Opening New Exploration Frontiers With The Micro-Flux Control Method For Well Design
Authors: Santos H. , Reid P. , Lage A. 
Published: October 2008

Abstract
Well design criteria for drilling conventionally are well established and have been in place for several decades. However, evolution and technical advances in the industry have meant that drilling in challenging areas has become more common. Kick tolerance, trip margin, wellbore stability considerations, hydraulics, and hole cleaning are just some examples of criteria used for designing a well, and they differ slightly from company to company.
The new Micro-Flux Control (MFC) method introduces several features which greatly reduce the risks of conventional drilling, allowing a revision of the current set of well design criteria. This paper describes these new criteria, showing the benefit in terms of risk reduction and increasing the operational limit; thereby allowing wells to be drilled more safely, extending phases beyond those achieved by traditional drilling methods, allowing the reduction innumber of casing strings needed. MFC introduces new well control concepts, as well as dealing with pore pressure uncertainties. The new features introduced by this drilling method allow reserves located in challenging areas to be more safely and explored more economically.
In addition to the new well design criteria proposed, the paper brings examples of applications of these criteria, by comparing a well drilled traditionally with a well drilled with the MFC method. The technical and economic benefits are highlighted and compared.

Introduction
The decline of reserves in mature basins has led the oil industry to move towards more challenging environments, where there are increased drilling costs and risks. It becomes clear that new drilling techniques need to be developed and used to exploit these new reserves economically.
As the industry is very conservative, it usually takes a long time for changes to be accepted and used to full potential. The risks have to be carefully assessed and evaluated, and the well design should also be revisited in order to take full advantage of the new techniques being used. This last point is usually the most difficult to implement. In many situations, where new and advanced techniques are used, a traditional well design is still carried out using the same old numbers and concepts. This does not allow the industry to take full advantage of the introduction of new ways to drill the wells.
Sometimes the regulatory bodies do not allow incorporation of more aggressive thinking, even when it is based on, and supported by successful tests. In other situations it is the reluctance of the rig contractor to accept the risks on their rigs, or it may be insurance restrictions that prevent rapid uptake. Last, but not least, it is ultimately the operator, who has to accept and understand the benefits of introducing new techniques, so that the wells can be successfully drilled to TD and achieve the objectives of drilling in that particular location.
In many cases new techniques take a long time to be effectively applied due to the lack of convincing evidence, mainly concerning the economics and safety. As well as being technically and fundamentally sound, the new technique must prove to bring significant improvements in terms of safety, in addition to generating measurable savings.