One of the fundamental things we are taught as part of our industry training is how to calculate pressures as they interact with our systems and tools. Any number of training materials have been produced for us both in-house and externally to better understand the concepts of pressure. The tool service providers will provide pressure rating guidelines to allow their end users to very precisely define the limitations of pressure across their intervention devices. In the strictly mechanical arena the calculation of allowable differential pressures, both in terms of pressure reductions (such as drawdown) or applied pressure (such as testing) is a relatively simple process following the basic principles of what we have been taught. The mechanical solution supplies us with a very two dimensional platform on which we have to base our calculations. The paradox comes when the same age old, tried and tested principles are attempted to be utilized when dealing with an inflatable solution to the well operation. A new third dimension is introduced whereby not only must pressure differentials across the device itself be considered, but also differences from the inside of the inflatable element to the outside of the element must be analyzed. One of the biggest precursors to the success of planning an inflatable operation is the understanding and acceptance of this third dimension pressure characteristic and its application to not only the performance of the inflatable tool when the operation is being conducted, but in the case of long term deployments, its performance throughout the cycles of the well while the inflatable element is in situ. This paper will attempt to describe and explain in detail the differences in calculation methods required across inflatable type packing elements and highlight these differences in such a way as to inform as to the criticality of getting these calculations correct and applying them to both the planning and implementation stage of both temporary and long term inflatable isolations.

You can access this article if you purchase or spend a download.