Microseismic Acquisition and Survey Design
Microseismic acquisition involves continuous passive seismic monitoring, using sensors in a number of different possible configurations. Although some refer to shooting a microseismic survey, the expression incorrectly implies an active source, whereas the passive nature means that terms such as recording, acquiring, or listening are more appropriate. Sensors can be deployed permanently or temporarily (Figure 1) in either an observation well or on surface, depending on the scope of the monitoring. Borehole arrays are the most common deployment (Maxwell et al., 2010), installed via wireline (as used for VSP or crosswell), cemented geophone arrays in shallow or deep observation wells (Smith, 2010). Alternatively, arrays can be deployed on surface (Duncan and Eisner, 2010), as used for reflection surveys or earthquake monitoring. Wireline arrays can be deployed in a near vertical borehole or conveyed into a horizontal borehole using a wireline tractor that pulls the array along. Surface arrays can use broadband seismometers (as in earthquake monitoring) or similar sensors to reflection surveys (Eaton et al., 2013) deployed in crosslines (radial lines away from the treatment wellhead or following gridlines), or in 2D patches over the target area (Pandolfi et al., 2013).
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Microseismic Imaging of Hydraulic Fracturing: Improved Engineering of Unconventional Shale Reservoirs
Microseismic monitoring is the key technology to image hydraulic fractures. With the recent industry focus on unconventional resources and the associated need for effective hydraulic fracture treatments to stimulate flow, microseismic monitoring has become a commonplace technology in the geophysical community. Microseismic has long been a niche geophysical technology to image fracturing, but the expansion of the technology over the last decade is evident by the increasing number of workshops, papers in various publications, and the sheer number of papers and associated dedicated sessions at the SEG annual meeting. This work aims to provide a practical user guide for survey design, quality control, interpretation, and application of microseismic hydraulic fracture monitoring. The book is intended to provide a comprehensive educational resource for microseismic hydraulic fracture imaging, with a focus on practical tips for executing a successful microseismic project. Limitations of the data and potential pitfalls are emphasized throughout.