Onshore

Onshore wells are normally drilled vertically, so their wellheads are scattered over the field’s surface. Flowlines radiate inward, connecting each well to a manifold at the central tank battery. Wellhead pressure, either naturally occuring or generated by artificial lift equipment, moves the produced fluids through the flowlines and tank battery. (Figure 8.1)

– The manifold valves are opened and closed to send one well at a time through the well test system, where the well’s production rate of oil, gas, and water is measured. Production of all the other wells is directed through the normal production system.

– The oil, gas, and water are separated by gravity segregation. Emulsion-breaking measures are usually required.

– The oil is metered and sold, usually through an ACT, into the purchaser’s pipeline or tank truck.

– The gas is sold by metering its volume through an orifice meter and its composition is periodically checked to determine the content of ethane and heavier hydrocarbons. The unit price of the gas is then adjusted to reflect the additional heat content.

This rich (high content of heavier hydrocarbon vapor) and wet (high water vapor content) gas cannot be transported very far before it cools and condenses liquid out in the pipeline or forms gas hydrates. From the tank battery, the gas is therefore pipelined to a nearby natural gas processing plant where the hydrocarbon liquids and water are removed and the residue gas is compressed into the sales pipeline.

– The produced water, which is usually too salty to be dumped into surface waters, must be disposed of into subsurface formations. If there is a waterflood in the vicinity, the water can be put to valuable use.