title: Two-scale analysis of a tight gas sandstone.
abstract: Tight gas sandstones are low porosity media, with a very small permeability (i.e., below 1 mD). Their porosity is below 10%, and it is mainly composed of fine noncemented microcracks, which are present between neighboring quartz grains. While empirical models of permeability are available, their predictions, which do not compare well with macroscopic measurements, are not reliable to assess gas well productivity. The purpose of this work is to compare the permeability measured on centimetric plugs to predictions based on pore structure data. Two macroscopic measurements are performed, namely dry gas permeability and mercury intrusion porosimetry (MIP), together with a series of local measurements including focused ion beam and scanning electron microscopy (FIB-SEM), x-ray computed microtomography (CMT), and standard two-dimensional (2D) SEM. Numerical modeling is performed by combining analyses on two scales, namely the microcrack network scale (given by 2D SEM) and the individual 3D microcrack scale (given by either FIB-SEM or CMT). The network permeability is calculated by means of techniques developed for fracture networks. This permeability is proportional to the microcrack transmissivity, which is determined by solving the Stokes equation in the microcracks measured by FIB-SEM or CMT. Good correlation with experimental permeability values is only found when using transmissivity from 3D CMT data.
authors.affiliation: Ecole Centrale de Lille, Cité Scientifique, CS20048, and LML FRE CNRS 3723, 59651 Villeneuve d'Ascq Cedex, France.
authors.forename: Yang
authors.initials: Y
authors.lastname: Song
authors.affiliation: Ecole Centrale de Lille, Cité Scientifique, CS20048, and LML FRE CNRS 3723, 59651 Villeneuve d'Ascq Cedex, France.
authors.forename: C A
authors.initials: CA
authors.lastname: Davy
authors.affiliation: Université Pierre et Marie Curie, Laboratoire Metis, Paris, France.
authors.forename: Thang
authors.initials: T
authors.lastname: Nguyen Kim
authors.affiliation: IEMN, UMR CNRS 8520, BP 60069, 59652 Villeneuve d'Ascq Cedex, France.
authors.forename: D
authors.initials: D
authors.lastname: Troadec
authors.affiliation: GDF SUEZ E&P International SA, 1 place Samuel de Champlain, 92930 Paris La Défense Cedex, France.
authors.forename: G
authors.initials: G
authors.lastname: Hauss
authors.affiliation: GDF SUEZ E&P International SA, 1 place Samuel de Champlain, 92930 Paris La Défense Cedex, France.
authors.forename: L
authors.initials: L
authors.lastname: Jeannin
authors.affiliation: Université Pierre et Marie Curie, Laboratoire Metis, Paris, France.
authors.forename: P M
authors.initials: PM
authors.lastname: Adler