Importance

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Abstract

The permeability and/or porosity of gas-containing substrates, particularly substrates of low permeability, can be determined by sealing a gas-containing substrate in a sealable 'core analysis vessel' of known or ascertainable volume as soon as possible after removing the sample from the subsurface. Because the sealed sample is still at about formation pressure, gas will leak from the sample into the space of the vessel. The pressure build-up over time in the core analysis vessel is measured. When the pressure has equilibrated, the pressure is vented through a flowmeter to determine gas volume, followed by venting to atmosphere. The system is resealed and then the process is repeated until no subsequent pressure build-up occurs. By knowing the internal volume of the chamber, the bulk volume of the core sample, and recording the pressure build-up as a function of the time, many substrate properties, such as pore volume and permeability, can be calculated via standard methods. The effective pore volume which the gas originally occupied can be directly measured by venting the gas in the core analysis vessel to the external pressure through a flow-volume measuring device.

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First Claim