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A wellhead choke controls the surface pressure and production rate from a well. Chokes usually are selected so that fluctuations in the line pressure downstream of the choke have no effect on the production rate. This requires that flow through the choke be at critical flow conditions. Under critical flow conditions, the flow rate is a function of the upstream or tubing pressure only. For this condition to occur, the downstream pressure must be approximately 0.55 or less of the tubing pressure.
Abstract Production allocation is of utmost importance for optimum reservoir development and production optimization. The need for quality oil, water and gas rate allocation has been increasing for determining the hydrocarbon delivery history for each well. The allocation becomes more complex when no periodic well test, no reservoir pressure recorded during pump shut in period, Malfunction of the pump sensors (Intake Pump pressure (Pi), Discharge Pump pressure (Pd)), Chock sizes per each well are not recorded with time, no surface gas/oil rate measurements or even the majority of well tests were conducted in commingle mode. This paper presents an iterative methodology for oil and gas rate allocation. It combines the inflow performance relationship and vertical lift performance with real time wellhead data to create the flow model for each well. Furthermore, by combining the down-hole sensor data from ESP pump with Gilbert choke equation using the upstream and downstream pressures, accurate oil and gas rate allocation can be predicted. This methodology provides the hydrocarbon delivery of the well to give the chance for production optimization. This methodology was applied on a field case from western desert in Egypt for oil and gas production rate allocation and it is verified against sporadic well test points