Fine Description And Physical Properties Main Controlling Factors Of Coal Reservoir In Hancheng Area

Taking coalbed methane exploration and development demonstration area as the research target zone in Hancheng the eastern margin of the ordos basin as example, this paper is about fine description of the coal reservoir, and analysis of main control factors to coal reservoir physical property; basing on geology theory, coal pore, fracture were observed directly and statisticed quantificationally by the conventional microscope and scanning electron microscopy,and coal pore size and proportion were obtained with the aid of mercury injection, low temperature specific surface analyzer; what’s more, the pore and fracture system was more subtle representation, by using nuclear magnetic resonance and X-ray CT technology, thus, the differences between three sets of coal seam was found out; In the end, this paper discusses the influences about metamorphic grade, coal petrography type and quality to coal reservoir adsorption and pore-fracture development characteristics, in addition, the pore fracture control mechanism to permeability was analyzed.According to the pore structure whether it benefits the CBM diffusion or not, mercury intrusion curves can be divided into three types, the comparison to the NMR experiment, the shape of curve have a good correspondence; the low- temperature nitrogen adsorption palindrome is helpful to reveals the pore throat form, also the syntagmatic relation of coal reservoirs’ three forms of pore type were shown in Hancheng.With the aid of optical microscope, and the microscopic fissure development status observed, and their shape and density were statisticed, C and D types microscopic cracks developed well in this medium to high coal rank reservoirs, while the numbers of A and B type cracks who owns a greater width is small, the microscopic cracks is well developed, the secondary interstice occupies a large proportion, and the space filled by the mineral, such as calcite and clay, mostly.Basing on peak number, position and other morphological characteristics of the NMR T2 spectrum, this paper distinguish different pore scale and fracture, and presents its space distribution and contact characteristics, combining X-ray CT technology which divided different components by their CT number, in addition, coal porosity and permeability can be predicted.those indicate that microscopic crack density, crack space filling condition and movable porosity selected as the main coal reservoir permeability index.The influence pore development good or bad on coal property is great. The pore development characteristics is changed with the coal rank produce different, also influenced and interacted by coal organic component, coal quality and others factors together. To some extent,the coal porosity can be used to reflect the coal permeability comprehensively; permeability is bigger in sample with a larger porosity.