Shear wave technology has had a remarkably consistent presence in the Canadian exploration community for almost 40 years. Although publications from the earliest days are sparse, Unocal and CGG were conducting some of the earliest shear-wave experiments in Canada (Omnes, 1978). Since the initiation of the CREWES Project at the University of Calgary in 1988, P-S converted waves have been acquired, processed and interpreted by many exploration companies for more than 25 years, so there is a fair amount of experience in the application of P-S converted waves to land data in the Calgary geophysical community compared to elsewhere in the world. The quality of acquisition, processing and interpretation has steadily improved over that time and the number of geophysicists who are familiar with the use of shear waves in exploration has gradually increased. Nevertheless, it would be an exaggeration to say that multicomponent exploration is widely established in Canada. Some individuals within some companies use it to gain value in their exploration effort.
Several recent examples of adding value with converted waves have primarily been applications to heavy oil in NE Alberta. Mayer et al. (2014) have demonstrated that joint prestack PP-PS inversion produced the best estimates of Pimpedance, S-impedance and density, allowing for excellent reservoir characterization of the Athabasca oil sands reservoir. The zone of interest is the unconsolidated sands of the Lower Cretaceous McMurray Formation reservoir within which the bitumen oil sands reside. Limited angles of incidence are available in the data because of a large velocity increase at the Paleozoic immediately below the McMurray. As a result, density could not be directly estimated using AVO inversion, but it was successfully estimated from the joint PP-PS inversion. Neural network analysis that used the PP and PS PSTM volumes, attributes from the PP and PS AVO analysis and attributes from the PP-PS prestack inversion as inputs further improved the resolution of the results. Figure 1 shows the result of density inversion with neural network analysis. This density inversion indicates the existence of upper and lower sands, which is also indicated by the wells, however there is a transition from bitumen to water within the sands that is not indicated by density.
Toe-to-Heel-Air-Injection (THAI™) is an in-situ combustion process that is used for the recovery of bitumen and heavy oil. It combines a horizontal production well with a vertical air injection well placed at the toe. Compressional and shear velocities for heavy oil are extremely sensitive to temperature. As the oil is heated by the combustion process the velocity decreases causing distinct time-delay anomalies on timelapse (4D) seismic. These time-delay anomalies indicate that the combustion front is moving from the toes of the wells, where the air injectors are located, towards the heels. Downhole thermocouples are used to measure the temperature and hence provide control/calibration points.
Potash and Oil Sands are now the largest and most valuable resources in western Canada, particularly as conventional petroleum supplies are depleted. To a large degree, geophysical efforts towards the exploitation of these resources do not need to focus on exploration so much as resource delineation as necessary for mine development or enhanced extraction. Time lapse monitoring should also be an important aspect in oil sand recovery.
Bailey, Jeffrey R. (ExxonMobil Upstream Research Co.) | Smith, Richard James (Imperial Oil Resources Ltd.) | Keith, Colum M. (Imperial Oil Resources Ltd.) | Searles, Kevin Howard (ExxonMobil Upstream Research Co.) | Wang, Lei (ExxonMobil Upstream Research Co.)
Cyclic Steam Stimulation (CSS) is a cost-effective means to produce heavy oil at the Cold Lake field in Alberta, Canada. The high viscosity of bitumen is the main obstacle to economic production, but the bitumen viscosity decreases significantly with temperature. Steam is injected at fracturing conditions, resulting in complex interactions of reservoir expansion (dilation) and contraction (recompaction) that propagate stress and strain fields in the overburden.
The mechanical loads on wells resulting from this production process are an important design consideration. To enhance operational integrity, a dedicated passive seismic monitoring well is installed on new development pads to provide early detection of casing failures and possible fracturing of the formation overburden. There is now an installed base of almost 90 such acoustic monitoring wells in the operator's field. With data acquisition of 15 to 30 geophones per system, recording continuously at 2000 or 3000 samples per second, the data management issues for this monitoring network are challenging.
Several classes of acoustic events have been identified, including those due to casing failure, formation heave, near-wellbore cement cracking, and production rod pump background noise, in addition to "Continuous Microseismic Radiation?? (CMR) that resembles harmonic tremors. Most casing failures are detected by observation of singular events. The detection of fracturing of the overburden, which may include the presence of bitumen and/or produced water that has migrated out of zone, is a more complex process that requires distinguishing shear events and CMR events from normal formation heave and other environmental noise.
The operator has stewarded the development of a cost-effective system that includes local pad data acquisition, uploading of selected data to a server with data archiving facilities, and downloading data to dedicated analysts. This paper will present a summary of the data management and processing technologies developed to address the challenge of managing this data-intensive problem.
Miyazawa, Masatoshi (Colorado School of Mines) | Venkataraman, Anupama (ExxonMobil Upstream Research Company) | Snieder, Roel (Colorado School of Mines) | Payne, Michael A. (ExxonMobil Upstream Research Company.)
Hyrdocarbon production from deep oil sands deposits relies on thermal processes such as steam stimulations to overcome the viscosity of the bitumen and make its flow to surface possible. These processes put well casings under fatigue and thermal stresses and can lead to their sudden failure. Microseismic monitoring has been undertaken over the last decade in order to detect such failures in the Cold Lake oil field in Alberta operated by Imperial Oil Resources. This paper describes results of the application of a seismic model in the detection of well casing failures and a new approach for such detections. Seismic energy was found to be a very reliable parameter for such detections through the comparison of seismic energies of P and S waves and, particularly, those of SH and SV components of seismic signals originating from casing failures.
Imperial Oil Resources is one of Canada''s largest producers of hydrocarbon liquids and their Cold Lake oil field is one of the largest sources of crude oil production in Canada (Fig. 1). The oil sands at Cold Lake, like the majority of Canada''s oil sands deposits, are too deep to be mined from surface and too viscous to be exploited using conventional extraction techniques. Thermal recovery processes such as Cyclic Steam Stimulation (CSS) are employed to overcome the viscosity of the bitumen and allow it to flow to surface. The extraction process consists of injecting large volumes of steam under high pressures and temperatures (300⁰C) into the oilbearing Clearwater formation (CW), located at the depth range 400-450m (Fig. 2). Steam injection is alternating with oil and water production for as many cycles as economic conditions permit (e.g. Kry 1989) and the process uses the same well for steam injection and bitume