Modeling Air and Water Perforator Swell for Better Risk Management
- Chenghua Han (Schlumberger) | Michael H. Du (Schlumberger) | Ian C. Walton (Schlumberger)
- Document ID
- Society of Petroleum Engineers
- SPE Drilling & Completion
- Publication Date
- September 2009
- Document Type
- Journal Paper
- 424 - 429
- 2009. Society of Petroleum Engineers
- 2.4.3 Sand/Solids Control, 7.4.4 Energy Policy and Regulation, 5.3.1 Flow in Porous Media, 2 Well Completion, 2.2.2 Perforating, 1.6 Drilling Operations, 7.3.3 Project Management, 3.3.1 Production Logging
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A detonated shaped charge fired from a perforating string or perforating gun will not only perforate its targets, but also possibly cause excessive damage or swell to its carrier. Comprehensive understanding of the post-perforating conditions of the perforator or perforator system is required if such damage and potential retrievability risks are to be avoided. In practice, the perforating design engineers do not have a well-established analytical tool to help them understand post-perforating behavior of perforators. They have to rely on their own experiences and previous perforating histories to roughly estimate the swell or damage conditions of similar perforators.
In this paper the failure modes of continuously phased perforators for both gas well and oilwell applications are analyzed. Important factors concerning carrier serviceability are discussed. A method based on energy conservation is used to establish a swell model to predict the post-detonation conditions of the perforator. The model takes the total expendable energy from the explosives into account, relates it to the energy consumed by the functional and nonfunctional processes, and describes the relationship of energy distribution among them. A criterion is proposed to establish the serviceability of the perforators.
Analytical results from the model are compared with the data collected from surface tests. The results indicate that the model can reasonably predict the perforator swell and damage after detonation, and as such will be a useful tool that shortens the required time to develop future perforators.
A perforating project manager has to carefully plan a perforating job for both maximized system performance and minimized risk associated with incidents such as perforating gun carriers stuck downhole. Maximized performance usually requires use of more powerful shaped charges or higher shot density of shaped charges, which consequently inflicts more damage to the perforator carrier or gun. Examples of serious damages are over swollen or split guns. It is true that all guns will swell after shaped charges are detonated. However, an over-swollen gun refers to the swell of the gun that exceeds the specified diametric tolerances and thus cannot be retrieved from the well without costly intervention operations. A split gun is one that is fractured, with a crack extending from one shot exit hole to adjacent shot exit holes, which is also unacceptable. The risk associated with either an over-swollen or split gun is extremely high and should be avoided during perforating job planning and system development. A validated analytical model for predicting perforating gun swell can certainly enhance the effectiveness of both job risk management and system development.
An analytical model of perforating gun swell can help risk management in at least two respects. First, analytical tools such as swell modeling can serve as a supplemental measure to further verify whether existing guns are adequately qualified within their respective ratings, and therefore, will be useful to both perforating job planners and perforating system developers.
A second application is to special perforating jobs that may require some alterations to an existing perforating system in order to meet a specific technical requirement. If the job is imminent with little time for engineers to run another round of full qualification tests, the engineers or project managers can decide whether the gun will survive (be retrievable) by using the modeling tool, instead of merely relying on their experiences to make the tough decision.
|File Size||352 KB||Number of Pages||6|
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