TX 75083-3836 U.S.A., fax 1.972.952.9435. AbstractThe Panna Field is located offshore West India and is operated by BG Exploration and Production India Limited. The reservoir is a tight limestone which is drained using multilateral wells. There are significant drilling challenges. Firstly, the well trajectories are complex to reach the reservoir and the laterals are three dimensional profiles requiring precise steering control to maintain position in the productive zones. Secondly, total fluid losses to the fractured limestone are frequently encountered. Thirdly, high levels of vibration and high drilling torque threaten the integrity of the drillstring and ultimately limit the reach to which the lateral sections can extend. A rotary closed loop drilling system had been use to successfully drill the wells, but the desire to improve gross drilling performance, reduce the risk to drillstring and extend the reach of the laterals prompted introduction of a new drilling system which was being tested in the North Sea. This new system integrates a high performance drilling motor with high speed rotary closed loop system to improving overall drilling performance in challenging areas, reduce stress on the drillstring and enable wells to extend past prior reach limits.On the first well; rate of penetration increased by 46%, the distance drilled per BHA increased by over 300% and the longest ever lateral in the field was successfully drilled. Based on the performance noted on the initial well, the new system was used on a further six Panna tri-laterals -completing the drilling campaign ahead of schedule.This paper discusses challenges drilling to and through the Panna field reservoir with the reasoning behind mobilization of the new drilling system to the area at an early phase of its introduction. The overall results of drilling the tri-laterals are then presented.

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This paper discusses approaches to improve the accuracy of onshore pipeline remaining life assessments and optimise the targeting of locations for field verification activities via detailed assessment of reported corrosion metal losses and corrosion feature interactions. The overall aim is to show how confidence in assessments can be increased while ensuring adherence to industry standards. Evaluation of interactions between corrosion features is a necessary consideration as specified in industry standard fitness-for-service (FFS) methodologies. In accordance with developed FFS standards, if corrosion features are sufficiently close together, they should be considered to act as a single, larger feature. However, in the authors' experience, detailed assessment of corrosion feature interactions is not always performed. This can lead to overly optimistic/pessimistic results, and a subsequent lack of focus for future field verification activities with respect to inspection locations and techniques. FFS assessments are often based on results from in-line inspections (ILIs), which, depending on the pipeline condition, can report many thousands of individual corrosion features. In the case of heavily corroded pipelines, where corrosion damage is reported along approximately the same orientation (for example at 06:00, the bottom of the line), inadequate consideration of corrosion feature interactions could significantly overestimate the maximum allowable safe pressure of the pipeline. In contrast, conservatively assuming a grooving metal loss morphology and simplifying FFS calculations to assume infinitely long corrosion can appreciably lower calculated safe pressures, resulting in premature remediation activities (such as repairs, de-rating). In both cases, neither method of assessment allows specific targeting of field verification activities as areas of maximum corrosion interaction will not have been determined. This paper will demonstrate the benefits of performing a detailed assessment of corrosion feature interactions during an integrity assessment in comparison to overly optimistic or simplified assumptions, and show the benefits of such detailed assessment with respect to future field verification activities.