Determination of Biot’s Effective Stress Coefficient for Permeability of Nikanassin Sandstone

ABSTRACT

In Alberta and British Columbia, a huge amount of tight gas is trapped in relatively low-permeability rock formations. Physical fracturing of these formations could enhance the overall formation permeability and thus improve tight gas extraction. One of the outstanding issues in rock fracturing is todetermine the magnitude of applied effective stress. The general effective-stress law is defined as seff=sc – asp, where sc and sp are total confining stress and fluid pore pressure, respectively. Each physical quantity of rock responds to total stress and pore pressure in a different way, and thus each quantity has its own unique Biot’s effective-stress coefficient. The main objective of this study is to experimentally determine the Biot’s coefficient for permeability of Nikanassin sandstone. A series of permeability measurements was conducted on Nikanassin sandstone core samples from the Lick Creek region in British Columbia under various combinations of confining stress and pore pressure. In addition,permeability values were measured both along and across bedding planes to investigate any anisotropy in the Biot’s coefficient.

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