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Title: Coupled reservoir-geomechanical analysis of the potential fortensile and shear failure associated with CO2 injection in multilayeredreservoir-caprock systems

Abstract

Coupled reservoir-geomechanical simulations were conductedto study the potential for tensile and shear failure e.g., tensilefracturing and shear slip along pre-existing fractures associated withunderground CO2 injection in a multilayered geological system. Thisfailure analysis aimed to study factors affecting the potential forbreaching a geological CO2 storage system and to study methods forestimating the maximum CO2 injection pressure that could be sustainedwithout causing such a breach. We pay special attention to geomechanicalstress changes resulting from upward migration of the CO2 and how theinitial stress regime affects the potential for inducing failure. Weconclude that it is essential to have an accurate estimate of thethree-dimensional in situ stress field to support the design andperformance assessment of a geological CO2 injection operation. Moreover,we also conclude that it is important to consider mechanical stresschanges that might occur outside the region of increased reservoir fluidpressure (e.g., in the overburden rock) between the CO2-injectionreservoir and the ground surface.

Authors:
; ;
Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE. Assistant Secretary for Fossil Energy.Coal
OSTI Identifier:
932479
Report Number(s):
LBNL-62675
R&D Project: G23001; BnR: AA3010000; TRN: US200813%%73
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Rock Mechanics; Journal Volume: 45; Journal Issue: 2; Related Information: Journal Publication Date: 02/2008
Country of Publication:
United States
Language:
English
Subject:
54; DESIGN; FRACTURES; FRACTURING; OVERBURDEN; PERFORMANCE; RESERVOIR FLUIDS; SHEAR; SLIP; STORAGE

Citation Formats

Rutqvist, J., Birkholzer, J.T., and Tsang, C.-F. Coupled reservoir-geomechanical analysis of the potential fortensile and shear failure associated with CO2 injection in multilayeredreservoir-caprock systems. United States: N. p., 2007. Web.
Rutqvist, J., Birkholzer, J.T., & Tsang, C.-F. Coupled reservoir-geomechanical analysis of the potential fortensile and shear failure associated with CO2 injection in multilayeredreservoir-caprock systems. United States.
Rutqvist, J., Birkholzer, J.T., and Tsang, C.-F. Tue . "Coupled reservoir-geomechanical analysis of the potential fortensile and shear failure associated with CO2 injection in multilayeredreservoir-caprock systems". United States. doi:. https://www.osti.gov/servlets/purl/932479.
@article{osti_932479,
title = {Coupled reservoir-geomechanical analysis of the potential fortensile and shear failure associated with CO2 injection in multilayeredreservoir-caprock systems},
author = {Rutqvist, J. and Birkholzer, J.T. and Tsang, C.-F.},
abstractNote = {Coupled reservoir-geomechanical simulations were conductedto study the potential for tensile and shear failure e.g., tensilefracturing and shear slip along pre-existing fractures associated withunderground CO2 injection in a multilayered geological system. Thisfailure analysis aimed to study factors affecting the potential forbreaching a geological CO2 storage system and to study methods forestimating the maximum CO2 injection pressure that could be sustainedwithout causing such a breach. We pay special attention to geomechanicalstress changes resulting from upward migration of the CO2 and how theinitial stress regime affects the potential for inducing failure. Weconclude that it is essential to have an accurate estimate of thethree-dimensional in situ stress field to support the design andperformance assessment of a geological CO2 injection operation. Moreover,we also conclude that it is important to consider mechanical stresschanges that might occur outside the region of increased reservoir fluidpressure (e.g., in the overburden rock) between the CO2-injectionreservoir and the ground surface.},
doi = {},
journal = {International Journal of Rock Mechanics},
number = 2,
volume = 45,
place = {United States},
year = {Tue Mar 27 00:00:00 EDT 2007},
month = {Tue Mar 27 00:00:00 EDT 2007}
}
  • In Salah Gas Project in Algeria has been injecting 0.5-1 million tonnes CO{sub 2} per year over the past five years into a water-filled strata at a depth of about 1,800 to 1,900 m. Unlike most CO{sub 2} storage sites, the permeability of the storage formation is relatively low and comparatively thin with a thickness of about 20 m. To ensure adequate CO{sub 2} flow-rates across the low-permeability sand-face, the In Salah Gas Project decided to use long-reach (about 1 to 1.5 km) horizontal injection wells. In an ongoing research project we use field data and coupled reservoir-geomechanical numerical modelingmore » to assess the effectiveness of this approach and to investigate monitoring techniques to evaluate the performance of a CO{sub 2}-injection operation in relatively low permeability formations. Among the field data used are ground surface deformations evaluated from recently acquired satellite-based inferrometry (InSAR). The InSAR data shows a surface uplift on the order of 5 mm per year above active CO{sub 2} injection wells and the uplift pattern extends several km from the injection wells. In this paper we use the observed surface uplift to constrain our coupled reservoir-geomechanical model and conduct sensitivity studies to investigate potential causes and mechanisms of the observed uplift. The results of our analysis indicates that most of the observed uplift magnitude can be explained by pressure-induced, poro-elastic expansion of the 20 m thick injection zone, but there could also be a significant contribution from pressure-induced deformations within a 100 m thick zone of shaly sands immediately above the injection zone.« less
  • Numerical models are essential tools for CO2 sequestration projects and should be included in the life cycle of a project. Common practice involves modeling the behavior of CO2 during and after injection using site-specific reservoir and caprock properties. Little has been done to systematically evaluate and compare the effects of a broad but realistic range of reservoir and caprock properties on potential CO2 leakage through caprock. Broad-based research addressing the impacts of caprock properties and their heterogeneity on seal permeation is absent. Efforts along this direction require obtaining information about the physically reasonable range of caprock and reservoir properties, effectivelymore » sampling the parameter space to fully explore the range of these properties, and performing flow and transport calculations using reliable numerical simulators. In this study, we identify the most important factors affecting CO2 leakage through intact caprock and try to understand the underlying mechanisms. We use caprock and reservoir properties from various field sites and literature data to identify the range of caprock thickness, permeability, and porosity that might occur. We use a quasi Monte Carlo sampling approach to ensure that the full range of caprock and seal properties is evaluated without bias. For each set of sampled properties, the migration of injected CO2 is simulated for up to 200 years using the water-salt-CO2 operational mode of the STOMP simulator. Preliminary results show that critical factors determining CO2 leakage rate through intact caprock are, in decreasing order of significance, the caprock thickness, caprock permeability, reservoir permeability, caprock porosity, and reservoir porosity. This study provides a function for prediction of potential CO2 leakage risk due to permeation of intact caprock, and identifies a range of acceptable seal thicknesses and permeability for sequestration projects. As a byproduct, the dependence of CO2 injectivity on reservoir properties is also evaluated.« less
  • No abstract prepared.
  • In this paper, coupled reservoir-geomechanical (TOUGH-FLAC) modeling is applied for the first time to the St. Lawrence Lowlands region to evaluate the potential for shear failure along pre-existing high-angle normal faults, as well as the potential for tensile failure in the caprock units (Utica Shale and Lorraine Group). This activity is part of a general assessment of the potential for safe CO 2 injection into a sandstone reservoir (the Covey Hill Formation) within an Early Paleozoic sedimentary basin. Field and subsurface data are used to estimate the sealing properties of two reservoir-bounding faults (Yamaska and Champlain faults). The spatial variationsmore » in fluid pressure, effective minimum horizontal stress, and shear strain are calculated for different injection rates, using a simplified 2D geological model of the Becancour area, located ~110 km southwest of Quebec City. The simulation results show that initial fault permeability affects the timing, localization, rate, and length of fault shear slip. Contrary to the conventional view, our results suggest that shear failure may start earlier for a permeable fault than for a sealing fault, depending on the site-specific geologic setting. In simulations of a permeable fault, shear slip is nucleated along a 60 m long fault segment in a thin and brittle caprock unit (Utica Shale) trapped below a thicker and more ductile caprock unit (Lorraine Group) – and then subsequently progresses up to the surface. In the case of a sealing fault, shear failure occurs later in time and is localized along a fault segment (300 m) below the caprock units. The presence of the inclined low-permeable Yamaska Fault close to the injection well causes asymmetric fluid-pressure buildup and lateral migration of the CO 2 plume away from the fault, reducing the overall risk of CO 2 leakage along faults. Finally, fluid-pressure-induced tensile fracturing occurs only under extremely high injection rates and is localized below the caprock units, which remain intact, preventing upward CO 2 migration.« less