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Using Microseismicity to Identify Changes in Fracture Behavior During Hydraulic Fracture Stimulations

Urbancic, Ted; Baig, Adam; Kocon, Ken; Tremblay, Krystal

Microseismic monitoring is routinely being used to identify overall hydraulic fracture characteristics such as geometry, half width, stage overlap, and estimated stimulated reservoir volume. Engineers utilize these data along with engineering data to assess the effectiveness of a stimulation program and to increase production. Here, as an example, we examine a particular stimulation approach being investigated by numerous producers often referred to as the Kiel process. In theory, the Kiel process is used to create a dendritic (branching) fracture network to enhance well productivity (up to 2 to 5 times over conventional fracturing) and to rapidly drain the reservoir around a wellbore as compared to bi-wing fractures. The process uses a cyclic injection procedure by shutting the well in or allowing it to flow back, and then resuming injection to open secondary fractures offset from the initial primary fracture orientation.

In this paper, we examine microseismicity associated with a stimulation utilizing the Kiel process in a naturally fractured shale formation. In addition to event locations, multi-array and multi-well configurations allowed for the assessment of general moment tensor solutions for the observed events. This provided an opportunity to examine the relative spatial and temporal behaviour of fracture orientations (azimuths and dips) and the failure components (opening, closure, shearing) as a function of the stimulation program. Our observations suggest that the Kiel process achieved its objective, with the dominance of natural fracturing early in the sequence as compared to secondary fracturing upon re-injection as a result of localized stress re-orientation. Additionally, during shut in and re-injection, fractures identified during the initial injection, with significant opening failure components, tended to exhibit closure whereas secondary fractures exhibited opening dominated fractures. Based on these analyses, it can be suggested that augmenting observations of microseismicity with moment tensor derived fracture data can be used to assess the effectiveness of different fracture stimulation programs as evidenced for the Kiel process.

 

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013