Feedback control means that the settings of one or more controls in a system, e.g. valve openings or set points for pressures, temperatures, levels or flows, are based on readings of one or more measurements in the same system. Feedback control can be automatic or manual. Manual feedback control means that the decision on the setting of the controls is done by a human, while automatic feedback control means that the decision is made by some device. The device could be mechanically based, electrically based, electronically based, hydraulically based or a combination thereof. Of course, there is an abundance of examples of both manual and automatic feedback control related to oil production.
ABB has achieved promising field results with a novel concept for stabilization of unstable production from an oil well. The main ingredient in this concept is the application of active feedback control to the production choke, relying on a measurement of the downhole pressure as well as measurements of the pressures at the wellhead. On the test well, which was impossible to operate manually, the variations in the wellhead pressure were decreased by 75-100% when active feedback control was in operation. In contrast to the situation with manual operation, it was not necessary to shut in the well for shorter or longer periods of time to build up pressure. Hence, as the well produced 900 - 1000 bbl/d in the test period, the benefit of employing active well control was quite obvious on this test candidate.