Society of Petroleum Engineers
Distinguished Lecturer 2004-05 Lecture Season

Analyzing Well Damage Risks and
Optimum Well Designs for Compacting Reservoirs
Dr. Michael Bruno
Terralog Technologies USA Inc.

Michael Bruno

Abstract:
The weight of sediments above an oil and gas bearing geologic formation is supported partially by the rock matrix and partially by the pressurized fluid or gas within the rock pore space. When fluid pressure is reduced, more of the load is transferred to the rock matrix and the pressure-depleted formation compacts slightly. Subsurface compaction, if it is significant or if the formation is relatively shallow, can produce measurable surface subsidence. Formation compaction can induce compression and buckling damage within the producing interval. More importantly, significant formation compaction also induces small-scale slip on bedding planes and faults within the reservoir and overburden material, causing severe shear damage to wells. Reservoir compaction and associated bedding plane slip and overburden shear has induced damage to many hundreds of wells in oil and gas fields throughout the world. Problems can be particularly acute in deep offshore operations, where individual well costs often exceed 10million dollars and specific wells often target individual sand formations or fault blocks. Hence the loss of even one or two wells may significantly impact recoverable reserves for the field.

The appropriate mitigation strategy and optimum well design will depend on the most likely location of casing damage, the expected type of damage, and the damage magnitude. This requires combining geomechanical analysis of deformations in the reservoir, overburden, and the well completion assembly, with quantitative decision analyses that compare the costs of various mitigation strategies to the economic benefit of reducing damage risk, while recognizing the inherent uncertainty and variability in each estimate or analysis.

In this presentation Dr. Bruno will describe field observations and case studies of reservoir compaction, surface subsidence, and well casing damage from around the world. He will review the state-of-the-art for analyzing subsidence and well damage risks, from simple analytical equations to 3D coupled fluid flow and geomechanical models at both the reservoir scale and wellbore scale. He will then describe mitigation strategies available to reduce well damage risks, the relative performance and damage limits for various completion designs, and quantitative decision analysis techniques that can be applied to compare the relative costs and benefits of alternative completion designs for compacting reservoirs.

Biography:
Dr. Michael Bruno, President of Terralog Technologies USA, Inc., has more than 20 years experience in various aspects of reservoir and wellbore geomechanics, with more than 30 publications related to petroleum geomechanics. He has developed and applied analytical and numerical models to estimate reservoir compaction and well damage risks, and has developed mitigation strategies and optimum well designs for oil and gas fields in the United States, Canada, South America, Southeast Asia, Europe, and Eurasia. Dr. Bruno holds a Ph.D. degree in Civil Engineering from the University of California, Los Angeles, and is a Licensed Professional Engineer in California. Before joining Terralog in 1994, Dr. Bruno gained thirteen years of experience with Chevron Petroleum Technology Company, where he held the positions of Geomechanics Group Leader and Senior Research Engineer. He has a long and active record of service to the Society of Petroleum Engineers. He has served as Chairman of the Los Angeles Basin Section twice, has been a member of the Program Committee for more than half a dozen SPE Western Regional Meetings, and is currently the Review Chairman for Geomechanics and Geophysics topics for the SPE Reservoir Evaluation and Engineering Journal.

LASPE Forum Committee:
Maryam Davari, 213-225-5900x209, mkashfi@breitburn.com
Brandy Fellers, 562-624-3237 brandy_fellers@oxy.com
Rick Finken 562-570-3961, richard_finken@longbeach.gov