Title: Distinct performance characters and inducing mechanisms of CO₂ and N₂ enhanced coalbed methane recovery

Authors: Jian Hou; Jintao Wu; Kang Zhou

Addresses: State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Qingdao, Shandong 266580, China; College of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong 266580, China ' College of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong 266580, China ' College of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong 266580, China

Abstract: The distinction of performance characters and inducing multiple mechanisms in CO₂ and N₂ enhancement are ambiguous, even though the different stimulation performances have been discussed in existing studies. This article establishes an essential mathematical model and a comparison of the recovery dynamics with CO₂ and N₂ injection is conducted. The results indicate that the distinct characters of CO₂ and N₂ enhancement derive mainly from the different properties of porosity, permeability and gas sorption. The N₂ injection appears more time efficient. The variation of porosity and permeability plays more complex roles when CO₂ is injected as the coal seam is divided into two regions of gas concentration, pressure and cleat permeability. The influence of the coal seam and gas properties is discussed. The parameters related to the porosity and permeability variation and gas sorption inflict quite different influences between CO₂ and N₂ injection, while the coal seam intrinsic properties impact similarly. [Received: November 22, 2013; Accepted: September 7, 2014]

Keywords: enhanced coalbed methane recovery; ECBM; performance characters; mathematical modelling; numerical simulation; CO2 injection; carbon dioxide; N2 injection; nitrogen; recovery dynamics; porosity; permeability; gas sorption; coal seams; gas concentration; pressure; cleat permeability.

DOI: 10.1504/IJOGCT.2016.074285

International Journal of Oil, Gas and Coal Technology, 2016 Vol.11 No.2, pp.204 - 227

Received: 22 Nov 2013
Accepted: 07 Sep 2014
Published online: 21 Jan 2016 *

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