Uinta Basin Geology
The Uinta Basin
is a lacustrine, or inland sea/lake, basin. It had periods of freshwater influx
and saltwater influx. It is rich in organic matter and much of it is thermally
mature. There is no thrusting as in some nearby basins in the Rockies. There is
tectonic extension, particularly in the western part of the basin. Uinta Basin
oil & gas targets are shown in the stratigraphy section below. The Eocene
and Paleocene Epoch targets of the Paleogene, or older portion, of the Tertiary
Period of the Cenozoic Era are the reservoirs currently being drilled for
horizontal oil production.
Drilling began in
earnest in the Uinta basin in the early 1950s after a 1948 discovery well. Much of
the basin’s acreage is now held by production from the extensive vertical
drilling in the basin, much of it targeting the Green River formation
sandstones.
A study by Joshua
Sigler, Lucas Fidler, and Ted Cross presented at the Unconventional Resources
Technology Conference (URTeC) in June 2024 applied machine learning to examine
the plays. The machine learning model was trained to predict per-well gas, oil,
and water production. The abstract notes:
“…a machine learning (ML) model was employed to provide a
data-driven assessment of variable importance and relationships with production.”
“Our analysis
identifies operator-controlled variables such as proppant intensity as most important
for the Uteland Butte, and geological variables such as pressure as most
important for the Castle Peak. Comparatively, the basin's productivity aligns
closely with that of the Delaware and Williston Basins, indicating its
competitive stature in the unconventional oil play landscape. Expected
long-term development density ranks above the Williston but slightly below the Permian.”
“With a
lacustrine depositional environment and waxy crude, the Uinta Basin is distinct
from the typical marine environments and high-API crude found in the other
North American resource basins. However, the emerging Lower Green River-Wasatch
play demonstrates the successful cross-application of the “unconventional
playbook” of extended laterals, intense completions, and cube-style
developments to this novel setting. This study provides the groundwork to understand
this exciting new play and contextualize the impact of development designs in
this setting. With new zones to explore vertically and lateral expansion away
from existing developments, the Uinta basin has immense potential left to be
explored.”
More from the paper:
“By the late Paleocene, the foreland of NE Utah had been
sufficiently partitioned that a large freshwater lake, known as Lake Uinta, had
formed and became a thriving habitat for freshwater mollusks of the lacustrine Flagstaff
Formation (Picard, 1985). The dominant lithologic unit of the earliest Eocene throughout
much of the Uinta Basin are fluvial-delataic sandstones of the Wasatch
Formation, suggesting that Lake Uinta had contracted significantly by this time.”
“The Green River Formation is a variable assemblage of
intracratonic sedimentary deposits ranging from lacustrine carbonates and
TOC-rich shales in the deep subsurface to oolitic grainstones and
fluvial-deltaic sandstones at the southern margin of the basin.”
“As of this writing, 610 horizontal wells have been
drilled in the Central Basin, with 57% drilled in the last 4 years alone. At
least 9 different horizontal target benches within the Lower Green River and
Wasatch Formations have proven to deliver economically-viable production in the
Central Basin, giving operators numerous strategies to capture in-place
resources. Despite the numerous development configurations tested by operators,
virtually all projects focus on producing the Uteland Butte member (Uteland
Butte) and Upper Castle Peak member (Castle Peak) of the Lower Green River
Formation due to their high productivity and consistent performance.”
Dominant porosity
systems for each section of the basin and total organic carbon (TOC) are shown
below, followed by a graph comparing the Uinta Basin to other basins, the horizontal cumulative oil production history, cumulative well counts, and the conclusions
of the paper.
Conclusions
● Unconventional
oil plays in the Uinta Basin of northeastern Utah demonstrate rapid production
growth and comparable well performance to established basins such as the Permian
and Williston, despite a lacustrine depositional setting and waxy crude.
● Utilization of
an integrated data approach and machine learning model facilitated analysis of
geological properties, operator-controlled production drivers, and cross-basin comparisons.
● Our machine learning models, taking a statistical
approach only, matched already-published geologic analysis, such as the sonic
slowness cutoff for identifying organic porosity in the Uteland Butte.
● Our findings suggest that certain areas of the Uinta
Basin could achieve development densities and oil production performance on par
with the Permian Basin, attributed to a similar responsiveness to intensive
completions and the presence of thousands of feet of stacked pay zones
Hart Energy’s Super DUG Conference email advert noted the
following regarding SM Energy's Uinta Basin wells:
“SM Energy has joined the hotter-than-ever western Uinta
Basin oil play that’s been cut loose from a Salt Lake City-only refining
destination to loading at in-basin rail terminals, destined for anxious buyers
in Oklahoma and the Gulf Coast. Just a few months in, SM already has 18 new
wells in the play, with some of them testing the shallower of 17 oil payzones
while it has one test underway in the deepest in addition to landing in the
traditional money pot: the middle zones.”
A recent Hart Energy
webinar moderated by Nissa Darbonne featured Juan Nevarez, EVP, Scout Energy
Partners, and Riley Brinkerhoff, CEO, Duchesne River Resources. The slides below
are from that webinar. The speakers noted that the Uteland Butte member in the
Green River Formation is the main horizontal target and the biggest producer. The
many vertical wells drilled in the basin, a significant number of them
penetrating the pay intervals, allow geologists to map the play in detail. Rock
quality has been shown to be consistent over a large area for some targets.
Oil Quality, Refining Capacity, Transport Options, and
Other Issues
Most of the oil
in the Uinta Basin is a waxy crude or a crude oil high in paraffin content.
This makes it very difficult to transport via pipeline. It must be heated in
order to transport it. It can also be cracked and mixed with other crude for
transport but that can be so problematic that it isn’t being done. It is
typically trucked to refineries in Salt Lake City, typically two to three hours
away. Salt Lake City refineries had upped their capacity in recent years to
200,000 Bbls/day from the previous 90,000 Bbl/day. It is very unlikely that any
more refinery capacity would be available in Salt Lake City due to the weather
inversions in the region which can create very significant smog from the refinery
emissions. Rail transport is considered the best option for further transport
to the Gulf Coast where it is desirable for mixing with Permian light oil for
refining there. Transport costs are high due to the need to keep it warm. If it
cools and the wax becomes less mobile it becomes more problematic and more expensive
to reheat. The associated gas that is produced in the basin, especially in some
parts of the basin that have less gas pipeline takeaway capacity, is burned to
keep the oil warm. Other uses for the stray gas are power pumping units, gas-fueled
drilling rigs, and a few Bitcoin mining ventures. More gathering and local gas pipelines
are being built. The gas-to-oil ratio (GOR) for the basin is lower than many of
the shale basins including the Permian so the associated gas production is not
expected to grow significantly, especially as local uses for any stray gas are employed.
Oil quality, of
course, varies by the thermal maturity of each zone. The oil generally varies from
black waxy crude at about 32 API, to 41 API in Uteland Butte and even higher
than that in Wasatch. The black wax and yellow wax variants have basically the
same economic value. Currently, the differential is $18 lower than WTI but
would come down considerably with more volumes moving to the Gulf Coast.
The Uinta Basin
overlaps both federally owned land and tribally owned land of the Ute Tribe.
The Utes have been pro-oil and gas for a long time and operate many oil &
gas service companies in the area. Utah has been an oil & gas friendly state
with fast permit times and one of the most favorable regulatory environments in
the U.S.
Porosity Zone Types and Future Play Potential
Most deals in the
future will likely focus on the margins of the plays where there is more unleased
acreage but also higher risk. The mature window boundary in the south may move
further south in Upper Cube – Lower Douglass. Below that in the Castle Peak formation, the play is clastics and organic porosity in the limestone. Lots of undrilled
section is left to be determined if economic. The Garden Gulch is rapidly
becoming economical. More plays that don’t include organic porosity are likely
as there is a lot of oil-in-place south of the organic porosity window. There are 12
other intervals that don’t include organic porosity but dolomite porosity, clastics,
and carbonate porosity. The south part of the play is lower temperature and pressure,
so requires lower mud weights to drill and also does not require intermediate
casing as the northern areas do. The organic porosity zones are more continuous
and thus generally more amenable to longer laterals. U-laterals can be executed
in the play but are not needed except in cases of acreage limitations which is
rarer here than in say the Midland Basin Permian. The organic porosity zone plays
do not require seismic in general but the fluvial-deltaic clastics do require seismic
to assess their continuity. There are publicly available 3D seismic shoots in
the basin.
Production Issues
The different
zones are still being evaluated for frac optimization with frac parameters such
as stage spacing and sand loading being tweaked up or down to find the right
recipes. The temperature and pressure are higher in the north part of the basin
which means higher mud weights are required for drilling there.
Stress variation
due to extensional fracturing, particularly in the western part of the basin.
The many joint sets lead to more fluid movement including water. Leak-off from
permeable sandstones a problem where many verticals drilled. Water production
is pretty high in the Uinta but varies by area and type of frac. Bigger fracs
have meant more water production. 50% water cut is the basic average. Uteland Butte
is as high as 70% water cut in clastics from the upper cube. Much of the water
production is reused for fracs. Much is re-injected into the Uinta Formation above
the oil pay zones in the Green River formation. Water issues are one aspect of
reservoir management that will be important to optimizing the play and
preventing unexpected problems as time goes on.
References:
Unpacking
the Uinta Basin: the next great oil play? Joshua Sigler, Lucas Fidler, Ted
Cross. XCL Resources, Novi Labs. Unconventional Resources Technology
Conference. June 2024. Uinta.pdf
SM’s
First 18 Uinta Wells Outproducing Industry-Wide Midland, South Texas Results. Nissa
Darbonne. Hart Energy. February 20, 2025. SM’s First 18 Uinta Wells
Outproducing Industry-Wide Midland, South Texas Results | Hart Energy
Hot in
Utah: Uinta Basin Oil Output Unleashed. Hart Energy Webinar. February 26, 2025.
Hart
Energy Webinar | Hot in Utah: Uinta Basin Oil Output Unleashed
Slide
Set from Webinar. Hart
Energy Webinars 02-26-25 Hot in Utah_Uinta Basin Oil Output
Unleashed_Presentation Slides.pdf
Major
Oil Plays in Utah and Vicinity. Thomas C. Chidsey, Jr. Utah Geological Survey. January
2010. Major
Oil Plays in Utah and Vicinity - Utah Geological Survey
Oil
and Gas in the Uinta Basin, Utah – What to do with the Produced Water. Thomas
C. Chidsey, Jr., May 2018. Utah Geological Survey. Oil
and Gas in the Uinta Basin, Utah – What to Do with the Produced Water - Utah
Geological Survey
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