Applications of standard and advanced statistical methods to TOC estimation in the McArthur and Georgina basins, Australia

Abstract

Multiple potential shale-gas plays have been identified in Australia. Th total estimates of recoverable dry and wet shale gas exceed 157 tcf. Technological advances and more informed estimations of total organic carbon (TOC) abundance and distribution might further increase the assessments of recoverable shale gas. TOC content is known only at the depths where laboratory measurements on recovered core samples are performed. However, reliable estimation of potential resources can be based only on information about vertical and lateral distribution in organic matter throughout the prospective gas-shale reservoir. Ths information commonly is obtained from conventional wireline logs such as gamma ray, density, transit time, and resistivity. Methods routinely used for these estimations were developed for organic-rich shales from Northern American basins, where organic matter of marine Type I and Type II typically is observed. In prospective Australian basins, organic matter ranges from marine Type I to terrestrial Type III. Ths fact, along with different depositional history of Australian reservoirs, might lead to quite different logging-tool responses. Ths, the relations between the amount of TOC and estimation from logs might be quite different.