Zonal isolation and long-term cement integrity in the high-pressure/high-temperature (HP/HT) environment are critical to optimizing production and minimizing future well intervention and replacement. In addition, the well stresses vary over a large amplitude during construction, testing, and production of such wells. There is, therefore, significant value in avoiding failure of the cement sheath.In 2007, Total E&P Borneo commenced an HP/HT caMPaign in Block B offshore Brunei to drill development wells with deeper exploration sections. These HP/HT wells are the most technically challenging for well cementing in terms of preserving long-term well integrity; these wells are exposed to high temperatures exceeding 165°C, pressures exceeding 69 MPa resulting from different operations, including production. Cementing these wells using conventional cement and practices has proven not to be effective. This leads to the introduction of new technologies and newer cementing techniques to ensure long-term seal of these wells.This study identifies first the risks associated with cement sheath failure under downhole stresses. Then it discusses the successful implementation of a solution that ensures a complete zonal isolation of these HP/HT wells, consequently avoiding unnecessary and costly well intervention.