This paper examines some mechanical aspects of formation damage as they apply uniquely to horizontal wells. First a seldom recognized phenomenon of mechanical damage due to drill string rotation is presented along with a method for estimating the extent of the damaged area. Next, the invaded zone is examined in some simple examples to ascertain qualitatively the geometry of the invaded zone due to varying exposure times of different parts of the horizontal section during drilling. The relative time scales between exposing new hole with the drill bit, the invasion rates into the formation, as well as the changing differential pressure in the horizontal annulus are incorporated into a simple model to determine the effect of changing annular pressure while drilling. Finally an inexpensive means of mechanically achieving zone isolation for damage removal treatments in unconsolidated zones is presented.

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