Conventionally, the Cretaceous shale in North Kuwait is drilled at a high angle with an invert emulsion-based drilling fluid. Environmental and operational considerations required the development of a water-based system capable of closing the performance gap between invert-based and water-based drilling fluids. A customized high performance water-based mud (HPWBM) was used successfully where previous attempts with alternative water-based mud (WBM) had experienced significant challenges. Key well challenges included wellbore instability with caving shale and the potential for differential sticking and pack-off. A HPWBM enhanced with an innovative sealing polymer was customized to maintain optimal drilling performance by minimizing shale erosion in these highly dispersible clays, while also decreasing pore pressure transmission via the micronized sealing polymer. These clays, having moderate reactivity, are prone to dispersion when there is communication between water or water-based mud. The improved levels of fluid invasion were optimized using the particle plugging apparatus (PPA) to achieve the minimum interaction between the fluid and shale. The formulation was finalized, based on laboratory testing, to optimize the bridging and inhibition package for the formations drilled. After finalizing the formulation, the control points were agreed upon between the operator and service company to ensure that the required inhibition and bridging package were implemented on the well and to define success criteria. Drilling was completed, and the casing was run successfully with no incidents; the fluids parameters were maintained to effectively stabilize the hole while drilling through geomechanically stressed formations in a challenging azimuth: the direction of minimum horizontal stress. The addition of the sealing polymer to the already-inhibited HPWBM effectively stabilized the wellbore, which helped reduce the caving tendency of the stressed shales. The two intervals were drilled and cased in two days less than the average time required with an invert emulsion fluid. There was no nonproductive time (NPT) related to wellbore instability, and differential sticking was avoided by the customized bridging and sealing across the depleted zones. This paper discusses the design, technical features, and benefits of a HPWBM system, enhanced by the addition of an innovative sealing polymer, which helped successfully drill the 12 1/4- and 8 1/2-in intervals. A customized HPWBM provided good shale inhibition, mechanical stability, and excellent lubricity, customizing the conventional fluid for the increased challenges posed by the stressed shale.