Horizontal Drilling has become a commonly used technology to increase the productivity index of single wells and to increase the recovery factor of entire fields. A rising number of horizontal liners are cemented and perforated to be able to solve production problems, such as water and gas coning. Cementation of a horizontal liner requires extensive planning and engineering. One of the important issues for mud removal is good string centralization. New types of centralizers designed specifically for the application in horizontal well applications have successfully been used in horizontal wells worldwide. Selection criteria for both types of centralizers, bow-type and rigid, and a comparison of their main parameters based on mathematical modeling, are described. P. 673

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