Monitoring CO2 migration in an injection well: Evidence from MovECBM

Carbon dioxide (CO2) geological storage relies on safe, long-term injection of large quantities of CO2 in underground porous rocks. Wells, whether they are the conduit of the pumped fluid or are exposed to CO2 in the storage reservoir (observation and old wells) are man-made disturbances to the geological storage complex, and are thus viewed by some as a possible risk factor to the containment of the injected CO 2. Wells are composite structures, with an inner steel pipe separated from the borehole rock wall by a thin cement sheath (∼2 cm) that prevents vertical fluid migration. Both carbon steel and cement react in the presence of CO2, although evidence from production of CO2-rich fluids in the oil and gas industry and from lab experiments suggests that competent, defect-free cement offers an effective barrier to CO2 migration and leaks. However, reactivity of cement and steel may result in CO2 migration pathways degrading over time, thus in the leakage risk increasing during the life of the storage project. The issue then becomes how to best integrate preventive verification of zonal isolation/well integrity in the storage site monitoring plan. An analysis of the order of magnitude of possible CO2 leaks, and of their path to potable aquifers or the atmosphere, is also necessary to optimize the assurance (mitigation) monitoring of the storage site. Evidence gathered during the MovECBM project indicates that migration of small quantities of CO2 happened during injection in a coal seam in Southwest Poland. The evidence, gathered from casing and cement logging as well as soil gas monitoring over a 3-year period, was coupled with laboratory testing and extensive modeling of the chemo-mechanical behavior of cement and steel to determine if CO2 migration might have been responsible of the observed behavior. The three lines of evidence were: the detection of very small CO2 fluxes, coupled with less controversial helium concentration in soil; the occurrence of a thin pathway at the interface between cement and casing; and the change in mechanical properties of cement, suggestive of partial carbonation. Whereas the observations suggest that limited CO2 migration might have happened in the well, they are by no means proof that the migration did happen. Nonetheless, the integration of measurement and modeling yields important lessons for wellbore monitoring. First, it puts a probable ceiling on the order of magnitude of expected leaks from reasonably well-cemented wells at around 100 metric tons per year (less than 0.05% of the injected mass in a well like Sleipner or In Salah). It also suggests that cement may be a very effective leak detector: exposure to CO2 modifies its mechanical properties, which in turn can be detected using cement evaluation logs. Finally, coupling with dispersion modeling suggests the precision and accuracy required from soil gas and atmospheric monitoring, as well as the placement of sampling points; it also suggest that hysteresis, due to the accumulation in CO2 in surface aquifers and to the time required for it to be transported to the survey points, may delay initial detection; the same hysteresis may at the same time prolong the occurrence of CO2 shows long after the leak has stopped. © 2010 Elsevier Ltd. © 2011 Published by Elsevier Ltd

Gouttes et champs électriques dans un système microfluidique

The thesis offers novel analyses of the breakup phenomenon at microfluidic junctions, along with new insights into the effect of electric fields on droplets in microfluidic channels. The first part studies droplet behaviour as they arrive at a microfludic junction. Three scenarios - two of them leading to breakup - are identified. We study them quantitatively usinglocal variables and control parameters. The results of this study lead to a design of a microfluidic phase extractor. In the second part, we analyse the effect of the electric field on a confined droplet. We develop a 2D theoretical approach of the problem using Shankar’s work. Then, we compare these theo-retical results with two experiments : we show that the theory successfully predicts the shape of confined droplets under electric fieldalong with the change in velocity as the droplet moves along a non-uniform field. The results are applied to propose novel ways of controling droplets.in microfluidic systems.Cette thèse propose une analyse originale des phénomènes de brisure de gouttes et d'action d'un champ électrique dans un système microfluidique. Une première partie présente l'étude d'une goutte traversant une jonction microfluidique. Après avoir identifié trois scénarios possibles - dont deux entraînent la brisure - nous proposonsune étude quantitative des comportements observés dans l'espace des variables locales puis des paramètres de contrôle. Ces résultats ont été appliqués à l'extraction de phase microfluidique. Dans une seconde partie, nous étudions l'effet du champ électrique sur une goutte fortement confinée. La pertinence de l'approche théorique bidimensionnelle est établie sur deux expériences modèles qui analysent l'évolution de la forme d'une goutte confinée sous champ et la variation de vitesse d'une goutte soumise à un champ inhomogène. Enfin, nous appliquons ces résultats au contrôle de gouttes dans des systèmes microfluidiques d'architectures variées

Gouttes et champs électriques dans un système microfluidique

Cette thèse propose une analyse originale des phénomènes de brisure de gouttes et d action d un champ électrique dans un système microfluidique. Une première partie présente l étude d une goutte traversant une jonction microfluidique. Après avoir identifié trois scénarios possibles dont deux entraînent la brisure nous proposons une étude quantitative des comportements observés dans l espace des variables locales puis des paramètres de contrôle. Ces résultats ont été appliqués à l extraction de phase en microfluidique. Dans une seconde partie, nous étudions l effet du champ électrique sur une goutte fortement confinée. La pertinence de l approche théorique bidimensionnelle est établie sur deux expériences modèles qui analysent l évolution de la forme d une goutte confinée sous champ et la variation de vitesse d une goutte soumise à un champ inhomogène. Enfin, nous appliquons ces résultats au contrôle de gouttes dans des systèmes microfluidiques d architectures variées.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

System and method for performing wellsite containment operations

A system and method for performing an adaptive wellsite operation about a wellsite having a subsurface system with a wellbore formed through at least one subterranean formation, wherein the subterranean formations are configured to store fluid. The system has a containment unit. The containment unit has a static model unit for generating a static model of a subsurface system. The static model unit further has a defect model unit for generating a defect model. The containment unit has a dynamic leak model unit for generating a dynamic leak model. The containment unit has a leak mitigation unit for providing at least one containment plan. The leak mitigation unit and the dynamic leak model unit are integrated for passing data therebetween and whereby the containment plan may be adapted as the static model, the defect model, and/or the dynamic model is generated

Stability of a leakage pathway in a cemented annulus

The risk minimization of carbon dioxide (CO2) storage relies to some extent on well integrity assurance. While chemical reactions between the constitutive materials of the wellbore - such as cement - and stored CO 2 do not jeopardize the efficiency of a defect-free cement sheath, the reactive flow through an existing pathway in a cemented annulus may alter its initial properties, and thus change the associated risk. On one hand, the cement will react with the CO2 rich fluid, and be leached away by the leaking flow. On another hand, under specific conditions, the released minerals can re-precipitate downstream and clog the pathway. The evolution of a CO 2 leak through a pre-existing leak path in the cement sheath is examined theoretically and numerically. A numerical model of the flow has been built, that takes into account the particular physics and geometry of the problem. The governing equations are investigated in order to identify the driving mechanisms and define the dimensionless groups that rule the process, leading to a reduction in the dimension of the parameters space. We use this analysis to predict the domain of stability of the defect by extracting a general criterion corresponding to the clogging conditions. © 2010 Elsevier Ltd. © 2011 Published by Elsevier Ltd

Interface debonding as a controlling mechanism for loss of well integrity: Importance for CO2 injector wells

The concept of CO2 storage relies on the long-term sealing properties of both the geological trap and the wells needed to inject and monitor CO2. Well integrity, a classical topic in the oil and gas industry, is thus critical for the performance of any CO2 storage complex in terms of containment. Thanks to the very low permeability of cement (typically less than 0.1 mDarcy); a properly cemented well ensures hydraulic isolation between reservoirs layers and shallow aquifers. Moreover, such low matrix permeability limits the cement/ CO2 interactions over the active period of a storage complex (of the order of 100 years) to a few meters. Leaks from a cased and cemented well, if any, are known to occur only through defects: mud-channel (in case of poor cement placement), cracks within cement and more importantly micro-annulus at the casing/cement or/and cement/formation interfaces. This last category of defects can lead to substantial leakage rate. Its importance has been recognized by the oil and gas industry since the 1960's leading to the study of cement "bonding" properties. In the scope of CO2 storage, the understanding, modeling and monitoring of the occurrence of micro-annulus becomes of prime importance. We analyze the complete loading history of a cemented completion from cement placement to routine well operations. Further to classical failure type assessment used in the oil and gas industry (i.e. fail/no fail, good cement/bad cement), we aim at quantifying the vertical extent, azimuthal coverage and width of the created defects to adequately transform failure types into leakage pathways. Such a prediction of connected defects/leakage pathways along a cemented well imposes to consistently integrate the effects of lithology, geomechanics, cement placement (fluid loss, hydration), completion design and knowledge of pressure and thermal variation during the life of the well. The modeling of such a problem can be made tractable by recognizing the intrinsic hierarchy of lengthscales of a cemented well (i.e. the cement annulus is much thinner than the well dimension). The original three-dimensional problem is reduced to a much simpler two-dimensional one, which in turn can even be further reduced to a one-dimensional configuration in a lot of practical cases. Typical cases of interface debonding due to well de-pressurization and thermal cooling taking place after cement placement are carefully analyzed. Furthermore, we specially focus on injectors. Despite the use of all current best practices during well construction, the injection in itself can lead to the propagation of a debonding crack between cement and casing or cement and formation due to the high pressure generated at the perforations level. Such a problem has already been reported in hydraulic fracturing operations, and is a reasonable explanation of observed well leaks for injectors. A consistent model predicting the initiation and propagation of interface debonding during injection operations is then compared to carefully designed laboratory experiments. Such experiments also confirm that the azimuthal coverage of the interface debonding is only partial (i.e. less than 360°), an observation consistent with cement evaluation logs acquired on CO2 injectors. Finally, best practices to achieve and retain well integrity of CO2 injectors are highlighted from a careful examination of the results of both the model and the experiment. © 2011 Published by Elsevier Ltd

Monitoring CO2 migration in an injection well: evidence from MovECBM

Carbon dioxide (CO2) geological storage relies on safe, long-term injection of large quantities of CO2 in underground porous rocks. Wells, whether they are the conduit of the pumped fluid or are exposed to CO2 in the storage reservoir (observation and old wells) are man-made disturbances to the geological storage complex, and are thus viewed by some as a possible risk factor to the containment of the injected CO2. Evidence gathered during the MovECBM project indicates that migration of small quantities of CO2 happened during injection in a coal seam in Southwest Poland. The evidence, gathered from casing and cement logging as well as soil gas monitoring over a 3-year period, was coupled with laboratory testing and extensive modeling of the chemo-mechanical behavior of cement and steel to determine if CO2 migration might have been responsible of the observed behavior. The three lines of evidence were: the detection of very small CO2 fluxes, coupled with less controversial helium concentration in soil; the occurrence of a thin pathway at the interface between cement and casing; and the change in mechanical properties of cement, suggestive of partial carbonation. Whereas the observations suggest that limited CO2 migration might have happened in the well, they are by no means proof that the migration did happen. Nonetheless, the integration of measurement and modeling yields important lessons for wellbore monitoring. First, it puts a probable ceiling on the order of magnitude of expected leaks from reasonably well-cemented wells at around 100 metric tons per year (less than 0.05% of the injected mass in a well like Sleipner or In Salah). It also suggests that cement may be a very effective leak detector: exposure to CO2 modifies its mechanical properties, which in turn can be detected using cement evaluation logs