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Important characteristics were identified including the use of NSAIDs, alcohol use, and non-compliance with routine long-term postoperative follow-up. Identifying those patients at high risk may decrease the incidence of this potentially life-threatening complication.

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With the widespread drilling of gas wells in Marcellus shale, there are high potentials for wellbore instability problems when wells are located in longwall mining areas, which in many areas such as southwest Pennsylvania, West Virginia, and eastern Ohio are being used for extraction of the coal seam overlaying the gas reserves. The ground deformation, caused by coal mining, could generate large horizontal displacement and complex stress change in subsurface rock. This in turn triggers ground movement which can cause casing failure, and thus interruption in the operation of the well that raises safety and environmental concerns. This could result in shutting down the well for repair, or permanent abandonment. Thus, it is critical to characterize the parameters related to the longwall mining process and to propose a general casing design guideline in such areas. In this paper, numerical modeling was utilized to simulate the complex ground conditions and resulting stresses and strains in longwall mining areas. A casing design spreadsheet was then constructed for design of appropriate selection of casings, based on the results of the numerical modeling. Our results were validated with field practices of wellbore design in southwest Pennsylvania. This paper also provides a methodology for investigating potential ground deformations, resulting stress/strain changes, and wellbore stability issues for oil and gas wells drilled in longwall mining areas in Marcellus shale or similar formations worldwide with active coal mining activities.

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A nonisothermal, ID, compositional, two-fluid, multiphase hydrodynamic model is used to describe the incipient formation and dynamic behavior of condensate in a natural-gas pipeline with undulating topology. The 26-in. [66-cm] -diameter case-study transmission pipeline traverses 180 elevation changes in its 30. 72-mile [49.4-lan] span. Results demonstrate the predictive and descriptive potential of the model in field applications and the significant effect of inclination and inclination changes on the hydrodynamics of gas/condensate flow in transmission pipelines. The model presented can serve both predictive and design purposes. IntroductionTwo-phase flow in natural-gas transmission pipelines is common. Accurate knowledge of the pressure profile and liquid distribution as predicted with an appropriate model is necessary for optimal design and siting of compressor stations and liquid catchers along the pipeline. Therefore. it is imperative to design such pipelines with appropriate models capable of predicting and handling two-phase fluid dynamics in pipelines. Such an approach is especially critical in the design of long-distance pipelines where the interactions between the two phases, coupled with varying inclinations, can significantly affect the pressure profile along the pipeline.Various approaches have been developed to describe the fluid dynamics of two-phase flow in pipe. Most are basically empirical and/or semiempirical, lack generality, and contain predictive inadequacies. Adewumi and Bukacek! reviewed these methods in detail. More-recent attempts have used a fundamental hydrodynamic approach to describe multiphase flow in pipes. This approach has been successful in a number of cases that are well documented in the literature. Refs. 2 through 4 report other examples of the use of this approach to solve practical problems of engineering interest.In this study, a numerical simulation package for two-phase flow in pipe was developed by coupling the hydrodynamic model and the phase-behavior package. The hydrodynamic formulation is a modification of the two-fluid model. Detailed formulation of the two-fluid model that uses the basic principles of continuum mechanics coupled with the volume-averaging technique is reported elsewhere. 2 A modified Peng-Robinson 5 equation of state (EOS) is used to describe the fluid phase behavior.A detailed analysis of the basic hydrodynamic equations used in this study was presented in Ref. 4, but the effects of gravitational force in the momentum equations are not included because that study was intended for horizontal pipelines. Several features distinguish the behavior of inclined transmission lines from that of horizontal pipes. In inclined pipeline, the effect of gravitational force must be taken into account in the hydrodynamic formulation, even for a very small inclination, because the gravitational force significantly affects the liquid velocity, the pressure gradient, and invariably the liquid holdup. Sharp changes in liquid velocity may occur several times in a pipe...

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