Borehole failure resulting from formation integrity (leak-off) testing in upper marine sediments offshore

Document Type

Conference Proceeding

Publication Date

12-1-1998

Abstract

This paper presents results of potential loss of external integrity around casing shoe resulting from leak-off testing (LOT) in upper marine sediments (UMS). Three types of possible failures from LOTs are considered. It is proved that vertical fracture is the most unlikely failure for most UMS. Horizontal fracture can be formed in the plastic zone at a wellbore pressure less than overburden pressure, but it can not extend beyond the plastic zone until the wellbore pressure exceeds the overburden pressure. An annular channel between cemented casing and rock is the other fracture way in UMS even though the cementing job is perfect. Fracture can be distinguished from LOT curve. Increasing the contact force between cemented casing and rock, such as using expanding cement, will prevent the formation of a harmful channel.

Publication Source (Journal or Book title)

American Society of Mechanical Engineers, Petroleum Division (Publication) PD

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