Field-Scale and Wellbore Modeling of Compaction-Induced Casing Failures

Abstract

Presented in this paper are the results and verification of field-and wellbore-scale large deformation, elasto-plastic, geomechanical finite element models of reservoir compaction and associated casing damage. The models were developed as part of a multidisciplinary team project to reduce the number of costly well failures in the diatomite reservoir of the South Belridge Field near Bakersfield, California. Reservoir compaction of high porosity diatomite rock induces localized shearing deformations on horizontal weakrock layers and geologic unconformities. The localized shearing deformations result in casing damage or failure. Twodimensional, field-scale finite element models were used to develop relationships between field operations, surface subsidence, and shear-induced casing damage. Pore pressures were computed for eighteen years of simulated production and water injection, using a three-dimensional reservoir simulator. The pore pressures were input to the two-dimensional geomechanical field-scale model. Frictional contact surfaces were used to model localized shear deformations. To capture the complex casing-cement-rock interaction that governs casing damage and failure, threedimensional models of a wellbore were constructed, including a frictional sliding surface to model localized shear deformation. Calculations were compared to field data for verification of the models.

Innovative Use of Open-Hole Wireline Formation Pressure Testing in Waterflood Optimization of an Ultra-Tight, Light Oil Reservoir, Belridge Field

“…By 1985, the number of subsidence-related producer failures approached historic levels (20% per year) 8 , leading to a reevaluation of reliance on primary recovery and of pattern configuration. Others have studied Diatomite reservoir compaction, subsidence-induced well casing failures, and large-impact surface subsidence 8,9,10,11,12,13 . As a result, the first Opal-A waterflood was instituted in the South Belridge Diatomite area in the mid 1980s, primarily for reservoir pressure maintenance to minimize elevated well failure occurrence.…”

Well Integrity Evaluation for Methane Hydrate Production in the Deepwater Nankai Trough

“…However, most of this work either assumed constant formation mechanical properties thereby ignoring the heterogeneity of the formation mechanical properties, or the detailed geometry of well completions was not considered. A few authors (Hilbert et al, 1998;Li et al, 2003;Rutqvist and Moridis, 2007) recognized the importance of honoring this complexity at both the field and near-wellbore scales but did not implement models that did so. Among them, numerical evaluation of well integrity in methane hydrate-bearing formation was very rarely published (Freij-Ayoub et al, 2007;Freij-Ayoub, 2009;Salehabadi et al, 2009).…”