辽东湾地区辽西低凸起油气田成藏地质条件的差异

Differences of geological conditions of hydrocarbon accumulation among fields in the Liaoxi Low Uplift,the Liaodong Bay

在油气藏特征、油气来源、输导体系等综合对比分析的基础上,总结了辽东湾地区辽西低凸起JZ20-2凝析气田、JZ25-1S油气田、SZ36-1油田3个大中型油气田成藏模式的差异性。JZ20-2为单向双源成藏模式,以东营组二段下亚段—东营组三段区域超压盖层分隔,上部东营组正常地层压力油藏为辽中北洼东营组三段烃源岩排出的油气沿东营组二段三角洲砂体运聚而成,下部沙河街组及潜山超压凝析气藏则是由辽中北洼沙河街组烃源岩释放出的超压凝析油气沿不整合运聚而成。JZ25-1S为双向油源混合型成藏模式,辽西凹陷的油气沿西侧辽西1号、辽西2号边界断层垂向运移到辽西低凸起,同时辽中凹陷油气沿东斜坡不整合、砂体侧向运移,最终两个方向油气在JZ25-1S构造沙河街组二段砂体或太古界潜山储集体混合聚集成藏。SZ36-1为单向油源成藏模式,辽中南洼的油气沿油源断层-三角洲砂体大规模、长距离运移至SZ36-1构造东营组二段砂体中聚集成藏。

Based on comprehensive analyses of reservoir features, source rocks and carrier systems, this paper summarizes differences of hydrocarbon accumulation among three middle and large oilfields （ the JZ20-2, JZ25-1S and SZ36-1 oilfields） in the Liaoxi Low Uplift, the Liaodong Bay area. For the JZ20-2 oilfield, the hydrocarbon accumulation pattern is single migration direction and double sources. Separated by the regional overpressure cap rocks consisting of the lower part of the 2na member and the 3rd member of the Dongying Formation, the upper oil pool in the Dongying Formation has normal pressure and its hydrocarbons were generated by source locks in the 3rd member of the Dongying Formation in the northern Liaozhong subsag, and migrated along the delta sandbodies in the 2＇＇j member of the Dongying Formation,while the lower condensate gas pool in the Shahejie Formation and buried hill has overpressure and the hydrocarbons were generated by source rocks in the Shahejie Formation in the northern Liaozhong subsag and migrated along unconformities. For the JZ25-1S oilfield, the hydrocarbon accumulation pattern is double migration direction and mixed sources. Hydrocarbons sourced from the Liaoxi sag migrated vertically to the Liaoxi low uplift along the Liaoxi-1 and Liaoxi-2 boundary faults, and hydrocarbons sourced from the Liaozhong sag migrated laterally along unconformities and sandbodies in the eastern slope.Finally, these hydrocarbons mixed and accumulated in the sandstone of the 2nd member of the Shahejie Formation in the JZ25-1S structure and the reservoirs in Archaeozoic buried hills. For the SZ36-1 oilfield, hydrocarbon accumulation pattern is single migration direction and single source. Hydrocarbon sourced from the southern Liaozhong subsag migrated in large scale and long distance along the faults connecting source rocks and reser- voirs and delta sandbodies to sandstones in the 2nd member of the Dongying Formation in the SZ36-1 structure.