Ellingson-DTD installed one single-ended (blind) coal ash dewatering well within a partially closed CCR basin. The well was constructed utilizing the Knock Off (KO) well completion technology. In this drilling/installation method, we used drillable casing to advance a pre-planned bore path to an underground termination point. Upon reaching the end of the bore, the crew pushed the well material down through the center of the casing.
When the well material reached the end, it latched onto and pushed the sacrificial drill bit off the drill string. The drillable casing was then tripped out of the bore, leaving the well in place. This method allows us to install long single-ended wells in unconsolidated ash that may not allow an open-bore installation approach. The bore path was navigated with a removable gyroscopic steering tool. The well screen (4” diameter, scheduled 80 PVC), 1,150’ in length, is completed about 45’ below the entry point. The total installed length of the well is 1,115’.
Biodegradable drilling fluid was used for drilling and well installation. Well development consisted of flushing and jetting with an enzyme breaker solution and overpumping with a submersible pump. Ellingson crews also completed a variable rate and long-term drawdown test.
Pump Test Details
· Fully screened piezometers installed 10’, 30’, and 60’ from the horizontal well.
· Transducers in horizontal wells and piezometers.
· Static water level 5’ below ash surface.
· Initial submersible pump produced approximately 18.5 gpm with 6’ drawdown within 48 hours.
· Pumped continuously for an additional 72 hours at 18.5 gpm – no change in drawdown.
· Pump removed and well allowed to recover.
· Higher flow rate pump installed with a flow rate of 40 gpm.
· Drawdown increase to 13.5’ within 36 hours.
· Continuous flow for 96 hours at 37-40 gpm. Draw down 19.4’.
· Test ended with ~412,000 total gallons pumped.· Piezometer 60’ from horizontal well showed 3’ of drawdown.
