Which of the following is NOT a kick warning sign?

A decrease in formation pressure is not typically considered a direct kick warning sign. Kick warning signs are indicators that suggest the possibility of a well control issue, often related to the influx of formation fluids into the wellbore. When formation pressure decreases, it usually indicates that the well is in a more stable condition or that the formation is not holding the pressure needed to maintain hydrostatic balance. In contrast, the other options listed can be considered more relevant indicators of an impending kick.

For example, variation in penetration rate can signal changes in formation density or fluid influx, raising a red flag about potential kicks. An increase in chloride content generally suggests the presence of formation water, which could point to an influx of fluids. Similarly, changes in the shape of cuttings observed on shakers can indicate variations in the type of rock being drilled or the presence of unexpected formation fluids. These factors are all associated with the potential for kicks, making a decrease in formation pressure distinctly different in that it does not imply an immediate risk of influx.