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The AAPG/Datapages Combined Publications Database

Indonesian Petroleum Association

Abstract


25th Annual Convention Proceedings (Volume 2), 1996
Pages 189-203

Rejuvenate Old Wells with Through-Tubing Workover

Steve Palar, Jeffry Tampi, DeWayne R. Schnorr

Abstract

Through-tubing workovers present an attractive solution to develop the marginal reserves, which otherwise would not be developed. With an increasing availability of different through-tubing formation evaluation tools and perforation guns, the quest to rejuvenate the old wells is greatly enhanced.

The objective of a completion is a compromise of high productivity, longevity and allowance for future operations, in order to maximize the profit. Substantial reserves were sometimes intentionally left behind pipe due to economic and engineering reasons. Less-productive intervals were often deferred to later in the well's life in order to maximize high-productive intervals. Moreover, old wells were sometimes completed without allowance for future economic workover operations.

A full-scale workover, where all the tubing is pulled out, is sometimes not economic and is also a highly risky operation. The reserves are often marginal to justify the workover. With the continuously decreasing well production, any potential reserves remaining in the well are worthy of another review.

In a producing field, the reservoirs are in a dynamic state with contacts constantly changing, depending on the reservoir drive and the fluid withdrawal rate. It is not surprising that the current fluid saturations are not the same as when the well was open hole logged. Determining hydrocarbon saturations behind casing is now possible without the need to pullout the existing tubing. A wireline-conveyed RST (Reservoir, Saturation Tool), run through-tubing, enables the fluid saturation measurement. Intervals chosen can then be perforated with through-tubing guns.

This paper discusses the workover unit and the through-tubing tools (i.e. RST, perforating guns). Several examples of through-tubing workovers highlight the usefulness of through-tubing workovers in rejuvenating old wells.


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