One of the most important hydrocarbon resources in the Western Canadian Sedimentary Basin (WCSB) is the Montney tight shale formation, which extends approximately 55,000 square miles from northeast British Columbia to northwest Alberta. Operations in the Alberta deep-basin Montney have proven this area to be one of the continent's most productive unconventional resource plays. As part of the field development plans, cores are cut from the reservoir rock to directly measure source rock properties through analysis of core samples and calibrating wireline logs with data extracted from the core samples.
The subsurface geology of the upper hole section in this particular area is complex, where reactive, swelling, and fissile shale as well as coal beds and lost-circulation zones extend across 2700 m of the openhole section. As such, historically in this field, the Montney has been cored using a weighted oil base system incorporating water contamination into the core; if zero water contamination is mandated, casing is run into the reservoir ahead of the coring section to allow coring with base oil, which leads to smaller core sizes. Additionally, coring operations can require several days when conventional coring technology is applied because of the multitude of necessary trips into and out of the hole.
Well engineers applied a systematic approach to achieve new targets by incorporating the latest available technologies and drilling techniques in the industry into a coring program while also optimizing well structural designs by minimizing use of casing strings. This allowed achieving the project's primary objectives of cutting larger-sized cores with no water contamination using minimal planned trips.
This paper discusses how managed pressure drilling (MPD) and wellbore strengthening techniques, as well as new coring technologies, were analyzed, planned, and incorporated into this project. This led to the successful execution of an optimized, cost-efficient well structural design with 100% core recovery and no water contamination while. At the same time, a new record was set in terms of the longest core length cut in one run in onshore North America.