The determination and characterisation of reservoirs in the Cambrian succession of the Stansbury Basin with a view to temporary gas storage

Temporary underground gas storage was first recorded in 1915 and is the process of injecting natural gas into porous underground rock formations to be withdrawn at a later date. The focus of this study was to identify and examine the reservoir quality of targets within the Cambrian succession of the Stansbury Basin and the Permian succession of the Troubridge Basin with a view to temporary gas storage. The scope of the study was limited to onshore Yorke Peninsula in South Australia, with two varieties of gas storage methods investigated, an evaporitic unit with halite deposits suitable for dissolution to create a gas storage void, and conventional reservoirs in trap configuration. Four potential reservoir targets were investigated through the study of core, wireline logs, thin sections and outcrops including, evaporites in the Cambrian Minlaton Formation, carbonate reservoirs in the Cambrian Kulpara Formation and Koolywurtie Member, and Permian sands of the Cape Jervis Formation. Regional geology maps, seismic, gravity and magnetics were investigated to gain a greater understanding of the structure and subcrop distribution of target horizons on the Yorke Peninsula. Seismic investigations highlighted a general thickening of the Permian and Cambrian succession towards the south of Yorke Peninsula. Folding of the Cambrian sequence emphasized the potential of structural trapping mechanisms occurring in the Stansbury Basin. Evaporites were investigated in core of the Minlaton 1 and Minlaton 2 wells. Only one evaporitic deposit of note has previously been intersected in wells drilled on the Yorke Peninsula. In Minlaton l evaporites were composed of thin (generally 450mD). The best core plug porosity (16.9%) and permeability (452mD) development is associated with sucrosic dolomite in Stansbury West l, which has completely replaced the original limestone fabric. However as porosity and permeability development generally appears to be restricted to relatively thin ( <2m) intervals, the chance of finding a suitable site for gas storage appears limited. The Koolywurtie Member was investigated as a conventional reservoir m trap configuration target in outcrop at Horse Gully near Ardrossan on the Yorke Peninsula and core in Minlaton 1. Vuggy porosity was observed in outcrop, however no significant porosity development (typically