Many stakeholders are concerned about the effects of Coal Seam Gas (CSG) developments on aquifers. Well integrity issues are often mentioned as potential leakage pathways which could lead to aquifer contamination or depletion.
This study involved the creation of simple models to represent the behaviour around a producing CSG well with a well integrity failure. A range of realistic scenarios were chosen, representing hypothetical well integrity failures at different stages of CSG production. Dynamic numerical models were built that represent each scenario, and simulations were run to forecast the flux of fluids around the wellbore. These models were parameterized based on data from literature related to well integrity studies, and should represent reasonable worst-case scenarios. The results of simulations using these models are then used to explain key concepts relating to well integrity in CSG wells in a manner which can be understood by interested parties from non-technical backgrounds.
The simulation results based on these simple models indicate that well integrity issues in producing (or previously produced) CSG wells are unlikely to have any significant impact on overlying aquifers.