Facies analysis and depositional model of late Permian Raniganj formation: Study from Raniganj coal bed methane block
详细信息 查看全文
- 作者：Souvik Sen ; Nayani Das ; Dipanjan Maiti
- 关键词：Depositional model ; Facies analysis ; Coal bed methane (CBM) ; Raniganj coal field ; West Bengal
- 刊名：Journal of the Geological Society of India
- 出版年：2016
- 出版时间：October 2016
- 年：2016
- 卷：88
- 期：4
- 页码：503-516
- 全文大小：3,137 KB
- 刊物类别：Earth and Environmental Science
- 刊物主题：Geology
Geosciences
Geography
Mineralogy - 出版者：Springer India, co-published with Geological Society of India
- ISSN：0974-6889
- 卷排序：88
文摘
The Raniganj Formation (late Permian) forms the uppermost economic coal-bearing unit of the Gondwana succession. The dominant facies interpreted from analysis of cores from the Raniganj formation are classified as Sandstone dominated facies, Sandstone - shale heterolith facies, Shale facies and Coal facies. The natural Gamma response of Raniganj Formation shows predominance of repetitive fining upwards cycles. Integration of core analysis and geophysical log data of the Raniganj formation indicates meandering fluvial environment. The lower part of Raniganj Formation is channel dominated which corresponds to thick amalgamated sand bodies while the upper part represent overbank shows predominance of channel avulsion indicating a gradual change in accommodation space. Five major fining upward depositional sequences, bounded by sub-aerial unconformities (sequence boundaries) have been dentified in Raniganj formation, based on changes in depositional style that are correlated regionally. Each sequence comprises of Low accommodation system tract (LAST) at base and high accommodation system tract (HAST) at top. LAST is characterized by vertically stacked, multistory amalgamated channel sandstone dominated facies, while floodplain dominated facies characterize HAST. The coal seams deposited in LAST are thicker and relatively more continuous than the frequent thin seams of HAST. Such facies distribution study would be helpful for the development strategy for CBM blocks based on production priority.