Abstract

Throughout the years, evolving industry practices have inspired new technology, and novel technology developments have led to new industry practices. This cycle continues, particularly since the industry has evolved to horizontal unconventional wells as one of its primary development mainstays. While unconventional fields progress beyond the early stages of development, the original wells in the field become candidates for mature asset considerations of how to economically extend the life of the aging wells. Completion design evolution in each of the major shale plays suggests that the early-time stimulations were inadequate for optimum recovery. Long laterals with reservoir exposure spanning across thousands of feet and having hundreds of perforation holes make precision during conventional restimulation methods complicated and/or costly, often with unpredictable production results.

Advancements in cement slurries and wellbore construction practices have enabled the development of a refracturing methodology that allows for complete renewal of stage isolation along the wellbore. Through installation of a smaller casing string inside a legacy well's existing production casing and effective cement isolation in the annulus, an existing wellbore can be transformed into a new closed system that can be subjected to a new completion design providing increased and accelerated reserves. Specialized casing sizes might be necessary and the refracturing completion might be rate-limited in comparison to a new drill completion, but the process has confirmed execution repeatability and less variance in production predictability than other refracturing techniques.

The successful implementation and economic return of this casing-in-casing refracturing method has caused a growth in popularity of this style of refracturing, both in total well count and in quantity of participating operators. In the Burleson County Eagle Ford formation, multiple recompletions using this technique have been performed. Of the six casing-in-casing refractures performed, five had sufficient production time to derive an average estimated ultimate recovery (EUR) increase of approximately 140% in comparison to the original well EUR in the detailed Eagle Ford acreage.

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