Publication Name: The Cooper & Eromanga Basins Australia
Authors: P.A. Robinson and G.F. Butler
Date Published: June 1989
Number of Pages: 21
Reference Type: Book Section
Abstract:
The Dullingari Murta Field was discovered in 1979 at Dullingari North-1, seventeen years after Dullingari-1 wasdrilled. The two main Murta reservoirs are the 48-5 and 48-6 sands of Cretaceous age. The 48-5 sand was deposited as a shoreline-bar sand whereas the 48-6 sand was deposited as a proximal turbidite at the head of a lacustrine fan. The two highly permeable oil reservoirs are approximately 1 ft thick and are separated by a shale
approximately 4 ft thick. Production and pressure data have proven that a low quality reservoir at the base of the 48-6 sand is also contriburing significant oil production by crossflow. A low pressure waterflood was implemented in order to improve the recovery from the high permeability reservoir and to retain the benefits of cross-flow from the lower permeability reservoir. The ultimate reserves of the Field as developed to 31 December 1988 are 6.4 million STB (1.02 million kL) of which the waterflood is expected to contribute 3.5 million STB (0.56 million kL) in addition to the 2.9 million STB (0.46 million kL) expected from primary recovery. A further 1.2 million STB (0.19 million kL) are possible based on further development drilling, the conversion of watered out production wells to injection wells, fracture stimulations and workovers.
The volumetrically calculated original oil-in-place (OOIP) for the high permeability reservoirs is 9.1 million STB (1.45 million kL). However, material balance calculations have indicated that the additional OOIP within the lower permeability reservoir could be 14-47 million STB (2.22- 7.47 million kL) assuming no water influx. There has been no primary water production and an oil-water contact has not been discovered in the Field. It is considered to be unlikely that pressure support is being derived from an aquifer.
The use of tracers is being considered to assist in the evaluation of the progress of the waterflood. Furthermore,
fracture stimulation of marginal wells is being evaluated to extend the development into the lower permeability flank areas of the Field. The deeper and lower permeability 49-0 sand is also under review as a recompletion candidate for wells where the 48-5 and 48-6 sands have watered out.