Physicochemical properties of methane storage and transport in Devonian shale. Annual technical report, June 1989-May 1990

The report deals with the determination of how natural gas is stored in Devonian shales. One hundred seventy-five helium and methane isotherms on 38 shale cores are presented. An additional 27 isotherms were determined from the constituents of Devonian shale: illite, chlorite, corrensite, quartz, kerogen, and oil. Using the isotherms for all samples, the following parameters were found: helium density and porosity, Langmuir-fit parameters, and relative amounts of methane present at gas-in-pore and in an adsorbed state, or in solution. Supporting mercury porosimetry results are also presented, and its relationship to the isotherm data is discussed. From the data it was determined that, for most samples, adsorption onto illite accounts for about 50% of the gas storage in the rock with gas-in-pore accounting for the bulk of the remainder. However, some samples will have sufficient oil or kerogen so that storage by adsorption onto, or solution into, these materials is the primary storage mechanism. Some preliminary measurements suggest that Devonian shale expands slightly in contact with water, and implications of this for formation damage are discussed.