In 2010 a noise test and microseismic emission detection test was performed in the Horn River Basin in northeastern British Columbia, Canada, to determine
the suitability for surface microseismic monitoring and
the character of the near-surface noise in an effort to determine the optimal depth to bury geophones.
The test consisted of a low density, low aperture array of 14 stations that covered the heels of eight wells. Initially the array was used to capture six treatments located outside of the array footprint. Two additional stages, located under the array footprint, were recorded and processed at a later date.
This coarse array allowed for the detection of several hundred events and a single moment tensor solution was determined. A dip-slip focal mechanism with a failure plane oriented NE-SW. This information, however not ideal, was adequate to create a limited amplitude based discrete fracture network (DFN) to be developed for the test results as well as a preliminary estimate of stimulated reservoir volume (SRV) for the test stages. Microseismic events that were imaged that were located outside of the array had larger positional uncertainty and reduced amplitudes compared to events recorded from stages within the array. This was a limitation imposed by the aperture of the array used in the test, as well as the low number of stations.
Test results indicate that the Horn River Basin is an adequate environment for surface microseismic monitoring, with good signal-to-noise characteristics. The test results suggest that adequate surface noise suppression is achieved by placing the sensors at or below 30m depth. The test also demonstrates that there is a need for appropriate array fold and wider aperture in order to fully describe the fracture network and obtain the most reliable estimates of SRV.
In 2010, a permanent shallow buried array consisting of 14 stations was deployed over an area of 2.5km × 2.3km on the Dilly Creek property in the Horn River Basin in northeast British Columbia, Canada (Figure 1). A buried array design was chosen based on a number of factors including; the long well lengths, which reached 2500m of lateral length, changing completions schedules and timing, and difficulties with event multipathing which can complicate downhole processing (Eisner, 2009). The array was designed to monitor 32 hours of completions activities on an 8 well pad. The limited monitoring time was due to the high monitoring and processing costs, and the noise test objective was met with 32 hours of recording.