The most efficient pattern of vertical degasification holes for a coalbed is dependent on cleat orientation. Surface joints, infrared photolinears, and Ronchi grating photolinears were investigated in southwestern Pennsylvania and northern West Virginia as potential estimators of cleat orientation in areas of virgin coal.
Directional data obtained from the three techniques investigated yielded satisfactory regional estimates of cleat orientations. Analysis of surface joints was the only technique considered sufficiently reliable on a local basis. Estimation of cleat orientation is based on the pairing of the principal directional sets into all reasonable combinations of fundamental systems. The system or systems composed of the most dominant sets nearest to 90° separation are likely to be a reliable estimate of cleat orientation. Relative dominance of individual sets is based on the number of readings that form the corresponding peaks of the rose diagrams on which the directional data were plotted. The most dominant set of the system selected is likely to be the face cleat.