摘要
渤海湾盆地烃源岩有机质类型以Ⅰ-Ⅱ型为主,是典型的富油裂陷湖盆。以渤海海域(渤海湾盆地海域部分)渤中地区为例,从天然气来源与成因判识剖析油型盆地干酪根的生气特征以及深层天然气勘探前景。结果表明,对于相同热演化程度的干酪根而言,其热解气的量与烃源岩的氢指数呈正相关关系,而且大部分干酪根热解气在R_(o)=1.5%之前已经生成。生气强度表明,即使对于热演化程度相对偏低的富油盆地,以干酪根热解为主的天然气生气量仍满足大中型气田形成的物质基础。高生产率主导的倾油型母质具有相对重的沉积有机碳同位素组成,因此乙烷碳同位素较重的天然气不一定是来源于偏腐殖型或者煤系烃源岩,也可能来自较高成熟度的倾油型母质。以R_(o)=1.5%为界,早期生成原油深埋裂解整体可分为两个阶段:第一阶段原油裂解轻质化,该阶段油裂解生成的天然气量相对少,第二个阶段轻质油大量裂解生成天然气,表明生油高峰期(浅层)充注的原油在深埋过程具有较高的热稳定性,深层仍可能富集规模轻质油或凝析油气。
The organic matter type of source rocks in Bohai Bay Basin is dominated by typeⅠ-Ⅱ,which is a typical oil-rich rift lacustrine basin.Taking the Bozhong area of Bohai Sea(the offshore area of Bohai Bay Basin)as an example,the gas generation characteristics of kerogen in the oil-type basin and deep gas exploration prospects were analyzed from the perspective of natural gas sources and genesis.The results show that for kerogen with the same degree of thermal evolution,the amount of cracking gas is positively correlated with the hydrogen index of source rocks,and most of the kerogen cracking gas has been generated before R_(o)=1.5%.The gas generation intensity indicates that the gas generation amount dominated by kerogen cracking gas still meets material requirements for the formation of large and medium-sized gas fields even for oil-rich basins with relatively low thermal evolution.The oil-prone source rock dominated by high productivity has a relatively heavy sedimentary organic carbon isotope composition.Therefore,the gas with heavy ethane carbon isotope may be derived from the oil-prone source rock with higher thermal maturity rather than from the humic-prone or coal source rocks.Taking R_(o)=1.5%as the boundary,the deep-buried cracking of early crude oil can be divided into two stages:the first stage is characterized by light crude oil cracking accompanied by relatively limited oil cracking gas;and the second stage is dominated by oil cracking gas due to intense cracking of light oil.It indicates that the crude oil charged within the peak of oil generation(shallow formation)has high thermal stability in the deep burial process,and large amounts of light oil or condensate oil may still accumulate in the deep strata.
作者
王奇
郝芳
邹华耀
薛永安
牛成民
WANG Qi;HAO Fang;ZOU Huayao;XUE Yong’an;NIU Chengmin(School of Geosciences,China University of Petroleum(East China),Qingdao 266580;Shandong 2.National Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China),Qingdao 266580;Shandong 3.State Key laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249;Tianjin Branch,China National Offshore Oil Corp.Ltd.,Tianjin 300452)
出处
《长江大学学报（自然科学版）》
2023年第5期47-54,共8页
Journal of Yangtze University(Natural Science Edition)
基金
国家自然科学基金项目“油气成藏机理”(41821002)
“基于环境生物协同演化的烃源岩有机碳同位素分馏机制研究”(42002146)。
