Fluid flow through porous media using distinct element based numerical method

Many analytical and numerical methods have been developed to describe and analyse fluid flow through the reservoir’s porous media. The medium considered by most of these models is continuum based homogeneous media. But if the formation is not homogenous or if there is some discontinuity in the formation, most of these models become very complex and their solutions lose their accuracy, especially when the shape or reservoir geometry and boundary conditions are complex. In this paper, distinct element method (DEM) is used to simulate fluid flow in porous media. The DEM method is independent of the initial and boundary conditions, as well as reservoir geometry and discontinuity. The DEM based model proposed in this study is appeared to be unique in nature with capability to be used for any reservoir with higher degrees of complexity associated with the shape and geometry of its porous media, conditions of fluid flow, as well as initial and boundary conditions. This model has first been developed by Itasca Consulting Company and is further improved in this paper. Since the release of the model by Itasca, it has not been validated for fluid flow application in porous media, especially in case of petroleum reservoir. In this paper, two scenarios of linear and radial fluid flow in a finite reservoir are considered. Analytical models for these two cases are developed to set a benchmark for the comparison of simulation data. It is demonstrated that the simulation results are in good agreement with analytical results. Another major improvement in the model is using the servo controlled walls instead of particles to introduce tectonic stresses on the formation to simulate more realistic situations. The proposed model is then used to analyse fluid flow and pressure behaviour for hydraulically induced fractured and naturally fractured reservoir to justify the potential application of the model

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International audienc

Hitting families of schedules for asynchronous programs

Asynchronous programming is a ubiquitous idiom for concurrent programming, where sequential units of code, called events, are scheduled and run atomically by a scheduler. While running, an event can post additional events for future execution by the scheduler. Asynchronous programs can have subtle bugs due to the non-deterministic scheduling of events, and a lot of recent research has focused on systematic testing of these programs. Empirically, many bugs in asynchronous programs have small bug depth: that is, the number of events d that must be scheduled in a specific order for a bug to be exposed is small. A natural question then is to find a d-hitting family of schedules: a set of schedules is a d-hitting family if for each set of d events, and for each allowed ordering of these events, there is some schedule in the family that executes these events in this ordering. A d-hitting family is guaranteed to expose all bugs with d events. By analyzing the structure of the tree of events in an asynchronous execution, we provide explicit constructions for small d-hitting families of schedules. When the tree is balanced, our construction is polylogarithmic in the number of events. We have implemented our algorithm for computing d-hitting families on top of a race condition checker for web pages. We empirically confirm previous findings that many bugs occur with small bug depth. We demonstrate that even with d = 2 we are able to detect bugs in real web applications and that we get a small 3-hitting family for d = 3.</p

HOW TO COMPARE BUNDLES OF NATIONAL ENVIRONMENTAL AND DEVELOPMENT INDEXES?

International audienc