This paper reviews the diagnostic data from vertical wells where operators targeted Burkett, Hamilton and Marcellus Shales and other deeper unconventional shale or tight gas reservoirs with vertical wells between the years 2006-2013. The learnings are then translated for their applicability in horizontal development wells. Its purpose is to deliver a better perception of fracture geometry and interactions between payzones that are separated by potential fracture barriers.
Multiple vertical wells employed the use of diagnostics in the form of proppant tracer, production logging and post-fracture temperature surveys to provide an improved understanding of hydraulic fracture and propped fracture height and the formations that serve as hydraulic fracture barriers. Completions variables such as treating rates, proppant volumes, perforation designs and frac fluid systems are examined to determine how they relate to propped fracture height growth.
In the majority of the logs reviewed, the proppant was contained to the perforated interval or just above and below. Some wells did have extensive proppant height growth. However, in most of those cases, the propped fracture height was the result of poor cement bonding, multiple fractured intervals growing towards one another and frac plug failures. As expected, hydraulic fracture height is typically significantly higher than the proppant height. Few vertical wells showed evidence of proppant connecting the Marcellus and Burkett zones. Formations acting as fracture barriers did not respond to many of the completions variables. Large treatment volumes, up to 500,000 lbs or more of proppant in a single stage, are often contained to propped fracture heights of less than 50 ft.
Few vertical unconventional wells are currently drilled now that most economic Marcellus fairways are well into their development phase. Vertical wells and their learnings are often forgotten with the many personnel and role changes, acquisitions, mergers and other fast paced changes in the industry over the last decade. The purpose of this paper is to reintroduce the valuable and still relevant vital information from these forgotten vertical wells.