Reservoir formation characteristics and co-exploration and concurrent production technology of Longtan coal measure coalbed methane and tight gas in Songhe field,western Guizhou

Based on a demonstration project of coal-formed gas co-exploration and concurrent production,this paper analysed the occurrence characteristics and development conditions of Longtan coal measure coalbed methane and tight gas,and discussed the suitable technology for the coal-formed gas co-exploration and concurrent production. The re- sults show that coal-formed gas is mainly hosted in the multiple coal seams of Longtan coal measures and closes to the gas bearing formation which contains fine sandstone and siltstone;it has enough resource and favorable development conditions that include the multi-layer commingling development and the concurrent production of coal-formed gas. The coal reservoir with the characteristics of high temperature,overpressure,high gas content and gas supersaturated is suitable to coalbed methane ground development;but some factors including the reservoir fracture closing and mineral fill- ing could lead to the lower original permeability at high ground stress area. Therefore,the coal-formed gas ground de- velopment needs to carry out the reservoir reconstruction. The key technology of discovering,recognizing and evaluating the optimization of gas bearing and producing layers in field coal-formed gas co-exploration and concurrent production are gas logging,uncorrected comprehensive logging and the comprehensive evaluation of gas bearing layer. They pro- vide the basis for establishing the coal-formed gas co-exploration and concurrent production scheme. In the develop- ment mode of collecting well group,the technologies including the small-layer perforating,group-segment fracturing and multi-layer drainage need to match with the topography and geology conditions of the field. Thus it can significant- ly improve the engineering effect of the multi-layer commingling development and the coal-formed gas co-exploration and concurrent production.