Abstract:

To evaluate the development potential of the coalbed methane (CBM) in Jixi basin, a series of experiments (including coal macerals, microfractures, adsorption isotherm and mercury porosimetry analysis and so on ) are conducted on the collected coal samples. The drilling data, gas desorption, coal and gas outburst data are integrated to study the geological and physical properties of the coal reservoirs in the area. The geological controlling factors for CBM gases include structure, hydrology, and the sealing nature of the roof and floor lithology. The Pingma thrust fault and its nearby compressive crumpled structures are favorable for CBM preservation while the Dunmi normal fault is conducive, hence is not favored for CBM enrichment. Hydrological controlling factors for CBM gases are divided into three main categories: the hydraulic migration, hydraulic seal and hydraulic blocking, their roles on CBM enrichment are different. Based on the research of the roof lithology, the upper Muleng thick mudstone has a good capability for CBM sealing. GIS-based multi-level fuzzy mathematical evaluation method is used to calculate the amount of the CBM resources in the Chengzihe Formation in Jixi basin and to predict favorable CBM targets. The total CBM resource of the Chengzihe Formation in Jixi basin is estimated at 1 334.52×10⁸m³, with an average resource concentration of 0.42×10⁸ m³/km². The EW trending belt of the northern sag and the central area of the southern sag in Jixi basin are considered to be the most favorable areas for future CBM exploration and development.

Key words: Jixi basin, coalbed methane, gas geological controlling, favorable areas, resources