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Characterising Previous HitGasNext Hit Shales by Laboraotry Adsorption and Field Desorption Analyses

Bustin, R. Marc
University of British Columbia, Vancouver, BC

Previous HitGasNext Hit shales as typically defined, include significant reservoir Previous HitgasNext Hit in the sorbed state. Additionally almost all shales have intergranular and to A lesser extent fracture porosity commonly in the range of 1-10% that is available to free (non-sorbed). In order to better understand the Previous HitgasNext Hit storage capacity of shales and try to resolve some of the discrepancies in early published data, a field, laboratory and numerical study was undertaken of selected Previous HitgasNext Hit shales and potential Previous HitgasNext Hit shales.

In Previous HitgasNext Hit shales, mass flow of the free Previous HitgasNext Hit occurs at similar rates to diffusion because of the low permeability (micro-darcy range) and high tortusity. Thus assessing Previous HitgasNext Hit-in-place of Previous HitgasNext Hit shales using typical canister desorption techniques results in erroneous data due to co-mingling of free and sorbed Previous HitgasNext Hit. Additionally, escape of free Previous HitgasNext Hit from the Previous HitshaleNext Hit retards diffusion of the sorbed Previous HitgasNext Hit. Typical in place analytical procedures treat all the Previous HitgasNext Hit captured during canister testing as sorbed Previous HitgasNext Hit and hence the sorbed Previous HitgasNext Hit component is markedly over estimated. Adding the free Previous HitgasNext Hit capacity calculated from porosity and water saturation measurements to the erroneous sorbed Previous HitgasNext Hit measurements for volumetric Previous HitgasNext Hit in place calculations results in over estimation of Previous HitgasNext Hit-in-place.

An additional problem replete in the early published data is the use of finely milled Previous HitgasNext Hit Previous HitshaleNext Hit samples for adsorption capacity analyses by the adsorption isotherm technique. Our experimental results show that milling Previous HitshaleNext Hit to micrometre sized particles prior to analyses results in an artificially high sorption capacities as measured by adsorption isotherms. Such results are readily attributable to the exponential increase in surface area with particle size reduction. This problem is not as evident with coal because of the higher internal surface area of coal. Our data show that most deeply buried Previous HitgasNext Hit shales hold more Previous HitgasNext Hit in the free Previous HitgasTop state than sorbed state.