Development of hydraulic fracturing in high stress conditions in Australian underground coal mines

Hydraulic fracturing has been used extensively in the petroleum and coalbed methane industries as a means of improving access to the reservoir and thereby enhancing production. In the Australian coal mining industry there has been an aversion to the use of hydraulic fracturing. One of the main reasons for the lack of application of this technology has been the perceived risk of damage to the strata and the resulting impact on future mining operations. A number of Australian mines are progressing toward areas where gas drainage is becoming increasingly difficult and these mines are seriously considering the use of hydraulic fracturing. In several cases where the use of hydraulic fracturing was trialled in mines operating in the Southern Sydney Basin the technique was found not to be effective due to the impact of wellbore damage. The damage caused by the high insitu stress conditions prevented the use of borehole straddle-packers, used to isolate sections of the borehole to enable hydraulic fracturing to be undertaken. This paper discusses the development of a method of borehole casing that enabled the application of hydraulic fracturing.