Hole Cleaning Efficiency of Sweeping Pills in Horizontal Wells-Facts orPhilosophy?

摘要

More than 35 million m3 of oil have been produced from the Mittelplate oilfield.Poor hole cleaning has beenidentified as a root cause for drilling problems in the horizontal sections of its ERD wells.Enhancing cuttingremoval in vertical wells,high-viscous pills are typically considered.However,literature is providingcontradicting guidance of using sweep pills in deviated/horizontal wells.Thus,the purpose of this study isto provide an overview about the theoretical background on hole cleaning and to experimentally identifythe best sweep pill for ERD wells.An apparatus has been designed as a closed flow-loop system consisting of coaxial pipes forming ahorizontal well with a drill-string inside,two mud tanks,and a mud pump.Two pressure sensors areplaced along the horizontal section,providing complementary information about the moving sweepingpill.Different pills(high-viscosity,medium-viscosity,high-density and a high-viscosity/high-densitycombination pill)have been circulated and the recovered model cutting material from one cycle ofcirculation has been re-weighted.To the best of our knowledge,it is the first time that such a fully scaled-down device including pressuresensors at the toe and heel of the horizontal section has been designed and used for the evaluation of sweeppills.It delivers an efficient and cost-effective method to optimize hole cleaning processes and preventcostly drilling incidents.