This paper outlines a drilling, completions reservoir guided analytical model to assess cased uncemented (CUC) multi-fractured horizontal wells (MFHW) in the Canadian Horn River Basin. 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 (MS) data shows that hydraulic fracture stimulation results in a very complex stimulated reservoir volume (SRV). Surveillance data including MS 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 MS.
The objective of the cased uncemented MFHW was to achieve improved productivity over the standard cased cemented horizontal well design. The hypothesis was that the CUC wellbore would have improved connection to the reservoir and the natural fracture system existing within the target shales. In addition, the CUC well would benefit by increased reservoir contact and connection to fractures created from offset wells on the pad. The first 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. A second generation cased uncemented well with mechanical packers was tested in 2013.
This paper will discuss how the conceptual model of this new technology can be translated into an analytical model by guiding the workflow with drilling, completions and reservoir understanding and how the surveillance data such as MS, production logs, and tracers validate the process along the way.
This approach allows generating production forecasting and reserves estimates of this new technology allowing economics to be run and decision to go forward to be made. Some of the design considerations and production indications will be addressed, concluding with a discussion of the results.