Quantitative analysis of fluvial sandbodies of the Toolachee Formation, Cooper Basin, Australia

Abstract

The Cooper Basin produces oil and gas from numerous fluvial channel sandstone bodies deposited within several formations such as the Late Permian Toolachee Formation; however, the geometry of these fluvial deposits are not well constrained. Five sandstone bodies (SS-1 to SS-5) have been identified within the Toolachee Formation. These sandstone bodies are characterized mainly by fining-upward packages, which have been interpreted to be deposited by high-sinuosity channels. This study aims to determine and interpret the size, geometry, and architecture of these fluvial sandstone bodies identified within the Toolachee Formation from well logs in the Meranji Field. The morphometric parameters examined in this study include channel width (w), channel depth (d), and meander-belt width (mbw). All of these parameters have been determined using empirical equations driven from modern rivers. The estimated maximum bankfull depth (d) ranges from 3.3 to 6 m, and the estimated channel width (w) ranges from 42 to 105 m, which indicates that these sandstone bodies were deposited by relatively small fluvial channels. The estimated meander-belt width (mbw) ranges from 800 to 2000 m, which indicates that some of these sandstone bodies (e.g., SS-1, SS-4, and SS-5) are connected and can be correlated between the adjacent wells within the Meranji Field. Furthermore, this indicates that these sandstone bodies are excellent reservoirs due to their good lateral extent. The empirical equations used in this study have improved the quantitative estimations of the channel dimensions and connectivity of the sandstone bodies. These equations can help to reduce the number of wells that are planned to be drilled in the Meranji Field.