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Frequently Asked Questions: Top Drive
The Top drive is a critical component of a rig hoisting, rotating and circulating system. This device has an elevator and links that operate hydraulically to pick up pipes from the mouse hole, V-door, or the vertical racked position in the derrick. The top drive has replaced the traditional Kelly or rotary table. It has effectively reduced the manual labor involved in drilling and other associated risks.
A top drive has one or more motors and moves up and down a rig’s mast. It connects to the top of the drill string, the length of pipe that goes down into a well and attaches to the drill bit at the bottom of the hole. This device provides torque and downward force as it rotates the bit through the formation below.
The high cost of top drive unit, derrick modifications, reduced bottom hole assembly working height and increased maintenance are some of the disadvantages of Top Drives.
From truck-mounted units to the largest offshore rig, top drives can be employed in all environment types.
Owing to the increase in exploration and production activities, technological advancements, safety issues, global energy demand and so on, the number of drilling rigs has increased greatly. Consequently, the relevance of top drives has assumed the center-stage.
There are two basic types of Top Drives: Hydraulic and Electric. On the basis of application, they are categorized as onshore and offshore- jackup, drillship, and semisubmersibles. .
Top Drives have certain advantages over Kelly such as enhanced efficiency, access to sophisticated targets and safer rigs. They are also cost-efficient.
Most of the manual labor that was previously required during drilling of wells has been eliminated by Top Drives. For most of the times, these top drives are completely automated.
On an offshore rig, the top drive moves up and down the vertical rails to avoid the mechanism from swaying with the waves of the ocean. Moreover, a 1000 short ton unit would be used for offshore and heavy duty use, while a smaller onshore rig may only need a 500 short ton device.