Application of Cross-Plotting Techniques for Delineation of Coal and Non-Coal Litho-Units from Well Logs

Abstract

Well log responses can be used to delineate coal and carbonaceous shale from other non-potential litho-units by cross-plotting technique. The cross-plotting between gamma ray and density had been carried out for 15 wells of Jharia coalfield, India. Through these different cross-plots across the study area, different litho-units like; coal, shaly coal, carbonaceous shale, shale, sand/sandstone, shaly sand, jhama and igneous intrusion (mica peridotite) have been identified. Clustering of points for different lithologies in the above cross-plots indicate that the different trends with marginal overlap between carbonaceous shale/shaly coal and shale as well as shaly sand and shale. The coal horizons are mostly overlain and underlain by shale or sandstone. Cross-plot analysis indicates the various coal lithologies which will play important role in CBM exploration and exploitation strategy.

The use of cross-plots in lithology delineation and petrophysical evaluation of some wells in the western Coastal Swamp, Niger Delta

“…The reservoir delineation results using well log crossplots in the wells show distinct lithologies of sand, shale and intercalations of sand and shale, which agrees with the results of Chatterjee and Paul (2012) in their application of well log cross-plots in distinguishing coal and non-coal litho-units in Jharia Coal Field, India. Sand connectivity analysis of the three wells shows good communication between wells M and N, with partial connectivity with well L. (Figure 1; Inset).…”

“…The objective of this study is to analyse well logs in order to delineate the lithofacies and predict the reservoir qualities of the sand units using the clusters of log cross-plots (Chatterjee and Paul 2012) and petrophysical evaluations.…”