| Abstract: |
The geothermal drilling process makes extensive use of drill cuttings ponds for the storage and disposal of drilling fluids and drill cuttings. Generally the local practise is to discharge the drilling fluid to the pond and rely on soakage for the ultimate disposal of the water content. This practise has a number of drawbacks: the lack of recycling means that the full drilling water supply budget must be sourced from surface water takes, which creates challenges with the ever reducing surface supply options. The existing pond geometry creates deltas of drill cuttings near the outfall, which are difficult to clean out. Finally the ultimate remediation of the ponds becomes challenging when the rig moves on as the Sodium Bentonite in the drilling fluids bind up the underlying soils, reducing soakage to ground, resulting in brine sitting in the ponds for years at a time. Computation Fluid Dynamics (CFD) models of both a typical pond installation and an optimised configuration were run, comparing the fluid dynamics and the most probable sedimentation profiles between the two. As a result, a pond design was produced that allowed for easy maintenance, a small change in footprint and shape with the attendant improvement in fluid quality that allows for the extraction of fluids for water recycling, thus reducing the environmental impact of the drilling process. |