Wind River Basin

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Introduction

In the Wind River Basin Province, located in Wyoming, the U.S Geological Survey (USGS) searched for unconventional oil and gas resources. What they found was two very different structures in the ground.

[1] Figure 1 - A regional map of the Wind River Basin depicting different stratigraphy zones.

One was a “lower soft clay-rich shale” and two, “an upper siliceous part composed of dark gray to brown organic-rich mudrock with numerous siltstone, very fine sandstone, and bentonite beds.”[1] The Wind River Basin Provence derived from the Late Cretacous by early Eocene. This caused the Laramide Orogeny to break up into smaller basins hence the Wind River Basin. This basin has both oil and gas within its borders. Due to geology, this basin contains both oil and gas within its borders. The oil boundary is classified as the Wind River Mowry Shale Oil AU and the gas boundary is classified as the Wind River Mowry Shale Gas AU.[1]


Stratigraphy

[2] Figure 2 - A regional map of the Wind River Basin depicting different stratigraphy zones.
[2] Figure 3 - This grid shows the different overlapping of rocks in areas shown in the Wind River Formation Map.

The Wind River Basin looks simple according to Figure 1, however beneath the surface it gets complex. The best way to depict the striations of this basin is through imagery. This is because of the different rock makeups that are in this basin. To the left there is a map of the Wind River Basin with labels on different areas A-G and I-V. A-G are more centralized in the basin and I-V are on the outer perimeter of the basin's boundaries. With labels A-D you see fine grained beds that vary in thickness with B, C, and D have lower fine grained beds.[2] A-D contains a Dry Coyote Conglomerate Bed. These also show prominent Muskrat Conglomerate Bed, excluding C and D. Area E-G shows absence in these fine-grained beds. E, being kind of an outlier was “was generally too high for deposition of lower finegrained member.”[2] Area F caused this absence due to erosion before the sediment was deposited in the area.

Areas I, II, III on the Wind River Formation Map indicate that it was removed by Quaternary erosion. Formations IV and V are the youngest sections to be examined. Some data has been recovered in these areas by digging drill holes[2]. The data gathered shows that they are younger beds with some dinner grain rocks.

Geologic Setting

With the Winder River Formation there is a lot of overlap with other formations that are older, specifically in the south central edge and the northern Sweetwater uplift[2]. The older formations folded during the Cretaceous and a little bit in the Teriary to give you a timeline and age of this basin. During this time, the subacent rock range eroded prior to the deposition of the Wind River basin. With the Wind River formation you see that it “dips about 1°-3° S., except in the northern part of the area, where beds are mostly horizontal or dip very gently north.[2]

Structual History

During the most recent Cretaceous time, the Laramide orogenic event took place caused by the mid-Atlantic ridge and the North American craton along a westward-moving line. When the ridge opened, during the Paleocene/Eocene time, it accelerated, and a shift in movement to southwestward occurred[3].

According to a lot of structural analyses, little or no vertical movement occurred on the east-west trending structures in the latest Cretaceous/Paleocene time. Most of the activity occurred on the northwest-southeast trending structures, this produced westward verging, linear thrust sheets. Back to the east-west trending structures, it is possible that strike-slip faults developed along zones of basement weakness[3].[4].

According to a Wind River Basin Analysis, “Development of east-west trending thrust sheets occurred during maximum compression (southward directed) in Eocene time. Detailed surface mapping has shown Eocene east-west trending thrusts and folds truncate or are superimposed on earlier Laramide north- and northwest-trending thrusts and folds[3].

Risk and Uncertainties

There are a number of plays to be made in the Wind River Basin for oil and gas. These plays can vary from a basin margin subthrust, to a base margin anticline, to a muddy sandstone stratigraphic. When focusing on all these plays as a whole you run into several similar risks and uncertainties throughout the basin. One big risk is lack of well control. This is due to the depths at certain plays in order to drill out oil and gas in this basin. Another risk you see throughout the basin is complex migration pathways to get to the desired reservoir. Due to the Structural Evolution of the basin, the geologic setting has made a lot of risks and uncertainties[3].

Trap and Seal

Sticking to one of the most explored methods in the Wind River basin, the Basin Margin Subthrust play, which is a conventional method of extract, we see a trap in place. I picked the Basin Margin Subthrust play to discuss because it is the most explored and is producing a lot of the basin’s reserves, so therefore it is most appropriate to key in on this one play. The petroleum is trapped in the structures with closure occur below the basin-margin thrust. It is sealed by associated rocks, or impermeable rocks, of the hanging wall of the thrust.[5]. By using the thrusting process the underlying beds are folded and often upturned or overturned with fault slivers typically present.[5]. James E. Fox and Gordon L. Dolton, state, in their Wind River Basin Province, “Oil and gas may also be trapped in these upturned, overturned, folded, and faulted strata. Depth to production is highly variable, ranging from more than 20,000 ft on the structurally steepest side of the asymmetrical basin to less than 10,000 ft in other basin-margin areas.”

Future Potential

Future Potential in the Wind River basin is prominent. This is depicted by the high exploration in the area. The Wind River basin is heavily unexplored if you look back to figure 3 you can look at the roman numerals. The roman numerals are most of the unexplored areas in the basin. I conclude that there is a lot of future potential in already existing plays and unexplored plays because of the geologic setting of the basin. In the basin-margin subthrust play it is found that there is roughly 2/3 of the play will be gas in the deeper sections and ⅓ will be oil in the shallower wells.[5].

Engineering Aspects

Currently, ( it is the year, 2021), extractors drill at depths between 3,000 ft and 14,500 ft to extract both oil and gas in the Wind River Basin. Because of the harsh landscape in the mountains of Wyoming, this basin proves to be both difficult and arduous to gather up drilling well materials to the well site. Engineers also have to calculate factors to drill at deep depths. Having such a challenge makes some of these drilling sites complex and causes a lack of control.

Important Papers

This section allows contributors to point to other important papers or books that have been written on the subject matter

External links

Wind River Basin Oil and Gas Assessments https://www.usgs.gov/centers/cersc/science/wind-river-basin-oil-and-gas-assessments?qt-science_center_objects=0#qt-science_center_objects

Wind River Mountain Range https://www.visitpinedale.org/destinations/wind-river-mountain-range

Wyoming Oil and gas Basins https://www.wsgs.wyo.gov/energy/oil-gas-basins.aspx

References

  1. 1.0 1.1 1.2 [1],Assessment of Continuous Oil and Gas Resources in the Mowry Shale, Wind River Basin Province, Wyoming, 2020 Fact Sheet 2021-3006 By: Thomas M. Finn, Christopher J. Schenk, Tracey J. Mercier, Cheryl A. Woodall, Marilyn E. Tennyson, Kristen R. Marra, Phuong A. Le, Heidi M. Leathers-Miller, and Geoffrey S. Ellis https://pubs.er.usgs.gov/publication/fs20213006.
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 [2],Stratigraphy of the Wind River Formation in South-Central Wind River Basin, Wyoming https://pubs.usgs.gov/pp/0594a/report.pdf.
  3. 3.0 3.1 3.2 3.3 [3],Wind River Reservation, https://www.bia.gov/sites/bia.gov/files/assets/as-ia/ieed/ieed/pdf/DEMD_OG_WindRiver_OilGasPlays_508_0.pdf.
  4. [4],Wyoming State Geological Survey, https://www.wsgs.wyo.gov/energy/oil-gas-basins.aspx.
  5. 5.0 5.1 5.2 [5],WIND RIVER BASIN PROVINCE (035) James E. Fox and Gordon L. Dolton, https://certmapper.cr.usgs.gov/data/noga95/prov35/text/prov35.pdf.

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