ABB has identified potential for increased oil production in offshore process plants through monitoring, control, and opti-mization. Studies show plants producing 10-20,000 b/d can achieve an increase of 1,200 b/d, while producers with output of 100-200,000 b/d, can increase by 4,000 b/d.
These production gains are achieved by using standard advanced solutions such as soft sensors, multivariable predictive control, and industry-specific software to handle issues such as unstable well flow, slugging in pipelines, hydrates, and other flow assurance challenges. Using these methods, ABB has developed control and optimization products that maintain production at an optimal level while eliminating disruptions to process plant operation. According to Bjørn Bjune, marketing manager for ABB's Enhanced Oil Production unit, the products can be installed and brought online while the facility remains in production.
One of the first installations was on Phillips' (now ConocoPhillips) Tor field in the Norwegian sector of the North Sea, where terrain-induced slugging was experienced in the export pipeline due to low production rates. The slugging caused large variations in the oil/gas inflow at the Ekofisk J platform to which Tor's output is exported, as well as back-pressure at Tor resulting in gas-lift processing problems and reduced production.
The Optimize IT Enhanced Oil Production Suite covers well control monitoring and flowline control.
The Optimize IT Active Flowline Control system was installed on the pipeline. The product uses a state-of-the-art AC800M controller from ABB, which uses pressure, flow and temperature measurements to control the valve at the pipeline outlet and thus modify the flow. By this means the inlet pressure was stabilized and the slugging eliminated, along with disturbances to the process operations at Ekofisk J and Tor. Production improved significantly.
The system is flexible with respect to information-gathering and can use the output of sensors and meters downhole, at the wellhead, on the topsides or on the pipeline. If there is a lack of sensors, ABB can provide a clamp-on density meter. The crucial parameter is pressure, which contains the slugging signature, Bjune says.