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Jack
An oil well pumping unit that operates with an up-and-down, or seesawing, motion; also called a pumping jack.

Jacket
The steel lattice structure that supports an offshore platform.

Jacket Platform
An offshore platform constructed entirely of steel. Such platforms generally are held in position by long steel piles driven deep into the seabed.

Jack-up Rig
A type of mobile offshore platform with retractable legs that stand on the seabed to help support the drilling platform.

Joint Venture
An investment undertaken by a consortium of companies, usually with one member acting as operator.