Distribution Characteristics and Accumulation Model for the Coal‐formed Gas Generated from Permo‐Carboniferous Coal Measures in Bohai Bay Basin, China: A Review

Abstract

Coal-formed gas generated from the Permo-Carboniferous coal measures has become one of the most important targets for deep hydrocarbon exploration in the Bohai Bay Basin, offshore eastern China. However, the proven gas reserves from this source rock are remain low to date, and the distribution characteristics and accumulation model for the coalformed gas are not clear. Here we review the coal-formed gas deposits formed from the Permo-Carboniferous coal measures in the Bohai Bay Basin. The accumulations are scattered, and dominated by middle-small sized gas fields, of which the proven reserves ranging from 0.002 to 149.4×10 8 m 3 with an average of 44.30×10 8 m 3 and a mid-point of 8.16×10 8 m 3 . The commercially valuable gas fields are mainly found in the central and southern parts of the basin. Vertically, the coal-formed gas is accumulated at multiple stratigraphic levels from Paleogene to Archaeozoic, among which the Paleogene and Permo-Carboniferous are the main reservoir strata.According to the transporting pathway, filling mechanism and the relationship between source rocks and reservoir, the coal-formed gas accumulation model can be defined into three types: " Upward migrated, fault transported gas" accumulation model, " Laterally migrated, sandbody transported gas" accumulation model, and " Downward migrated, sub-source, fracture transported gas" accumulation model. Source rock distribution, thermal evolution and hydrocarbon generation capacity are the fundamental controlling factors for the macro distribution and enrichment of the coal-formed gas. The fault activity and the configuration of fault and caprock control the vertical enrichment pattern.

The Development Characteristics and Distribution Predictions of the Paleogene Coal‐measure Source Rock in the Qiongdongnan Basin, Northern South China Sea

“…Data sources: Jin, 1989;Liu and Jin, 1997;Qiu and Gong, 1999;Li and Lv, 2002;Liu et al, 2002;Zhou, 2005;Zhang et al, 2007;Zhu et al, 2007Zhu et al, , 2010Jiang et al, 2019;Rao et al, 2020. Formation; Huangliu Formation; Upper Ocene Yinggehai Formation, and so on. Generally speaking, the coal bearing strata are mainly developed in the Oligocene Yacheng Formation of the Lower Oligocene, which is a set of coal bearing delta-shore shallow sea deposits, whereas the upper Oligocene Lingshui Formation is a set of shore shallow sea fan-delta deposits containing slight amounts of coal.…”

Origin Type and Generating Mechanism of Coal Measure Limestone Gas: A Case Study of L1 Limestone Gas in the Taiyuan Formation of the Shenzhou Coal Mine, Eastern Edge of the Ordos Basin, China

“…The multiple values of coal resources are reflected in the symbiotic combination and comining potential of multiple mineral resources in coal measure. The symbiosis and coexistence of coalbed methane, shale gas, tight sandstone gas, natural gas hydrate, and other coal measure gases have attracted widespread attention. − The resources potential of global coal measure gas is huge. The San Juan Basin in the United States, the Surat Basin in Australia, the Western Siberian Basin in Russia, the Albert Basin in Canada, and the Qinshui Basin and Ordos Basin in China are all typical enrichment basins of coal measure gas.…”