Definition - What does Crossover mean?
A Crossover is a one-piece threaded tubular subassembly that is used to connect two different or same thread type components. It is also used to connect two tubular sections such as casings, tubing or drill pipes together. Crossovers are widely used during completion activities to connect two same or different types or size of components which otherwise cannot be screwed together because of difference in their thread size or type.
Petropedia explains Crossover
Drilling rigs contain drill strings which transmit torque and drilling fluid to the drill bit so as to enable it to carry out drilling services. These drill strings contain parts that may not be screwed together because due to the different types or sizes of their threads. A crossover is used to connect such components so as to ensure well integrity and enable the circulation of slurry. The crossover acts as a service tool connecting two different tubular components or sections having same or different thread sizes or types. Crossovers are also used as disposable components to prolong the connection life of a more expensive drill stem member.