Proper management of ground water resources requires knowledge of the rates and spatial distribution of recharge to aquifers. This information is needed at scales ranging from that of individual communities to regional. This paper presents a methodology to calculate recharge from readily available ground surface information without long-term monitoring. The method is viewed as providing a reasonable, but conservative, first approximation of recharge, which can then be fine-tuned with other methods as time permits. Stream baseflow was measured as a surrogate for recharge in small watersheds in southeastern Wisconsin. It is equated to recharge (R) and then normalized to observed annual precipitation (P). Regression analysis was constrained by requiring that the independent and dependent variables be dimensionally consistent. It shows that R/P is controlled by three dimensionless ratios: (1) infiltrating to overland water flux, (2) vertical to lateral distance water must travel, and (3) percentage of land cover in the natural state. The individual watershed properties that comprise these ratios are now commonly available in GIS data bases. The empirical relationship for predicting R/P developed for the study watersheds is shown to be statistically viable and is then tested outside the study area and against other methods of calculating recharge. The method produces values that agree with baseflow separation from streamflow hydrographs (to within 15% to 20%), ground water budget analysis (4%), well hydrograph analysis (12%), and a distributed-parameter watershed model calibrated to total streamflow (18%). It has also reproduced the temporal variation over 5 yr observed at a well site with an average error < 12%.

Shale formations have laminated structures which result in significant differences in mechanical properties along the orientations parallel to and perpendicular to laminations (bedding planes). These differences lead to anisotropic horizontal stresses. Failure to consider the effect of anisotropic behavior of shale can have severe consequences for drilling. In rocks with anisotropic mechanical properties and strength, there is a high risk of wellbore instability while building deviation angle from vertical sections. Conventional wellbore stability analysis approaches do not consider material anisotropy and laminated nature of shales, which can result in underestimated stresses leading to incorrect safe trajectory or mud-weights.Shale formations in the Horn River Basin (HRB) are strongly anisotropic with anisotropic ratios varying from 1.2 to 3.5. In this paper, the authors demonstrate the importance of considering anisotropy in estimation of in-situ stresses and wellbore stability analysis. Two field case study examples are presented to underscore the consequences of neglecting anisotropy in wellbore stability analysis.

Shale formations have laminated structures that result in directionally dependent mechanical properties. Conventional completion design approaches do not consider the material anisotropy or the laminated nature of shales. This can result in an underestimation of stresses, and lead to incorrect conclusions about the lateral landing points and the perforation intervals. In this paper, the authors demonstrate the importance of considering the anisotropy in the completion design using a case study from the Horn River Basin (HRB), the largest shale gas play in Canada. Shale formations in the HRB are strongly anisotropic with horizontal to vertical Young's modulus ratios varying from 1.2 to 3.5. Field data from the HRB is examined to evaluate the impact of mechanical anisotropy on break down pressure, fracture initiation and fracture containment. Numerical simulation of the completion design was conducted using a planar 3D fracture model.Results of the numerical simulation indicate that the mechanical anisotropy greatly influences the minimum horizontal stress which in turn impacts the fracture containment and fracture geometry. Strong mechanical anisotropy results in lower fracture initiation pressures and lower tortuosity at the wellbore face. Consequently, selecting the landing point in sections with high anisotropy will minimize the fracture initiation problems. The authors conclude that the heterogeneous and anisotropic nature of shales needs to be properly characterized and taken into account when making decisions on lateral landing points and completion design.

Recombinant tissue plasminogen activator (rtPA) is the only available therapy for acute ischemic stroke. Current clinical protocols limit its use to a three-hour window from symptom onset. The role of thrombolytic therapy between 91 and 180 minutes after stroke onset remains highly controversial. However, studies have shown that rtPA given within six hours of stroke reduced death or dependency (i.e. more patients alive and independent) at three to six months, and this was statistically significant in favor of treatment. [1][2][3][4] Late presentation continues to be a primary cause of exclusion from thrombolytic therapy ABSTRACT: Introduction: There are no studies from Pakistan that describe stroke presentation rates or factors associated with early or delayed presentation. This is important to know because current clinical protocols limit the use of recombinant tissue plasminogen activator (rtPA), the only available therapy for acute ischemic stroke, to a three-hour window from symptom onset. Methods: All patients aged 14 years or above with acute ischemic stroke of ≤ 48 hours duration were prospectively identified from the Aga Khan University Stroke Data Bank over a 22-month period ending May 2001. Results: 269 ischemic stroke patients presented within 48 hours of stroke onset. 55 out of 269 (21%) presented within first three hours and 110 out of 269 (41%) within first six hours. Unawareness of treatment options (p <0.001) and inappropriate diagnosis and field triage (p=0.005) were associated with delayed presentation. Small vessel occlusion or lacunar stroke in the TOAST (Trial of ORG 10172 in Acute Stroke Treatment) ischemic stroke subtype was associated with delayed presentation (p=0.047) and cardioembolic stroke was associated with earlier presentation (p=0.048). Stroke severity assessed with the National Institutes of Health Stroke Scale at a cut off score of ≥15 was not associated with earlier time to presentation at three hours (p=0.114) but there was some tendency at six hours (p=0.097). Conclusions: The rate of early stroke presentation in a Pakistani tertiary care facility is comparable to certain developed countries. To increase the proportion of patients who can benefit from thrombolytic therapy, programs need to be instituted to increase public awareness of treatment options for stroke and expedited referral by the primary care provider. cardioembolique était associé à une consultation plus précoce (p = 0,048). La sévérité de l'AVC évaluée au moyen du National Institutes of Health Stroke Scale avec un point de coupe de 15 et plus n'était pas associée à une consultation plus précoce dans le groupe qui avait consulté en dedans de 3 heures (p = 0,114), mais on notait une tendance en ce sens dans le groupe qui avait consulté en dedans de 6 heures (p = 0,097). Conclusions : Le taux de consultation précoce chez les patients présentant un AVC aigu dans les hôpitaux de soins tertiaires au Pakistan est comparable à celui de certains pays industrialisés. Il faudra établir des programmes d'information pour q...

Ensuring long-term containment of CO2 is critical for a safe geological storage of carbon. Although Carbon Capture and Storage (CCS) is feasible in depleted hydrocarbon fields, it can pose significant risk to safety and the environment if its containment is not ensured. An integrated geomechanics workflow to evaluate caprock integrity is presented in this paper. This approach integrates reservoir simulation which typically computes variation in formation pressure and temperature with geomechanical simulation which models variation in stresses. Coupling between these two simulation modules is done iteratively until an equilibrium state between formation pressure and stress is achieved within a given tolerance. The efficiency of this approach is demonstrated through a case study of a proposed carbon storage site in Canada where an injection rate of 600 tonne/day for 25 years is planned.