SPE EVENING PRESENTATION

SPE BRUNEI SECTION


Better Well Design with Borehole Stability Analysis

Patrick McLellan

Advanced Geotechnology Inc.

Abstract

Borehole instability during drilling can take many familiar forms such as stuck pipe, hole squeezing, lost circulation, severely enlarged hole or difficult directional control. Many related problems can arise when such boreholes are finally drilled to target, including uncertain formation evaluation, poor cementing, casing deformations, and ineffective perforating. These issues cost the industry several billions of dollars a year around the globe in downtime, well construction costs, and lost production.

This lecture will provide an overview of the types of borehole instability problems experienced in several geological settings around the world, including tectonically- stressed brittle fissile shales, smectite-rich shales, poorly-cemented sandstones and fractured carbonates. Several novel well designs, new drilling fluids and drilling practices that have been developed to solve these problems using advanced borehole stability analysis will be described.

Techniques for modeling the onset and extent of rock yielding, failure, and eventually detachment around boreholes will be highlighted, including new approaches for barefoot completions, reactive shales, underbalanced drilling, and partially-depleted reservoirs. Practical methods for estimating relevant rock mechanical properties and in-situ stresses from offset wells, in the absence of high quality core or log data, will be shown. Predictions from simple analytical and complex 2D and 3D numerical models will be described to illustrate some of the different analysis methods being used to design better wells.

Several solutions to borehole instability such as casing drilling, wall-coating drilling muds, trajectory optimization, expandable tubulars, and underbalanced drilling will be compared using recent examples.

Biography

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Patrick McLellan is the president of Advanced Geotechnology Inc., an international petroleum engineering consulting, training and software company. He has over 20 years experience in petroleum rock mechanics problems including borehole instability, sand production risk assessment, hydraulic fracturing, casing integrity, compaction, subsidence, permafrost, reservoir monitoring and subsurface waste disposal. He is the co-developer of the STABView software package for well planning and analysis. He was previously employed at Shell Canada and Petro-Canada in drilling and production engineering positions. He has a B.Sc. degree in Geological Engineering from Queen’s University and an M.Sc. in Civil Engineering (Geotechnical) from the University of Alberta

Advances in computational hardware and software offer geophysicists, geologists, and engineers the possibility of solving problems that were impossible a decade ago. Still, we are uncomfortable making decisions with limited information. This lecture provides new information and offers an optimistic view of the future of esoteric computing in the petroleum industry. 

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