In 1989 and 1990 during the development program of the Potter sands on the Alberta lease, 21 TOW's (Temperature Observation Wells) were drilled on the 40 acre Alberta Lease in the North Midway Field for use in a high density surveillance program. Since that time, temperature surveys have been obtained from the TOW's on a monthly basis.
The temperature data was used to create temperature log profiles as well as temperature maps on various subzones throughout the Potter sand. The profiles and the maps were used to identify cold areas within the reservoir which aided the cyclic steaming policy. After identifying the cold spots in the reservoir, massive group steaming was utilized to uniformly preheat the reservoir areally and vertically prior to continuous injection.
The temperature log profiles and temperature maps were also used to identify steam movement downdip into the water column and preferential steam movement into channel sands. The temperature log profiles were integrated to calculate the average monthly reservoir temperature, fractional reservoir heat retention, average monthly temperature, and heat losses to the overburden and underburden layers.
With the data above, only two pieces of information were needed to calculate a total energy balance. These were the producing fluid heat losses and casing annular vent heat losses. Systems were installed to measure and record the data necessary to calculate these heat losses, and then, a total energy balance was calculated from the above data.