Field Data vs. Theoretical Model to Quantify Drilling Efficiency and Disruption

Mechanical and kinematics data at the bit have been collected during drilling operations and organized to identify optimal drilling efficiency. Transitional conditions towards abnormal behavior have been distinguished. Normal drilling is usually characterized by regular linear relationships between global control variables at the bit, which approximately correspond to an up scaling of a local Mohr Coulomb type failure mechanism of the rock. Most of our experimental data confirm this classical disposition. However, considerable departure from these relationships is noted, especially when there is BHA resonance or when there is partial balling at the bit. The field tests presented here allows us to verify classical theory and to draw up new guidelines for behavior in non- optimal or dangerous, evolving operating conditions, such as those that occur under poor cleaning conditions. The main features of a mechanical structuring model involving transition towards low efficiency conditions are presented, and it is shown how this model confirms our interpretation of field data. The model couples the drillability of rock and the general dynamics of the bit in an original and synthetic way. It makes it possible to understand and test the sensitivity of bit response to variables such as "weight on hook", torque on the drillstring and flow rate of the fluid

Polynomial function intervals for floating-point software verification

The focus of our work is the verification of tight functional properties of numerical programs, such as showing that a floating-point implementation of Riemann integration computes a close approximation of the exact integral. Programmers and engineers writing such programs will benefit from verification tools that support an expressive specification language and that are highly automated. Our work provides a new method for verification of numerical software, supporting a substantially more expressive language for specifications than other publicly available automated tools. The additional expressivity in the specification language is provided by two constructs. First, the specification can feature inclusions between interval arithmetic expressions. Second, the integral operator from classical analysis can be used in the specifications, where the integration bounds can be arbitrary expressions over real variables. To support our claim of expressivity, we outline the verification of four example programs, including the integration example mentioned earlier. A key component of our method is an algorithm for proving numerical theorems. This algorithm is based on automatic polynomial approximation of non-linear real and real-interval functions defined by expressions. The PolyPaver tool is our implementation of the algorithm and its source code is publicly available. In this paper we report on experiments using PolyPaver that indicate that the additional expressivity does not come at a performance cost when comparing with other publicly available state-of-the-art provers. We also include a scalability study that explores the limits of PolyPaver in proving tight functional specifications of progressively larger randomly generated programs

Modèle de foration fondé sur le couplage des effets de destruction de la roche et évacuation des déblais.

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Field data versus theoretical model to quantify drilling efficiency and dysfunction

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Field data vs theoretical model to quantify drilling efficiency and disruption

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The effect of dynamical parameters on precession in rotary drilling

International audiencePrecession, which is the rolling motion of the drillstring on the walls of the borehole, is investigated by considering the various possible motions of a rotating disk in a circular hole. Due to the simplicity of the model, closed-form results are derived on the stability of precession and on the evolution of impacting motions towards precession. It is found that increasing coefficients of friction and contact damping have a favoring effect on precession, while the stiffness and damping of the drillstring bending mode have an opposing effect

Uncertainty propagation using probabilistic affine forms and concentration of measure inequalities

Conference of 22nd International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2016 and held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2016 ; Conference Date: 2 April 2016 Through 8 April 2016; Conference Code:173509International audienceWe consider the problem of reasoning about the probability of assertion violations in straight-line, nonlinear computations involving uncertain quantities modeled as random variables. Such computations are quite common in many areas such as cyber-physical systems and numerical computation. Our approach extends probabilistic affine forms, an interval-based calculus for precisely tracking how the distribution of a given program variable depends on uncertain inputs modeled as noise symbols. We extend probabilistic affine forms using the precise tracking of dependencies between noise symbols combined with the expectations and higher order moments of the noise symbols. Next, we show how to prove bounds on the probabilities that program variables take on specific values by using concentration of measure inequalities. Thus, we enable a new approach to this problem that explicitly avoids subdividing the domain of inputs, as is commonly done in the related work. We illustrate the approach in this paper on a variety of challenging benchmark examples, and thus study its applicability to uncertainty propagation

Évaluation de la prescription du furosémide chez la personne âgée de 75 ans et plus dans un service de gériatrie aiguë

International audienceINTRODUCTION: Furosemide is very often prescribed in France. It may cause important adverse effects especially in elderly persons. In order to limit its misuse and excessive expenditure for health insurance organizations, the European Society of Cardiology drafted strict guidelines for its prescription. We conducted a study in this population to determine the rate of prescription of furosemide in elderly persons outside the guidelines.METHOD: This was a prospective, single-centre, observational study bearing on elderly persons aged 75years and more admitted to a geriatric acute-care unit over a period of 6months. The prevalence of furosemide prescription and the proportion of prescriptions outside guidelines were calculated. The sociodemographic and medical characteristics of patients treated with furosemide were studied as were the modalities of furosemide prescription.RESULTS: In the 818patients hospitalized during the period of the study, 267 were taking furosemide at admission (32.6%). Among these prescriptions, 69.2% were outside the guidelines. Arterial hypertension was the leading indication for furosemide (38.2%), followed by chronic heart failure (24.3%).CONCLUSION: This study confirmed the high prevalence of furosemide prescription and its misuse. Furosemide is often re-prescribed with no medical re-evaluation.IntroductionLe furosémide est très prescrit en France. Il serait responsable d’effets indésirables non négligeables surtout chez la personne âgée. Afin de limiter son mésusage et un surcoût pour la sécurité sociale, la Société européenne de cardiologie a édité des recommandations de prescription strictes. Nous avons conduit une étude dans une population âgée dont l’objectif principal était de déterminer le taux de prescription du furosémide chez la personne âgée hors recommandations.MéthodeIl s’agissait d’une étude prospective, monocentrique et observationnelle portant sur des personnes d’âge ≥ 75 ans, admises dans un service de gériatrie aiguë sur une période de 6 mois. La prévalence de prescription de furosémide et son taux de prescription hors recommandations étaient calculés. Les caractéristiques sociodémographiques et médicales des patients traités par furosémide étaient étudiées, ainsi que les modalités de prescription du furosémide.RésultatsSur les 818 patients hospitalisés durant la période d’étude, 267 avaient du furosémide à l’admission (32,6 %). Parmi ces prescriptions, 69,2 % n’étaient pas conformes aux recommandations. L’hypertension artérielle était la 1re indication du furosémide (38,2 %), suivie de l’insuffisance cardiaque chronique (24,3 %).ConclusionCette étude confirme la grande prévalence de prescription du furosémide et son mésusage. Le furosémide est souvent reconduit sans réévaluation médicale