Global energy demand has driven the oil and gas industry to search for hydrocarbons in increasingly challenging reservoirs including those at high pressure and temperature (HPHT) such as found in the South Malay Basin of Malaysia. Competent well designs and enabling HPHT technologies such as advanced drilling fluid designs that are stable at HPHT conditions are critical to successful drilling and completion of these wells.

This paper discusses the laboratory evaluation of potential HPHT drilling fluid designs considered for a deep gas exploration well in the Duyong Deep-1 field located in the South Malay basin of Malaysia expected to reach 455 °F (235 °C) and 13,683 psi. Laboratory testing encompassed fluid rheology, fluid loss, sag, electrical stability and chemical analysis before and after extended dynamic and static aging up to this temperature and pressure. Results were examined to identify strengths and weaknesses of the fluid designed. Improved-performance drilling fluid formulations underwent further pressure, temperature and hydraulic simulations to ensure adequate hydraulics and hole cleaning. As a result, suitable drilling fluid formulations for the ultra-HPHT gas well were successfully formulated with a maximum density of 18 ppg and thermal stability of 455 °F. The selected drilling mud design was stable and maintained desirable rheological properties including shear strength less than 200 lb/100 ft2 at static BHT at 16 and 48 hours.

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