Coal Ply Distributions and Quantitative Prediction in Tipton Gas Field

Abstract

The geometries and distributions of coal plies are very important for the development of coalbed methane. The hundreds of coal plies developed in the Jurassic Walloon Coal Measures of Tipton field in Surat basin of east Queensland, Australia are thin and show splitting, merging, pinching frequently, which have highly variable in the spatial continuity and are difficult to be predicted even the boreholes are closer. With the core data and mud logging, density and gamma logs of the 167 wells in the field are normalized and the lithology interpreted chart is acquired. Five lithologies of coal, shaly coal, sandstone, siltstone and shale are classified. Isochronal stratigraphic framework of coal members, sublayers and plies is built by sedimentary multi-cycle correlation method. The horizontal distributions and geometries of the 125 coal plies are analyzed and the quantitative relationship between coal ply thickness and area is established. Results show that the thickness of coal plies in Kogan, Macalister, Wambo and Argyle is relatively thin, generally less than 1 m, and the spatial continuity is relatively isolated. The thickness above 1 m of coal plies in Upper Taroom and Condamine is relatively developed and the coal plies extends relatively far. The distribution area of coal ply has obvious double logarithmic correlation with coal ply maximum thickness. The thicker coal ply has larger distribution area and better continuity of spatial extension. The spatial distribution range of coal ply can be quantitatively predicted through the thickness of the coal ply. The results in the study can be used to better understand the coal reservoir characterization and can be helpful for the geological modelling, optimal well location and well spacing design.KeywordsCoalbed methaneWalloon Coal MeasuresCoal plyGeometryQuantitative prediction