| Summary: | Horizontal well completions are considered to reduce concerns about formation damage because the extra completion interval length in the pay zone offset production lost from reduced permeability around the wellbore.The control of sand flow from unconsolidated formations can be one of the most critical problems in well completion, because holes in weakly consolidated sandstone tend to collapse. Wellbore collapse problems can result in a vertical wellbore completion that performs better than a horizontal completion. It must also be recognized that a workover to remove sand from a horizontal hole may be extremely difficult to perform and very expensive. Remedial efforts will also be endangered by fluids loss to the formation over the long productive interval.Formation damage in most horizontal wells may not reduce performance to that of a vertical well in the same reservoir, but if the reservoir is a weakly consolidated sandstone the hole will tend to collapse and cause untenable problem.A sufficient number of horizontal wells have now been drilled and completed in practically as many different reservoir as countries, to make it possible to use them as a guide on how and where horizontal well technology offers the best return on investment. If horizontal holes in weak formation sands can be successfully gravel packed, the result could be significantly higher well productivity than with a liner, screen or pre-packed screen alone
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