Measurements of gas permeability and diffusivity of tight reservoir rocks: different approaches and their applications

被引:506
作者
Cui, X. [1 ]
Bustin, A. M. M. [1 ]
Bustin, R. M. [1 ]
机构
[1] Univ British Columbia, Vancouver, BC V5Z 1M9, Canada
基金
加拿大自然科学与工程研究理事会;
关键词
coalbed methane; diffusivity; gas shales; permeability; PULSE-DECAY PERMEABILITY; AMERICAN COALS; HIGH-PRESSURE; ADSORPTION; TRANSPORT; GRANITE;
D O I
10.1111/j.1468-8123.2009.00244.x
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Permeability and diffusivity are critical parameters of tight reservoir rocks that determine their viability for commercial development. Current methods for measuring permeability and/or diffusivity may lead to erroneous results when applied to very tight rocks including gas shales, coal, and tight gas sands, as well as rocks considered as seals for nuclear waste repositories and strata for geological sequestration of CO2. The use of He as routinely applied to measure porosity, permeability, and diffusivity may result in non-systematic errors because of the molecular sieving effect of the fine pore structure to larger molecules such as reservoir gases. Utilizing gases with larger adsorption potentials than He, such as N-2, and including all reservoir gases to measure porosity or permeability of rocks with high surface area is a viable alternative, but requires correcting for adsorption in the analyses. This study expands several approaches to measure permeability and diffusivity with considerations for gas adsorption, which has not been explicitly considered in previous studies. We present new models that explicitly correct for adsorption during pulse-decay measurements of core under reservoir conditions, as well as on crushed samples used to approximate permeability or diffusivity. We also present a method to determine permeability or diffusivity from on-site drill-core desorption test data as carried out to determine gas in place in coals or gas shales. Our new approach utilizes late-time data from experimental pressure-decay tests, which we show to be more reliable and theoretically (and practically) accurate than the early-time approach commonly used to estimate gas-transport properties.
引用
收藏
页码:208 / 223
页数:16
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