Seismicity and casing failures due to steam stimulation in oil sands

This paper describes observations of seismicity and casing failures associa ted with steam stimulation operations at Imperial Oil Ltd.'s Cold Lake oil held in Alberta, Canada. A total of 11 oil-producing pads were monitored ov er a 1-2 year period using 3-component geophones cemented at depths ranging from 160 m to 400 m and data acquisition systems with a hat frequency resp onse up to 1.5 kHz. Most of the seismicity was detected during the steaming operations and was located in the formation overlying the oil-bearing laye r. Some activity was observed in the shales above, however, the reservoir i tself showed almost no evidence of seismicity. The estimated seismic moment of the observed events was in the range 10(5)-10(7) N.m(-2.7 < M < - 1.3). According to a theoretical model (TALEBI et at., 1998) and in situ observa tions, the seismic source corresponding to casing failure events should be well described by a dipole registering seismic moment in the order of 2.10( 6) N.m. Seismic signals of a total of four observed casing failures were an alyzed. The partial failures produced seismic moments slightly lower than t his value while total failures were stronger by about one order of magnitud e. The use of the SV/SH amplitude ratio, in conjunction with accurate sourc e locations, provided a robust technique for the detection of casing failur es.