Resources and reservoir formation of unconventional gas in coal measure,Hebei Province

In order to find out the potential of the unconventional gas resources in coal measure and reveal its effect of coupling reservoir in Hebei Province,the geochemical and physical characteristics of coal measure reservoir were in- vestigated by adsorption isotherm experiment,total organic ( TOC) measurement,X-ray diffraction experiment,Rock- Eval experiment, high-pressure mercury intrusion experiment, low temperature N2 adsorption experiment, macerals identification and pulse permeability,et al. The unconventional gas resources in coal measure were evaluated and its reservoir formation was revealed combining with the evolution history of coal measure sedimentation-tectonic. The re- sults show that the unconventional gas in coal measure is abundant in Hebei Province,with 39 015 ×108 m3 coalbed methane (CBM),33 447×108 m3 shale gas and 24 000×108 m3 tight sandstone gas,which is dominated by the Permo- Carboniferous. The organic types are mainly type Ⅲ,and the Ro between 0. 5% to 3. 0% ,which are mainly at the ma- ture to over mature stage. Coal plays a decisive role and organic-rich mud-shale plays a key role on coal measure reser- voir,while the thickness of the mud-shale makes up the deficiency of organic matter. The connectivity of coal measure reservoir is good and overall is low porosity and permeability,the second hydrocarbon-generation is the key to coal measure reservoir. In terms of symbiotic regulation mechanism,CBM behaves as a layer adjustment,shale gas behaves as a layer of regulation and tight sandstone gas behaves as a coordination adjustment. Three types of coal measure res- ervoirs were distinguished by symbiotic regulation mechanism and spatial overlap,including the “ far-source” tight sandstone gas reservoir,the “self-source” shale gas / CBM reservoir and the “ self-source and other-source” superim- posed gas reservoir,three patterns were introduced to clarify the characteristics of the latter type reservoir.