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Integration of microseismic and time-lapse seismic data with application to a heavy oil reservoir
- Author / Creator
- Feroz, Amna
Thermal heavy oil extraction techniques are high temperature and pressure procedures to produce heavy oil. Elevated temperature and pressures alter the subsurface stresses, causing shear failure of rock within and surrounding the steam front. The steam also introduces volumetric changes at the reservoir level, and its impact may also propagate to the surface resulting in surface heaves. Furthermore, extraction of fluid/bitumen from the reservoir reduces the pore pressure and alters the petrophysical properties, ultimately causing reservoir compaction and surface subsidence.
The heavy oil fields in northern Alberta are under commercial production since 1986, several recovery methods have been applied to extract the bitumen cost-effectively. Grids of vertical injector/producer, horizontal injector/producers, CSS and SAGD have all been utilized. However, a horizontal well CSS strategy is being used in the most recently drilled pads. Despite applying several recovery operations and obtaining commercial-scale bitumen over the past 20 years, it is still unclear what exactly happens in the reservoir when steam is injected. It is also not certain how the steam moves laterally and vertically in the reservoir, thus adding uncertainty to the understanding of the recovery processes. Therefore a monitoring experiment was conducted, incorporating multiple remote sensing techniques, e.g., 2D and time-lapse reflection seismic data, microseismic data, production data, and tiltmeter recordings over a single CSS pad. The experiment recorded the data for four years to evaluate these technologies for field-wide monitoring. This experiment provided a testing ground to integrate several geophysical data to study the unknown associated with heavy oil extraction procedure.
The first aim of the thesis is to focus on microseismic data analysis and interpretation. The second part of the thesis aims to focus on time-lapse seismic data analysis and interpretation. The final part of the thesis links and integrates the observations from the two geophysical techniques by showing how one may help confirm or contradict the interpretation from each data.
A single deviated downhole microseismic monitoring array was installed at the pad of horizontal wells, to record the data. Before analyzing the recorded data, complete processing and quality workflow was proposed and applied to the recorded data to obtain event locations. As a result, approximately 2100 events were recorded during four cycles of steam injection and production. The spatial and temporal analysis and engineering data revealed that 95% of microseismicity is located in the overburden and recorded during the steam injection. I interpreted two fault planes in the overburden responsible for triggering the high number of microseismic activity.
I then focus on the time-lapse seismic data to process and identify time-lapse amplitude anomalies and isochrone time delays associated with the injection of a high volume of steam into the reservoir. The observations were integrated with surface tiltmeter data and temperature logs to interpret the spatial and vertical extent of the steam zones. It was concluded that the steam movement in the reservoir is non-homogenous, both spatially and vertically. Several zones were identified where steam has partially or fully reached inside the reservoir.
Finally, the findings from several geophysical data sources were integrated to validate the initial geomechanical model, and a theoretical model is proposed for the study area. The proposed model shows that during the heavy oil recovery method, microseismic activity is more likely to occur in the overburden due to stress changes and the brittle nature of the rock. The reservoir also undergoes several changes due to high pressure and temperature, including dilation, compaction, and alterations of rock physics properties. These changes are interpreted by analyzing the time-lapse seismic data and surface tiltmeter data. The theoretical model also helped validate the hypothesis that seismic reflection data are expected to highlight the changes at the reservoir level. In contrast, microseismic data would give a detailed picture of the changes in the overburden, and combining both is likely to give an elaborated insight of reservoir-caprock response to steam injection and the associated physical mechanisms.
- Graduation date
- Fall 2021
- Type of Item
- Doctor of Philosophy
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