Influence of Mineral Composition to Rock Strength on UCG Process

Underground coal gasification (UCG) process needs the stability of cavities around the coal seam for continuation of its the process. The stability of the cavities depends on the rocks strength adjacent of the coal seam, especially the rocks on the roof cavities. UCG process will lead to changes in rock mineralogy structure due to high thermal load around 700 - 900 oC or above and the existence of the thermal load also resulted in changes of the rock strength. To know these changes has been investigated experimentally in the laboratory the behavior of claystone samples from originating from the proposed of UCG pilot plant in Musi Banyuasin district, South Sumatera-Indonesia. Laboratory tests have been done with X-Ray diffraction (XRD), X-Ray Fluorescence (XRF) and geomechanics test to claystone samples before and after thermal treatment. The thermal load has been done by giving the variation of temperature at 30 1100 oC. This is assumed as the condition of temperature variation at the space of UCG gasifier. In this paper also discussed the consequences of the changes of mineral structures and chemistry element to rock strength and conditions cavity after the UCG process.