Importance

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Abstract

The present invention generally relates to a method for recovering productivity of an existing well. First, an assembly is inserted into a wellbore, the assembly includes a tubular member for transporting drilling fluid downhole and an under-reamer disposed at the end of the tubular member. Upon insertion of the assembly, an annulus is created between the assembly and the wellbore. Next, the assembly is positioned near a zone of interest and drilling fluid is pumped down the tubular member. The drilling fluid is used to create an underbalanced condition where a hydrostatic pressure in the annulus is below a zone of interest pressure. The under-reamer is activated to enlarge the wellbore diameter and remove a layer of skin for a predetermined length. During the under-reaming operation, the hydrostatic pressure is maintained below the zone of interest pressure, thereby allowing wellbore fluid to migrate up the annulus and out of the wellbore. After the under-reaming operation, back-reaming may be performed to remove any excess wellbore material, drill cuttings and fines left over from the under-reaming operation and to ensure no additional skin damage is formed in wellbore. Upon completion, the under-reamer is deactivated and the assembly is removed from the wellbore.

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First Claim