Studies and Field Data on a Cypress Sandstone ROZ in Illinois...• Through a university grant...
Transcript of Studies and Field Data on a Cypress Sandstone ROZ in Illinois...• Through a university grant...
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
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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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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
[email protected] 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.