HIGH RATIO, ELASTIC REGION TUBULAR EXPANSION (Continued)

In addition to the intended radial growth, one unintended by-product of the deformation work is shrinkage along the longitudinal axis of the tubular. This is due to the reorientation of the steel material’s microstructure, effectively contracting the material. The effect is unavoidable and is inherent to all conventional expansion systems. If the longitudinal material ‘feeding’ requirement is not almost perfectly supplied, further significant stress is working against expansion reliability and final casing integrity.

Simple expansion reliability downhole is a first major technical difficulty and most common industry complaint. These types of technical difficulties are inherent, however, given the high amounts of work required to alter steel while simultaneously negotiating difficult well conditions. Currently, in order to mitigate risks of deployment failure in the field, the borehole must be thoroughly conditioned and control maintained throughout the expansion operation. For the driller to provide essentially ideal conditions in problem zones downhole comes with high costs. This is proving a barrier to wide-scale acceptance and ultimately to commercial value.

Solid expandables are increasingly being used as cladded casing extensions in order to prevent premature loss of non-expanded ID. Currently, these extensions come with not only the conventional casing-job-costs, including, first, the need for repair and conditioning of the problems downhole; then, the added costs associated with the risk of expansion failure; and, finally, the costs for the expandable products and services themselves. For most drilling operations, these combined costs and risks are not at acceptable economic levels.

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