Could a structurally controlled, hydrothermal dolomite play be operative in Cambro-Ordovician carbonates of the southern Georgina Basin, Queensland?

Abstract

Hydrothermal dolomitisation of carbonates can create zones of favourable porosity and permeability in otherwise tight carbonate successions. In North America, a number of fields produce oil and gas from such reservoirs that developed along and adjacent to pre-existing fault zones acting as loci for hydrothermal fluid flow. Seismic data across these North American fields are characterised by linear zones of disturbance evident along fault zones where porosity development has occurred. Similar zones of disturbance have been observed on newly acquired seismic over the Toko Syncline in Queensland. Here, these zones extend through a thick Cambro-Ordovician carbonate succession that includes platform carbonates of the Thorntonia Limestone, overlying deeper water deposits of the Arthur Creek Formation that are organic rich and hydrocarbon generative at their base, and also in younger shallow water carbonates of the Arrinthrunga, Ninmaroo, Kelly Creek and Coolibah formations. If these zones of disturbance on seismic also reflect the development of hydrothermal dolomite reservoirs, they provide a new exploration target in the southern Georgina Basin.