Temporary chemical block brings efficiency and economy to eastern U.S. workover operations

Operators performing workovers on gas-storage wells in the eastern regions of the U.S. have improved operations and reduced expenses by using GP's to control wells while work is in progress. A large number of the gas-storage wells were drilled in the 1950's and 1960's and have nonstandard equipment that limits the use of other well-control methods during the initial stages of workover. The GP is a highly viscous fluid that can be crosslinked to form a viscous plug. GP's can be tailored to break back to a less viscous fluid for removal, or they can be broken by acid. Using this type plug can eliminate the need for various packers, bridge plugs, and associated surface equipment usually needed to control or kill a well while remedial workovers are performed. This paper describes chemistry, operating ranges (temperature), and application procedures pertinent to GP's. Also presented are field case histories where GP's were successfully used to plug a well for running casing inspection logs, to plug a ell to permit replacement of tubing and wellhead equipment, and to kill a well temporarily to replace an old wellhead and then place a mechanical plug for a cement squeeze job or additional workover operations.