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Title: Integrity of Pre-existing Wellbores in Geological Sequestration of CO 2 – Assessment Using a Coupled Geomechanics-fluid Flow Model

Abstract

Assessment of potential CO 2 and brine leakage from wellbores is central to any consideration of the viability of geological CO 2 sequestration. Depleted oil and gas reservoirs are some of the potential candidates for consideration as sequestration sites. The sequestration sites are expected to cover laterally extensive areas to be of practical interest. Hence there is a high likelihood that such sites will contain many pre-existing abandoned wells. Most existing work on wellbore integrity has focused on field and laboratory studies of chemical reactivity. Very little work has been done on the impacts of mechanical stresses on wellbore performance. This study focuses on the potential enhancement of fluid flow pathways in the near-wellbore environment due to modifications in the geomechanical stress field resulting from the CO 2 injection operations. The majority of the operational scenarios for CO 2 sequestration lead to significant rise in the formation pore pressure. This is expected to lead to an expansion of the reservoir rock and build-up of shear stresses near wellbores where the existence of cement and casing are expected to constrain the expansion. If the stress buildup is large enough, this can lead to failure with attendant permeability enhancement that can potentiallymore » provide leakage pathways to shallower aquifers and the surface. In this study, we use a numerical model to simulate key features of a wellbore (casing, annulus and cement) embedded in a system that includes the upper aquifer, caprock, and storage aquifer. We present the sensitivity of damage initiation and propagation to various operational and formation parameters. We consider Mohr-Coulomb shear-failure models; tensile failure is also likely to occur but will require higher stress changes and will be preceded by shear failure. The modeling is performed using the numerical simulator FEHM developed at LANL that models coupled THM processes during multi-phase fluid flow and deformation in fractured porous media. FEHM has been developed extensively under projects on conventional/unconventional energy extraction (geothermal, oil, and gas), radionuclide and contaminant transport, watershed management, and CO 2 sequestration.« less

Authors:
 [1];  [1];  [1];  [2]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  2. Monmouth Univ., West Long Branch, NJ (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Fossil Energy (FE)
Contributing Org.:
Monmouth Univ., West Long Branch, NJ (United States)
OSTI Identifier:
1360692
Report Number(s):
LA-UR-14-27148
Journal ID: ISSN 1876-6102
Grant/Contract Number:  
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Energy Procedia
Additional Journal Information:
Journal Volume: 63; Journal ID: ISSN 1876-6102
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES

Citation Formats

Kelkar, Sharad, Carey, J. William, Dempsey, David, and Lewis, Kayla. Integrity of Pre-existing Wellbores in Geological Sequestration of CO2 – Assessment Using a Coupled Geomechanics-fluid Flow Model. United States: N. p., 2014. Web. doi:10.1016/j.egypro.2014.11.606.
Kelkar, Sharad, Carey, J. William, Dempsey, David, & Lewis, Kayla. Integrity of Pre-existing Wellbores in Geological Sequestration of CO2 – Assessment Using a Coupled Geomechanics-fluid Flow Model. United States. doi:10.1016/j.egypro.2014.11.606.
Kelkar, Sharad, Carey, J. William, Dempsey, David, and Lewis, Kayla. Wed . "Integrity of Pre-existing Wellbores in Geological Sequestration of CO2 – Assessment Using a Coupled Geomechanics-fluid Flow Model". United States. doi:10.1016/j.egypro.2014.11.606. https://www.osti.gov/servlets/purl/1360692.
@article{osti_1360692,
title = {Integrity of Pre-existing Wellbores in Geological Sequestration of CO2 – Assessment Using a Coupled Geomechanics-fluid Flow Model},
author = {Kelkar, Sharad and Carey, J. William and Dempsey, David and Lewis, Kayla},
abstractNote = {Assessment of potential CO2 and brine leakage from wellbores is central to any consideration of the viability of geological CO2 sequestration. Depleted oil and gas reservoirs are some of the potential candidates for consideration as sequestration sites. The sequestration sites are expected to cover laterally extensive areas to be of practical interest. Hence there is a high likelihood that such sites will contain many pre-existing abandoned wells. Most existing work on wellbore integrity has focused on field and laboratory studies of chemical reactivity. Very little work has been done on the impacts of mechanical stresses on wellbore performance. This study focuses on the potential enhancement of fluid flow pathways in the near-wellbore environment due to modifications in the geomechanical stress field resulting from the CO2 injection operations. The majority of the operational scenarios for CO2 sequestration lead to significant rise in the formation pore pressure. This is expected to lead to an expansion of the reservoir rock and build-up of shear stresses near wellbores where the existence of cement and casing are expected to constrain the expansion. If the stress buildup is large enough, this can lead to failure with attendant permeability enhancement that can potentially provide leakage pathways to shallower aquifers and the surface. In this study, we use a numerical model to simulate key features of a wellbore (casing, annulus and cement) embedded in a system that includes the upper aquifer, caprock, and storage aquifer. We present the sensitivity of damage initiation and propagation to various operational and formation parameters. We consider Mohr-Coulomb shear-failure models; tensile failure is also likely to occur but will require higher stress changes and will be preceded by shear failure. The modeling is performed using the numerical simulator FEHM developed at LANL that models coupled THM processes during multi-phase fluid flow and deformation in fractured porous media. FEHM has been developed extensively under projects on conventional/unconventional energy extraction (geothermal, oil, and gas), radionuclide and contaminant transport, watershed management, and CO2 sequestration.},
doi = {10.1016/j.egypro.2014.11.606},
journal = {Energy Procedia},
number = ,
volume = 63,
place = {United States},
year = {Wed Dec 31 00:00:00 EST 2014},
month = {Wed Dec 31 00:00:00 EST 2014}
}

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