Drilling technique helps ensure full production

The geology of south central Kentucky consists of numerous limestone formations. One of these, the Tyrone Limestone is anywhere from 55 to 155 feet thick and contains at lease five layers of potassium bentonites. Two of these bentonite deposits have been named by drillers because of the problems they can cause during the drill: the Mud Cave bentonite at the top of the formation, and the Pencil Cave located 16 to 30 feet below the top. Both the Mud Cave and Pencil Cave bentonites are locally as much as 2 feet thick.

The reason these formations are troublesome is because potassium bentonites are a whitish, chalky type of clay composed mostly of montmorillonite, a porous mineral which swells into a gel like substance when it gets wet. Water is commonly encountered during a drill and the collapse of the pencil or mud cave can seriously impede oil flow during or after the drill.

“Tripping the Cave,” explains Mammoth Field Services Manager Chris Burchett, “is a technique used during the drilling process to help prevent the collapse of the pencil and mud cave formations.”

The well is drilled using a typical size bit to a depth of 10 feet below the pencil cave or to a point below the known water table. The drill stem is removed, cement and then water is poured into the hole, steel casing pipe is inserted and then before the cement sets up air pressure is used to blow the cement and water mixture up the outside of the casing pipe. This helps prevent contamination of the water table and potential obstruction of the wellbore through collapse of the wall.

A smaller bit is then attached to the drill string to finish the well. At that point, if oil is found, smaller diameter steel casing pipe is inserted, effectively helping to support the pencil cave.

This procedure is more costly initially, but saves money in the long term by keeping the wellbore open and cleaner than traditional open hole methods and is just one of the extra steps taken by Mammoth Resource Partners, Inc. to provide the best service possible.