Understanding Heterogeneities in a Mixed Carbonate-Siliciclastic Reservoir of the Perth Basin, Australia

The heterogeneities of mixed carbonate-siliciclastic reservoirs are not well understood, despite the importance of this type of deposit as a proven hydrocarbon reservoir in many oil and gas fields. This study aims to advance our understanding of the heterogeneities of the mixed carbonate-siliciclastic reservoir with three main objectives: (1) to characterize sedimentary facies and depositional environment of the Beekeeper Formation; (2) to better understand the mixing of siliciclastic and carbonate materials; and (3) to better understand the main influences on the development of a mixed carbonate-siliciclastic reservoir. Integrated geological analyses (sedimentary logging, acetate peels, acid digestion, and petrographic) have been conducted to achieve the aim and objectives of this study. Results show that the Beekeeper Formation consists of seventeen facies grouped into carbonate-dominated facies group, siliciclastic-dominated facies group, and mixed carbonate-siliciclastic facies group, and was deposited within a ramp type platform. Both compositional and stratal mixing were identified as present within the Beekeeper Formation. The mixing of carbonate and siliciclastic materials/minerals within this formation occurred at three different scales, which are small scale (mm to cm scale), moderate scale (cm to a few m scale), and large scale (a few m to >100 m scale). The presence of fracture systems, highly varied facies, and the mixing of carbonate and siliciclastic materials/minerals are evident in the evolution of the Beekeeper Formation which was strongly influenced by tectonic activities, climatic conditions, eustasy, sea-level fluctuations, rate of carbonate production, and terrigenous influx.