Exploration & production in the oil & gas industry

The upstream sector of the oil and gas industry is here defined to cover Exploration & Production (E&P). Exploration includes searching for potential crude oil and natural gas fields, including drilling of wells. Production is subsequently operating the wells to produce crude oil and raw natural gas.

Once a well has been drilled and the reinforcement casing has been cemented in place in the borehole, a collection of valves, called a ‘Christmas tree’ is fitted on the top to provide various access points and oil and gas instrumentation connections. Most important are connections to measure and regulate the pressure, and for oil or gas production measurement and control. Other connections are used for well water and CO₂ injection, which might be used to increase the flow and pressure from the reservoir – these lines are usually fitted with pressure and flow measurement instrumentation. Gas lift techniques might also be used later in the life of the well, to reduce the density of the fluids being forced up to the surface.