This paper outlines an experiment conducted in the Horn River shales involving the testing of a cased uncemented multi-fractured horizontal well (MFHW). The typical Horn River shale gas development involves drilling and hydraulically fracturing multiple horizontal wells from a single surface pad location. The wells are hydraulically fractured in a sequential manner from the toe to the heel of the horizontal section, alternating from well to well. This manner of hydraulic fracturing allows concurrent operations that maximize operational efficiency and reduce completion costs. Microseismic data shows that hydraulic fracture stimulation results in a very complex stimulated reservoir volume. At a pad level, there is a very high degree of complexity created within the stimulated reservoir volume (SRV). Surveillance data including microseismic as well as proppant and fluid tracer data shows that hydraulic fractures reactivate the natural fracture system and can extend beyond inter-well distances. Production analysis however indicates that the effective drainage volume, post stimulation, is significantly smaller than what is observed with microseismic. Field results have also shown that multiple cluster perforations versus single perforation intervals per frac stage improve reservoir contact and the complexity of the stimulated reservoir volume.
The objective of the uncemented MFHW was to achieve improved productivity over the standard cased cemented horizontal well design. The hypothesis was that the uncemented wellbore would have improved connection to the reservoir and the natural fracture system existing within the target shales. In addition, the uncemented well would benefit by increased reservoir contact and connection to fractures created from offset wells on the pad. The experimental well was drilled on Nexen's 18 well pad, completed in 2012. A swellable packer system was conveyed as part of the casing string to isolate each hydraulic fracture stage. This paper will discuss details behind the surveillance data collected in previous wells and the conceptual model behind the connected fracture network within the stimulated reservoir volume that led to testing cased uncemented technology in this shale reservoir. Furthermore, some of the design considerations, surveillance data and production indications will be addressed, concluding with a discussion of the results.
URTeC 1619860
