Definition - What does Leakoff Test mean?
A Leakoff Test is a test carried out to determine the pressure of fracture or the strength of an open formation. It is conducted instantly after drilling below a new casing shoe. The well is shut during the test and fluid is pumped into it to increase the pressure gradually. The test is conducted to ensure the cement bond around the casing shoe is strong and that there is no flow path established in the formations of the previous annulus or above the casing shoe.
Petropedia explains Leakoff Test
Leakoff Tests are conducted to find the fracture gradient of a formation. The output of the test dictates the maximum similar mud weight that must be applied to the well during drilling operations. The mud weight retrieved is then recorded and afterwards reported to various government agencies as strength of casing shoe. The test is also used to investigate the capability of the well to combat the additional pressure below the casing shoe and collect regional data on the formation strength for upgrading the future well design. Drilling engineers depend on the records of the test and use them as maximum pressure which can be enforced on the formations to avoid the process of fracturing. Outpacing the maximum pressure can result in serious after-effects like list circulation which is among the most expensive events in the drilling operations.