How Oil Flows
North Slope oil lies trapped within microscopic pores of the rocks in underground formations. It flows under its own pressure similar to what happens when a bottle of soda is opened. When the cap is popped, the gas escapes, bringing up fluid with it. In the case of some North Slope fields, that gas also brings up oil and water. Crude oil reaches the surface at a temperature averaging 160 degrees Fahrenheit.
From the surface wellhead, oil flows into a manifold building, where it is tested for the oil, gas and water content. Produced fluids from all the wells on a single drill site are pumped into gathering lines for delivery to processing facilities. Wellheads and manifold buildings are built on gravel “pads” to protect the permafrost. Once oil is processed to pipeline specifications, it goes to Pump Station 1, the beginning of the Trans Alaska Pipeline System.
How Oil is Processed
Wells in North Slope fields produce a mixture of oil, natural gas and water – these three streams need to be separated before the oil can enter the Trans-Alaska Pipeline System. Most fields on the North Slope have separation facilities designed to process millions of barrels of liquids per day. Recovered gas and water goes back into the formation to help maintain reservoir pressure and enhance oil recovery. Treatment plants also process seawater for additional injection into the reservoir as part of a field-wide, waterflood program to maintain pressure and sweep oil from the reservoir rock.
Each separation facility contains sophisticated gas detection, fire and trouble alarm systems; several fire suppression systems, and firewater storage tanks. Each facility can shut down rapidly should the need arise. Control centers orchestrate the production process. Aided by sophisticated computers handling tens of thousands of data points, production controllers monitor and control the flow of oil from well sites to production facilities and into pipelines. Controllers can quickly shut down the field by remotely closing valves at the wellhead, the perimeter of the drill sites and at the production facilities. A surface safety valve at the wellhead automatically shuts in a well if operational problems arise.