The purpose of this paper is to show the reserve estimation procedures used by KUFPEC on the NW Shelf of Australia production license WA-49-L, which is currently under development as part of the Chevron's Wheatstone LNG project. The gas in the WA-49-L permit was discovered in a combination of structural and stratigraphic traps of a regional fluvial channel sand complex within the Triassic Mungaroo Formation. These channel sands contain gas trapped on a large structural ridge with up-dip terminations below a regional, angular unconformity and overlain by the Cretaceous Muderong Shale. Some of the deeper channel sands are trapped against the bounding fault of the ridge. These channel sands are stacked as a result of amalgamation of numerous channels, with the individual sand thickness of up to 60 meters but typically in the 15 to 30 meters range. These channel sands are discrete with individual gas-water-contacts, and clearly visible on seismic and inversion data as low impedance, Class 3 AVO (amplitude versus offset) anomalies.The estimation of gas resources is delineated by 20 wells drilled through April 2011 on WA-49-L. Limitations of the seismic frequency content result in channel thicknesses of less than 5 meters not being visible. Seismic inversion attributes are used to estimate gas sand probability, sand thickness and porosity. Rather than using large scale net-to-gross assumptions commonly used in the industry for reserves calculations, KUFPEC used maps of individual sand bodies based on the inversion impedance amplitudes and gas sand probability (GSP) attributes to compute each sands' likely range of resources values.

Time-dependent measurements of uniaxial compressive strength, and ionic and water transport were conducted to analyze the alteration of shale’s strength, as a function of time, when exposed to aqueous solutions. Results showed that the compressive strength of shale is time-dependent, and it relies highly on water activity and ionic concentration differences between shale and aqueous solutions. Data obtained from this work showed that time-dependent water and ion transport into shale correlated well with compressive strength measurements. It was revealed that initial water extraction by osmosis strengthened shale until ions and their associated water clouds invaded shale causing reduction in its strength. It is quite possible that water flow by diffusion osmosis may have counteracted water flow by chemical osmosis rendering ionic diffusion as the primary regulator on shale strength alteration. Furthermore, it was found that alteration of compressive strength when it interacted with aqueous solutions could be adequately explained within the confines of chemical osmosis, ionic diffusion, and diffusion osmosis. Data suggests that the impact of chemical osmosis on compressive strength is observed earlier than ionic diffusion and diffusion osmosis. Data also showed that potassium ions seem to contribute to the enhancement of the compressive strength of shale.

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