New foam drilling hydraulics calculations by using two foam flow regimes

Document Type

Conference Proceeding

Publication Date

1-1-2015

Abstract

In spite of its complexities, foam underbalanced drilling has unique advantages such as reduced formation damage, improved rate of penetration, higher cutting-transport capacity, and lower circulation losses. Recent experimental studies in a wide range of experimental conditions show that foam flow in pipe can be represented by two different flow regimes: (i) the low-quality regime showing stable plug-flow pattern with fine-textured foams and (ii) the high-quality regime showing unstable slug-flow pattern with alternating free-gas with fine-textured foam segments. Such a new concept was successfully captured by a foam modeling technique with five model parameters, reproducing two distinct pressure contours. This study, for the first time, constructs foam drilling hydraulics model with two foam-flow regimes handling both stable and unstable flow characteristics, and investigates how the model improves current foam drilling hydraulics modeling based only on stable foam flow behavior. The results from three different scenarios (scenario 1: a vertical well, scenario 2: a deviated well with relatively short horizontal section, and scenario 3: a deviated well with relatively long horizontal section) with the transition foam quality between the two flow regimes (fg∗) around 75-85% showed that significant differences in drilling hydraulics calculations might occur when the conventional technique was replaced by this new technique. For example, a drilling scenario tested with 10,000 ft deep vertical well (scenario 1) was shown to have as much as 32%, 48%, and 25% deviations in foam density, total velocity, and pressure gradient, respectively, at the bottomhole. Examples from two other deviated well trajectories (scenario 2 and scenario 3) exhibited similar responses, showing even more deviations. These results clearly demonstrate why incorporating two foam flow regimes into the current drilling hydraulics calculations is a crucial step toward evaluating and designing foam drilling practice accurately and reliably.

Publication Source (Journal or Book title)

Proceedings - SPE Annual Technical Conference and Exhibition

First Page

605

Last Page

629

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