Himalayan Geology, Vol. 38 (2), 2017, pp. 141-155, Printed in India
Characteristics of the superposed gas reservoirs of coal-bearing series and its pool-forming dynamic mechanism in Jiyang depression, Bohai Bay Basin, China
JIA JINLONG1,2, SANG SHUXUN3,4,*, CAO LIWEN4, HAN SIJIE3,4, LIU SHIQI2, ZHOU XIAOZHI3,4
1School of Resources and Civil Engineering, Wuhan Institute of Technology, Wuhan, Hubei 430073, China
2The Key Laboratory of Coal-based CO2 Capture and Geological Storage, Jiangsu Province,
Low Carbon Energy Institute, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China
3School of Resources and Earth Science, China University of Mining and Technology, Xuzhou, Jiangsu, 221116 China
4The Key Laboratory of CBM Resources and Reservoir Formation Process of Ministry of Education,
Xuzhou, Jiangsu 221116, China
Email (Corresponding author): shxsang@cumt.edu.cn
Abstract: The superposed gas reservoirs of coal-bearing series represent a new type of gas reservoir, and the coal seam adjacent to the sandstone layer is an important subtype of superposed gas reservoirs (C-S-SGR) popular in Jiyang depression of Bohaiwan basin, China. This paper presents an investigation on the lithological characteristics of C-S-SGR elements (considering source-rock, reservoir and cap-rock), distribution, geometric and physical characteristics and also analyzing the data of exploration wells in Jiyang depression. Based on these parameters, a mathematical model for simulating the pool-forming dynamic process of the C-S-SGR is suggested. The results indicate that the C-S-SGR is deposited under the depositional environment of shallow water delta of epicontinental sea paleogeographic setting in North China Permo-Carboniferous prototype basin. C-S-SGR source rock is swamp microfacies coal seam, while the binary-structural reservoir contains coal seam and fluvial microfacies sandstone layer, and cap-rock is interdistributary bay microfacies mudstone layer. The hydrocarbon-generation potential of source rock, thickness and the burial depth are the main controlling geological factors of C-S-SGR accumulation. In Jiyang depression, the favorable areas of C-S-SGR are distributed in Gubei area of Zhanhua sag, southern of Huimin sag and central of Dongying sag. The pool-forming process of C-S-SGR is accompanied with gas migration between coal seam and sandstone layer, and the binary-structural reservoir presents the characteristic of overpressure.
Keywords: Superposed gas reservoirs, Coal-bearing series, Dynamic process, Jiyang depression.
