Study on coal reservoir features and fracturing reconstruction in Changgang Syncline of Qianbei Coalfield

In order to guide the exploration, development and block selection of coalbed methane in Changgang Syncline of Qianbei Coalfield, based on the exploration, test well information and coal sample test data, the paper had an analysis and study on the coal reservoir features in Changgang Syncline of Qianbei Coalfield. In combination with the trial drainage effect of coalbed methane wells, from the coal structure and the seam as well as the surrounding rock features, a study was conducted on the fracturing reconstruction of the coal reservoir. The study results showed that Changgang Syncline seam was many and thin, mainly the lean coal- anthracite coal with a low ash content - medium ash content, high sulfur content and the seam depth was moderate. The coal specific surface area was large, the adsorption was strong and the gas content was high and the resource base was good. Also the coalbed methane desorption difficulty was high, the porosity was low and the borehole crack system was not developed. The seam was a low porosity, low permeability and over pressure reservoir and would cause a certain difficulty to coal seam development. In the north area of the syncline,due to the failure by faults, the coal structure was broken and mainly the broken partical coal and fine coal were not be favorably fractured. In the south syncline, the coal structure was relatively completed, the mechanics property of rock in each seam was strong, the roof and floor were mainly thin mudstone and were obviously different to coal and rock mechanics property.Only coalbed methane would be mined,the fracturing of No. 3 seam and No. 7 seam would be optimally selected. If the co-mining of the coal measure gas, thus most seams could be the fractured seams suitably.