Horizontal drilling and multi-stage fracturing has sky-rocketed the economic development of ultra-low permeability shale gas resources in North America. The same technology has the potential to be applied to extremely low permeability tight gas (sandstone) reservoirs.
In this paper, we discuss the results of evaluating if we can successfully apply shale-like stimulations in developing and improving the performance of extremely low permeability tight gas reservoirs. The focus of the study is on doing sensitivity model runs to investigate the effects of reservoir permeability, drainage area, fracture surface area, and fracture conductivity on both initial and long term gas production rates, using single well simulation models for a generic tight, dry gas reservoir. The study compared transverse multiple fractures in a horizontal well with 40, 20, 10, and 5 hydraulic fractures, for permeabilities from 1 mD down to 1 nD, and for drainage areas of 80 to 1,275 acres. The impact of fracture conductivities and fracture half-lengths on gas production was also assessed.
A typical horizontal tight gas completion has a lateral length of 2,500 ft to 3,500 ft with 5 to 7 fracture stimulation stages using open-hole completion style system. The results from this study show that there is potential for improving well economics by targeting more fracture initiation points similar to that of shale gas wells, when permeability of the tight gas reservoir is between 0.1 µD to 10 µD. The findings can be used not only to design better tight gas wells, but also helps in understanding the fundamental behavior of the low quality tight gas production system. In conclusion, this paper clearly illustrates that in extremely low permeability tight gas reservoirs, horizontal wellbores with shale-like stimulation programs may be the only robust option for achieving commercial gas production rates.