Leak Off Test (LOT)

A leak-off test (LOT) is a pressure integrity test that is carried out to determine the strength of the formation or fracture pressure. The leak-off test provides important information required for safely drilling the next hole section by establishing the maximum mud weight, kick tolerance, maximum allowable surface pressure for shutting in a well, etc.

LOT is carried out immediately below the casing shoe. A small portion of the new formation is drilled below the casing shoe, the well is shut in and pressure is increased gradually in small increments by slowly pumping fluid in the well. The surface pressure is closely monitored with every increase. At some point, the fluid will leak into the formation either due to the opening of a fracture or a permeable flow path in the formation. This provides information on the strength of the formation below the shoe.

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