The Uinta Basin is a sedimentary basin that is characterized by both conventional and unconventional plays that exist in the majority of Northeast Utah branching into parts of Western Colorado. This basin is a subsection of the Colorado Plateau Province that encompasses a large portion of the Southwest U.S. including Arizona, Colorado, and Utah . It is also bounded by the Uinta Mountain uplift to the North, and characterized by the western Wasatch Mountain uplift and the faulting of the Wasatch plateau . Major oil fields in the Uinta include the Altamont and Bluebell fields along with a large variety of gas fields, illustrated in the figure below. These distinct depositional environments provide an array of sedimentary features that influence the physiographic makeup of the basin.
Uinta's Geological and Production History
Uplift can be credited as the source of the Uinta Basin formation which began in the Cretaceous to the Eocene era ranging from 55-150 million years ago. The major faulting from the surrounding mountainous areas has caused the basin to display steep to overturned beds with multiple unconformities. According to the NGI, four main categories of formations can be characterized that have been targeted for hydrocarbon production are the Green River, Wasatch, Mesaverde, and Deep formations . In 1925, the Uinta Basin began producing commercially but was at a steady decline until the horizontal innovation which lead to an increase in 12% growth rate of oil production from a low at 20,000 barrels a day . The Uinta Basin today contributes the most to Utah’s oil and gas production in the Duchesne and Uintah counties at about 25 million barrels of oil combined in 2020 and around 187 MCF of natural gas as well .
Uinta's Petroleum Geology
The source rocks of the Uinta can be characterized by marine transgressions to deposit limestone and sediments to define an organic-rich source rock . Due to previous dense marine environments, source rocks can be characterized by shales and mudstones for unconventional gas plays which are from more lacustrine environments, there are more marlstones and shales that are the source for the waxy oil in the area. Migration in the basin is characterized by current oil and gas field production spurring overpressure within the basin. While overpressure and gas expansion are among the major drive mechanisms of this basin, the Altamont-Bluebell field, being next to the most profitable member of the Uinta Basin, produces from solution gas drive. The Uinta basin has a unique relationship with depth and hydrocarbon generation as a unique mixing between oil and gas has created more oil deposits at deeper depths and vice versa, which contradicts average relationship of oil and gas with depth. Many of the traps in the basin are stratigraphic in nature formed partially by lenticular sandstone, some more specifically are caused by the dense unconformities that make up the Uinta Basin. Many of the seals in the basin are characterized by the presence of shale facies and carbonate formations, these are divided into the different oil fields which are illustrated in the figure below. Reservoir porosity in the area ranges between just less than 10% and just more than 15% and is composed of sandstone from the Wasatch formation and some limestone at greater depths .
Potential for Production
Even though there are some downfalls with Uinta’s production, it is still highly profitable and has a bright future as a producer. The high paraffin content in this oil does have benefits in that it makes an excellent feedstock for gasoline refining and petrochemical supply which will always be in demand. The Basin is the leading producer in Utah and has had great success with companies like Chevron drilling successful fields including the leaders like the Altamont, Bluebell, and North Myton Bench . Since Uinta crude is so unique in makeup, about 5 refineries in Salt Lake City, Utah handle most of the crude refining processes resulting in maximum output for the local economy. This activity causes a spill off by increasing demand for refineries therefore stimulating other markets outside the locality. With demand for energy consistently increasing, the spill off could continue to grow. In a strongly consumer based market in the U.S., demand for petrochemical feed stocks will continue to rise along with the Uinta waxy crude which will further benefit refineries outside of Salt Lake City.
Risks and Uncertainty
Although, the Uinta Basin is a hub for production in Utah, it’s oil is not the most desired because of its content. Whereas the highest priced oil is light and sweet with lower paraffin content, Uinta’s is very high in paraffin content causing multiple difficulties, many having to do with transportation. The price of this crude is usually sold at a discount as the result, and according to the NGI in 2015, both yellow (42 degree API) and black (32 degree API) sold at about 13%-39% discount to WTI prices, this affect is illustrated well in the figure below, showing black and yellow wax postings vs WTI for Chevron. The Green River member of the Uinta basin is a major portion of the production which is particularly waxy in the yellow-black paraffin content, consistent with the basin. In order to transport, it has to be heated from 105-120 degrees Fahrenheit inhibiting deliverability and accessibility to target demand throughout the country . Since Uinta is characterized by unconventional production, there has been an increase in what are known as “super-extended laterals” which are about 11,000 ft. sparking more uncertainty about the applicability of the basin's reserves to the nationwide economy.
The Uinta is pushing the depths of hydraulic fracturing with “super-extended laterals,” these have seen decent production with 800 to 2000 barrels a day of crude oil . These operations pose a question with how well the Uinta basin can keep up production with some of the hot basins like the Anadarko or Bakken, there will have to be large technological innovation to keep up. Companies have seen earlier success with exploring the opportunities that super-extended laterals pose, Newfield exploration has reduced completion costs while drilling a 10,000 ft well in the early days of this engineering innovation. The company even saw averages from this well ranging from 900 boe/d to 1,200 boe/d, which shows promise, but for the Uinta basin in particular, lower yields should be expected because of it's unique geological makeup .
- Geology of Tight Oil Reservoirs in Green River Formation
- Oil and Gas in the Uinta Basin, Utah – What To Do With the Produced Water
- Adpoting Longer Laterals In the Uinta
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