Distribution of Gas Enrichment Regions Controlled by Source Rocks and Geothermal Heat in China Offshore Basins
详细信息
- 责任者：Zhang Gongcheng (Research Institute ; CNOOC ; Beijing 100027 ; China) ; Miao Shunde
- 刊名：Natural Gas Industry
- 出版年：2013
- 卷期：33(4)
- 关键词：天然气 ; natural gas ; 中国 ; China
- 页码：p.1-17
- 图表：illus., 1 table, 28 refs.
- 分类号：1003
- issnNo：ISSN1000-0976
- isbnNo：CN51-1179/TE
摘要
This paper aims to offer a good map for the distribution of gas enrichment regions in China offshore basins by use of the theory of hydrocarbon generation controlled by source rocks and geothermal heat flow.The Xihu,Baiyun,Yanan and Yingzhong sags are proved gas-rich in the external belts of China offshore basins,the dominating source rocks of which are mainly marine-continental transitional facies and are distributed either in coal-bearing delta depositional system or in the depositional environment with neritic facies mudstones.The former is mainly distributed in the slight slopes of the sag with coal beds,carbonaceous mudstones,and dark mudstones as good to extremely good source rocks with a high abundance of terrestrial organic matters.The latter is mostly distributed in the deep subsag area,where hydrobios is not abundant but the semi-closed sediment environment is good for the preservation of organic matters belonging to a mixed type with a moderate to better abundance,mostly from the terrigenous plants or animals,and some from marine algae;the main moderate source rocks are mudstones.Thus,it is concluded that the coal-bearing delta has a high potential to form medium-and large-sized gas fields with high gas charge,while a shallow sea mudstone environment has a low potential to form small-and medium-sized gas fields with low gas charge.Thence the gas pooling in Cenozoic offshore basins are distributed firstly in coal-bearing delta with a high enough maturity and its hydrocarbon kitchens lying on the slope area,and secondly in a neritic facies mudstone environment with a high enough maturity and its hydrocarbon kitchens lying in the subsag.Coal-bearing deltas in China offshore basins can be divided into mature exploration areas and prospective areas.The mature exploration areas include the western slope in the Xihu sag,the northern slope in the Baiyun sag,the northwestern of the Yanan sag,and the Yingxi slope in the Yinggehai Basin;the prospective areas include the northern delta in the Liwan Basin,the northern slope delta in the Songdong sag,Qiongdongnan Basin,and the Lishui delta in the Lishui sag,Donghai Basin.Plays in the neritic facies mudstone environment include sub-sags in Xihu,Baiyun,Yanan,Liwan sags,and those in the Yingzhong sag,Yinggehai Basin,and in the central sag,Qiongdongnan Basin.