be divided, namely, the Mahu Sag-East Slop of Circum-Mahu Sag subsystem (the MM subsystem), the Sag West of Well Pen-1 to the Shinan Oilfield subsystem (the PS subsystem) and the Sag West of Well Pen-1 to the Luliang Oilfield subsystem (the PL subsystem). In the MM subsystem, the source rock was the Fengcheng Formation in the Mahu Depression, with petroleum accumulation times being Late Triassic and late Middle Jurassic. The pathways were mainly unconformities and fan-shaped sand-bodies. In the PS subsystem, the source rock was mainly the Fengcheng Formation in the Sag West of Well Peng-1, with petroleum accumulation times being Early Cretaceous and Late Paleogene. The pathways were mainly faults and unconformities, and the accumulations being ladder-shaped. In the PL subsystem, the source rock was mainly the Wuerhe Formation in the Sag West of Well Peng-1, with petroleum accumulation times being late Middle Jurassic-Early Cretaceous and Late Paleogene. The pathways were mainly faults, unconformities and connected sand-bodies, and the accumulations being ring-shaped. The characteristics of crude oil in every subsystem was different from each other. The distribution of above-mentioned 3 subsystems was controlled by structural modes and source rocks, so that the MM subsystem was comparatively independent, and the PL subsystem was a continuance and further development of the PS one. The pathway frameworks formed by faults and unconformities created some favorable conditions for hydrocarbon accumulation in the multiple hydrocarbon accumulation systems.