Objectives Cerebral vasospasm in subarachnoid hemorrhage (SAH) is associated with high morbidity and mortality. There is a lack of consensus on the risk factors leading to cerebral vasospasm in patients with aneurysmal subarachnoid hemorrhage (aSAH). In this retrospective study, our objective was to determine the association of risk factors for cerebral vasospasm aSAH. Methods A total of 259 charts of aSAH patients consecutively admitted to the surgical intensive care unit of Hamad General Hospital from January 2007 to December 2016 were reviewed and included. The patient's demographic data, including comorbidities like hypertension (HTN), was recorded. Variables of interest included measurements of the neurological deficit on admission, the severity of SAH, treatment modality, and the initial computerized tomography scan of the head for intraventricular hemorrhage, intracerebral hemorrhage, or hydrocephalus. Multivariate analysis and multiple logistic regression analyzed the relationship to identify the association of independent variables. Results Out of the 259 patients, 34% (n = 87) suffered from cerebral vasospasm. The severity of SAH was associated with the development of cerebral vasospasm (p < 0.05). The presence of HTN and neurological deficits on admission were associated with an increased risk of cerebral vasospasm (p < 0.05, p < 0.01, respectively). Hydrocephalus requiring treatment using external ventricular drains decreased the risk of cerebral vasospasm (p < 0.05). Intraventricular and intracerebral hemorrhage were not associated with cerebral vasospasm (p = 0.25, p = 0.16). The endovascular treatment of cerebral aneurysms was associated with an increased risk of cerebral vasospasm (p < 0.05). Conclusion Cerebral vasospasm is common among patients admitted with aSAH. It is significantly associated with the history of HTN, the neurological deficit on admission that corelates more strongly to the motor deficit on admission, the severity of hemorrhage (modified Fischer score), and endovascular treatment. External ventricular drainage was associated with a decrease in cerebral vasospasm. The present study's findings shed light on cerebral vasospasm's risk factors in the country and the region.
The Jauf formation of Bahrain's Awali brownfield is currently underdeveloped due to an extremely challenging geological environment. Because of high heterogeneity, the formation requires fracturing to produce economically. However, the Jauf sandstone is unconsolidated, and formation sand production does not allow for high gas rates. A combined solution was introduced using a completion assembly with frac ports and screens to restrict sand production with a tip screenout approach in the stimulation stage. The studied well was completed with a 4 1/2-in. cemented liner that had been plugged and abandoned and left with 7 5/8-in. casing across the prolific Jauf sandstone. A completion string with screens and production sleeves, fracturing ports, and packers was deployed to compartmentalize and fracture the Jauf. Fracturing ports, while production sleeves were later manipulated with coiled tubing (CT) to allow production across the sleeve filter media, thereby preventing proppant or formation sand from being produced. A large fracturing treatment was placed in an aggressive tip-screenout mode to achieve optimum fracture length and maximize fracture conductivity. Afterwards, CT was used to close the fracturing port and open the screen ports to flow back the well and proceed with testing operations. A hydraulically activated shifting tool was used to manipulate the fracturing ports (open and closed) as well as the production ports enabling gas production through the included screens. This technology enabled the fracturing operation to be executed in conjunction with sand management hardware during production, further providing more flexibility for future intervention operations when compared to frac-and-pack type assemblies. Considering the significant depth of the formation (11,700 ft), degradable fibers were used to minimize friction pressure and, respectively, maximize fracturing treatment rate to allow for optimum height coverage and lateral fracture penetration. The post-stimulation sand-free gas production rate through the screens was greater than 20 Mscf, which was confirmed with choke-variability testing operations conducted after manipulation of the completion ports. The trial well proved that proppant fracturing combined with innovative sand control hardware provides an effective method for producing gas from the prolific Jauf reservoir. The described completion system represents an alternative to a traditional frac-and-pack hardware solution, enabling full control of the well with CT interventions. A tailored stimulation design and advanced placement technique coupled with detailed description of completion design and operations sequence will be of interest to experts dealing with tight unconsolidated formations in the Middle East and other regions.
Depletion of conventional hydrocarbons reservoirs have led oil and gas operators to extend the boundaries and pursue production from reservoirs with high viscosity hydrocarbons that in the past were impossible to be produced and allow the hydrocarbons in place to flow to the surface with conventional production methods. With the introduction of enhance oil recovery techniques (EOR) operators has been able to economically produce from these reservoirs. The steam flood is an EOR technique that allows heavy oil hydrocarbons to be produced and increase the recovery of original oil in place (OOIP). This technique requires high temperature steam to be injected into the reservoir in order to allow hydrocarbons production, introducing challenges in order to maintain well integrity and long term life of the well. Suitable surface facilities, equipment and materials that withstand these challenging conditions are required in order to guarantee the success of the project. In a heavy oil shallow reservoir in Bahrain, a steam flood pilot project has been executed, injecting steam up to 650ºF into the injectors wells in order to enhance the hydrocarbons production in the adjacent production wells. Conventional cement systems will fail when exposed to the given conditions as the mechanical properties of such cements are not sufficient to withstand the stresses created in this extreme temperature environment. This will consequently threaten the well integrity and success of the project. In order to provide a reliable and durable zonal isolation, an engineered cement system has been introduced. This cement system possesses sufficient flexibility (low Young's modulus), and a high coefficient of thermal expansion to withstand the metal casing expansion during the heating step of the process, without failure. This cement system exhibits stable mechanical properties for a long duration during the whole process of the heavy oil production and can be mixed and pumped with conventional cementing equipment. It is placed at low (110-140°F) temperature, acquires sufficient compressive and tensile strength to withstand the heating cycles. Over 50 wells have been cemented using this technology in Bahrain. Cement bond longs and temperature logs demonstrate well integrity has been achieved, allowing the steam to be injected into the target reservoir. Furthermore, no issues have been seen related to steam break through to surface. The project has been implemented for over 4 years with no sign of wellbore integrity failure. This study covers several aspects of the design, execution and evaluation of the cement system.
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