Project Overview
As part of expansion projects to build natural gas gathering, compression, and processing assets, Meritage Midstream proposed construction of a pipeline system to transport natural gas to a processing plant south of Grande Prairie, Alberta. Several crossings were required along the pipeline route, with the most significant being the Smoky River. BlueFox Engineering was retained by Meritage Midstream to provide engineering, subsurface investigation, detailed HDD design, HDD contractor tendering, environmental monitoring, construction engineering, and on-site HDD inspection services to complete the crossing.
Subsurface Investigation
An extensive geotechnical and geophysical investigation program was executed, consisting of 5 boreholes up to 115m depth and 3 ERT lines to cover the 152m elevation change over the course of the crossing. Subsurface conditions consisted of sands, silts, and gravel underlain by highly fractured sandstone and mudstone bedrock containing several coal layers.
Installation Method and Casing Design
Following an initial casing installation, ongoing fluid loss to formation and eventual loss to surface was experienced on the entry side. BlueFox designed an extended telescoped casing program on entry which extended to 217m, and was supplemented by using a pressure injection cement program to 505m in order to isolate the HDD from the fractured formation. Following completion of the borehole isolation techniques, fluid returns were established to 100%, and the 17 ½” pilot hole was successfully completed to the design length of 1,521m.
Environmental Monitoring
Due to the steep and challenging terrain, environmental monitoring was aided by the use of thermal imaging by an unnamed-aerial-vehicle in order to detect fluid release to the surface.
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