MEASURING WETTABILITY OF UNCONSOLIDATED OIL SANDS USING THE USBM METHOD

The commercial development of bitumen production by cyclic steam stimu lation in Cold Lake, Alberta, Canada has prompted the need to acquire relevant capillary pressure and wettability data. The USBM method was used to determine the wettability of four adjacent Cold Lake Clearwate r cores at 40 degrees C using a heated centrifuge. A centrifuge core h older that provides confining pressure and enforces zero outlet capill ary pressure was used to perform the tests. Heating was necessary to m obilize the viscous bitumen (50 Pa s at 20 degrees C). The theories of Hassler and Brunner [Hassler, G.I., Brunner, E., 1945, Measurement of capillary pressures in small core samples. Trans. AIME, 160, 114-123. ] and Rajan [Rajan, R.R., 1986. Theoretically correct analytical solut ion for calculating capillary pressure-saturation from centrifuge expe riments. SPWLA 27th Annual Logging Symposium (Jun.), pp. 1-17.] were u sed to interpret capillary pressure from the test data. One core that was unaltered was weakly water-wet. The other three cores were pre-flo oded at 280 degrees C with large pore volumes (> 8) of bitumen and bri ne either as a co-injection mixture (1:1 and 19:1 bitumen to brine) or as alternate slugs. Their final wettability state was water-wet to st rongly water-wet. This work shows that field cyclic steam stimulation promotes water-wetness after large throughput of bitumen and brine, (C ) 1998 Elsevier Science B.V. All rights reserved.