Title: Comparison of a novel coupled hydro-mechanical model with typical analytical models in subsidence of coal seam gas extraction

Authors: Guojun Wu; Shanpo Jia; Bailin Wu

Addresses: State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Bayi Road, Wuhan 430071, Hubei, China ' Research Center of Geomechanics and Geotechnical Engineering, Yangtze University, Nanhuan Road, Jingzhou 434023, Hubei, China ' CSIRO Energy, 71 Normanby Road, Clayton, Melbourne 3168, Australia

Abstract: Although the influence of conventional oil and gas extraction on surface subsidence has been widely recognised and studied, few studies are carried out on the surface subsidence in coal seam gas fields and its impact on surface infrastructure and the environment. In predicting land subsidence caused by coal seam gas extraction, the hydro-mechanical behaviour of geological strata are different and their hydraulic connections to the coal seams are not well-understood, which makes the analytical models are difficult to be applied in the prediction of land subsidence. This paper develops a coupled fluid flow-geomechanical model which can consider the interrelation of fluid flow and geomechanics of the ground. By comparison of dewatering and degassing with typical analytical models including the disc-shaped reservoir model and the uniaxial compaction model, the typical analytical models cannot estimate the potential pressure distribution and predict the real subsidence induced by coal seam gas extraction; however, the coupled fluid flowgeomechanical model is capable of describing the transport properties of coal seam, including water flow, gas flow and desorption and rock deformation. Therefore, the proposed coupled model can be better used in analysis of subsidence of coal seam gas extraction. [Received: April 15, 2017; Accepted: October 17, 2017]

Keywords: land subsidence; depressurisation; gas extraction; analytical model; coal seam.

DOI: 10.1504/IJOGCT.2019.102783

International Journal of Oil, Gas and Coal Technology, 2019 Vol.22 No.2, pp.246 - 268

Received: 15 Apr 2017
Accepted: 17 Oct 2017
Published online: 07 Oct 2019 *

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