The seafloor temperature in deepwater locations is approximately 40 F, but it can approach 32 F. The temperature downhole can exceed 300 F. The drilling fluid should exhibit the appropriate rheological properties throughout this wide range. In the riser near the mudline, the fluid is apt to thicken excessively from exposure to the cold seafloor temperature. SBFs that contain little or no commercial clay appear to remain the most stable under these conditions. These clay-free and low-clay systems rely on emulsion characteristics to achieve the desired rheological properties and provide sufficient barite suspension. Seismic data can help operators to predict and evaluate the risk of encountering an SWF on a given well.