Stoneley wave dispersion in a high permeability sandstone: Perth Basin, Western Australia

Abstract

There is increasing support for the existence of a relationship between Stoneley wave characteristics and permeability in sandstone formations. We evaluated monopole full waveform sonic data sets acquired in a mudded drill hole at the Mirrabooka Aquifer Storage and Recharge trial site in Perth, Western Australia. To increase the spectral range of the full wave form sonic data the hole was logged three times with transmitter centre frequencies at 1, 3 and 15 KHz. Data were recorded in four receivers spaced at 1ft intervals with the first receiver at 3ft from the transmitter. Stoneley waves were clearly identified in the low frequency range of 1?5 KHz, which is characteristic of Stoneley wave propagation in a slow formation. A semblance slowness technique was used to determine the slowness of Stoneley wave. Slowness values ranged from 950 µs/m (VST = 1050 m/s) for sandstone to 1650 µs/m (VST = 600 m/s) for shaley sediments. Observations of the dependence of phase velocity on frequency were made by using multi filter and phase shift transform techniques. The relationship between Stoneley wave dispersion and fast flow, high permeability pathways, as identified in flow and time lapse induction logging data, was clearly observed in an interval from 330 to 333m below ground level. This high permeability sandstone layer can be identified in dispersion curves by assessing frequency and phase velocity shifts. Our outcomes are significant, as they present the possibility of identifying narrow high permeability layers in wells where full waveform sonic logs have been completed.