Over 300 hydraulic fracturing operations have been performed at Prudhoe Bay. The available data have been analysed to examine the effects of well deviation and azimuth on fracture treating pressures, job placement success and, most importantly of all, post-frac well performance. Clear conclusions emerge. Proppant production is an expensive problem at Prudhoe Bay. Factors affecting proppant production are examined, together with the results of a field evaluation of Resin Coated proppant.

This paper was prepared for presentation at the SPE Applied Technology Workshop on Risk Based Design of Well Casing and Tubing held in The Woodlands, Texas, U.S.A., 7–8 May 1998.

Unbonded flexible risers are a key technology in existing and proposed offshore developments. With increasing water depth, the demands on risers increase and the design against hydrostatic and tension loads becomes more of a challenge. In addition, many existing subsea production systems are approaching the end of their design life and operators need to know if they can remain in-service. To enable the benefits from deepwater production and life extension projects to be realized while minimizing risks to life, property and the environment, accurate modelling and analysis tools are required to improve the prediction of failure modes and to develop a better understanding of the conditions leading to progressive failure. In this work, a multi-scale approach is adopted whereby a global dynamic analysis model is employed to determine the overall displacements of the riser and this is linked with a local model that can provide accurate forces and stresses for the prediction of collapse, fatigue damage and buckling of tensile armour wires. Firstly, we describe a nonlinear constitutive model for use in large-scale dynamic analysis of flexible risers based on an analytical homogenization of composite cylinders using the analogy between slip between pipe layers and plastic flow in continua. The model is able to reproduce the bending hysteresis behaviour observed in flexible pipes and its dependence on internal and external pressure. Secondly, we show a procedure for obtaining equivalent material parameters for this model from finite element local analyses of a flexible pipe. Finally, we show the implementation of this constitutive model in a riser system using two-dimensional co-rotational hybrid beam finite elements.

Existing offshore platforms are valuable assets for operators, and optimizing their useful life to maximize profitability is an ongoing challenge. Reassessment is required from time to time to ensure that the structures remain safe and reliable. This can be instigated for a variety of reasons such as increased topside or environmental loading or damage. Wave‐in‐deck loads resulting from rare events pose a particular concern. Nonlinear pushover models enable the full benefit of structural capacity to be realized, while structural reliability assessments allow risk‐based decisions to be made. This article reviews the present methodologies for nonlinear structural modeling, pushover assessments (including static, cyclic, and dynamic procedures), environmental statistics including wave‐in‐deck loading, and structural reliability assessments and provides a comment on some of the limitations and potential pitfalls of these.