SPE Drilling & Completion
Volume 26, Number 4, December 2011, pp. 531-539

Summary

Leakoff tests (LOTs) are performed to test the strength or pressure containment of the shoe after a cement job to help ensure that the new hole has been securely isolated from what has been cased off. A successful LOT can also be used to calibrate the least principal stress (many times, in the case of a vertical well, the minimum horizontal stress), or for geomechanics modeling. This will require initiating a fracture at the wellbore. Because of the near-wellbore stress concentration, for the purpose of geomechanics calibration, it is preferred to take the leakoff to the far-field stress region. To perform this extended LOT (XLOT), a relatively long fracture has to be created. Though an XLOT is needed for these reasons, some engineers tend to refrain from performing this test for fear that the test may damage the wellbore and consequently cause drilling problems.

This paper addresses this issue by investigating the effect of wellbore damage on wellbore "strength" or pressure containment. Various issues are discussed to help engineers determine when it may or may not be a concern. This should give practicing engineers the necessary insight into this complex rock-mechanics issue. The discussions are supported with results from analytical and numerical simulations based on rock-mechanics principles.

© 2011. Society of Petroleum Engineers

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History

• Original manuscript received: 4 November 2010
• Meeting paper published: 19 September 2010
• Revised manuscript received: 7 July 2011
• Manuscript approved: 11 July 2011
• Published online: 5 December 2011
• Version of record: 27 December 2011