Optimising seismic data acquisition parameters for open-cut coal exploration using a shallow high resolution reflection seismic test survey

Abstract

A shallow high-resolution seismic reflection test survey was conducted in the Maryborough Basin in an area near Gundiah, Queensland. The purpose of the seismic reflection test survey was to evaluate the application of using high resolution seismic data acquisition methods to detect thin coal seams at between 30m to 150m depth for open-cut coal exploration. The seismic test survey tested three seismic sources which included a 50kg weight-drop from 2m height, a 7kg sledgehammer, and a 12g (blank cartridge) in-hole shotgun. Seismic forward modelling indicated that thin coal seams (1 to 2m thickness) should provide seismic reflections at shallow depths of 30m, using 72 channel recording with 2m geophone intervals. The seismic source tests showed that the 12g in-hole shotgun produced the strongest seismic signal at the furthest geophone offsets. The seismic recording spread consisted of 96 seismic channels with single spiked 30hz geophones spaced at 2m geophone intervals. Based on the seismic source tests, the 12g in-hole shotgun was used to record a seismic test line with shot-points recorded from one end of the 96 channel spread through to the other end of the spread. The recording arrangements provided seismic data to both test data quality with shot to receiver offset, and examine the optimum common depth point (CDP) fold coverage to use for a larger seismic survey. Based on the seismic data processing results, a larger seismic survey could be conducted using a 72 channel recording spread with 4m geophone and shot-point intervals and achieve production rates of 400m per day with a 3-man crew.