Geology

On September 12^th, Scott Ellingson, a contract Petroleum Geologist with the Enhanced Oil Recovery Institute, and John Frederick, a consulting Geophysicist, presented Alpha Field - Exploitation and reservoir characterization of the Minnelusa C Sand using sequence stratigraphy and modern 3-D seismic, Powder River Basin, Wyoming.  Mr. Ellingson and Mr. Frederick summarized their work, concluding that calculations for the original oil in place at Alpha Field has increased to 19.1 MMBO and that the new data indicate two proved undeveloped locations. (PUDs). Furthermore, their work enabled them to predict rates of deliverability for these two new potential drill sites.

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New thoughts and queries about the Muddy Formation in the Powder River Basin focusing on ways that could improve production.

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The rock layers surrounding Alcova Lake are not only breathtaking to see, they are also windows to a portion of the earth’s history. This guidebook hopes to introduce anyone interested to a brief explanation about what the geology is revealing.

EORI shares this guidebook as part of its commitment to facilitating technology transfer through publications and oral presentations.

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At Rozet Field, the lack of abundant core analyses or modern logs necessitates the adoption of more assumptions than usual in order to estimate OOIP and remaining recoverable reserves. Two different methods for calculating the recovery efficiency of the waterflood were applied withinnine 5-spot patterns resulting in maximum rates of 40% and 30% respectively. Average recovery factors in the combined 5-spot patterns are 27.5% and 24.4% respectively. Both values indicate the waterflood is probably not as effective as it could have been when compared to similar fields producing from the Muddy Formation.

The calculated OOIP for the Muddy Formation at Rozet is about 74.7 million barrels, of which a little over 19 million barrels have been recovered. The recovery factor for the field is then about 25.5%. If a 40% recovery factor is achievable with an efficient waterflood, then the remaining recoverable oil reserves from the Muddy Formation at Rozet Field are approximately 10.8 million barrels. This magnitude of a target should warrant further investment in improved and enhanced recovery methods there.

At nearby Windmill Field, secondary recovery has yet to be implemented in the Muddy reservoir. Wireline log suites containing porosity logs in this field enable more confidence in the geologic mapping and OOIP calculations than at Rozet. Cumulative oil production there is 677,735 barrels, resulting in a recovery factor of about 14.8%. Assuming the clay content does not vary significantly from that observed at the adjacent Rozet Field, a well-designed waterflood should be effective at increasing production in Windmill Field. If a recovery factor of 40% could be achieved by implementing secondary recovery efforts there, it could result in the production of an additional 1,157,465 barrels of oil.

• Nine different reservoirs in seven fields have employed fieldwide CO2 EOR in Wyoming.
• Between 2010 and 2020, incremental oil recovery from the nine CO2 EOR projects accounted for over 10% of Wyoming’s total oil production.
• Wyoming is not constrained by CO2 sources that can be used for EOR projects.
• Wyoming is also not constrained by fields potentially amenable to CO2 EOR.
• Wyoming is not constrained by pipeline capacity for additional CO2 transport, but is hampered by the existing pipeline system not reaching many of the best-potential fields, especially in the Big Horn Basin.
• The most successful CO2 floods resulted from proper reservoir characterization and associated optimized project design. Wyoming has seen incremental oil recovery from individual CO2 EOR projects as high as 18% of OOIP and volumes as high as 30 million barrels.
• Where net CO2 efficiencies could be calculated, CO2 efficiency is as low as 6 Mcf/bbl of incremental oil recovered, which compares very favorably to other successful projects around the world.

Reservoir characterization and predictive modeling has provided options for enhancing production in a recently discovered trend in the Muddy Formation near Hirsch Field, in northeastern Campbell County, Wyoming. This report outlines the procedures followed to develop a detailed 3-D geologic model of the Muddy Formation in the Hirsch area and provides the results of simulations run on 73 different scenarios for developing the reservoir. This study can serve as a template for operators interested in exploring possible ways to improve production in their own fields.

Nick Jones of EORI explores the application of Permian Basin ideas to the Bighorn Basin through the use of cores, cuttings, well logs, PI cards, and more.

Osage Partners, LLC. a Wyoming based operator contacted EORI and requested the institute’s assistance regarding their Muddy/Newcastle assets. The operator provided EORI with core from four wells and associated data related to the Osage field in the Powder River Basin. The operator requested that EORI characterize the clay mineralogy of the pay sands using XRD, SEM, and CEC analysis of samples from the provided core.

Eolian petroleum reservoirs are found worldwide, many having high-volume production of both oil and gas. As with any geological rock unit, each oil/gas field has production characteristics peculiar to its geological history. However, certain common factors link most eolian reservoirs. Cross-stratification due to bedform migration can influence sweep direction and efficiency. The various kinds of primary eolian strata have different poroperm characteristics. Moreover, stacking of sand seas or bedforms through geological time can create distinctive reservoir flow units in the subsurface. Tectonic activity, especially faults, may create shear zones with reduced poroperm, or partition a reservoir into structurally defined flow units. Faults may also create high-permeability zones that allow water breakthrough. Eolian reservoirs are commonly thought of as clean, and rather simple. However, in some places they are complex in terms grain composition or texture. They are commonly cemented by carbonates, anhydrites or salt, which sets up fabricselective or non-fabric selective patterns of secondary porosity in reservoirs.

There are two main themes of this poster. The first theme is to provide an update on the stratigraphy and sedimentology of the Tensleep/Casper Formation of Southeast Wyoming (and parts of Northern Colorado), and oil production from these rocks. We incorporate new measured sections, stratigraphic analysis and petrographic work undertaken by the authors. To this end we created a new database in ArcGis (geographic information software) of tops and other information that updates the historical well database of the Wyoming Oil and Gas Commission archived in Casper. This new database has been used to create Common Risk Segment (CRS) maps of the Upper Tensleep oil play in Southeast Wyoming. These CRS maps indicate trends in Tensleep reservoir, charge and trap that are useful in planning further exploration. It is possible that use of advanced seismic techniques applied over the complex structural terrains in the identified high potential areas of SE Wyoming will produce new leads and ultimately, new discoveries.

Thermal maturity, the degree to which the total organic carbon in a formation has been transformed from kerogen to producible hydrocarbons due to heat and pressure, is an important measure for not just the quality of a source rock, but also helps for delineating areas more favorable for unconventional drilling. EORI’s report of thermal maturity of the Mowry Shale in the Powder River Basin provides a detailed map based on a large public T_max data set.

Key observations include:

• Nearly all of the Mowry deeper than 8000’ currently generates hydrocarbons
• The basin axis has shifted slightly westward since the Mowry began generating hydrocarbons
• The Mowry 8000’ line plays an important role in demarcating the over-pressured Mowry and related clay diagenesis.
• The maximum maturity levels in the Mowry are in the “wet gas” stage

Wyoming, perhaps more than any other state, is dependent on revenues generated from the development and sales of minerals within its borders and has a vested interest in ensuring that its resources are properly and efficiently exploited. Maximizing the efficiency of oil and gas production in Wyoming is one of the primary goals of the Enhanced Oil Recovery Institute (EORI). Potential methods or practices that can improve or enhance the recovery efficiency of oil and gas production in the state are of paramount interest. Likewise, those policies or practices that hinder such efforts are also important to discuss.

Wyoming has nearly one billion barrels of proved oil reserves, a significant portion of which is still on primary production. Assessing the potential for secondary recovery from current oil fields is always a daunting task and requires evaluations regarding whether any given field will respond favorably to secondary recovery efforts.

This paper makes general assumptions regarding the feasibility of using a water flood to enhance oil recovery in a field based on publicly available data. The conclusions resulting from these assumptions are meant to be a guideline for the potential of future water flooding and are not meant to provide detailed evaluations of any given field’s ultimate recovery.

Ash Minnelusa Unit Conclusions

• Monitor, monitor, monitor. Make changes based upon reservoir response.
• Improved understanding of the problem improves process application and results
• Volumetric sweep (gels) should be applied before mobility control
• Implement gel processes early for maximum benefits
• Incremental oil expected to exceed 400,000 BBLS (18.4%%5 OOIP) for $0.88/BBL
• Field experience is critical with gel processes. Experience at Ash can be applied to other reservoirs

Background and objective

How do the high K strikes in core data possibly impact oil production Ash Creek field in Pilot 3?

Outline:

• Introduction & model settings
• Comparison of the simulation results
• Primary analysis of Ash Creek data
• Conclusions

Conclusions

1. The synthetic models of Pilot 3 area are generated and the simulations are completed.
2. The high values of core permeability do impact the production, injection efficiency, and sweep efficiency.
3. In general, an uniform permeability distribution over the entire field is better for high production, high injection and high sweep efficiency over the entire field.
4. However, in a small local area, cells having high permeability seems better for production. seems better for production.
5. High heterogeneity of the field made a high remaining oil in place and a high homogeneity field will produce a high amount of oil.

Polymer-augmented waterflooding of the Minnelusa in Wyoming has proven to be a successful method for improving production in most cases compared to normal waterfloods. Polymer is a lowcost, low-risk option when considering a method for enhancing production of a particular field. Its primary function is to improve the mobility ratio of the injected water by increasing its viscosity, thereby improving the volumetric sweep and conformance within the reservoir.

Advantages of using polymer include: (1) low cost, (2) preventing early water breakthrough, (3) improving volumetric sweep and conformance, (4) increasing oilwater ratios, (5) mobilizing oil that would likely have been bypassed under normal waterflood conditions, (6) mitigating heterogeneous permeabilities within the reservoir, and (7) other enhanced oil recovery injection technologies can still be applied after the polymer flood. Most, but not all, Minnelusa fields examined exhibited improved recoveries using polymer compared to fields under conventional waterfloods. Uneconomical polymer floods can be caused by a variety of factors, chief of which is the failure to properly understand the internal architecture of the reservoir prior to initiating the flood.