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Title: Three-dimensional pore networks and transport properties of a shale gas formation determined from focused ion beam serial imaging
Authors: Thomas A. Dewers; Jason Heath; Russ Ewy; Luca Duranti
Geomechanics Department, Sandia National Laboratories, Albuquerque, New Mexico, 87185, USA.
Geophysics and Atmospheric Sciences Department, Sandia National Laboratories, Albuquerque, New Mexico, 87185, USA.
Chevron Energy Technology Company, San Ramon, California, 94583, USA.
Chevron Energy Technology Company, San Ramon, California, 94583, USA
Abstract: Three-dimensional pore network reconstructions of mudstone properties are made using dual focused ion beam-scanning electron microscopy (FIB-SEM). Samples of Jurassic Haynesville Formation mudstone are examined with FIB-SEM and image analysis to determine pore properties, topology, and tortuosity. Resolvable pore morphologies (>~10 nm) include large slit-like pores between clay aggregates and smaller pores in strain shadows surrounding larger clastic grains. Mercury injection capillary pressure (MICP) data suggest a dominant 1-10 nm or less size of pores barely resolvable by FIB-SEM imaging. Computational fluid dynamics modelling is used to calculate single phase permeability of the larger pore networks on the order of a few nanodarcys (which compare favourably with core-scale permeability tests). This suggests a pore hierarchy wherein permeability may be limited by connected networks of inter-aggregate pores larger than about 20 nm, while MICP results reflect smaller connected networks of pores residing in the clay matrix. [Received: May 12, 2011; Accepted: September 14, 2011]
Keywords: shale gas formation; Haynesville formation; 3D pore networks; focused ion beam; FIB serial imaging; transport properties; mudstone properties; image analysis; pore properties; topology; tortuosity; pore morphologies; capillary pressure; computational fluid dynamics; CFD; modelling; permeability; clay matrix.
Int. J. of Oil, Gas and Coal Technology, 2012 Vol.5, No.2/3, pp.229 - 248
Available online: 03 Apr 2012