ABSTRACT:

The maximisation of crude oil throughput from a well platform to a centrally located process platform ln an offshore field, through a sub-sea feeder line calls for optimisation of individual well head pressures of wells attached to the well platform considering the pressure requirement at the process platform. Generally the well heads in a well platform are unmanned and flow of crude from the wells are controlled by fixing bean/surface choke sizes. A "Systems Approach" has been presented in the present paper where all aspects of two phase flow of oil and gas through the feeder line has been considered for optimisation. The critical parameter of the system is the feeder line upstream pressure which must be such maintained that two phase flow of oil and gas reaches the process platform at a minimum required pressure(separator pressure). The feeder line upstream pressure should also not be more than any individual well head pressure, otherwise there may be a chance of "Flow Seizure Condition". Thus maximisation of crude throughput In the feeder line requires "Optimum Operating Conditions" for individual wells in a well platform. The "Systems Analysis" identifies these optimum conditions using a "SYSTEM SOFTWARE" being developed by the authors. The basic approach of this software is to employ iterative techniques to identify optimum well head pressures and feeder line upstream pressure. The reservoir parameters as well as a suitable two phase flow correlation have been incorporated in the software. A sample study considering the characteristics of a typical offshore field has also been presented in this paper. The study reveals that the system has got three distinct operating regions, namely: REGION I : This region is characterized by medium crude throughput, medium pressure drop and medium GOR.

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