Editorial

The technological challenges for the oil industry in deep offshore production and exploitation of mature fields, the environmental challenges about management of discharges and sour gases sequestration, or the optimization of refining processes, require the development of more and more powerful simulation tools and the design of ever innovative equipments. To answer these challenges, theoretical and experimental skills are developed by the Applied Mechanics Department of the Institut français du pétrole in some advanced domains of primary importance. Models describing mechanical behaviors are then implemented into simulation codes and innovative concepts are proposed to design industrial equipments for reservoir, drilling, oil production, transportation and refining engineering. Two special issues of the Oil & Gas Science and Technology journal present a selection of articles illustrating some of the recent achievements from the Applied Mechanics Department of IFP. The first issue (Vol. 56, No. 6) concerns geomechanics and mechanics of materials and structures. A paper deals with reservoir engineering where skills in geomechanics are used for an accurate estimation of the available oil in place. It presents the implementation of a porovisco-elastic model of rock behavior successfully compared against experimental data obtained on clay. This development uses the framework of the thermodynamics of open systems developed at IFP for rock mechanics in the oil industry domain. The following four papers deal with applications using mechanics of materials and structures. The first one presents a method of determination of the movements of the flexible pipe structural layers. It is part of a fundamental domain for our industrial partners in which a high-level competence is maintained. The second paper deals with the development of an innovative twophase model describing the mechanical behavior of semicrystalline polymers and allowing calculations of structures including these polymers. The third paper is concerned by unidirectional glass-epoxy composites, which should lower weight and increase lifetime of industrial pipes. Corrosion models were used for ageing study of those composites and for helping the definition of specific mechanical tests. The fourth paper shows how the application of the theory of the homogenization is used to define an anisotropic elastic plate replacing a Johnson grid and then to validate a new refining reactor internal. The second issue (Vol. 57, No. 1) concerns drilling, riser vibrations and multiphase production. Drilling is the subject of two papers. The first one summarizes the state of the art on drillstring fatigue and uses the fracture mechanics concepts to propose research direction in order to improve drillstring reliability in the case of complex well and extended reach drilling or when abnormal drillstring mechanical behaviors occur. The second paper describes a methodology to design riser, which has given way to the engineering of the Clip Riser. This concept was developed several years ago by IFP and is now prepared for use in deep water. For deep offshore production, the design of connection risers needed between surface and seabed facilities is of primary importance. It is addressed in two papers where studies of riser vibrations due to sea currents are presented. Vibrations can create important damages influencing lifetime of such mechanical elements. Multiphase production is the scope of the last two papers. The first one deals with the modeling of transient multiphase flows and the definition of production control scenarios optimized by using simulations. The case studied illustrates a pipe subjected to flow instabilities, which for instance can occur during production of a mature field. The second paper relates to multiphase pumping, currently a widely accepted technology by the oil industry. It presents the performance of the helicoaxial technology invented and developed by IFP, its current utilization, and the new approaches such as sour gas reinjection in solution, required by environment concerns. The works of the Applied Mechanics Department are led, in most cases, within the framework of diversified industrial and university partnerships. We gratefully acknowledge the contribution of ANDRA, Coflexip Stena Offshore, the École centrale de Lyon, the École supérieure des ingénieurs de Marseille, the École polytechnique, TotalFinaElf and Johnson which joined us to allow the release of these issues.