A semianalytic time‐resolved poro‐elasto‐plastic model for wellbore stability and stimulation

Wellbore stability problems and stimulation operations call for models helping in understanding the subsurface behaviour and optimizing engineering performance. We present a fast, iteratively coupled model for the flow and mechanical behaviour that employs a time-sequential approach. Updates of pore pressure are calculated in a timestepping approach and propagated analytically to updates of the mechanical response. This way, the spatial and temporal evolution of pressure and mechanical response around a wellbore can be evaluated. The sequential approach facilitates the incorporation of pressure diffusion and of time-dependent plasticity. Also, it facilitates the implementation of permeability evolving with time, due to plasticity or stimulation. The model has been validated by means of a coupled numerical simulator. Its capabilities are demonstrated with a selection of sensitivity runs for typical parameters. Ongoing investigations target geothermal energy operations through the incorporation of thermo-elastic stresses and more advanced plasticity models

Management of simultaneous traumatic brain injury and aortic injury

Simultaneous traumatic brain injury (TBI) and aortic injury has been considered unsurvivable for many years because treatments such as sedation and blood pressure goals conflict for these 2 conditions. Additionally, surgical interventions for aortic injury often require full anticoagulation, which is contraindicated in patients with TBI. For these reasons, and due to the relative rarity of aortic injury/TBI, little data are available to guide treating physicians. A retrospective review was performed on all simultaneous TBI and aortic injury cases from 2000 to 2012 at a university-affiliated, Level I trauma center. Patient demographics, imaging studies, interventions, and outcomes were analyzed. Traumatic brain injury/aortic injury cases treated with endovascular stenting were specifically studied to determine trends in procedure timing, use of anticoagulation, and neurological outcome. Thirty-three patients with concurrent TBI and aortic injury were identified over a 12-year period. The median patient age was 44 years (range 16-86 years) and the overall mortality rate after imaging diagnosis was 46%. All surviving patients were awake and neurologically functional at discharge, and 83% were discharged home or to rehabilitation facilities. Patients who died had a higher Injury Severity Scale score (p = 0.006). Severe TBI (p = 0.045) or hemodynamic instability (p = 0.015) upon arrival to the hospital was also correlated with increased mortality rates. Thirty-three percent of aortic injury/TBI patients (n = 11) underwent endovascular stenting, and 7 of these patients received intravenous anticoagulation therapy at the time of surgery. Six of these 7 anticoagulation-treated patients experienced no significant progression on postoperative brain CT, whereas 1 patient died of hemodynamic instability prior to undergoing further imaging. Simultaneous TBI and aortic injury is a rare condition with a historically poor prognosis. However, these results suggest that many patients can survive with a good quality of life. Technological advances such as endovascular aortic stenting may improve patient outcome, and anticoagulation is not absolutely contraindicated after TBI