Plugging Ruby 43-15-4674BG With Bentonite

The conventional method for plugging and abandonment of coal bed methane wells utilizes concrete which is pumped down the well casing and sets to form a permanent plug. An alternative method for plugging wells is to replace concrete with bentonite. The benefits of using bentonite as a replacement for concrete include lower material costs, no need for specialized pumping equipment, as well as the flexibility and self-healing capabilities of hydrated bentonite. One issue encountered with using bentonite is its tendency to bridge-off before reaching the intended depth. Additionally, bentonite is not yet approved as a concrete replacement in the State of Wyoming. This research focuses on the production and implementation of a bentonite cylinder which resists bridging-off. Development and production of the cylinders is discussed including the design of the production equipment and plug composition. Additionally, the plugging of a coal bed methane well using the developed cylinders is presented. The original design and subsequent modifications of the well plugging procedure are discussed along with the results of pressure testing. A comparison of the actual costs for the plugging of this well and the estimated cost of using concrete make a case for replacing concrete with bentonite.