The use of low-solids, water-based reservoir drilling fluids has generally been restricted to fields with temperatures of less than 300°F, primarily due to the limitations of fluids in more aggressive environments. The Miano and Sawan fields in Pakistan are both classified as high temperature (up to 340°F BHST), and some wells have been recognised as requiring sand control for optimal production.The operator of this field is dedicated to the application of water-based muds in all activities to reduce the environmental impact of operations.

Based on these criteria and extensive laboratory testing for thermal stability and expandable screen (filter cake quality) compatibility, a formate-based, low-solids, reservoir drilling fluid was selected. The laboratory performance of the fluid will be confirmed by the performance in the world's first field application of high-temperature formate drilling fluid run with expandable screens.

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