Rediscovering North Perth Basin in Unconventional Arena

Abstract

North Perth Basin, known for its potential since its initial commercial discovery in 1964, holds about 10km thick sediments. Irwin River Coal Measure (IRCM) and Carynginia Shale (both Permian), Kockatea Shale (Triassic) and Catamarra Coal Measure (Jurassic) are proven source in the basin. Dandaragan trough, the main depocentre and source area in North Perth sinks deep into the realm of metagenesis towards east. Hydrocarbon fields Woodada (gas), Behara Springs (gas), Jingemia (oil), Hovea (oil), Dongara etc. are located on its gentler western flank. Such preferential migration towards the gentle flank of half grabens is well known, e.g., Cauvery, India and Reconcavo, Brazil. Though endowed with multiple zones of reservoir and source facies, the conventional hydrocarbon pools in North Perth are limited in size. Considered sub-commercial based on conventional practices at that time, well AS-1 flowed 4mmscfd gas during testing (1965). Mountain Bridge-1 (1993) demonstrated gas flows from other prospective formations during DST widening and deepening the resource potential of North Perth Basin. Decades later, basin wide review led to exploration and hydraulic stimulation of the unconventional zones demonstrated that sustained hydrocarbon flow could be maintained from the formations and provided critical evidence to underpin multi TCF unconventional resource bookings in Perth basin (GIIP 167TCF, EIA, 2013). Recent wells drilled with shale objectives from north to south at Senecio, Arrowsmith (AS), Woodada Deep and Drover flowed oil and gas from three of the four identified source facies in addition to tight sands. The current paper discusses results of vertical well AS-2 (5 tested zones) in conjunction with public domain information of the other three wells to bring out its significance in North Perth Basin as a whole. Fault breach has been cited as reason for absence of a hydrocarbon pool in recently drilled shallow offshore well Red Hill South. The low permeability inherent to unconventional shale reservoirs makes them less prone to leakage. The encouraging flow of gas from multiple hydrocarbon zones in Permo-Traissic from four wells located wide apart in the axial direction has put North Perth on a firm footing for future hydrocarbon search within these reservoirs. Aid of 3D seismic, sweet spot identification and a few horizontal wells to frac-test would give fillip to further unconventional hydrocarbon exploration in North Perth basin.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015