Characterization of Belloy, Kiskatinaw, and Debolt Water Disposal Zones in the Montney Play Area, NEBC Brad J. Hayes Petrel Robertson Consulting Ltd. www.petrelrob.com
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 BC Oil & Gas Commission 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
Disposal Zone Considerations 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
Strat Column MONTNEY Production Preferred Disposal Zones
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 Favourability map area 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
Debolt Regional Dolomitization Durocher and Al-Aasm, 1997 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
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 structures with 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 End Golata time End Kiskatinaw time Reduced influence by Belloy (Permian) time End Taylor Flat time Barclay et al, 1990 End Belloy time
FSJ Graben Correlations West (Monias) East (Dunvegan) Barclay et al, 1990
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 Barclay et al, 2002 Sharply-defined estuarine valley-fill trends host substantial reservoir-quality rock Quartzose sandstones, variably carbonate-cemented
Kiskatinaw Structure Complex structural / stratigraphic relationships in Fort St John Graben DEPOSITIONAL LIMIT Published fault trends provide some insights, but well control demonstrates abrupt thickness and stratigraphic changes that require detailed seismic work to resolve
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 Favourability map area Regional structural / stratigraphic trap at Eagle-Stoddart Most other pools relatively small
Belloy Biostratigraphy (Fossenier) Complex stratigraphic relationships not resolvable without detailed biostratigraphic analysis 20
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 WATER DISPOSAL ACID GAS DISPOSAL
Summary and Conclusions 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
Characterization of Belloy, Kiskatinaw, and Debolt Water Disposal Zones in the Montney Play Area, NEBC Brad J. Hayes Petrel Robertson Consulting Ltd. www.petrelrob.com