[1] Geologic CO 2 storage (GCS) has been proposed as a potentially viable climate change mitigation option. Among the trapping mechanisms known for permanent CO 2 storage in saline aquifers, solubility and residual trapping are important for safe short-term entrapment. These storage mechanisms are hampered by density-driven upward CO 2 movement that inhibits the lateral migration of the plume, leaving a large portion of the aquifer volume unexposed to CO 2 and unavailable for storage. Heterogeneity of aquifer hydraulic properties and high horizontal/vertical hydraulic conductivity ratio of geologic formations are two competing mechanisms that can hinder upward CO 2 migration. Postinjection displacement of free-phase CO 2 is somewhat controlled by the heterogeneity in rock permeability and porosity distributions. In particular, low permeability shale layers that act as vertical flow barrier and high-permeability horizontal channels that form flow conduits can spread the CO 2 plume laterally in the aquifer. In this paper, we consider CO 2 storage in heterogeneous saline aquifers and propose controlled CO 2 injection, based on existing knowledge of heterogeneity, to increase CO 2 contact with brine and improve the solubility and residual trapping and the overall aquifer storage potential. We examine two optimization methods: directly maximizing the total stored gas in the aquifer, and maximizing the sweep efficiency of the CO 2 flood to promote uniform displacement in all directions. We consider the effect of geologic uncertainty on the performance of the controlled injection schemes by using an ensemble of model realizations to represent the uncertainty in aquifer property distribution. We also show how a controlled injection can be used to mitigate the risk of leakage from potential pathways, such as an abandoned well, by restricting CO 2 movement toward the leakage zone. Our results suggest that controlled injection can lead to substantial improvements in residual and dissolution trapping and can be used to divert a CO 2 plume from approaching sensitive zones or leakage pathways.Citation: Shamshiri, H., and B. Jafarpour (2012), Controlled CO 2 injection into heterogeneous geologic formations for improved solubility and residual trapping, Water Resour. Res., 48, W02530,

Background: Cerebral venous sinus thrombosis (CVST) causes significant problems for patients in the working age and may therefore negatively affect their quality of life (QOL). In the present study, we sought to evaluate the QOL and its predictors in subjects with CVST. Methods: This observational, prospective study investigated several outcomes of 56 CVST patients after thrombosis onset. Demographic characteristics, medical history, neurological signs and symptoms during hospitalization, and the employment status of the patients were retrospectively collected. Stroke-related functional scales, including the modified Rankin Scale (mRS) and Barthel Index (BI) were employed. For physical and mental aspects of the QOL, we used the validated Persian version of the Stroke Specific Quality of Life (SS-QOL) scale. Results: The physical and functional outcomes in the long-term were promising according to mRS and BI tools, as well as the improved rate of return to work. Mental domains of the SS-QOL, such as energy and personality represented the lowest scores. According to the multiple linear regression analysis, lower mRS score, and longer time interval between CVST onset and interview were associated with higher physical function of the patients while their better mental function was correlated with lower mRS score and thrombosis in merely one cerebral venous. Conclusion: CVST patients experience an acceptable alleviation of the primary physical disabilities, while residual symptoms, mostly in psychologic/mental domains, impair their QOL.

Optimization of waterflooding sweep efficiency has been widely applied in reservoir engineering to improve hydrocarbon recovery while delaying water breakthrough and minimizing the bypassed oil in reservoirs. We develop a new framework to optimize flooding sweep efficiency in geologic formations with heterogeneous properties and demonstrate its application to waterflooding and geological CO 2 sequestration problems. The new method focuses on equalizing and delaying (under constant total injected volume) the breakthrough time of the injected fluid at production wells. For application to CO 2 sequestration where producers may not be present, we introduce the concept of pseudo production wells that have insignificant production rates (with negligible effect on the overall flow regime) for quantification of hypothetical breakthrough curves that can be used for optimization purpose. We apply the new method to waterflooding and CO 2 sequestration optimization using two heterogeneous reservoir models. We show that in water flooding experiments the proposed method improves the sweep efficiency by delaying the field breakthrough and equalizing breakthrough times in all production wells. In this case, the optimization results in increased oil recovery and decreased water production. We apply a modified version of the proposed algorithm to geologic CO 2 sequestration problems to maximize the storage capacity of aquifers by enhancing the residual and dissolution trapping. The results from applying the proposed approach to optimization of geologic CO 2 storage problems illustrate the effectiveness of the algorithm in improving residual and solubility trapping by increasing the contact between available fresh brine and the injected CO 2 plume through a more uniform distribution of CO 2 in the aquifer.