Oilfield Production System
Production in an oilfield starts after the exploration activities including exploratory wells and modeling indicate the presence of hydrocarbon structure of commercial viability.
A hydrocarbon reservoir normally contains hydrocarbon liquid (oil or condensate), natural gas and water together. Depending on which useful component is more it can be an oilfield (mainly oil production), gas field (mainly gas production or a condensate field (large condensate production along with gas). The word ‘field’ indicates earth surface above the reservoir (which is deep below the ground). A brief system description is given below.
A hydrocarbon field may be a few hundred or a few thousand square KM in area. A large number of wells need to be drilled. The ‘well fluid’ (normally a mix of hydrocarbon liquid, gas, water and sand) is gathered to a central location for processing before dispatch to the buyers. In an offshore field, the wells can be completed with valving on a small platform (well platform) or on the sea bed itself (subsea completion). The lines collecting and gathering the well fluid to a central location are called flow lines. Typical gathering configuration is given below.
The Central Process Platform (called Group Gathering Station, Oil Collection Station etc. for onshore field) has the main processing facility. It involves separation of oil or condensate with water and gas. Water is treated and discharged. The natural gas is compressed and dehydrated before dispatch to the gas pipeline. Oil or hydrocarbon liquid is also dehydrated to the desired water level (0.5%) and pumped to the liquid pipeline (see flow diagram).
The pipelines carry the hydrocarbon liquid and gas to the consumers i.e. refiners and gas processors/distributors.