Abstract

Major operators are using solid expandable tubulars in existing wells to tap added reservoir pay. This use of the technology is the result of close collaboration between the contractor and the operator, particularly the reservoir engineering and drilling departments. Together they have devised plans that maximize the return-on-investment (ROI) and the long term sustainability of the reservoir.

The use of solid expandable tubulars to provide a larger drainhole in existing wellbores is proving to be a considerable benefit to many operators. Aside from the obvious production gains from a larger borehole, the operator also gains on the drilling side of the equation. The larger inside diameter (ID) through the solid expandable casing allows for the use of larger drilling tools. These larger tools typically drill farther and faster than smaller tools and suffer far less non-productive time due to failures.

This paper reviews the value derived from using solid expandable tubulars in the casing design of existing wells with actual case history data. Further, the paper details ancillary benefits that can be factored into the value gained by the operator.

Introduction

Enhanced completion options and the potential to achieve higher sustainable production rates are two major factors that have led to the acceptance of solid expandable tubular technology. Combined with certain drilling techniques, the technology can be used to facilitate workovers previously thought impossible.

During the late 1990's, the development of solid expandable tubular technology was still in its infancy. Conventional casing designs were the primary means of well construction. The need to extract as much oil as possible from proven reserves drove the adoption of the new casing technology. The wells that have been drilled using solid expandable tubulars have been able to expose increasing amounts of reservoir rock while maintaining optimum control of the production profile.

The ongoing improvements in drilling equipment, drilling fluids, downhole tools and ancillary items continue to further expand the application realm for solid expandable tubulars. However, as with any evolving technology, limitations exist that must be addressed. Wellbore preparation and well path architecture must meet certain minimum requirements to facilitate placement of the solid expandable liner. Bits and underreaming devices are now available to enable isolation of longer intervals while maintaining the required casing geometry. Additionally, wellbore cleanup tools are aiding in the successful placement of the solid expandable tubulars.

Drilling equipment has also been evolving. Bottomhole assemblies that drill straighter holes and eliminate the spiraled tortuosity normally associated with conventional drilling assemblies are now available. These help place the solid expandable liner on depth by enhancing hole cleaning and reducing torque and drag.

Changing Attitudes

In many cases the reservoir engineering and drilling departments of operating companies embraced the idea that the use of solid expandable tubulars in workover applications might offer significant benefits over standard casing options. Previously, attitudes existed that accepted limitations as inevitable, no matter what casing design was applied. Blame for failure to achieve the desired results would often fall on the drilling group or service companies for not following proper procedures. Management soon recognized that the failures were not with the aforementioned groups but the result of an attitude that "a certain degree of not attaining the desired results was unavoidable".

When management decided to search for a casing design plan that was superior to the one currently in use, the focus moved from the groups that would carry out the work to the casing design philosophy itself. Managers determined that the existing casing design plans lacked imagination and required a fresh look. Problem areas with existing casing designs were identified and a search began for a practical alternative.

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