渤海海域南部盆缘凹陷天然气成藏特征及地质意义  

Characteristics of natural gas accumulation and geological significance of basin margin depression in southern Bohai Sea

作　　者：汤国民 王德英 王飞龙 叶涛 于倩 何俊辉 TANG Guomin;WANG Deying;WANG Feilong;YE Tao;YU Qian;HE Junhui(CNOOC Tianjin Branch Company,Tianjin 300459,China;CNOOC Experimental Center,CNOOC Ener Tech-Drilling&,Production Co.,Tianjin 300459,China)

机构地区：[1]中海石油(中国)有限公司天津分公司,天津300459 [2]中海油能源发展股份有限公司工程技术分公司中海油实验中心,天津300459

出　　处：《中国矿业大学学报》2022年第4期757-768,共12页Journal of China University of Mining & Technology

基　　金：中海石油(中国)有限公司“七年行动计划”重大科技专项课题(CNOOC-KJ 135 ZDXM 36 TJ 08 TJ);现代古生物学和地层学国家重点实验室开发课题研究计划(203117)。

摘　　要：为了厘清渤海南部盆缘凹陷中—浅层天然气成藏特征,通过天然气组分、天然气碳同位素、原油物性、生物标志物、烃源岩热解及壁心包裹体等数据分析,利用油气源对比、地球化学分析及盆地模拟手段,开展了天然气成因类型、油气源特征以及成藏期次分析.认为研究区天然气包括原生生物气和次生生物气两类,原生生物气来源于沙三段低成熟阶段烃源岩,次生生物气来源于周边稠油油藏生物降解作用.研究结果表明:渤海海域南部盆缘凹陷烃源岩成熟度(R)整体低于0.9%,处于低熟至成熟阶段早期,庙西南洼沙三段是其主力烃源岩,其TOC为1.0%~5.5%,R整体低于0.7%;龙口31-1构造天然气为原生的生物—热催化过渡带气,天然气中含少量凝析油(气油比为11 545.16 m~3/m~3),密度为0.730 g/cm~3,色谱图主峰碳仅为C和C,其来源于气体萃取低熟油轻质组分形成,下部可能存在一定规模低熟油,是庙西洼陷下一步原油勘探的重要目标;蓬莱19-3构造天然气以次生的原油生物降解气为主,混有大量溶解气,蓬莱31-3南和蓬莱25-2构造天然气为次生的原油生物降解气;盆缘凹陷已发现原油生物降解气储量整体较小,但与稠油伴生,估算渤海海域伴生稠油储量为2.5×10~8~11×10m~3,是下一步勘探有利方向.In order to clarify the characteristics of middle-shallow natural gas accumulation in the basin margin depression of southern Bohai Sea, based on the data analysis of natural gas composition, carbon isotope of natural gas, crude oil physical properties, biomarkers, source rock pyrolysis and wall-core inclusions, the genetic types of natural gas, characteristics of oil and gas sources and accumulation stages of natural gas were analyzed by means of oil-gas source correlation, geochemical analysis and basin simulation. It is believed that the natural gas in the study area includes two types: proto-biogas and secondary biogas. The proto-biogas is derived from the source rock of the low maturity stage of the third stage of Shahejie formation, and secondary biogas is derived from the biodegradation of the surrounding heavy oil reservoirs. The results show that the maturity(R) of source rocks in the southern basin margin depression of Bohai Sea is less than 0.9%, which is in low maturity to early maturity stage. The third member of Shahejie formation is the main source rock in the south of Miaoxi depression, with TOC of 1.0%—5.5% and Rbelow 0.7% as a whole;The natural gas in Longkou31-1 structure is native bio-thermocatalytic transition belt gas, which contains a small amount of condensate oil(gas-oil ratio is 11 545.16 m~3/m~3) with a density of 0.730 g/cm~3. The chromatogram main peak carbon is only Cand C, which is derived from the formation of light components of petroleum low-mature oil by gas extraction. Petroleum low mature oil may exist under the Longkou 31-1 structure, which is an important target for further oil exploration in Miaoxi depression;The natural gas in Penglai 19-3 structure is mainly composed of secondary crude biodegradation gas, mixed with a large number of dissolved gas. The natural gas in south of Penglai 31-3 structure and Penglai 25-2 structure are secondary crude biodegradation gas;The crude oil biodegradable gas reserves in the basin margin depression is generally small and mostly associ

关 键 词：天然气成藏特征 天然气成因类型 生物—热催化过渡带气 原油生物降解气 低熟油 盆缘凹陷 

分 类 号：TE122[石油与天然气工程—油气勘探]