The Athabasca Landing tar sands borehole project that started in 1894 broke ground on the 1st of August, drilling to a final depth of 1731ft in 1896. And considered one of the oldest wells in Alberta.
During the month of February of 2021, only 125 years later, drilling has once again returned to the borehole, only this time with different intention. The Alberta Energy Regulator (AER) has adopted the responsibility of properly abandoning and putting the exploratory borehole to rest. Titanium Energy Services, based out of Lloydminster Alberta had been chosen by Codeco-Vanoco Engineering Inc. as the primary service for the project. Due to the geographical difficulties and environmental concerns with the well’s extremely close proximity to the Athabasca River, coiled tubing was the operational means chosen to abandon the borehole. The coiled tubing unit application would provide the service required, as well as providing the smallest environmental footprint. The surroundings of the well could remain mostly undeveloped and in their natural state as equipment would not need immediate access to the well.
Parked next to the CTU was a 275T crane to lift the injector head over the riverbank and nipple on to the well. The primary goal was to mill down as deep as possible, set a permanent bridge plug in what casing remained then spot a cement plug on top to seal off any natural gas from migrating to the surface. Drilling would be conducted using a 2 7/8’’ mud motor with a tri cone drill bit or a tapered mill on the end. Fluid pumped through the coil tubing using Titanium’s fluid pumping unit would turn the bottom of the motor attached to the coil end which would in turn rotate the drill bit. The rotating drill bit would allow the coil tubing to travel down the casing as it chewed through shale and other borehole solids encountered years ago. Preparations were made around the borehole to ensure worker safety during operations. Wood and steel rig matting were placed around the borehole as work platforms, along with a temporary staircase down the riverbank for access.
On March 1st work commenced to mate modern well head flanges to the 7 ½’’ casing that protruded from the ground allowing for an orbital valve and blow out preventer to be installed as a secondary precaution for containing gas and well bore fluid. Blow out preventers (BOP) can weigh a considerable amount, so a bracing structure was manufactured onsite to absorb and remove the weight from the aged well. With BOP in place the coil tubing injector was installed onto the well, fresh water was pumped through the coiled tubing that that initiated the rotation of the mud motor. At 2.5ft below ground level the 4.875’’ mill tagged an obstruction. Mud, sticks, and gravel was noted at the return tank on top of the riverbank as fluid was pushed up the hill through metal line piping from the well. After 30 mins of drilling only 0.5ft of hole was made. It was decided to shut down pumping operations investigate the impediment. Operations were suspended for the night as new approaches were to be considered by Codeco-Vanoco Engineering Inc..
On the morning of the 2nd a decision had been made from the results of their analysis. A smaller tri-cone bit would be installed on the mud motor and soon after drilling commenced it seemed the drill bit was doing its job. Drilling seemed to be progressing well, however, at 164ft fluid returns at the return tank ceased. This posed a cause for concern as it was clear something had changed down hole. Further analysis of the operation uncovered that the 3 5/8’’ casing had disappeared. Operations were suspended for the day as new approaches were to be discussed and considered.
The following day it was decided to do away with the drilling assembly and try a less abrasive approach. A 3.5’’ ported nozzle was installed on the coil end with the purpose of pumping water through to clean out to the depth of 213 achieved the prior day.
A Titanium Wireline logging unit had been summoned to location to provide further insight into the downhole dilemma. The wireline logging unit lowered a gamma ray CCL tool to analyze on how far the 7 ½’’ casing protruding from the riverbank extended. The wireline professional notice an obstruction tagged at 88.5ft. The wireline was pulled to surface while logging its scan of the wellbore discovered that the 7 ½’’ casing penetrated the riverbank to 36ft, which coincided with the 1894 drilling report. Beyond that was clearly open hole. Operations were shut down for the day as decisions on how to proceed were discussed.
The Alberta Energy Regulator decided to proceed with pumping cement into the borehole following an engineered plan to seal off any gas or fluids from migrating to surface. Titanium Coil Tubing Unit swept in and out of hole while pumping fluid to clean up with open hole of debris. Once the cementing units had arrived, liquid cement was pumped through the coiled tubing followed by fresh water to push the cement through the coil and out of the nozzle tip. The coil and nozzle were positioned at the bottom to ensure cement was placed at the deepest depth achieved. With cement flowing out of the nozzle tip the injector slowly pulled the coil tubing towards surface. When coil had arrived at surface all the cement had effectively been flushed out of the tubing. It was noted that liquid cement had made its way up and around the outside of the 7 ½’’ casing. This was good news as it would perhaps add some stability and offer a seal from possible fluid and gas migration. The cement would take approximately 12 hours to fully solidify, so operations were suspended for the day.
Returning to site it was discovered that the cement was proving to do what was intended. Any noticeable seeping of gas up the 7 ½’’ casing during the operation had ceased. The well would now be monitored over the following years to ensure that this remained the case. The exploratory borehole then and now had proved to be a challenging undertaking. The monitoring of the well over the coming years will tell us whether the Athabasca Landing exploration hole has seen its last day of drilling.