Technical Paper: Optimizing Drilling Performance by Wellbore Stability and Pore-Pressure Evaluation in Deepwater Exploration

Society: IPTC
Paper Number: 10933
Presentation Date: 2005


This paper discusses the most important drilling hazards related to borehole instability and pore pressure in deep water wells. A case study from a deep water well, which has experienced wellbore stability and loss of circulation problems, especially over intervals with higher angles of hole deviation, is presented. The answers provided by the study included properties, such as, recommended mud-weights (minimum & maximum) as a function of angle of deviation, rock strength and computed pore pressure. The determination of rock strength along with the optimum mud-weight windows improved overall the drilling performance in the next deep water well by minimizing washouts, loss of circulation and optimizing casing design by elimination of unnecessary casing strings. Moreover, improvement of bit performance was achieved by using the predicted rock-strength values. As a result, drilling time and well construction costs were significantly reduced.

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