Advances in SAGD Drilling in Western Canada Using Innovative Bit Technology
Authors: Okusanya A.O. , Roberts D.V. , Dach J.D. 
Published: March 2010

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 wellbores are drilled for concurrent steam injection into the upper well and oil production from the lower. The bitumen cemented sands of the McMurray Formation have challenged both operational and engineering personnel responsible for drilling these difficult 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 operator engineers and drilling personnel, together with field engineers, bit designers and office personnel from the bit manufacturer, joined together to analyze the challenges and fast track fit-for-purpose solutions for all SAGD projects in Alberta.

Steel tooth 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 (RG) and shirttail damage (SD), which again require tungsten carbide and hard facing wear pads and shirttail protection. Elastomer or metal-faced seals have been enhanced to prevent sand encroachment on the bearings during motor drilling.

Polycrystalline Diamond Compact (PDC) bits were also faced with significant erosional problems drilling horizontally, which have required special wear pads and updrill features to ensure hole gauge, steer ability and the ability to back ream through the cuttings bed. Depth-of-cut (DOC) features for build rates of 9 degrees per 30 m, ensure steer ability 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 optimized 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 re-run on future wells, further reducing cost per metre.

Introduction

Steam-assisted gravity drainage (SAGD) is the most popular enhanced oil recovery technology being adopted by Canadian heavy oil producers. It is very effective in mobilizing bitumen and achieving high recovery from thick, high permeability reservoirs (low gravity &lt;10 °API). An estimated 174 billion barrels of oil in the Athabasca, Cold Lake and Peace River deposits are potentially recoverable with the present technology(1–3). However, with technological improvements, Canada oil sands reserves could be close to 315 billion barrels. The biggest deposit is the Athabasca, which is thicker and shallower; the Cold Lake deposit is thinner and deeper. Surface mining is only feasible for recovering 10% of the oil sands deposits between 70 and 75 m of surface. SAGD is the current method of choice to access resources too deep to mine and will recover the potential 90% of the remaining oil sands deposits with cyclic steam stimulation (CSS).