渤海湾盆地潜山油气藏保存条件探讨

Study on hydrocarbon preservation conditions of buried hill reservoirs in Bohai Bay Basin

渤海湾盆地潜山油气藏的保存条件至关重要,探讨保存条件对潜山油气勘探具有重要意义。基于大量统计资料,结合潜山油气成藏条件分析,探讨渤海湾盆地盖层、抬升剥蚀作用和断裂作用对潜山油气保存及富集的影响。结果表明:渤海湾盆地不同层系潜山油气相态及来源不尽相同,前古生界、下古生界和中生界以油藏为主,为它源型油气藏,而上古生界以气藏为主,主要为自源型油气藏;研究区共发育5套区域盖层,石炭—二叠系盖层对天然气封盖能力强,新近系泥岩仅能作为油藏的盖层;不同时期形成的潜山油气藏的保存条件存在差异,早期形成的潜山油气藏因后期构造作用遭到破坏,大多数潜山油气藏主要为古近纪末和新近纪—第四纪形成;断盖配置及断层封闭性控制潜山油气藏的保存,可划分为A型、B型和C型3类断盖组合样式,其中C型断盖组合样式最有利于潜山油气的富集与保存。

The preservation conditions of buried hill reservoirs in Bohai Bay Basin are crucial,and it is of great significance to explore the preservation conditions for buried hill oil and gas exploration.Based on a lot of statistical information,this paper dissected the effects of caprock,uplift denudation and faulting on hydrocarbon preservation and enrichment by considering hydrocarbon accumulation conditions of buried hill.The results show that the oil and gas facies and sources of buried hill in Bohai Bay Basin are different:the Mesozoic,Lower Paleozoic and pre-Paleozoic are mainly oil reservoirs,with secondary other source oil and gas reservoirs;while the Upper Paleozoic are mainly gas reservoirs with secondary self-sourced oil and gas reservoirs.There are five sets of cap rocks developed in the study area.The displacement pressure of Carboniferous-Permian cap rocks is high and the sealing ability of gas reservoirs is strong.The displacement pressure of Neogene cap rocks is low and the oil reservoirs can be sealed.There are differences in the preservation conditions of buried hill reservoirs formed in different periods.The early formed buried hill reservoirs were destroyed due to late tectonic activities.Most buried hill reservoirs are mainly formed at the end of Paleogene and Neogene to Quaternary.The configuration of fault-caprock and fault sealing control the preservation of buried hill reservoirs,which can be divided into three types of fault-caprock combination styles:A-type,B-type and C-type,corrpondingly.Among them,the C-type fault-caprock combination is the most favorable for the enrichment and preservation of buried hill reservoirs.