Hydraulic Fracturing in Coal Mining

This project was conceived as a follow up to ACARP Project C9024 “Development of Hydraulic Fracturing to Control Windblast” which focussed on the experience of successfully introducing hydraulic fracturing to control windblast at Moonee Colliery. A range of potential applications were identified in Project C9024 and, as a result of the success at Moonee Colliery, there was interest shown by West Wallsend Colliery, Crinum Mine and Moranbah North Mine in applying the technology to the particular face control issues that each mine was either experiencing at the time or anticipating in the near future.

This project had three main goals:

• to further develop the understanding of the mechanics and methods of creating hydraulic fractures, particularly in stress fields modified by proximity to mine openings,
• to develop specialised equipment to improve the effectiveness of systems used to create hydraulic fracturing,
• to make hydraulic fracturing more available to mine operators.

These goals have been successfully reached.

A successful laboratory program has progressed the understanding of the mechanics of hydraulic fracturing close to free surfaces. Various items of specialised equipment, including a gel mixer, downhole packer inflation system and borehole notching systems, have been developed. This equipment has been used in a project where hydraulic fracturing was successful in controlling a windblast hazard. It has also been used in a field investigation study aimed to modify the in situ stress field to more effectively place hydraulic fractures for control of periodic weighting.  Improvements in numerical modelling technique produced better simulation of caving behaviour and allowed various treatment strategies to be evaluated at four sites.

The project was designed to run for 36 months with the ACARP contribution leveraged against a project run by CSIRO Division of Petroleum Resources and several field-based commercial projects that scoped the potential for hydraulic fracturing.

The results of the hydraulic fracturing program have been transferred to the wider industry through local and overseas conference papers, a successfully completed PhD thesis, and commercial work focussed on specific issues of relevance to the Australian coal industry.