The basin that keeps on giving: The successes and challenges of horizontal drilling in the Uinta Basin, Utah
Abstract
The Uinta Basin in northeastern Utah has been a major source of oil and
gas since the 1950s, with over 16,000 wells targeting oil from the Eocene
Green River Formation (GRF) and natural gas from both the Paleocene/Eocene
Wasatch Formation and Upper Cretaceous Mesaverde Group. Since 2010,
operators have drilled nearly 300 horizontal wells, both ~5000 ft laterals (XL)
and ~10,000 ft laterals (SXL), targeting tight oil reservoirs in the GRF and
underlying Flagstaff/Wasatch Formation. Many of these wells have been very
successful, on par with other major U.S. shale plays, but several challenges
exist including limited sweet spot extent, variable reservoir pressure, and rapid
changes in lacustrine facies, as well as other logistical challenges (waxy crude,
transportation, limited market, etc.). The most successful horizontal target is
the Uteland Butte member of the lower GRF. To date, 86 XL and 51 SXL
horizontal wells have been drilled with a cumulative production of 22 million
barrels of oil equivalent (BOE
). The SXL wells average ~1400
BOE
per day
initial production (IP - first full month) with the best performing well
producing ~2500
BOE
per day IP. The XL wells average ~400
BOE
per day
IP but range from <100 BOE up to 1600 BOE per day, depending on reservoir
pressure. Gas to oil ratios (GORs) for Uteland Butte wells (first year of
production) average 1.3 mcf/bbl. The underlying “Wasatch” interval is the
second most successful target but could soon become the first. The
“Wasatch,” as defined by operators, consists of interbedded lacustrine
carbonates (Flagstaff?) and fluvial/deltaic sandstone. Currently 62 horizontal
wells target the Wasatch, mostly in the upper carbonate benches (Wasatch 5
and 4), with cumulative production of 11 million BOE. The 38 SXL wells
average ~1300 BOE per day IP, while the 23 XL wells average ~700 BOE per
day IP but range from <100 BOE to ~2000 BOE, again depending on location
and pressure. GORs for Wasatch wells average 0.9 mcf/bbl. Several
additional horizontal targets (Castle Peak, Black Shale, Douglas Creek) show
potential in the GRF and will be discussed in terms of current and future
production. The expansion and continued success of unconventional
development in the Uinta Basin indicates that a comprehensive resource
assessment is needed to address overall potential in these new targets.
AAPG Datapages/Search and Discovery Article #90357 ©2019 AAPG Rocky Mountain Section Meeting, Cheyenne, Wyoming, September 15-18, 2019