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The introduction of expandable metal technology to the oil and gas industry in recent years has allowed a change in the traditional well construction design. The advent of this technology is allowing operators to drill wellbores that do not subscribe to the traditional telescoping reduction in casing sizes as well depth increases. This capability will allow deep wells to be drilled without sacrificing well hole size, which has many advantages, ranging from wellbore construction costs to greater production potential. This paper will outline a method of creating a monobore well over a finite length of well path. Introduction The ability to drill wellbores that do not subscribe to the traditional telescoping reduction in casing sizes as well depth increases will allow deep wells to be drilled without sacrificing well hole size has many advantages over the traditional telescoping, reducing ID, wellbore construction method. A primary benefit of the monobore well is the ability to reach the desired drilling depth with out having to sacrifice casing size. (Fig. 1) This capability could in theory allow for much deeper or deviated wells to be drilled due to the elimination of the hole reducing aspect. Further, should an unexpected hole problem be encountered while drilling, a monobore well design allows the ability to set a section of casing across this problem zone and continue wellbore construction without once again sacrificing hole size. This capability could ultimately allow the reservoir section of the reservoir to be entered with the initial size diameter production casing and thereby maintain the production capability that would have been comprised had a smaller size casing been used to enter the production zone. In developing wells from the surface to total depth utilizing the monobore design, it is possible to reduce the size of surface equipment, such as wellhead, along with the overall size of the well's casing program. The use of smaller size equipment and casing may translate to direct cost savings. Expandable Material and Expansion Methods The use of expandable metal technology to construct a monobore well requires the selecting of the correct material and method of expansion to achieve desired expansion percentages and final performance properties. The performance properties are not only measured in empirical numbers such as burs/collapse/tensile rating but also in ability to provide a suitable solution to an application. Both these factors must be developed and analyzed in unison in order for a system to perform as expected. Expandable Material Selection. Material for use in expandable applications is evaluated and tested in regards to how it performs pre expansion, during the expansion process, and post expansion. The criteria used most commonly to classify and capture these material properties and performances in the three states are: toughness, work hardening, and the Bauschinger Effect. In the pre expanded state the main criteria for an expandable material is its ability to resist tearing during the expansion process as a result of external marking which may develop during shipment, handling or installation. The materials ability to resist tearing is quantized as ductility or "notch toughness."

Solid expandable tubular technology was commercially introduced to the oil and gas industry over four years ago. With more than 250 wells having been completed using solid expandable tubulars, this technology has made the transition from novel concept to accepted downhole application. As the oil and gas industry continues to push into deeper water, and the cost of wells increases, it is imperative that every effort be made to drill wells to depth as quickly and efficiently as possible. An obvious challenge for all operators to overcome is to reduce or eliminate flat time on the drilling curve. This paper will explore how the application of solid expandable tubulars enables drillers to reduce both the flat time on a drilling curve and steepen the angle of the curve. The result of this synthesis will enable the operator to reach total depth (TD) in less time. A probabilistic approach will be used to demonstrate the value of expandables.This paper presents case studies where solid expandable tubulars have reduced or eliminated flat time on the drilling curve and show how the technology has enabled faster drilling of wells. Decision analysis will be used to demonstrate how solid expandable tubular technology can be deployed to reduce costs significantly when an operator faces a myriad of well problems. Through the use of expandables, operators have shown that many technical challenges can be overcome in a cost effective manner. Solid expandable tubulars have enabled a step change in how wells are drilled. This paper addresses several ways in which those changes have occurred and how the technology continues to move forward.