L072 BMR 12 (Cockroach) well seismic velocity survey, NT, 1964

In November 1964, the Bureau of Mineral Resources Seismic Party No. 1 carried out a velocity survey in CBMR 12 (Cockroach) Well, Northern Territory, which had been drilled to 4000 feet and logged using sonic and other logging methods. The time/depth values obtained in the velocity survey were in good agreement with those obtained by integration of the sonic log. A curve showing the variation with time-of'the coefficient of reflection calculated from the sonic log showed an outstanding feature, which appeared to correlate with the best reflection recorded on an experimental seismic traverse nearby. According to the geological interpretation of the well log, this reflection arises from velocity changes near the boundary of the ArrinthrungaTormation and the Marqua Beds at a depth of 2,721 feet.