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www.petrelrob.com
Characterization of Belloy, Kiskatinaw,and Debolt Water Disposal Zonesin the Montney Play Area, NEBC
Brad J. HayesPetrel Robertson Consulting Ltd.
Introduction
• Intensive development activity in the Montney fairway has substantially increased volumes of flowback and produced water being injected into deep reservoirs
• B.C. Oil & Gas Commission has noted issues with performance of deep injection wells, indicating inadequately-understood variability of reservoir quality and capacity
• A study was commissioned, with support from Geoscience BC, to investigate Belloy, Kiskatinaw, and Debolt disposal zones
• Petrel Robertson – reservoir characterization to identify capacity to act as secure disposal zones
• Canadian Discovery – reservoir engineering and geomechanics
Montney Play Fairway
• Most development is currently in the Peace River Block and northwestern Foothills areas
• Continued expansion taking place, although at a reduced pace in the current economic environment
BC Oil & Gas Commission
• OGC sees several important factors influencing the “favourability” of potential disposal zones
• Proximity to mapped faults / fractures / structures • Seismicity risks when large water volumes are injected?
• Hydrocarbon exploration / development potential in underlying reservoirs
• Risk in new wells drilled through high-pressure disposal zones?• Hydrocarbon exploration / development potential in bounding
formations that are expected to provide a seal to injected fluids –e.g., lower Montney just above Belloy
• Could development jeopardize seal integrity?• Proximity to existing production in the disposal formation
• Potential to reduce recovery factors?
• “Favourability” maps will be drawn to include these factors, in addition to reservoir quality
Disposal Zone Considerations
Debolt Depositional Setting
• Carbonate ramps prograded regionally northwestward during Early Carboniferous (Mississippian) time
• Spectrum of proximal to distal carbonate ramp facies
• Dominantly limestones, locally and sub-regionally dolomitized
• Internal stratigraphy not well documented
Richards et al, 1994
Debolt Situation
• Xxx wells
• Very few penetrations in SW
• Gas pools and Blueberry oil pool in conventional Foothills fault traps
• Reservoir rock in the NW primarily in thin zones of fractured hydrothermal dolomites
• More substantial contribution from low-temperature dolomites in Blueberry area
Favourability map area
Debolt – Regional Dolomitization
• Regional, low-temperature, fabric-selective dolomites
• Focused in proximal ramp and shoal carbonates with good primary reservoir quality in upper 50m
• Continuous vuggy / moldic / intercrystalline porosity
Durocher and Al-Aasm, 1997
Debolt Structure
• Northwesterly Disturbed Belt structure a product of both Laramide and Antler orogenic episodes
• Structural features are taken from existing papers, reports, pool studies, and verified using structural elevations from wellbores
• Insufficient well control to define FSJ Graben structureswith confidence
Debolt Favourability
• Favourable area governed primarily by distribution of low-temperature dolomites in uppermost Debolt
• Many existing disposal wells are close to major faults
Stoddart-Belloy Setting
• Carboniferous – Permian subsidence of Fort St John Graben exerted profound influence on Stoddart Group and Belloy deposition
Barclay et al, 1990
Stoddart-Belloy Deposition
• Progressive subsidence in tensional (normal faulting) regime created huge accommodation space in the middle of the FSJ Graben throughout the Carboniferous
• Reduced influence by Belloy (Permian) time
Barclay et al, 1990
End Golata time
End Kiskatinaw time
End Taylor Flat time
End Belloy time
Stoddart-Belloy Stratigraphy
Barclay et al, 2002
• Substantial and mappable reservoir quality in proximal Belloy and Kiskatinaw facies
• Belloy / Taylor Flat boundary difficult to pick regionally, particularly in basin centre
Kiskatinaw Situation
• Xxx wells• Very few penetrations in SW• In NW, the section is
extensively faulted and in distal, thinly-bedded facies, so has little reservoir capacity
• Existing production and best continuous reservoir quality in thick, quartzose sandstones,
• Deposited primarily in estuarine valley-fill and related environments
Favourability map area
Kiskatinaw Valley-Fill Reservoirs
• Sharply-defined estuarine valley-fill trends hostsubstantial reservoir-quality rock
• Quartzose sandstones, variably carbonate-cemented
Barclay et al, 2002
Kiskatinaw Structure
• Complex structural / stratigraphic relationships in Fort St John Graben
• Published fault trends provide some insights, but well control demonstrates abrupt thickness and stratigraphic changes that require detailed seismic work to resolve
DEPOSITIONAL LIMIT
Kiskatinaw Favourability
• Faulting and existing production restrict favourable areas
• Broad favourability trends require refinement with additional well control
ACID GAS DISPOSAL
Belloy Situation
• Xxx wells• Some penetrations in the far south,
but most are incomplete• In NW, the section is extensively
faulted and in distal, thinly-bedded facies, so has little reservoir capacity
• Regional structural / stratigraphic trap at Eagle-Stoddart
• Most other pools relatively small
Favourability map area
20
Belloy Biostratigraphy (Fossenier)
• Complex stratigraphic relationshipsnot resolvable without detailedbiostratigraphic analysis
Belloy Stratigraphy, Eagle-FSJ Area
• Complex intra-Belloy stratigraphic relationships
• Channelized reservoirs limit aquifer / disposal zone continuity
Leggett et al, 1993
Belloy Structure
• Structural and stratigraphic offsets are notable across mapped faults, but much less pronounced than at Kiskatinaw level
• Equivalent strata not readily picked in NW area
Belloy Favourability
• Faulting and existing production restrict favourable areas
• Broad favourability trends require refinement with additional well control
ACID GAS DISPOSAL
WATER DISPOSAL
• Areas favourable for disposal are significantly restricted by reservoir quality, faulting, and existing production
• But many existing Debolt disposal wells are close to major Laramide thrust faults, and should yield data to support determination of risk arising from fault proximity
• Reservoir lithologies in all three formations are intricate blends of clastics and carbonates, and are difficult to characterize from logs
• Analysis of core and cuttings crucial to understanding reservoirs locally
• Development of lower Montney targets may pose risks to seal integrity for underlying disposal zones in SE and NW, and require further assessment
Summary and Conclusions
• Substantial disposal zone potential exists in shallower zones (e.g., Halfway Fm), but these would be penetrated by Montney development wells
• Reservoir engineering and geomechanical work should better define potential disposal zone capacity and risks
Summary and Conclusions