Three-Dimensional Modelling of Dryland Reservoir Analogues From Lake Eyre, Central Australia: The Kalaweerina Terminal Splay Complex
Alqasim, Othman, Alsubhi, Abdullah and Baltyoor, Abdulaziz
Engineering Honours Degree, 2010
University of Adelaide
In many sedimentary basins world-wide, dryland environments resulted in the deposition of what are now considered to be important reservoirs. As modern sedimentary systems provide valuable information for better understanding ancient deposits and hydrocarbon systems in the subsurface, oil and gas companies are interested in investigating the sedimentology of previously studied dryland reservoir analogues. Lake Eyre is a dryland playa, and is the fourth largest terminal lake in the world and the largest in Australia. It has one of the largest inland drainage basins in the world, it covers one sixth of the Australian continent with an area of 1,140,000 km2 and has an arid to semi-arid climate. Important reservoir analogues from Lake Eyre are the Terminal Splay Complexes, which form where ephemeral rivers reach the playa. The Kalaweerina Terminal Splay Complex is the focus of this investigation, which aims to improve understanding of the reservoir characteristics of Terminal Splay Complexes and the application of modern analogue data from Terminal Splay Complexes to hydrocarbon reservoirs. The Kalaweerina Terminal Splay Complex has five main depositional sub-environments: Fluvial Channel, Proximal TSC, Medial TSC, Distal TSC and Playa. Sixteen facies are associated with these five depositional sub-environments.
This study involved simplifying high-resolution facies data in order to assign one overall facies to each depositional sub-environment. Three models were then constructed using Schlumberger Petrel 2009 based on these depositional sub-environments; one model with real data and two models with hypothetical scenarios that reflect some of the uncertainty in application of modern analogues to ancient deposits (at a grid size of 10 x 10 m). These models were then populated with petrophysical properties (porosity and permeability) to understand the sedimentology of the Kalaweerina Termianl Splay Complex reservoir analogue in terms of the impact of application of modern analogue data on flow in these deposits and reservoir production. Petrophysical properties were estimated for each sub-environment based on facies observation data (samples) taken from the Kalaweerina Terminal Splay Complex. A moderate variation in the petrophysical properties was observed in each depositional sub-environment within the Kalaweerina Terminal Splay Complex due to differences in their facies. The models were then upscaled to a bigger grid size (50 x 50 m), a more realistic scale for industry modelling. A comparison was finally conducted between the Kalaweerina Terminal Splay Complex model and the other three Terminal Splay Complexes models from Western Lake Eyre. It is expected that this study would provide a better understanding of the sedimentology of this Terminal Splay Complex reservoir analogue in terms of the impact on flow in these deposits and reservoir production. Also, it would help in describing the likely variation in reservoir properties of different Terminal Splay Complex deposits.