Lessons Drilling Through Accretionary Wedge/Prism

06 April 2010 All,

Our well planning has identified that an accretionary wedge/prism exists within our acreage.

What specific lessons/concerns have you experienced when drilling through an accretionary wedge/prism.

I have posted a couple of papers about accretionary wedge for reference.

Definition of Accretionary Wedge:
A mass of sediment and oceanic lithosphere that is transferred from a subducting plate to the less dense, overriding plate with which it converges.

The mechanics of the Barbados accretionary wedge can be considered as analogous to that of a wedge of soil being pushed by a bulldozer (Fig. 2). The bulldozer corresponds to the stable rearward parts of the overlying plate, and the earth which is beneath both the soil and the bulldozer corresponds to the underthrust plate.
Reference: 30. THE COMPRESSIVE MECHANICS OF ACCRETIONARY WEDGES APPLIED TO THE LEG 78A STUDY AREA NEAR BARBADOS
Dan M. Davis, Department of Earth and Planetary Sciences, Massachusetts Institute of Technology

At convergent plate boundaries or convergent margins, two plates, at least one of which is oceanic, move toward each other. But rather than butting each other like angry rams, one oceanic plate bends and begins to sink down into the asthenosphere beneath the other plate. This sinking process, termed subduction, is shown in the following animation.

Go to this website to view movie showing subduction:
http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm
Scroll down to ”œ2.9 The Process of Subduction” and view the animation.

Documents uploaded by user:

30 Compressive mechanics of accretionary wedges applied to leg 78a Davies.pdf

Sediment subduction offshore C America ODP Leg 170.pdf

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