High-Pressure Methane Sorption Isotherms of Black Shales from The Netherlands

Abstract

High-pressure methane sorption isotherms were measured on one Paleozoic and five Mesozoic shales, considered as targets for shale gas exploration in The Netherlands. The samples varied in mineralogy, organic richness, and thermal maturity. Four of the samples were clay-rich (total clay content 60–71 wt %), one contained equal amounts of clays and quartz (36 wt % and 33 wt %, respectively) and one was a marl sample (clays 34 wt %, carbonates 49 wt %). The total organic carbon contents (TOC) ranged from <1 wt % to 10.5 wt %, and the thermal maturity, as inferred from Rock-Eval analysis, from immature to overmature. Excess (Gibbs) sorption isotherms for methane were measured at 65 °C on dry samples up to 25 MPa. The maximum excess sorption capacities within this pressure range varied from 0.05 to 0.3 mmol/g (1.1–6.8 m3 STP/t). No correlation of excess sorption capacity with TOC was found. Low-TOC, clay-rich shales had comparable or even higher methane sorption capacities per unit rock mass (mmol/g) than orga...