Using Expandable Metal Technology to Create a Monobore Well
Authors: Cales Gerry , Grant Tom , Book Larry 
Published: October 2008

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."