Description
The subdivided areas of the sea for the purposes of licensing to a company for exploration or production rights. In the UK, a block is one thirtieth of a quadrant (one degree by one degree) and is approximately 200 to 250 km2; OR any assembly of pulleys on a common framework; in mechanics, one or more pulleys, or sheaves,mounted to rotate on a common axis. The crown block is an assembly of sheaves mounted on beams at the top of the derrick. The drilling line is reeved over the sheaves of the crown block alternately with the sheaves of the travelling block, which is raised and lowered in the derrick by the drilling line. When elevators are attached to a hook on the travelling block and drill pipe latched in the elevators, the pipe can be raised or lowered. See crown block and travelling block.
Source :
Alpha Thames Ltd 2004