Simulation uncertainties in tight gas reservoirs; Case-study on Whicher range field in western Australia

Modelling tight gas unconventional reservoirs can be a complex task, as there are different uncertainties involved due to geological complications. Moreover, intrinsic characteristics of tight gas reservoirs, makes them very prone to formation damage which can affect the future production rates and increases the simulation uncertainties. The Whicher Range field in Perth Basin is a large undeveloped ‘unconventional’ tight gas reservoir in Western Australia. Gas‐in‐place estimations of up to 6 TCF have been reported. Other tight sand reservoirs have been identified in the Perth Basin, but none has been put into commercial production. Whicher Range provides a long and comprehensive case history of drilling and testing programs which, thus far, have not provided a viable well completion or field development plan. To study the associated simulation uncertainty, we developed there reservoir model and the model calibrated with available production data to be used to evaluate the reservoir behavior and possible future production scenarios. Simulation outcomes were compared with the field history data and the deviation from the field results was discussed. Result show that, if the uncertainties such as geological complexities, or formation damage (either phase trapping or fines migration) are not taken into account, the production rate can be significantly overestimated. It is also pointed out that due to the lack of lateral continuity in fluvial systems the deterministic estimation Gas Initial in Place (GIIP) can also be significantly over estimated. Associated risk of occasioning a dry well in fluvial meandering reservoirs with this degree of heterogeneity is very high. It is recommended that a thorough and meticulous study should be carried out and proper field development strategies should be established to enable the further development of this type of fields. It is very important to implement these data to construct a representative model. From the data obtained from the Whicher Range field, it is concluded that the field has potential to be developed and to be produced if the right strategy and technique is put in place.