DETERMINATION OF CAPILLARY PRESSURE, RELATIVE PERMEABILITY AND PORES SIZE DISTRIBUTION CHARACTERISTICS OF COAL FROM SYDNEY BASIN-CANADA

Abstract

Global warming due to anthropogenic emission of greenhouse gases notably carbon dioxide, could lead to the irreversible melting of the polar ice and significant increases in global mean temperature. One of the mitigating strategies that can be carried out on a larger scale is the capture and geological sequestration of this gas. Notable among proven geological resources is deep unmineable coal seams. Geological sequestration in these systems has a value added advantage because of coal bed methane production which is a source of cleaner burning fuel than coal. Accordingly the injection of carbon dioxide to a coal seam for long term storage accompanied by the production of methane requires adequate knowledge of the two phase flow characteristics of the methane/brine and carbon dioxide/brine systems. The most important characteristics of the two phase flow are relative permeability and capillary pressure. The coal core was characterized by proximate and ultimate ASTM measurements, x-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. These analyses identify the existence of clay minerals in the coal structure, which shows that origin of coal formation was from swamp plants. These minerals were used to fill the pores and reduce the permeability. Relative permeability and capillary pressure data for Sydney basin coal samples were collected. This study has also obtained pore size distribution and its indexes both from capillary pressure data and statistical methods based on the hyperbolic model of capillary pressure versus saturation data. The elaborate experimental design and precise measurements using capillary pressure unit (TGC-764) with a pressure control module makes the acquired petro-physical data a valuable asset for future carbon dioxide enhanced coal bed methane production.