The Green River and Wasatch formations in the Lake Uinta, and

DCA ~280m Oil-stained Sandstone Consortium Proposal: Lacustrine Reservoirs from Deep to Shallow: Facies Distribution, Architecture, and Source Rock Formation Green River Formation, Utah & Colorado Microbial Bioherm Kati Tänavsuu-Milkeviciene, Rick Sarg, and Jeremy Boak Department of Geology and Geological Engineering, Colorado School of Mines, Golden, CO Emails: ktanavas@mines.edu, jsarg@mines.edu, jboak@mines.edu Purpose: Integrated lacustrine stratigraphic and reservoir studies, including source rock analysis and characterization of the reservoir type and heterogeneity. Microbial carbonates Deltaic sandstones Figure 1. Architecture and lateral continuity of siliciclastic and carbonate intervals in the Upper Wasatch/Colton and Green River formations, White Face Butte (length of outcrop is ~4 km). Project Rationale (Why?): Predictive lacustrine models are few as compared with their marine counterparts. Recent discoveries in the lacustrine deposits and developments in unconventional gas and oil research have challenged existing depositional models for lake environments and understanding of the unconventional reservoir deposits. Models that have been used to characterize deposits and reservoir architecture are outdated, and there is a lack of good outcrop and subsurface analogues. The Green River and Wasatch formations in the Lake Uinta, and UT especially in the Douglas Creek Arch (DCA) area (Figs. 1 and 2), are exposed over tens of square miles. This, together with Lake Uinta thousands of subsurface electrical well logs and core, gives a unique possibility to study shallow to deep lake deposits in strike and dip directions over long distances and throughout the CO subsurface of the basin. Exposed lake deposits include microbial and non-microbial carbonates, sandstones, mudstones, and oil http://cpgeosystems.com/coloplat shale. Gilsonite veins, and carbonate and siliciclastic deposits impregnated with oil occur in the area. Organic rich intervals Figure 2. Location of Lake Uinta. follow carbonate or siliciclastic units and are separated by nonporous fine grained mud rocks. This outcrop area is directly adjacent to Green River producing oil fields where dense subsurface control and core exists and which contain both conventional (carbonate and siliciclastic and unconventional (shale oil) reservoirs. Superb exposure and continuous outcrops over long distances, core, and abundant subsurface control gives an excellent possibility for study of these mixed lake deposits both laterally and vertically and into the Uinta basin, to develop 3D depositional reservoir models for microbial and non-microbial carbonates, and for siliciclastic deposits. Oil at surface (Fig. 3) and organic-rich shale provide an opportunity to understand source rock

100m 5m properties, to study richness variation both laterally and through the entire stratigraphic section from the top of the North Horn to the bed 44 marker, and to document migration of oil in the Uinta basin area. Nearby Wasatch and Green River producing fields allow a direct tie and comparison to subsurface reservoirs and organic-rich shale. 5m Figure 3. Oil-bearing sandstone, middle Green River Fm., Three Mile Canyon. Objectives: 1. Construct regional well log cross sections tying the outcrop area to all producing Wasatch and Green River fields in Duchesne and Uintah counties. The outcrop covers a critical part of the eastern Uinta basin and encompasses exposures from the southeastern Uinta lake margin and transition to the lake center in a tectonically quiescent area, to the northeastern lake margin at Raven Ridge in a more tectonically active area. Log calibration will come from core and outcrop gamma ray logs previously collected by Jim Borer at Raven Ridge and augmented with our own outcrop logs to be collected further south. Westward from this outcrop area any changes in the depositional environments and facies of the Wasatch to Green River (Bed 44) stratigraphic section will be analyzed and documented into an overall basin depositional model. 2. Document the architecture and formation of reservoir intervals and critical/main source rock zones in the Wasatch and Green River formations in the basin (Fig. 1), using previously developed large-scale predictive basin models (Tänavsuu-Milkeviciene & Sarg, 2012), based on lake stages and large-scale sequence boundaries. Siliciclastic lithofacies comprise fluvial, deltaic (Figs. 1, 3 and 4), and shoreline sandstones that can be mapped in 3D over tens of square miles in both depositional dip and strike directions. Reservoir quality and continuity will be mapped over the outcrop area and tied to the subsurface. A Master s student (O Hara) (Fig. 4) is currently documenting and mapping two of these sandstone units in an area of transition from channels to channel mouth bars. The depth to the top and base of these various reservoir intervals and source rock zones will be identified and documented throughout the Uinta Basin at a density of one well per square mile in a spreadsheet database that ties the depth information to well identification numbers (API) for easy import into mapping databases. Master s student project Oil-bearing sandstone Figure 4. Continuous sandstone bodies, middle Green River Fm., Evacuation Creek (length of outcrop is ~2 km). 3. Build reservoir models for microbial carbonates and non-microbial carbonate grainstones based on the superb exposure of the shallow lake carbonate bodies (Figs. 1, 5 and 6). Oolitic grainstone units comprise the Cow Ridge Member of the Wasatch Fm. (Uteland Butte unit in subsurface), and crop out in a lake margin facies belt that extends over ten miles in the strike direction and on the scale of miles in the dip direction (Fig. 5). Microbial facies are present in the Green River Fm., and are persistent over miles in both depositional strike and dip directions (Fig. 6).

10m ~90m 4. Characterize organic-rich rocks throughout the subsurface of the Uinta basin, initially focusing on the lateral and vertical changes of organic-rich shale within R0-R1 interval (Black Shale of subsurface) (Fig. 7). Analyses will include changes in the richness, TOC, pyrolysis outputs, composition, and fracture patterns. 5. Construct regional isopach and facies maps of the various reservoir intervals and source rock zones throughout the Wasatch to Green River (Bed 44) interval. Utilize existing well control at a minimum density of one sample per square mile. 6. Provide an explanation or hypothesis as to the relationship between the lithology of these intervals and the electrical log responses of common subsurface logging suites (SP, Gamma Ray, Density and Neutron). Laterally continuous carbonates capping hill ~400m Basinward Figure 5. Channelized and shale-rich fluvial and lake deposits overlain by planar-bedded oolitic and skeletal lime grainstones, lower Green River and Upper Wasatch/Colton formations, Hells Hole Canyon. Figure 6. Biohermal microbialite, middle Green River Fm., Three Mile Canyon. Black shale interval Figure 7. Thick channel deposits that cut into black shale below lower Green River Fm., White Face Butte. Scope and Investigation plan: 1. Construct sub-regional well log cross sections tied to core and logs from subsurface oil field areas and outcrop gamma ray logs to extend the working regional framework developed by our group throughout the producing oil fields of the Uinta basin in Duchesne and Uintah counties. This work will incorporate the previous work of Jim Borer at Raven Ridge and incorporate correlation criteria developed in our own work in the Piceance basin outcrop and subsurface. This stratigraphic framework will provide the context for the following plans. 2. Conduct outcrop, core, and log based sedimentologic, and stratigraphic analysis at a minimum subsurface density of one well per square mile to a) determine depositional architectures, b) vertical and lateral changes in depositional trends, c) build 3D depositional models for different reservoir rocks (carbonates and siliciclastics), and d) document fracture patterns of the Wasatch to Green River (Bed 44) interval

throughout the oil producing areas of the Uinta basin. Construct regional isopach and facies maps of the various reservoir intervals and source rock zones throughout the Wasatch to Green River (Bed 44) interval. Utilize existing well control at a minimum density of one sample per square mile. The depths of the various bounding surfaces will be documented in a spreadsheet database that is tied to well identification (API) numbers. Theses surfaces will be documented in the subsurface at a minimum density of one well per square mile. 3. Document source characteristics of key organic-rich shale intervals, determine oil migration timing and migration pathways to describe source rock properties. 4. Provide an explanation or hypothesis as to the relationship between the lithology of these intervals and the electrical log responses of common subsurface logging suites (SP, Gamma Ray, Density and Neutron). 5. Integrate ongoing outcrop, core, and wireline log studies based on sedimentary investigations from the Lake Uinta (e.g. Tänavsuu-Milkeviciene, Sarg, Boak COSTAR; Vanden Berg, Birgenheier, Plink- Björklund Uinta basin). We will use the CSM inter-lake stratigraphic framework to determine the larger-scale lake evolution and smaller-scale 400Ky sequences that indicate changes during the lake evolution. Targeted strata and regions include: Upper Wasatch/Colton and Green River formations in the Douglas Creek Arch area and in the eastern portion of the Uinta basin. Deliverables: 1. Stratigraphic sections, isopach and facies maps of various depositional environments utilizing cores, well logs, and outcrops with lithofacies interpretations and photos. 2. Detailed GIS-based paleogeography maps of key time-slices in various formats including shape files and spreadsheet databases. 3. 3-D reservoir geo-models for carbonate and siliciclastic deposits. 4. Two yearly meetings for sponsors, including core workshops and field trips. 5. Exclusive consortium website for members. Team: Dr. Kati Tänavsuu-Milkeviciene, CSM, Co-PI (Sedimentology, stratigraphy of mixed and siliciclastic deposits) Dr. Rick Sarg, CSM, Co-PI (Petroleum geology and stratigraphy of carbonates and mixed deposits) Dr. Jeremy Boak, CSM, Co-PI (Mineralogy, organic-rich shale) Two-three graduate students (exact number will depend on available funding Advisors and collaborators: Drs. Piret Plink- Björklund and Steve Sonnenberg Timetable: Project start: Fall 2012 Duration of Phase I: 3 Years Membership: $35,000 per year per company, and/or in-kind contributions.

ADDENDUM CARBONATE PROJECTS For the carbonate lithofacies in the upper Wasatch and Green River Formation, the general objective is to build 3D reservoir models for microbial carbonates and non-microbial carbonate grainstones based on the superb exposures of the shallow lake carbonate bodies. Oolitic and bioclastic grainsupportstone units comprise the Cow Ridge Member of the Wasatch Fm. (Uteland Butte unit in subsurface), and crop out in a lake margin facies belt that extends over ten miles in the strike direction and on the scale of miles in the dip direction. Microbial facies are present in the Green River Fm., and are persistent over miles in both depositional strike and dip directions. The following specific projects are proposed: 1) Description of lithofacies, diagenesis, and pore architecture of the oolitic and bioclastic grainsupportstones of the Cow Ridge Member of the Wasatch Formation and construction of a 3D geomodel for these grainsupportstones. This unit crops out in three major canyons in eastern Utah (Evacuation Creek, Missouri Creek, and Hells Canyon) that comprises laterally continuous outcrops in both dip and strike directions for distances of 2-3 miles in dip direction and 10+ miles in the strike direction. This allows a unique opportunity to document the lateral and vertical facies and pore system variability over 20 square miles. Meso-pore types identified to date include interparticle, moldic, and vuggy porosity. Pore system analysis will include high resolution QEMSCAN imaging of pore structure tied to CMS-Mercury-N gas absorption measurements to identify the macro- to nano-porosity. This project is conceived to be a Ph.D dissertation. A simulation ready Petrel geo-model will incorporate the results of this work. 2) Description of the lithofacies, diagenesis, and pore architecture of 1-2 of the microbial carbonate units within the Green River Formation, and construction of a 3D geo-model for these bindstone and associated breccia and pisolitic facies. These facies display a high permeability, macro-pore system of fenestral and vuggy pores. Several of these microbialite units can be traced in canyons and across almost continuous valley walls for distances of 4-5 miles in both dip and strike directions, providing the opportunity to develop a 3D depositional model for these rocks. Diagenetic analysis will include SEM and stable isotope analyses to supplement standard petrographic description. Pore system analysis as described in No. 1 above will be supplemented with serial polished slabs to help construct a 3D digital image of the macro-pore system within these microbialites. This project is conceived to be a Ph.D dissertation. A simulation ready Petrel geo-model will incorporate the results of this work. 3) A number of microbial bioherms are present in the area and are on the scale of meters across and up to 15 meters thick. Detailed depositional and diagenetic study of one or two of these bioherms is proposed to understand their facies composition, growth, and diagenetic alteration. Diagenetic and pore system documentation will be as above. As these bioherms are thought to be part of more extensive sheet-like carbonate beds, results from this work will be incorporated into the 3D Petrel geo-model in No. 2 above. This project is conceived as an Master s project, but could be expanded if necessary. 4) Small microbial and non-microbial spring deposits are present in the outcrop area within the Green River Formation. These tend to occur within shoreline microbial and non-microbial grain-rich carbonate units. These provide the opportunity to document the character of these tufa and travertine deposits and to document their relationship to the adjacent non-spring carbonates. Detailed petrographic and geochemical analyses are proposed to document spring development, spring water character, and the ensuing diagenetic alterations. Pore system analysis is as above. This project is conceived as an Master s project, but could be expanded if necessary. The above list of projects is preliminary and can be added to as work progresses. Feedback is welcome.