The geological settings of Birkhead Formation oil fields in the study area are characterised by access to Permian-sourced hydrocarbons. This study has shown that in over 60% of the fields the main Nappamerri Group seal is absent; for those fields where the Nappamerri is present, either diminution of the thickness of Nappamerri section and/or deep faults could have resulted in viable oil conduits. About 75% of Birkhead fields incorporate additional Eromanga Basin sequence oil pools, most commonly at the Namur Sandstone Member and Hutton Sandstone levels. The vertical stacking of oil pools and their geological settings support a Permian source for the oil, with the main avenues of migration into the Jurassic being either via direct subcrop or fault conduits. The Birkhead cannot be completely discounted as a source, and in some instances there may have been some indigenous contribution, e.g. as at Moorari Field. A critical consideration in many Birkhead fields is the nature of the Hutton - Birkhead transition. The transition represents a time transgressive facies change from braided fluvial (Hutton proper) to degrading fluvial (Birkhead) to lake / floodplain (Birkhead). This study has defined two main categories of Birkhead reservoir. The first relates to degrading fluvial reservoirs in the Hutton - Birkhead transition zone: these reservoirs are usually ascribed to the basal Birkhead interval. In a number of fields this transition zone denotes a tight, oil-saturated waste zone above and in communication with the main top Hutton section reservoir. Reservoir performance is largely a function of channel development within the degrading fluvial sequence, and lateral facies changes make reservoir prediction difficult. The main fluvial facies involved are anastomosing fluvial and meandering fluvial. The second reservoir category relates to lacustrine reservoirs within the lower-mid Birkhead interval. The main reservoir types are upward coarsening lake fill cycles and distributary channels. Broadly speaking, the regional pattern of Birkhead reservoir development relates to trends in palaeogeography. The most prolific Birkhead oil fields occur in the south where sediment influx was highest (e.g. at Wancoocha, Spencer North and Spencer South). In the north lower energy distal facies dominate and reservoir development is relatively poor (e.g. at Callabonna, Charo and Moorari). The productivity of Birkhead oil pools can be divided into three categories based largely on the above reservoir types. Type I fields relate to degrading fluvial facies in the basal Birkhead interval which are in reservoir communication with the top Hutton interval. These reservoirs are developed less than 50 feet above the top Hutton boundary, and have recovery factors varying between 0.3 and 0.45. Edge water drive is the most common drive mechanism. Type IIA fields relate to lacustrine reservoirs developed 50 feet or more above the top Hutton boundary. These reservoirs are not in communication with the Hutton reservoir, and show recovery factors of less 0.3. Edge water drive is also common in this field type. Type IIB fields are similar, but have a depletion drive mechanism with recovery factors at or below 0.03. Oil-saturated zones within the Birkhead often display a subdued resistivity response and minor hydrocarbon indications. A review of Santos electric log and hydrocarbon show records has revealed numerous wells in which there are possible by-passed oil zones, the most important instance occurring in the southern Merrimelia Field where there appears to be an untested oil pool developed in the mid-Birkhead.