Accurate measurement of drilling fluid rheological properties is essential in order to optimize wellbore construction, and in particular to properly manage hydraulics. It becomes even more crucial during deepwater drilling when a "narrow mud window" is present which may require the use of more advanced drilling technologies such as Managed Pressure Drilling (MPD) and Dual Gradient Drilling (DGD). Operating these technologies properly requires the use of sophisticated hydraulic models that require accurate rheological information as input. However, a full mud check with determination of all relevant rheological parameters is usually only carried out once a day, and augmented with one or two partial checks in the 24h period. The results are also highly dependent on the mud engineer carrying out the tests. Such intermittent and unreliable measurements are unfortunately not sufficient to provide the required inputs for "real-time" hydraulic modeling and control. A more practical approach for a continuous, automated monitoring of the drilling fluid properties is therefore called for. In this paper, we introduce a practical automated approach with minimum maintenance efforts to continuously monitor the drilling fluid rheological parameters at the rig site. The method is based on the pipe viscometer approach rather than the traditional rotational viscometer method. Additional inputs for hydraulic models, such as mud density, transition to turbulent flow (critical Reynolds number), and real-time friction factor for non-Newtonian drilling and completion fluids can also be obtained using a pipe viscometer. A prototype of this equipment was constructed, tested, and fully automated in the lab. It was tested with several weighted and unweighted mud systems. During the measurement process, the driving pump was ramped up and held intermittently at various flow rates to measure the laminar frictional pressure loss in the pipe section. The data thus obtained was analyzed by software that generated a flow curve and from it derived relevant mud rheological parameters using a suitable rheological model. It also proved possible to extend the test to the turbulent flow regime and obtain the "true" friction factor in real-time for each particular fluid, rather than relying on a limited number of correlations that quite often exhibit inaccurate results, particularly for the Yield Power Law (YPL) fluids. Several successful tests with different mud systems indicate the reliability and robustness of the proposed technique. We believe that this approach is a major step towards achieving an effective fully automated system for mud rheology measurement, mud maintenance, and real-time management of ECD without any direct human interaction. The simple equipment set up and its fully automated measurement and data analysis processes make it highly suitable for field application. The days when mud engineers were laboriously working rotational viscometers are coming to an end, and the "one-click automated mud check" is becoming a reality.

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International audienceWe propose a simple model of two-phase gas–liquid flow by imposing a quasi-equilibrium on the mix- ture momentum balance of the classical transient drift-flux model. This reduces the model to a single hyperbolic PDE, describing the void wave, coupled with two static relations giving the void wave velocity from the now static momentum balance. Exploiting this, the new model uses a single distributed state, the void fraction, and with a suggested approximation of the two remaining static relations, all closure re- lations are given explicitly in, or as quadrature of functions of, the void fraction and exogenous variables. This makes model implementation, simulation and analysis very fast, simple and robust. Consequently, the proposed model is well-suited for model-based control and estimation applications concerning two- phase gas–liquid flow

Real-time estimation of annular pressure profile and formation pressure is crucial for the execution and planning of a well control operation, especially when drilling formations with narrow pore and fracture pressure margins. A simple transient multi-phase simulator, capable of accurately representing gas and liquid dynamics while minimizing complexity and computational requirements, is highly desirable for real-time kick mitigation and control applications. Such a simulator is presented here in the form of a coupled ODE-PDE model composed of a first order ODE and a first order hyperbolic PDE. This model is shown to retain the dominating two-phase dynamics encountered during gas kick incidents. As a particular application, we demonstrate the use of the model in design of switched control algorithms for kick handling in a Managed Pressure Drilling setting. A Recursive Least Squares algorithm is employed for estimation of unknown model parameters.