Uncertainty of stress path in fault stability assessment during CO<inf>2</inf> injection: Comparing smeaheia 3D geomechanics model with analytical approaches

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AZ ÉLELMISZERGAZDASÁG KÜLKERESKEDELME 2016. év I–X. hónap

A mezőgazdasági és élelmiszeripari termékek kivitele 6607 millió eurót, behozatala 4216 millió eurót tett ki 2016 első tíz hónapjában. Az agrár-külkereskedelmi forgalom 2391 millió euró aktívumot eredményezett. A kivitel értéke 1,4 százalékkal, a behozatalé 4,8 százalékkal emelkedett, az aktívum 4,1 százalékkal, 103 millió euróval elmaradt a 2015. január–októberi értéktől. A mezőgazdasági és élelmiszeripari termékek részesedése a teljes nemzetgazdasági exportból 2016 októberében 8,9 százalék, 2016 január–októberi időszakában 8,5 százalék, az importból 2016 októberében 6,3 százalék, 2016 január–októberi időszakában 6,1 százalék volt. Az agrárexport aránya 2016 január–októberi időszakában 0,1 százalékponttal alacsonyabb, míg az import aránya 0,2 százalékponttal magasabb volt, mint 2015 első tíz hónapjában

Effect of brine-CO2 fracture flow on velocity and electrical resistivity of naturally fractured tight sandstones

Fracture networks inside geological CO2 storage reservoirs can serve as primary fluid flow conduit, particularly in low-permeability formations. While some experiments focused on the geophysical properties of brine- and CO2-saturated rocks during matrix flow, geophysical monitoring of fracture flow when CO2 displaces brine inside the fracture seems to be overlooked. We have conducted laboratory geophysical monitoring of fluid flow in a naturally fractured tight sandstone during brine and liquid CO2 injection. For the experiment, the low-porosity, low-permeability naturally fractured core sample from the Triassic De Geerdalen Formation was acquired from the Longyearbyen CO2 storage pilot at Svalbard, Norway. Stress-dependence, hysteresis and the influence of fluid-rock interactions on fracture permeability were investigated. The results suggest that in addition to stress level and pore pressure, mobility and fluid type can affect fracture permeability during loading and unloading cycles. Moreover, the fluid-rock interaction may impact volumetric strain and consequently fracture permeability through swelling and dry out during water and CO2 injection, respectively. Acoustic velocity and electrical resistivity were measured continuously in the axial direction and three radial levels. Geophysical monitoring of fracture flow revealed that the axial P-wave velocity and axial electrical resistivity are more sensitive to saturation change than the axial S-wave, radial P-wave, and radial resistivity measurements when CO2 was displacing brine, and the matrix flow was negligible. The marginal decreases of acoustic velocity (maximum 1.6% for axial Vp) compared to 11% increase in axial electrical resistivity suggest that in the case of dominant fracture flow within the fractured tight reservoirs, the use of electrical resistivity methods have a clear advantage compared to seismic methods to monitor CO2 plume. The knowledge learned from such experiments can be useful for monitoring geological CO2 storage where the primary fluid flow conduit is fracture network.acceptedVersio

Regolith and Host Rock Influences on CO\u3csub\u3e2\u3c/sub\u3e Leakage: Active Source Seismic Profiling Across the Little Grand Wash Fault, Utah

Understanding carbon dioxide (CO2) reservoir to surface migration is crucial to successful carbon capture and sequestration approaches; especially fault/reservoir interactions under injection pressure. Through seismic imaging, we explore regolith and shallow stratigraphy across the Little Grand Wash fault. The presence of natural CO2 seeps, travertine and tufa deposits confirm modern and ancient fault-controlled CO2 leakage. We consider this an analogue for a long-failed sequestration site. We estimate bulk porosity and fracture density for host rock, regolith, and fault zone from petrophysical relationships. When combined with existing geochemical and geological data, we characterize a 60 m wide damage zone that represents the primary surface delivery channel for CO2 originating from reservoir depths. Within this damage zone, low seismic velocities suggest sediments have formed through host rock chemical dissolution or mechanical weathering. In contrast, velocities within the adjacent host rock are consistent with low fracture density clastic rocks. We measure anomalously high seismic velocities within the fault zone along one profile that best represents a sealed (cemented/plugged) low permeability, relic flow channel. This suggests that shallow fault zone permeability varies along strike. While regional stress changes may account for decadal- to millennial-scale changes in CO2 pathways, we speculate that the total fluid pressure has locally reduced the fault\u27s minimum horizontal effective stress; thereby producing both low- and high-permeability fault segments that either block or promote fluid migration. Studying CO2 migration in this system can inform potential risks to future sequestration projects and guide monitoring efforts

Characterizing along- and across-fault fluid-flow properties for assessing flow rates and overburden fluid migration along faults: a case study from the North Sea

Assessing fault zones as fluid-migration pathways requires the characterization of permeability both across and along faults, as well as the adjacent volume. The hydraulic properties of the Vette Fault Zone, North Sea, are described by modelling the mixing of host-rock lithologies into the fault zone, and the fault width is derived from empirical relationships as a function of throw and clay content. To better understand the sensitivity related to the uncertainties in overburden lithologies and fault-width correlations, a parametric study with 1125 model realizations were solved in a 2D steady-state, single-phase, subsurface flow model. The fault zone, included as a discrete permeable structure, significantly alters the flow field compared to a model that only considers lithological juxtaposition. The most prominent hydraulic communication in the Vette Fault Zone is downwards from the storage reservoir where sand is mixed into the fault zone. Increasing the host-rock permeability in the overburden also increases the fault permeability and shifts the inflection point for down-fault flow, causing the pressurized reservoir to drain towards the overburden and the top surface. For CO 2 storage application, the models highlighted the potential for downward communication along the fault for brine, and the CO 2 capillary sealing towards the overburden. Thematic collection: This article is part of the Fault and top seals 2022 collection available at: www.lyellcollection.org/topic/collections/fault-and-top-seals-2022 </jats:p

Improved quantification of CO2 storage containment risks - an overview of the SHARP Storage project

Carbon Capture and Storage (CCS) is now maturing in Europe and worldwide with several Net Zero projects emerging. Hence, the need for safe and reliable CO2 storage sites is accelerating and the accurate assessment of large-scale storage options at the gigatonne-per-year is critical. The SHARP project addresses the main priority areas required to improve current technologies to deliver CO2 storage volumes at the scale needed to meet demands for large scale storage. Research needs identified in the industry has provided the base for this well-integrated project with the ambitions to reduce the uncertainty in the geomechanical response to CO2 injection. Six case studies from sites in the North Sea and India will be matured during the projects. Ongoing work includes review of existing stress data, updating and integration of seismic catalogues and planning of new experimental data for improved constitutive models and rock failure attributes. Improved data analysis, compiling data from different sources, and new data generated in the project is expected to provide a base for updated failure risk assessment and more targeted monitoring. An initial assessment of rock failure risk in in progress and will be updated with a "Round 2" failure assessment incorporating new learnings and more mature data. The improved failure risk assessment includes the use of Bayesian statistical approach for quantification of uncertainties in geomechanical properties. Methods to quantify geological containment risk will be developed by reading across event tree techniques from other industries (e.g. nuclear). A set of generic release diagrams have been derived in a series of interdisciplinary workshops as a starting point for risk modellingImproved quantification of CO2 storage containment risks - an overview of the SHARP Storage projectpublishedVersio

Comparison of initial stress state and rock-failure risks for five prospective CO2 storage sites

We report initial assessments of the state of stress and the estimated conditions for rock failure at five prospective CO2 storage sites which are being considered in the ACT SHARP Project. This multinational project aims to improve understanding of stress history and reservoir pressure to enable improved quantification of CO2 storage containment risks. The goal is to improve the accuracy of subsurface CO2 storage containment risk management through the improvement and integration of subsurface stress models, rock mechanical data and seismicity observations. The case studies considered in this assessment are: • Norway – Horda/Smeaheia region; • UK – Southern North Sea, Bunter storage play; • Netherlands – Aramis site, Rotliegend pre-salt; • Denmark – Lisa Structure; • India – Bhagewala Heavy Oil Field, Rajasthan. These case studies have different levels of maturity of site development and data availability, which is useful for understanding what data is needed at different stages of a project. While detailed site characterisation and rock failure studies have been conducted for the Horda/Smeaheia region offshore Norway and for parts of the UK Southern North Sea (SNS) Bunter storage play, rock failure characterisation studies at the Aramis site and Lisa Structure are limited to regional studies. The Bhagewala Heavy Oil Field in India is the least mature of the case studies in terms of storage assessment

Fluid‐Rock Interactions in Clay‐Rich Seals: Impact on Transport and Mechanical Properties

Fluid‐rock interaction in low‐permeable clay‐rich seal units is an important topic for the evaluation of the long‐term seal integrity during geological storage of CO2. In low‐permeable sealing units, the diffusion of CO2 into the matrix is a slow process, and studies of CO2‐initiated fluid‐rock interaction in seals are challenging. In this paper, we present an overview of CO2 transport mechanism and fluid‐rock interaction processes that might alter mechanical and transport properties of seals. The review includes theoretical considerations and simulations, experimentally demonstrated processes, and field examples of flow and fluid‐rock interaction in intact clay‐rich seals as well as for fractures. For clay‐rich seals dominated by minerals like quartz, illite, and smectite, the reactivity due to drop in pH is found to be low, and most reaction observed is found to involve calcite. Only minor porosity changes are observed, and implications for flow and CO2 transport are uncertain due to limited data available. Swelling and shrinking property of smectites due to CO2 sorption and CO2 alterations within fractures in clay‐rich seal is hardly addressed in the literature.Fluid‐Rock Interactions in Clay‐Rich Seals: Impact on Transport and Mechanical PropertiesacceptedVersio

Upscaled Geocellular Flow Model of Potential Across-and along-Fault Leakage Using Shale Gouge Ratio

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