Towards a Mono-Diameter Well - Advances in Expanding Tubing Technology

Abstract

Abstract Solid steel tube can be readily expanded using forces, either mechanical or hydraulic available on most drilling and workover rigs. The process of drawing or pumping a mandrel through a length of tube can be used to expand the tube in situ. This process can be used to repair casing and tubing, shut off unwanted fluid entry into, and egress from the wellbore, repair sand screens, and act as a contingency liner in drilling applications. The ultimate use of expanded tubulars will be in the mono-diameter well, whereby the entire well is drilled and cased using effectively one hole size. The impact on drilling costs and performance will be dramatic. Expandable tubing technology has been applied in the three market segments of remediation, wellbore construction and sand control. A broad range of products is currently available for implementation in all three segments. A review of the principles of expandable tubing technology leads to a discussion of the likely evolution of the technology towards the monodiameter well. The implementation of expandable tubing will follow a pattern of replacement of conventional technologies, use through necessity, maintenance of diametric efficiency which will lead to the use of the technology within the basis of design of well construction. From this is but a small step to the monodiameter well. The principles of expandable tubing technology are well understood. The complexity arises from the system interactions between the materials, expansion process and the wellbore environment. These are explained and discussed. Introduction The basic principle of solid tubing expansion is simple - take a length of well construction tubular and expand it using a mechanically drawn or hydraulically pushed cone. The implications are dramatic - drill a wellbore from spud to total depth using one hole size. This is the monodiameter well. The monodiameter well concept can be realised if we replace conventional casing and liner sizes with expandable solid pipe. It is easy to visualise the concept. A monodiameter well might be spudded with a driven conductor of say 7 5/8" - 9 5/8" in diameter. From thereon each hole section, perhaps of 7" diameter is drilled using reaming while drilling (RWD), an underreamer, bi-centre bit or equivalent and then lined using an expandable tubing. The annular pressure seal may be cement or some other innovative sealing element. The next section of hole is drilled using the same sized underreamer and then lined again with the same size expandable tubing. The process is repeated to T.D. A well would then be designed based on the hole size required across the reservoir. The rig capacity and all the drilling and completions equipment for the entire well would be sized to the reservoir hole size. The telescoping well design with all its associated and myriad selection of drilling and completions equipment would be consigned to history. The size of the prize is dramatic. The industry E&P spend in 1999 was $65 billion. Of this, around $25 billion was spent on well construction and a further $11.5 billion was spent on facilities construction. The monodiameter well has the potential to reduce annual recurring well construction costs by 50% or more. Table 1 provides comparative data for a conventional well, slim-hole well and a monodiameter well drilled to a total depth of 14,000 feet. In addition, the effect on the sizing of platforms and total field development costs will also decrease by a significant amount. With reductions in well construction costs of this order, the opportunity to develop marginal fields in mature provinces such as the North Sea, cannot be overlooked.