A New Insight into Shale-Gas Accumulation Conditions and Favorable Areas of the Xinkailing Formation in the Wuning Area, North-West Jiangxi, China

Abstract

Abstract:In north-west Jiangxi, China, most shale-gas exploration has been focused on the Lower Cambrian Hetang and Guanyintang formations, whereas the Upper Ordovician Xinkailing formation shale has been ignored for years due to heavy weathering. This study systematically analyzed gas source conditions, reservoir conditions and gas-bearing ability in order to reveal the shale-gas accumulation conditions of the Xinkailing formation. The results show that the Xinkailing formation is characterized by thick deposition of black shale (10-80 m), high organic content (with total organic carbon between 1.18% and 3.11%, on average greater than 2%), relatively moderate thermal evolution (with vitrinite reflectance between 2.83% and 3.21%), high brittle-mineral content (greater than 40%), abundant nanopores and micro-fractures, very good adsorption ability (adsorption content between 2.12 m 3 /t and 3.47 m 3 /t, on average about 2.50 m 3 /t), and strong sealing ability in the underlying and overlying layers, all of which favor the generation and accumulation of shale gas. The Wuning-Lixi and Jinkou-Zhelin areas of the Xinkailing formation were selected as the most realistic and favorable targets for shale-gas exploration and exploitation. In conclusion, the Wuning area has great potential and can provide a breakthrough in shale gas with further investigation.

Use of Outcrop as Substitute for Subsurface Shale: Current Understanding of Similarities, Discrepancies, and Associated Challenges

“…Values for the TOC content of shale, as the most important geochemical property with commercial potential, are generally more than 2 wt %. 93 The maturity of the shale formation also defines its potential for hydrocarbon generation. Hence, these parameters are very important to be evaluated in the studied outcrop analogs as a potential prediction of the hydrocarbon economic viability of the shale resource.…”

“…In a comparative study by Li et al, 93 statistical data were analyzed of 30 core samples and 33 outcrop samples from the Xinkailing Formation in China's Wuning area. The TOC content of the core samples ranged from 1.18 to 3.11 wt % (averaging 2.11 wt %), while for the outcrop samples it ranged from 0.1 to 1.21 wt % (averaging 0.4 wt %).…”

“…Outcrop and equivalent subsurface shale formations might have comparable geochemical properties. Values for the TOC content of shale, as the most important geochemical property with commercial potential, are generally more than 2 wt % . The maturity of the shale formation also defines its potential for hydrocarbon generation.…”

Effective Exploitation Potential of Shale Gas from Lower Cambrian Niutitang Formation, Northwestern Hunan, China

“…Shale gas exploration drilling is already underway in China. Most studies have explored the Sichuan Basin [13][14][15] and Yangtze Platform areas [16,17] to evaluate the potential of shale gas for commercial exploitation by discussing the optimization of the indicator system, the determination of parameters standard, and the selection of methods. He et al [13] and Zhang et al [14] studied the shale gas enrichment mechanism and reservoir capacity by analyzing the micropore characteristics of the Wufeng-Longmaxi Formation shale in the Sichuan Basin.…”

“…Yong et al [14] used the structural analysis method to combine the burial depth and fault length of the Longmaxi Formation in the southeastern Sichuan Basin to evaluate the shale gas reservoir conditions and favorable exploration targets. Li et al [16] and Wang et al [17] systematically analyzed the shale gas source conditions, reservoir conditions, and gas-bearing properties in northwest Jiangxi, providing a basis for further gas exploitation and development.…”