Near-surface microseismic recordings from four wells completed in British Columbia, Canada, are analyzed to evaluate completions efficiency and to identify cost savings on future pad completions. Wells were completed using the plug and perforation method in a zipper sequence with slickwater and sand. The wells were monitored utilizing a near-surface array of geophones with an aperture that is twice the depth of the target. Located microseismic events are used to assess the overall success of the completions program in terms of the efficiency of fracture generation, stimulated reservoir volume, propped reservoir volume, stage spacing, well spacing, and well placement. This is accomplished using advanced interpretation methods that include discrete fracture network modeling and propped stimulated reservoir volume estimates.
Analysis shows that the presence of a preexisting natural fracture network that is parallel to SHmax enhances fracture growth in this orientation. Fracture lengths mapped with microseismic tend to exceed wellbore spacing by up to 400% unless they intersect local geologic structure, in which case fracture growth perpendicular to the wellbore is truncated. One outcome of creating these long fractures is that most of the created volume will not be propped. Three of the wells exhibited two microseismic event trends per stage and the fourth well generated a single event trend per stage. When two fractures are generated during a single stage, the first fracture tends to locate within the completions interval and the second in the upcoming interval. This creates significant overlap, which has implications for proppant distribution, stage spacing and production. Wells with two trends also generate a greater number of microseismic events early in the treatment, whereas stages with single fracture trends show more consistent event generation over the duration of pumping.
Advanced analysis of this microseismic data indicates that changes in stage and wellbore spacing as well as a reduction in fluid volumes or change in fluid type could result in significant completions cost reduction.