Underground Test Facility: Shaft and Tunnel Laboratory for Horizontal Well Technology (includes associated papers 17469 and 17654 )

Abstract

SPE Members Abstract The Alberta Oil Sands Technology and Research Authority has initiated an extensive, long term program to evaluate horizontal wellrecovery processes in a shaft and tunnel complexin the Athabasca tar sands, 35 miles NW of FortMcMurray, Alberta. The 213 m twin shafts, the initial pitbottom, tunnel development and the surface minesupport equipment have been contracted. Shaftsinking started February 1985. Shaft No. 1 took55 days to drill; No. 2 took 46 days. Theaccess facilities are scheduled to beoperational March 1986. Mine extension andpilot startup will be completed by mid ‘87, pilot startup will be completed by mid ‘87, after which horizontal well drilling/completiontechnology and a variety of recovery strategieswill be evaluated. The commercial economics of the shaft andtunnel concept for bitumen recovery from theAthabasca tar sands will also be firmed upduring this period. Initial feasibility studieswere positive for this reservoir with 15 km oftunnel and 356 horizontal wells over theproject life. Preliminary designs for well project life. Preliminary designs for well completion and process service facilities havebeen based on a steam recovery process. Ultimate production capacity is intended to be1,600 m3/day or 10,000 BPD. HORIZONTAL RECOVERY PROCESSES Theory and experience teaches that mobilityratios dominate volumetric sweep efficiency of areservoir. The bitumens in the Alberta tarsands are so viscous that, if this experienceholds for these reservoirs, heating to severalhundred degrees would produce little improvementin overall volumetric recovery efficiency. Yettwo of the current in situ tarsands projectsthat are expanding to commercial levelsShell's Peace River project and Esso's ColdLake project - are reporting recoveries inexcess of 20%, and in the case of the ShellProject, estimates of volumetric sweep Project, estimates of volumetric sweep efficiency indicate +50% possible. Clearly theinconsistency between theory and practice liesnot with the reported performance of the fieldprojects but with the theory. Gravity drainage projects but with the theory. Gravity drainage is one factor that plays a considerable role. At Shell's Peace River pilot a pressurecycling strategy is used. Steam is injectedinto a thin transition zone at the base of thereservoir. The steam rises and heats thebitumen which drains downward toward this higherpermeability, water saturated zone. The hot oil permeability, water saturated zone. The hot oil is produced during the drawdown cycle. Theexcellent areal conformance of the steam throughthis bottom water zone combined with theimproved vertical conformance caused by thedownward movement of the mobilized bitumenappears to be the rational for the excellentrecoveries already obtained after only severalcycles of pilot operation. With Esso's Cold Lake pilot, verticalfractures are created to achieve the requisiteinjectivity of steam for their steam stimulationoperations. The lack of native injectivityconfines the steam to the near-fracture region. Efficient flowback of the confined steam appearsto be a dominant driving force for producing theheated bitumen. Gravity also plays a part. Theheated bitumen can drain downward in the regionof the fracture, allowing for further extensionof the steam heated zone away from the fractureplane. plane.