f Passive seismic monitoring for operations integrity at Cold Lake, Alberta

Passive seismic monitoring has been ongoing at Imperial Oil's heavy oil operation in Cold Lake, Alberta since 1998. There are currently 81 dedicated monitoring wells with 5 or 8 tri axial geophones deployed in each well at depths ranging from 150 to 400 meters. The Cyclic Steam Stimulation process used to extract the bitumen, involves injecting large volumes of 300°C steam at greater than fracture pressure into the Clearwater bitumen-bearing formation at around 450m depth causing significant stresses and strains on the wellbores. The main objective of the monitoring is to detect casing failures and inadvertent fluid releases into the overlying Colorado shales caprock and the aquifers above them, thereby reducing the financial and environmental consequences. Daily interaction between the seismic analysts and field operations personnel, along with a systematic response plan ensures appropriate operational interventions are taken when passive seismic alarms occur. One challenge associated with operating a passive seismic system within a producing oilfield is managing the amount of noise generated by production operations. Data reduction is achieved with processes to reduce noise triggers, filter noise events that are triggered and compute channel specific statistics. Integration of the data acquisition sites, with a central data management server and through to Matlab-based analysis software, allows for seamless review of the daily statistics and daily analysis of the seismic events. Examples of the data types recorded and subsequent operational interventions are presented demonstrating a successful application of passive seismic technology.