Coal reservoir characteristics and coalbed methane development mode in Zhangjiawan block of Zhina coalfield
Zhina Coalfield in Guizhou Province is rich in coal resources,and the development potential of coalbed meth-ane resources is huge.Taking Zhangjiawan block of Santang syncline in Zhina coalfield as the research area,according to the coring data of parameter wells,the coal structure,gas content,porosity and permeability characteristics and mechani-cal properties of coal reservoirs are analyzed,and the corresponding exploration and development mode of coalbed meth-ane is discussed.It shows that this block is distributed in thin-medium thickness complex coal seams with 10 minable coal seams and buried depth of 200-500 m.As a high-order coal reservoir,the coal body structure of most coal seams is good,and the gas content of coal seams is 9.36 to 18.05 m3/t,with an average of 14.14 m3/t,which shows a trend of increas-ing with depth,and has good development potential of coalbed methane.The permeability of coal seam is low,especially the permeability of No.6 and No.7 coal seam is extremely low,which is suitable for fracturing reconstruction or indirect permeability enhancement mode development.The strength and brittleness of coal reservoir increase with depth.It is dis-cussed that the preferred development mode in this area is cluster well"staged fracturing and combined layer drainage".For thick coal seams,small-scale horizontal wells can be considered for forward exploration,while for coal mining areas,it is suggested to actively explore the coordinated development of"coal-gas"resources.The research results can provide a useful reference for the establishment of coalbed methane exploration and development technology system in Zhangjiawan block.
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