Application of 3-D seismics to mine planning at Vaal Reefs gold mine, number 10 shaft, Republic of South Africa

Abstract

During 1994, a 3-D seismic reflection survey was undertaken at Vaal Reefs No. 10 shaft with the objective of mapping the detailed structure of the Ventersdorp contact reef gold orebody. This would provide vital input into future mine planning and development. The survey benefitted from 10 years of 2-D seismic experience and one previous 3-D mine survey, conducted in the Witwatersrand Basin. The seismic survey at No. 10 shaft accurately and spectacularly delineated the 3-D structure of the Ventersdorp contact reef at depths ranging from 1000 to 3500 m, imaging faults with throws in the 20- to 1200-m range. The resultant structure plans were satisfactorily validated by subsequent surface drilling and underground mapping mining operations during the period 1994 to 1996. These plans have been merged with drillhole, underground, and sampling data into an integrated mine modeling, gold reserve estimation, and mine scheduling package. The geology department now manages the planning function at No. 10 shaft, and 3-D seismics has played a significant role in placing this important responsibility firmly within the geologists’ domain. Building on the success of the No. 10 shaft survey, two other 3-D seismic surveys were concluded over mines during 1996 and 1997.