Thousands of horizontal wells have been drilled world-wide over the last ten years. Most of them are completed openhole and do not produce as well as expected. In their design phase, adverse reservoir and wellbore effects are often underestimated, such as permeability anisotropy, well stand-off, fonnation damage, formation face damage, and sand control screen plugging.

Recent statistical surveys of the production of openhole horizontal wells have confirmed that actual performances are disappointing. They are leading to major re-evaluations of drilling and completion strategies in many present reservoir developments.

In offshore environments where a limited number of slots are available, horizontal wells remain the best choice. However they are increasingly cased, cemented, perforaled and stimulated, in order to alleviate the problems affecting openhole wells.

This paper describes how this new trend is expanding in the North Sea, and gives all necessary guidelines to successfully design and execute multiple fracturing treatments in horizontal wells. Production and treatment cost estimates are provided for all cases of fracture orientation vs. the wellbore. Radial flow effects in non-collinear geometry are detailed and Tip Screen Out (TSO) designs recommended.

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