Technology Update: Top-Drive Casing-Running Tool Solves Tough ERD Problems

Abstract

Over the past 15 to 20 years, top-drive technology has brought substantial improvements in efficiency and safety to drilling operations. However, casing-running methods have evolved more slowly and have not taken advantage of all the potential offered by top-drive drilling. Weatherford International has designed its new Overdrive system for running casing and drilling with casing to make full use of the weight and power of top drives (Fig. 1). The system won a Spotlight on New Technology Award at the 2007 Offshore Technology Conference. This top-drive casing-running system was used recently by Shell to land casing on bottom at more than 18,200 ft depth on a troublesome North Sea extended-reach-drilling (ERD) well with hole restrictions caused by inability to clean the hole completely. Torque-Drive Tool The centerpiece of the technology is the torque-drive tool that combines several conventional casing-running tools into one—power tongs, main hoisting elevators, bails and single-joint elevators, a fill-up/circulation tool, and a weight compensator. All system operations are remote so that no personnel are required in the derrick or on the rig floor, resulting in a significantly lower safety risk (Fig. 2). The removal of equipment and scaffolding from the rig floor also creates a safer work environment. The torque-drive tool is connected below the rig's top drive and can be run with any topdrive system. To run casing, the tool's integral bails and single-joint elevators are used to retrieve each joint or stand of casing, lift it into the derrick, and lower it into position for makeup. The torque-drive tool is then hydraulically clamped onto the casing, and the connection is made up using the rotational power of the top drive to transfer the torque through the torque-drive tool and casing connections. A key component used in conjunction with the torque-drive tool is an integral electronic-load cell called the torque sub, mounted at the top of the torque-drive tool and used to measure the makeup torque of the casing connections. The sub is independent of the top drive and measures true torque, as opposed to conventional techniques that calibrate torque from the voltage that supplies rotational power to the top drive. This new level of accuracy is especially important when making up premium connections, which require torque-turn monitoring and a very low margin of torque-measurement error. Once the connection is made up, the driller can instantly perform a number of operations as needed, including fill-up of the casing string while lowering, and simultaneous circulation, rotation, and reciprocation of the entire casing string. This combination enables the driller to overcome virtually any unexpected hole problems, such as ledges, lost-circulation zones, shallow-water flows, and swelling formations. This greatly enhances the ability to run the casing string to bottom in a predrilled well.