Studies and Field Data on a Cypress Sandstone ROZ in Illinois

Nathan D. Webb

CO2 & ROZ Conference

December 6, 2017

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AcknowledgmentsProject Co-PIs• Scott Frailey, Hannes Leetaru

Geology• Zohreh Askari, Leo Giannetta, John Grube, Kalin Howell, Yaghoob

Lasemi, Nathan Webb

Geocellular modeling and well log analysis• Nate Grigsby

Reservoir Simulation• Roland Okwen, Fang Yang

• Research herein was supported by the US Department of Energy contract number DE-FE0024431

• Through a university grant program, IHS Petra, Geovariences Isatis, and Landmark Software was used for the geologic, geocellular, and reservoir modeling, respectively

http://isgs.illinois.edu/research/ERD/NCO2EOR

Outline• Motivation

• ROZ Potential in the Cypress Sandstone of the Illinois Basin

• Identifying ROZs• Formative Mechanism

• Direct and Indirect Indicators

• Geologic Characterization

• Well Log Analysis

• ROZ Development Strategies (Oilfield Studies)• Modeling of Geology and Fluid Saturation Distributions

• Reservoir Simulation Strategies and Preliminary Results

• Summary

• Challenges for ROZ Identification

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Motivation: ROZ Potential in the Cypress Ss

• Thin oil reservoirs developed in the top of thick Cypress Sandstone in the Illinois Basin• Residual and mobile oil

above thick brine column

• Difficult to produce economically due to water coning • Underproduced resource in

the Basin

• Potential for underlying ROZ

MPZ

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Motivation: ROZ Potential in the Cypress Ss

• Nonconventional CO2-EOR and storage opportunity• NE-SW trending thick

sandstone fairway

• Bypassed oil in the conventional reservoir

• 0.2 to 2.3 Gt saline CO2 storage potential (DOE/MGSC, 2012)

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Identifying ROZs: Formative Mechanism

• ROZs form through successive oil migration in the subsurface

Modified from Lewan et al. 2002

May 2013

• Fairway of hydraulically connected sandstone bodies

• Strong regional northward water-drive• Related to Cretaceous

uplift of the Pascola Arch?

• Oil exited Cypress into Pennsylvanian sandstones• Along faults in drape

folded strata along the La Salle Anticline

• Via incised valley fill sandstones stratigraphically juxtaposed with the Cypress

Mariño et al 2015

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Identifying ROZs: Known Indicators

• ROZs generally identified via direct and indirect indicators• Direct

• Imbibition profile, oil degradation (tar/bitumen), fresh water• Indirect

• Oil shows in cuttings (florescence/odor), log estimated So, tilted OWC, native sulfur, calcite, basin evolution models, evaporite dissolution, solution enhanced fractures, high pressure, low oil cut

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Identifying ROZs: Cypress Study Indicators

Log Estimated So

• Analysis of existing logs

• Analysis of new logs coupled with core

• New cased hole pulsed neutron logs

Biodegraded oils

• Geochemical analysis of oil samples via GCMS

Oil Shows in Rock Samples

• Testing for oil saturation in new and existing cores via visible cut

• Evidence of petroleum trapped in mineral cements via petrography

Tilted OWCs

• Mapping of OWC in fields using log and perforation data

• Identification of potential relict oil-water contacts represented by mineral cements

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Geologic Characterization

• Interpreted the Cypress Sandstone as part of an incised valley fill system (LST-TST)• Erosional base, multistory sandstone, overall fining upward (f-vf)

• Amalgamated multistory fluvial channels• Heterogeneity exists but is subtle in an otherwise thick, clean very-fine to fine-

grained sandstone body; low lateral/vertical anisotropy• Channel storys constitute flow units

• Interconnected channel bodies form regional conduit for fluid flow

Howell et al. 2017

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Geologic Characterization• Depositional environment and diagenetic history

control reservoir properties

Field Depth to Cypress, ft Typical porosity, % Typical perm, mD

Loudon 1,600 19 81

Noble 2,600 18 482

Kenner West 2,600 18 106

Dale 2,900 14 63

Challenge for ROZ Identification – High φ, Low So

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Well Log Analysis

Water Saturation Profiles Fluid Contact Curves

Movable Hydrocarbon Index, Bulk Volume Water, Water Resistivity

Archie, Ratio, Dual Water

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Well Log Analysis• Micropores in clay minerals are sources of excess

conductivity• Conductivity can prevent detection and accurate estimates of low

oil saturation via well log analysis

Challenge for ROZ Identification – Clay minerals mask low So

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Well Log Analysis

2583

2588

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0% 5% 10% 15% 20% 25% 30% 35% 40%

Dep

th (

ft)

Clay Volume

Effective Clay Mineral Volume (Ve) and GR Volume of Shale (Vsh) Estimations vs. Depth

Ve Vsh (Clavier) Vsh (Stieber) Vsh (Larionov)

• SEM characterization of clay mineral microporosity allowed calibration of log analysis to clay mineral suite

• Also calibrating to new pulsed neutron cased hole logs

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ROZ Development Strategies (Oilfield Studies)

Oilfield Studies

• Noble

• Kenner West

• Loudon

• Dale

• Oilfields are mature with mostly old data

Challenge for ROZ Identification – Dearth of modern data

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Reservoir Characterization

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Year

Comingled Cumulative Cypress Cumulative

Comingled Yearly Cypress Yearly

• Cypress Production = 24 MMBO

• MPZ OOIP = 95 to 110 MMBO

• ROZ OOIP estimated at 60 MMBO

• Cypress Production = 1.3 MMBO

• MPZ OOIP = 8.5 to 10 MMBO

• ROZ OOIP estimated at 22 MMBO

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YearComingled Cumulative Cypress Cumulative

Comingled Yearly Cypress Yearly

Noble Field Kenner West Field

• Depth ~2,600 ft; Temperature ~90°F

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Reservoir Characterization – Noble Field

• 170 ft sandstone obliquely intersects anticline; structure/stat trap

Cypress net sandstone isopach mapOWC structure map

Oil reservoir isopach map

• SW tilted OWC; down dip oil saturation; Paleo-OWC related calcite cement?

• MPZ ~55 ft thick, ROZ ~20 ft; 110 ft closure – underfilled structure

Challenge for ROZ Identification – No physical samples from suspected ROZ

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Reservoir Characterization – Kenner West Field

• 100 ft thick, one mile-wide N-S sandstone trend intersects small dome forming structure/strat trap

Cypress net sandstone isopach map Oil reservoir isopach mapBase of Barlow Ls structure map

• MPZ ~35 ft thick, ROZ ~80 ft; 40 ft closure; SW tilted OWC

Challenge for ROZ Identification – No physical samples from suspected ROZ

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Modeling of Geology• Built geocellular models to reflect Cypress Sandstone geology in

oilfields• Encapsulated depositional and diagenetic facies

• Shaly, floodplain to estuarine facies at the top of the model

• Few thin shale interbeds and calcite cements within the sandstone

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Fluid Saturation Distribution

• Populated geocellular models with fluid saturation distributions based on well log analyses

• These models represented initial conditions for calibrating reservoir simulations

So (%)706050403020100

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Development Simulation Strategies

• Simulated field development strategies including different well patterns, spacing (including a horizontal well), and conformance scenarios

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Preliminary Simulation Results

• EOR produces additional oil over waterflood in the MPZ and MPZ+ROZ• 9.8% of MPZ OOIP produced via EOR

• 5.6% of MPZ+ROZ OOIP produced via EOR

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Summary

• Multistory valley fill Cypress Sandstone dominated by high energy fluvial deposits with good reservoir properties• Creates fairway for fluid migration and large, generally homogenous containers

for ROZ development

• Tilted OWCs were observed and possible relict OWCs were indicated by calcite cements supporting postulated ROZs

• Log analyses indicate possible ROZs below MPZ at Noble and Kenner West Fields• Interpretations of fluid saturation distributions are supported by historical

records (depths of producing perforations) and pulsed neutron logs

• Method is being used to look for ROZs elsewhere in the basin

• Reservoir simulations show CO2-EOR and CO2 storage potential in the Cypress Sandstone• Ongoing simulations to determine how to co-optimize oil recovery and CO2

storage

• ROZ can contribute incremental oil as part of EOR

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Challenges for ROZ Identification in the Illinois Basin

• Low So means the ROZ can easily be overlooked• Careful analyses required to make accurate assessments of the ROZ resource

• Microporosity in clay minerals provides an excess source of conductivity• Well log analysis must be calibrated to clay mineral suite to provide reliable

estimates of So

• Direct, physical evidence of ROZ resource is still needed• Core through entire thickness of the Cypress where an ROZ is suspected

• Old data is of lower resolution and is less reliable for identifying low oil saturations

• Thin MPZs and high water cut means little incentive to drill new wells

• Need to extend method developed at Noble/Kenner West to rest of Basin• Local calibrations may not be applicable regionally

• Not many documented clastic ROZs

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Nathan D. WebbAssistant Petroleum Geologist

ndwebb2@illinois.edu615 E. Peabody Dr. – Champaign, IL 61820-6918

+1 217 244 2426

http://isgs.illinois.edu/research/ERD/NCO2EOR

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References

• Howell, K.J., N.D. Webb, J.L. Best, 2017, Reservoir architecture and heterogeneity of multistory fluvial sandstones of the Mississippian Cypress Formation, Illinois, USA: Implications for CO2 storage and EOR: 11th International Conference on Fluvial Sedimentology, July 2017, Calgary, Canada.

• Lewan, M. D., M. E. Henry, D. K. Higley, and J. K. Pitman, 2002, Material-balance assessment of the New Albany-Chesterian petroleum system of the Illinois basin: AAPG Bulletin, v. 86, no. 5, p. 745–777.

• Mariño, J., S. Marshak, and M. Mastalerz, 2015, Evidence for stratigraphically controlled paleogeotherms in the Illinois Basin based on vitrinite-reflectance analysis: Implications for interpreting coal-rank anomalies: AAPG Bulletin, v. 99, no. 10, p. 1803–1825.

• May, M. T., 2013, Oil-saturated Mississippian–Pennsylvanian Sandstones of South-central Kentucky, in F. J. Hein, D. Leckie, S. Larter, and J. R. Suter, eds., Heavy-oil and oil-sand petroleum systems in Alberta and beyond: p. 373–406.

• Nelson, W. J., L. B. Smith, J. D. Treworgy, L. C. Furer, and B. D. Keith, 2002, Sequence Stratigraphy of the Lower Chesterian (Mississippian) Strata of the Illinois Basin: Illinois State Geological Survey, Bulletin 107, 70 p.