Abstract-The demand for the total production of oil from an Electric Submersible Pump (ESP) lifted oil field may vary with time. It may not always be economically profitable to use all of the available oil wells for varying production rates. Depending on the amount of oil to be produced from the oil field, some of the oil wells may have to be shut down. The number of oil wells to be used should be properly selected. Not only the number of oil wells should be known, but which wells to use should also be exactly identified. The operating speed of the ESP and the production choke valve opening of each selected oil well should be optimally chosen so that the profit from the oil field is maximized by keeping the operational expenses at the minimum. The oil well scheduling problem is formulated as a Mixed Integer Nonlinear Programming (MINLP) problem. The cost of the electrical power consumed by the pumps, the operational cost of separation process and the income from the oil production are considered for the MINLP formulation. In the first part of the paper, the production choke valves are always fully opened and the number of wells and their respective pump speeds are calculated for varying total production flow rates. However, in the second half of the paper, it is shown that the operation of the oil field can be improved in terms of power consumption through production valve choking.Index Terms-Mixed integer nonlinear programming, ESP lifted oil field, well scheduling, optimal operation, production valve choking.
I. INTRODUCTIONIn an ESP lifted oil field, multiple oil wells are connected in parallel to a common gathering manifold. The oil produced from each of the wells is collected by the gathering manifold and then transported to the separator through the transportation lines (see Fig. 4). Each oil well is fitted with a multistage centrifugal pump. The main operational expense in the oil field is the total cost of power consumed by the pumps and the cost of operating the separator. The income is the production of crude oil from the field. The energy costs associated with the operation of the pumps in an ESP lifted oil field is of great significance when multiple oils wells are considered. The cost of operating the separator is less significant compared to the energy costs of the pumps.The total amount of oil to be produced from the field may vary. For higher production rates from the oil field, all of the available oil wells may be used to meet the demand. On the contrary for lower production rates, some of the oil wells of the oil field can be shut down to meet the lower production demand. The lower the pump speed, the lower is the fluid flow rate through the well. However, running all of the available oil wells at lower pump speeds for fulfilling lower production demands might not be beneficial. The wells might be consuming more power than what is actually needed. Shutting down an oil well reduces the consumption of electric power as the ESP for the well is turned off. So, the balance between fulfilling the to...