Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 125
Managing Wellbore Instablility Risk in Gas-Hydrate-Bearing Sediments
Tan, C.P., Freij-Ayoub, R., Clennell, M.B., Tohidi, B., and Yang, J.
SPE 92960, The 2005 Asia Pacific Oil and Gas Conference, Jakarta, Indonesia, April 5-7 (2005).
With the petroleum industry endeavouring to develop oil and gas fields in deepwater and to increase its activities in onshore arctic environments, greater emphasis should be placed on quantifying the hazards to drilling operations posed by gas hydrates. In spite of gas hydrate-bearing sediments having been drilled successfully in the past, it is important, as future drilling operations progress into deeper and ultradeep waters, to develop a sound understanding of gas hydrate-related hazards and thereby identify ahead of time when problems are likely to occur. It is also highly desirable to define the envelope of risk-free operations so that unnecessary costs and delays associated with mitigation of the problems are not incurred. This paper describes the specific requirements to develop a comprehensive risk management capability for drilling in gas hydrate-bearing sediments. The methodology adopted concentrates on reducing risk and uncertainty associated with gas hydrates and associated shallow gas geohazards in deep water. These will be achieved by means of determining the petrophysical, mechanical and thermodynamic properties of gas hydrate-bearing sediments, and developing a fully coupled model for wellbore stability in the sediments, and methodology for drilling fluid design optimization and a risk assessment and optimization framework. Examples of laboratory measured petrophysical and mechanical properties of gas hydrate-bearing sediments, and results of time-dependent wellbore stability in such sediments are presented and discussed.

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