摘要
通过对区域构造演化、沉积背景、盖层特性以及油气生成和运聚条件等的分析,结合前人研究成果,重新建立了平湖油气田的成藏模式。平湖油气田含上部渐新统花港组和下部始新统平湖组两套储层,呈上油下气的油气分布特征。古新世—始新世的断块阶段在区域上初步形成了大断裂控制下的断背斜构造,在平湖组形成圈闭。中新世中期(平湖组沉积后期)发生玉泉运动,花港组开始沉积,同时平湖组内的油源岩大量排烃注入平湖组内部砂体,发生第一期液态烃充注。伴随着花港组的沉积和区域构造运动,平湖组砂体中的液态烃发生部分二次运移,向上运移至花港组储层中。中新世末—现今,平湖组之下的气源岩生气,发生第二期气态烃充注。平湖组被气态烃充注,原先残留的液态烃进一步向上运移,逐渐形成以气藏为主的成藏特征;向上运移的液态烃被进一步注入花港组储层,而向上运移的气态烃则因花港组顶部盖层的缺陷而大量散失,形成花港组以油藏为主的成藏特征。在平湖组下部的深部地层存在异常地层压力段,其泥岩的突破压力相对减小,显示盖层质量变差,不利于气的保存,但可以保存油藏。未受断裂运动影响、砂体规模较大的异常高压地层是形成深部油藏的有利部位。
There are two sets of reservoirs,Oligocene Huagang oil reservoir in the upper and Eocene Pinghu gas reservoir in the lower,in Pinghu Field,East China Sea Basin.The anticline structure controlled by the large fault formed during Paleocene to Eocene and traps formed in Pinghu phase.Accompanying with Yuquan movement that happened after deposition of Pinghu Formation,deposition of Huagang Formation started during middle Miocene,meanwhile hydrocarbon expelled and immigrated from the Pinghu source rock into sandstone reservoir within Pinghu Formation,which is the first injection for liquid hydrocarbon.Accompanying with the deposition of Huagang Formation and regional tectonic movement,hydrocarbon in Pinghu sandstone reservoir migrated up partly into Huagang reservoir.From the end of Miocene till now,gas generated from source rock below Pinghu Formation,which is the secondary injection for gaseous hydrocarbon.Since gaseous hydrocarbon injected into Pinghu Formation,the liquid hydrocarbon was forced to migrate upwards to Huagang Formation and gas-dominating reservoir formed gradually.The upwards-migrating liquid hydrocarbon injected into Huagang reservoir and oil-dominating reservoir formed because of the weakening breakthrough pressure in cap rock at the top of Huagang,which resulted in escaping of gas but was favorable to preservation of oil.The large-scaled sandstone bodies with abnormal high pressure without affection of a tectonic movement are the promising oil reservoirs in deep.
出处
《海相油气地质》
2011年第1期51-55,共5页
Marine Origin Petroleum Geology
关键词
油气成藏
成藏模式
构造演化
盖层
新生代
平湖油气田
Hydrocarbon accumulation
Model
Tectonic Evolution
Cap Rock
Cenozoic
Pinghu Oil and Gas Field
East China Sea Basin
