Extended Leak Off Test

Published: February 5, 2020 | Last updated: July 5, 2023

What Does Extended Leak Off Test Mean?

The extended leak-off test (XLOT) is a technique used to measure the stress in oil and gas wells and is used to obtain horizontal stress data for predicting wellbore stability. Surface pressure is applied to the fluid column to determine the pressure at which fracture will propagate into the exposed formation.

XLOT test procedures are similar to routine leak-off tests but with multiple leak-off cycles, longer data collection time, and better data acquisition and analysis.


Trenchlesspedia Explains Extended Leak Off Test

An XLOT is similar to a leak-off test (LOT) but carried out for an extended period of time and is similar to the hydraulic fracturing test used to measure stress. For conducting an XLOT, pumping is continued beyond the LOP point until the pressure peaks at formation breakdown pressure, creating a new fracture in the borehole wall. Pumping is continued for some more time until sufficient fluid has been injected so that the undisturbed rock formation has a stable propagation of fracture.

The pumping pressure now stabilizes to a somewhat constant level and is called the fracture propagation pressure (FPP), after which the pumping is stopped also called shut-in.


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