Advances in SAGD Drilling in Western Canada Using Innovative Bit Technology

摘要

Western Canada's massive oil sands are being exploited at deeper levels by steam-assisted gravity-drainage (SAGD).Carefully geosteered parallel pairs of large-diameter horizontal well bores are drilled for concurrent steam injection into the upper well with oil production from the lower.The bitumen-cemented sands of the McMurray Formation have challenged both operational and engineering personnel responsible for drilling these challenging wells.Bits of all designs have required custom features to combat the highly abrasive sands with sloughing and hole cleaning problems while delivering an optimally steered well path through tight reservoir tolerances.A cross-functional team of operators' engineers and drilling personnel,together with field engineers,bit designers,field,and office personnel from the bit manufacturer,came together to analyze the challenges and fast-track fit-for-purpose solutions for all SAGD projects in Alberta.Steel teeth roller cone bits require extensive extra-thick layers of hard-facing to resist tooth wear.Sand washing through the cones causes high levels of erosion which is hindered by extensive hard-facing.The gauge areas of the bits are rotated and/or slid through a cuttings bed of coarse abrasive sand particles,resulting in rounded gauge and shirttail wear,which again require tungsten carbide and hardfacing wear pads and shirt-tail protection.Elastomer or metalfaced seals have been enhanced to prevent sand encroachment on the bearings during motor drilling.PDC bits were also faced with significant erosional problems drilling horizontally which have required special wear-pads and updrill features to ensure hole gauge,steerability,and the ability to back-ream through the cuttings bed.Depth of cut features for build up rates of 9 degrees per 30 meters ensure steerability when linked to wear resistant cutters,especially when placed on the gauge.Spiral gauge features work like an auger to clean sand away from the bit,while customized gauge lengths ensure a match between bit and motor for optimised steerability.Collectively,these PDC and steel-tooth bits have become the enabling technology for drilling and completing SAGD wells,especially now that bits can be rerun on future wells,further reducing cost per metre.