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Evaluation of Established Cleanup Models in Dynamic Underbalanced Perforating

Topics: MPD/UBD

Dynamic underbalanced (DUB) perforating is a process that creates a negative pressure differential, or underbalance, causing fluid to move toward the wellbore even in an initial overbalanced static condition. A DUB condition can be controlled by understanding and carefully managing the temporal pressure transients by use of multiple methods within the wellbore during and after gun-system detonation. Recently, a series of instrumented perforation experiments demonstrated that existing cleanup models do not accurately predict perforation cleanup when perforating in a DUB condition.

Introduction 

Underbalanced perforating methods have been applied successfully since the 1950s, shooting both wireline and tubing-conveyed perforating guns. As shaped-charge jet-perforator systems became more advanced, using powdered metal liners, performance steadily improved. The art of minimizing the compacted and damaged area surrounding the perforation tunnel, commonly known as the crushed zone (Fig. 1), began shortly afterward. Much of the initial work involved shooting charges into prepared Berea sandstone cores while documenting the effect of a differential pressure toward the wellbore upon perforation efficiencies. As the benefits of an underbalanced pressure differential were observed, extensive testing established criteria for flow volumes and differential pressures required to remove or minimize the crushed zone created during the perforating event. Specifically documented was the role of trapped atmospheric pressure inside a perforating gun surrounding the shaped charge and components, known as free gun volume (FGV), which enabled the formation pressure to act as a differential and expel charge and crushed formation into the gun.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 159413, “Evaluation of Established Perforation-Cleanup Models in Dynamic Underbalanced Perforating,” by Dennis Haggerty, G.G. Craddock, and Clinton C. Quattlebaum, SPE, Halliburton, prepared for the 2012 SPE Annual Technical Conference and Exhibition, San Antonio, Texas, USA, 8–10 October. The paper has not been peer reviewed.
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Evaluation of Established Cleanup Models in Dynamic Underbalanced Perforating

01 September 2013

Volume: 65 | Issue: 9

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