CONVENTIONAL EXPANSION

Conventional tubular expansion utilizes cold-working processes to permanently deform low-alloy steel. Basically, a specialized mandrel is forced through standard casing, which has been modified slightly to accept the cold-work processes. High mud pump pressure is applied internally to assist the expansion work. While applying expansive stresses to commonly available casings was a logical starting approach for early development, many technical drawbacks also exist. These technical and operational disadvantages have prevented wide-scale uptake of the technology by the E&P industry.

The forces required to initiate deformation of oilfield casings are deliberately high. Obtaining full expansion of such material is difficult when the already resistant casing assembly is placed into complex downhole environments, such as in eccentrically-loaded, deviated or stuck conditions. Additionally, abrasion or other surface damage as shallow as .012” or less creates stress risers as the metallurgy is later altered through plastic regions – regardless of the effects of the external environment. Maintaining the mechanical and pressure integrity of an entire assembly of such material while it is being subjected to compound expansion stresses – particularly through the coupled intervals – is a notable but unreliable engineering accomplishment.

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