Environmental Report 2000 Index

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Case Studies Case Study 1 Design for Environmental Efficiency A development project illustrates how addressing environmental issues at an early stage enabled performance improvements to be incorporated at the facility design stage. Most notable is the elimination of oil in produced water discharged to the sea, waste heat recycling and maximising efficient use of gas. The field produces some associated gas and this is used for power generation. The new platform includes waste heat recovery units that utilise hot exhaust gases from the platform gas turbines and redistribute the waste heat to production process areas. This measure significantly improves energy efficiency and reduces combustion emissions by reducing fuel demand. Excess gas not required for power generation is exported through a new gas line. The rationale behind construction of the line is that exporting the relatively small amount of surplus gas will reduce flaring and when the field becomes gas deficient in the future, the line will be used to import gas, removing the need to import and burn diesel. The new facility has also been designed to eliminate overboard discharge of produced water. Produced water can be returned to the sea after a cleaning process to remove the oil it contains to within approved limits. In this case, however, due to the particular characteristics of the oil, the separation process would have required higher than usual energy use to achieve the required performance specification, resulting in additional atmospheric emissions from burning the extra fuel. The answer was to design in the capability of complete reuse of the produced water either downhole to maintain reservoir pressure or as power water to drive submersible pumps. This not only eliminates oil in water discharge to the sea, it also reduces the platform's energy requirements and, consequently, its atmospheric emissions.