Which of the following is NOT an essential parameter for an accurate Leak-Off Test (LOT)?

In a Leak-Off Test (LOT), the primary goal is to evaluate the integrity of the formation and the pressure at which it begins to allow fluid to escape, helping to assess the risk of fluid loss during drilling.

Drilling with water is not an essential parameter for conducting an accurate LOT. While water can be used for certain types of tests due to its properties, the test can be effectively executed with a range of drilling fluids, depending on the well’s requirements and the conditions of the particular wellbore. The essential aspect is ensuring that the fluid used is appropriate for the formation being tested, rather than specifying water as the exclusive medium.

In contrast, a calibrated surface pressure gauge is crucial as it ensures precise measurements of pressure during the test, allowing for accurate data gathering related to the formation's integrity. Knowing the true vertical depth for the casing shoe is also vital, as it provides a reference for interpreting the test results in relation to the geological structures encountered. Additionally, tracking the mud volume pumped until leak-off starts is necessary to determine the pressure at which the formation begins to take in the fluid, directly influencing the overall understanding of the formation's behavior under pressure.

Thus, option A reflects an aspect that is not necessarily required for a Leak-Off