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Sixth EAGE Shale Workshop
- Conference date: April-May 28-01, 2019
- Location: Bordeaux, France
- Published: 28 April 2019
61 - 67 of 67 results
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Novel Finite Element Approach on Evolution and Stabilization of Breakout in Shales
SummaryThis paper describes a novel approach to model breakout failure whereby cell removal is introduced to account for actual breakout geometry and stabilisation. Finite element modelling was conducted in several selected wells with good quality image log and caliper data to develop and subsequently validate the approach.
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Heating Induced Shale Barriers
Authors A. Bauer, X. Xie, J.F. Stenebråten, S. Bakheim, A. Lavrov, E. Fjær and T.G. KristiansenSummaryIn this work, it was investigated if heating of a cased borehole in a shale formation can induce plastic deformations that are sufficiently high to close the annulus between shale and casing and form a hydraulic barrier. This is of interest for plug and abandonment (P&A) of wells. Both laboratory experiments and numerical simulations have been carried out. Borehole heating experiments were performed with hollow-cylinder shale samples, using a novel experimental setup that allows for temperature and pore pressures measurements at different radial positions inside the shale samples. The results show that borehole heating results in a relatively large increase of pore pressure in the shale, inducing rock failure and annulus closure under certain temperature and stress conditions. A finite-element model was used for simulating the experimental data and obtaining relevant thermo-poro-elasto-plastic parameters. Those parameters were used in field-scale finite-element models to assess the possibility of forming shale barriers by borehole heating. The numerical models provide a good description of the experimental data; they indicate that under certain conditions heat induced displacement at the borehole wall is large enough to close the annulus around a casing.
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Hydration State and Interlayer Cation Type (Ca2+, Na+) Control CO2 Sorption Behavior of SWy-2 Montmorillonite
Authors R. Fink, P. Bertier, B. Krooss and P. WenigerSummaryCO2 uptake behavior of smectitic clays is less predictable compared to other geomaterials as molecules (especially H2O) and ions sorb in the interplayer space leading to a volumetric expansion. In the context of geologic sequestration of carbon dioxide, it is important to understand how this multi-component system reacts upon exposer of supercritical CO2. In this study, we performed high-pressure CO2 adsorption experiments on expandable clays (Na+ and Ca2+ exchanged SWy-2 Montmorillonite) at relevant conditions for CO2 sequestration. With increasing hydration from dry (0W) state to one-layer hydrate (1W) the CO2 excess sorption capacity sharply increases and then decreases again with hydration to two-layer hydrate (2W). The magnitude of this effect is strongly controlled by the interplayer cation type (Ca2+, Na+). We interpret that this behavior is closely linked to the structure and swelling behavior of these clays by CO2 adsorption. Dry montmorillonite hardly expands when exposed to CO2 whereas a strong shift in the mean basal spacing d001 between the hydrated clay layers upon exposure to CO2 is observed around the sub1W hydration state. This indicates that high-pressure CO2 adsorption in the presence of water is strongly influenced by the intercalation of CO2 into the expandable interplayers.
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Organic Matter of Bazhenov Formation: Chemical and Isotope Composition, Microstructure, Thermal Maturation, Generation Potential and the Effect on Rock Properties
Authors M. Spasennykh, A. Voropaev, E. Kozlova, E. Leushina, V. Polyakov, A. Vasiliev, N. Bogdanovich, Y. Popov and A. MaximovSummaryThe Bazhenov shale Formation is one of the largest source rock formation in the world. In this research the chemical and isotope compositions, the microstructure and other parameters of organic matter of the Bazhenov Formation from the Central, East, West and North parts of Western Siberia have been studied. A wide spectrum of analytical methods has been applied, including Rock-Eval pyrolysis, kinetics of kerogen thermal decomposition, electron-ion microscopy, X-ray micro-tomography, gas chromatography–mass spectrometry, solid state NMR and X-ray photoelectron spectroscopy, isotope measurements and other. It was shown that geochemical parameters of the organic matter of Bazhenov Formation, including kerogen, oil and gas chemical and isotope compositions, microstructure of kerogen and other considerably vary for different oilfields of Western Siberia depending on thermal maturity and other geological and lithological factors. Correlations between geochemical characteristics and petrophysical properties of rocks, including density, fluid saturation, geomechanical, thermal and other properties have been studied. Obtained results provide good opportunities for the development of advanced methods for shale reservoir characterization basing on logging and core analysis data
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Is the Uranium Content in Black Shale a Suitable Parameter to Assess the Alteration of Organic Matter and Petroleum Potential?
By H. SchulzSummaryThe simultaneous occurrence of high TOC and high uranium contents in black shale indicates that uranium is concentrated in the organic matter. Nevertheless, such uranium-OM correlations may be misleading as uranium-bearing minerals also occur in black shale. Thus, the spatial uranium distribution in black shale, but also the diagenetic timing of uranium fixation or possible later remobilization are critical factors, and control when and to what degree the OM may have been degraded due to the natural decay of high uranium contents. Previous studies only considered the bulk uranium content of samples as a parameter in estimating the degree of irradiation effects on the OM, and the sample sets were normally from different locations with different thermal maturities. Moreover, vertical and lateral variations in lithology and mineralogy as result of depositional environments as well as thermal maturation during burial are additional controls for different uranium contents and phase occurrences. In this contribution, published data from Schulz et al. (2019) will be presented about the approximately 4 m thick and thermally immature western Russian Koporie Formation (“Dictyonema” Shale) using an interdisciplinary analytical approach in order to answer questions about the source of uranium, its occurrence in the shale, both spatially and temporarily, and the consequences for the OM and the petroleum potential.
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Origins of Shale Gases Based on Revised Gas Genetic Diagrams
Authors A.V. Milkov and G. EtiopeSummaryWe collected a large dataset of gas samples recovered from shale formations around the world and interpreted the origin of shale gases using recently revised gas genetic diagrams. Gas in most shale plays has thermogenic origin. Some shale plays contain secondary microbial gas. Primary microbial gas is not common in shale play.
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Developing Unconventional Reservoirs Using Limited Natural Fractures Statistics – Challenges and Opportunities
By A. OuenesSummaryGiven the recognized importance of the natural fractures in the development of unconventional reservoirs, the sparse statistics created by the lack of cores and image logs requires practical engineering approaches and solutions. Among these solutions is the use of a continuous fracture model that uses a representative volume to describe the fracture density that can be estimated from seismic and surface drilling data. This approach leads to a quantitative use of these natural fractures and their interaction with hydraulic fracture using a robust geomechanical simulation able to predict microseismicty thus validating both the used natural fracture model and the geomechanical modelling approach.
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