During drilling operations, downhole conditions may deteriorate and lead to unexpected situations which can result in significant delays. In most cases, warning signs of the deterioration can be observed in advance, and by taking proactive actions, drillers can avoid serious incidents like pack-offs or stuck-pipes. A new analysis methodology, relying on an automatic real-time computer system, has been developed to detect those early indicator conditions.

The methodology comprises constantly computing the various physical forces acting inside the well (mechanical, hydraulic and thermodynamic). These physical forces are coupled by an automatic model calibration, which then gives a reliable picture of expected well behavior. Through analysis of the deviations between modeled and measured values, an estimation of the current state of the well is derived in real-time. Changes in the well condition are an early warning of deteriorating well conditions. This paper describes precisely the real-time analysis and the results during some drilling operations.

The software has been used for monitoring fifteen unique wells located in five different North Sea fields. All major situations were warned in advance at different event time scales: rapidly changing downhole conditions (such as pulling a drill-string into a cuttings bed) were typically warned 30 minutes ahead of the actual event, medium duration deteriorations were detected up to 6 hours before the incident, and slow changing downhole conditions were signaled up to 1 day in advance. Several examples that illustrate the detected incidents over distinct time periods are described.

The availability of good quality real-time data streams makes it possible to implement such analysis tools in an integrated operation setup. Early symptom detection can be used to take decisions in a timely fashion, based on quantitative performance indicators rather than subjective feelings and personal experience.

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