Source mechanism characterization and integrated interpretation of microseismic data monitoring two hydraulic stimulations in Pouce Coupe field, Alberta

Abstract

The study of the Pouce Coupe Field is a joint effort between the Reservoir Characterization Project (RCP) and Talisman Energy Inc. My study focuses on the hydraulic stimulation of two horizontal wells within the Montney Formation located in north-western Alberta. The Montney is an example of a modern-day tight, engineering-driven play in which recent advances in drilling of horizontal wells and hydraulic fracturing have made shale gas exploitation economical. The wells were completed in December 2008 and were part of a science driven project in which a multitude of data were collected including multicomponent seismic, microseismic, and production logs. Since this time, a number of studies have been performed by students at Colorado School of Mines to better understand the effects the completions have had on the reservoir. This thesis utilizes the microseismic data that were recorded during the stimulation of the two horizontal wells in order to understand the origin of the microseismic events themselves. The data are then used to understand and correlate to the well production. To gain insight into the source of the microseismic events, amplitude ratios of recorded seismic modes (P, Sh and Sv) for the microseismic events are studied. By fitting trends of simple end member source mechanisms (strike-slip, dip-slip, and tensile) to groups of amplitude ratio data, the events are found to be of strike-slip nature. By comparing the focal mechanisms to other independent natural fracture determination techniques (shear-wave splitting analysis, FMI log), it is shown that the source of recorded microseismic events is likely to be a portion of the shear slip along existing weak planes (fractures) within a reservoir. The technique described in this work is one that is occasionally but increasingly used but offers the opportunity to draw further information from microseismic data using results that are already part of a typical processing workflow. The microseismic events are then used as a tool to analyze the effectiveness of the hydraulic stimulation and why production varies on a well and stage basis. The study shows that production disparities may be related to communication between horizontal wells, a potential weak zone of sub-seismic scale faults/fractures at the toe of one of the completed horizontal wells, and most importantly the quality of the stimulated rock. The results suggest that the quality of the stimulated reservoir rock is a greater driver of production than the total stimulated volume. By integrating the microseismic with other data (seismic and engineering), this work shows that the key to the understanding of these engineering-driven plays is an integrated solution. The methods shown in this thesis are applicable to many similar plays across North America and the world. The complicated nature of these tight reservoirs underscores the need for effective well planning, placement, and stimulation for economical development of shale resource plays.