Novel experimental/numerical approach to evaluate the permeability of cement-caprock systems

Abstract This study presents a novel laboratory-scale experimental/numerical approach that contributes to our understanding of micro-annular flow paths in cement-caprock interfaces. The approach is based on studying single-phase fluid flow in composite specimens with imperfect bonding between cement and caprock. Imperfect bonding and defect zones in the cement were initially characterized by X-ray micro computed tomography. Subsequently, the bulk permeability of the specimens was determined through single-phase fluid permeability measurements. Permeability was also evaluated numerically by finite-element modelling of steady single-phase flow in the specimens. The numerical modelling revealed that the average permeability of defect zones mapped from μ-CT images was likely to be within 1–10 D (0.1 × 10−11 to 1 × 10−11 m2). If a connected region of elevated permeability is established in situ, it can create a potential well integrity risk by providing a flow path up the annulus of the well. The integrated experimental and numerical framework employed in this study can form the basis for future systematic evaluation of leakage risks related to well integrity issues during underground CO2 storage, as well as in other applications such as drilling and completion of geothermal wells.

[1]  Marshall D. Bishop,et al.  A Robust, Field Friendly, Cement Spacer System , 2008 .

[2]  P. Gouze,et al.  Hydro-dynamically controlled alteration of fractured Portland cements flowed by CO2-rich brine , 2013 .

[3]  P. Nawrocki,et al.  Why Oilwells Leak: Cement Behavior and Long-Term Consequences , 2000 .

[4]  Michael Batzle,et al.  Anisotropic Elastic Moduli of the Mancos B Shale- An Experimental Study , 2010 .

[5]  S. Walsh,et al.  Experimental calibration of a numerical model describing the alteration of cement/caprock interfaces by carbonated brine , 2014 .

[6]  Torbjørn Vrålstad,et al.  A Visual Journey Into the 3D Chemical Nanostructure of Oilwell Cement , 2013 .

[7]  F. K. Mody,et al.  Borehole-Stability Model To Couple the Mechanics and Chemistry of Drilling-Fluid/Shale Interactions , 1993 .

[8]  P. Jacobs,et al.  Applications of X-ray computed tomography in the geosciences , 2003, Geological Society, London, Special Publications.

[9]  Pierre Cerasi,et al.  Near-Well Integrity and Thermal Effects: A Computational Road from Laboratory to Field Scale , 2014 .

[10]  Waqas Mushtaq,et al.  Experimental Study of Cement-Formation Bonding , 2014 .

[11]  J. Carey,et al.  Experimental investigation of wellbore integrity and CO2–brine flow along the casing–cement microannulus , 2010 .

[12]  S. Walsh,et al.  Permeability of Wellbore-Cement Fractures Following Degradation by Carbonated Brine , 2013, Rock Mechanics and Rock Engineering.

[13]  A. Lothe,et al.  Reservoir geology of the Utsira Formation at the first industrial-scale underground CO2 storage site (Sleipner area, North Sea) , 2004, Geological Society, London, Special Publications.

[14]  J. Clayton,et al.  Geology, Thermal Maturation, and Source Rock Geochemistry in a Volcanic Covered Basin: San Juan Sag, South-Central Colorado , 1997 .

[15]  Benoit Vidick.  Critical mixing parameters for good control of cement slurry quality , 1990 .

[16]  Andrew Duguid,et al.  Well Integrity Assessment of a 68 year old Well at a CO2 Injection Project , 2014 .

[17]  P. Lichtner,et al.  Analysis and performance of oil well cement with 30 years of CO2 exposure from the SACROC Unit, West Texas, USA , 2007 .

[18]  D. T. Snow.  ROCK FRACTURE SPACINGS, OPENINGS, AND POROSITIES , 1968 .

[19]  Olav-Magnar Nes,et al.  Nanostructure vs. Macroscopic Properties of Mancos Shale , 2012 .

[20]  Arild Saasen,et al.  Permanent Abandonment of a North Sea Well Using Unconsolidated Well-Plugging Material , 2011 .

[21]  S. Bachu,et al.  Evaluation of the Potential for Gas and CO2 Leakage Along Wellbores , 2009 .

[22]  Michael A. Celia,et al.  Pre-injection Baseline Data Collection to Establish Existing Wellbore Leakage Properties☆ , 2013 .

[23]  Eric W. Lemmon,et al.  Thermophysical Properties of Fluid Systems , 1998 .

[24]  P. Gouze,et al.  Characterization of the mechanisms controlling the permeability changes of fractured cements flowed through by CO2-rich brine. , 2013, Environmental science & technology.

[25]  Steven L. Bryant,et al.  Reactive transport of CO2-saturated water in a cement fracture: Application to wellbore leakage during geologic CO2 storage , 2016 .

[26]  Stuart L. Scott,et al.  Sustained Casing Pressure in Offshore Producing Wells , 1999 .

[27]  Timothy Gareth John Jones,et al.  The Cement-to-Formation Interface in Zonal Isolation , 2005 .

[28]  Torbjørn Vrålstad,et al.  Potential Leakage Paths along Cement-formation Interfaces in Wellbores; Implications for CO2 Storage☆ , 2014 .

[29]  O. C. Zienkiewicz,et al.  The Finite Element Method: Its Basis and Fundamentals , 2005 .

[30]  A. P. Hibbert,et al.  Effect of Mixing Energy Levels During Batch Mixing of Cement Slurries , 1995 .

[31]  J. Carey.  Geochemistry of Wellbore Integrity in CO2 Sequestration: Portland Cement-Steel-Brine-CO2 Interactions , 2013 .

[32]  S. Walsh,et al.  Chemical and mechanical properties of wellbore cement altered by CO₂-rich brine using a multianalytical approach. , 2013, Environmental science & technology.

[33]  J. Carey,et al.  Geochemical effects of CO2 sequestration on fractured wellbore cement at the cement/caprock interface , 2009 .

[34]  S. Bryant,et al.  Experimental evidence for self-limiting reactive flow through a fractured cement core: implications for time-dependent wellbore leakage. , 2013, Environmental science & technology.

[35]  R. H. McLean,et al.  Displacement Mechanics in Primary Cementing , 1967 .