Development of conventional and unconventional gas resources, including CSG, has many similarities; however, there are some key differences that may lead to potential impacts on groundwater supply. Conventional reservoirs are usually located at greater depths than commonly exploited groundwater resources and develop when gas becomes trapped by impermeable bounding layers.
In the CSG industry, reservoirs are often lower in permeability than aquifers that commonly provide groundwater supply for agricultural, industrial, urban and other uses; the CSG plays may be located above and below these aquifers. The management of reservoir/aquifer interconnections necessitates a program of focused-data acquisition. For example, groundwater transfer from shallow aquifers to underlying CSG reservoirs may occur where CSG-containing units subcrop beneath shallow aquifers, possibly at significant distances from operating wells.
Arrow Energy is undertaking investigations of connectivity between aquifers, including the connection between the Condamine Alluvium and the CSG-containing Walloon Subgroup. This extended abstract explores the use of analytical and numerical modelling to represent the aforementioned situation as follows:
The behaviour of numerical models at the point of contact between CSG-containing units and overlying alluvial aquifers is being examined in detail—there is specific focus on how horizontal and vertical hydraulic conductivities are assigned at the interface between aquifers. This localised sub-region within a regional scale groundwater flow model has the potential to control the estimations of flows that are most interesting to stakeholders.
The relationship between modelling approaches used by reservoir engineers and hydrogeologists is also explored.
Unconventional gas sources: characterization and assessment. Final report for 1979. [Coalbeds; geopressured; eastern gas shales; western gas sands]
