Technological Development Synergy: Kisbey, Saskatchewan—A Case History
David L. Sturrock, Gilbert M. Cordell, Don C. Westacott, David M. Fitzpatrick, 1991. "Technological Development Synergy: Kisbey, Saskatchewan—A Case History", The Integration of Geology, Geophysics, Petrophysics and Petroleum Engineering in Reservoir Delineation, Description and Management, Robert Sneider, Wulf Massell, Rob Mathis, Dennis Loren, Paul Wichmann
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Synergy between geology, petrophysics, and engineering in the development of the Kisbey Oil Field has led to significant economic benefits in all stages of field exploitation. Detailed integration of advanced petrophysical technology and geological analysis created an enhanced reservoir description which provided input to a synergistic reservoir simulation model. This model fed back into the development drilling strategy and provided a basis for production operations optimization. Data from innovative production techniques was fed back into the reservoir simulation model to create an overall production plan which has led to dramatically lower operating costs.
The Kisbey Oil Field is located in Township 8, Range 6 W2 in the Mississippian "buried hill" trend on the northwest flank of the Williston Basin in southeastern Saskatchewan, Canada. Trapping is caused by a major erosional valley on the Mississippian erosional surface truncating the reservoir units updip and on the flanks of the field. Production is obtained from the Mississippian Kisbey Sandstone with several wells providing additional production from the Mississippian Frobisher and Alida Beds.
Detailed core examination and Mineralog* analysis show the Kisbey to be a complex lithologic mixture. It consists of reservoir quality dolomitic sandstone interbedded with high porosity-low permeability sandy dolomite, both cemented to varying degrees with anhydrite. It is difficult, with conventional log analysis of the Kisbey interval, to determine lithology. In addition, conventional log analysis yields 60 to 80 percent water saturations for intervals producing with a negligible water cut.
Petrographic examination of the Kisbey sandstone reservoir reveals a two-porosity system consisting of intergranular porosity between sand grains and micro-intercrystalline porosity in the dolomite cement. Using this concept together with accurate cementation and saturation exponents determined from core analysis and Electromagnetic Propagation Tool (EPT)** log calculations, a detailed lithologic and pore geometry model for the Kisbey interval was constructed. Recently developed high resolution wireline log measurements processed with thin-bed definition techniques were interpreted using a multi-mineral log analysis program constrained by the lithologic model.
Data from this evaluation was integrated with extensive relative permeability, capillary pressure, and PVT analyses into field-scale reservoir simulations. An interactive approach was employed involving engineers, a geologist, and a petrophysidst to "fine tune" the model to actual field results. The reservoir model recognized a strong aquifer as the dominant depletion mechanism and identified a number of drilling opportunities.
The model also predicted that recovery is not rate sensitive, which led to individual well optimization. Full life forecasts for the field provided the basis for field consolidation and battery construction.
In summary, the integrated approach optimized field development by drilling fewer wells in better places, optimizing individual well production, and planning a production facility designed specifically to the long-term requirements of the field.
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The Integration of Geology, Geophysics, Petrophysics and Petroleum Engineering in Reservoir Delineation, Description and Management
Bima Field, offshore northwest Java, is a sizeable reservoir containing reserves of approximately 700 MM bbls OOIP with a 50 BCF gas cap. At present only the northern 1/3 of the field is developed, with 7 platforms and 54 producing wells, of which 20 are horizontal. The field has multiple drive mechanisms and high viscosity oil (21 cp), resulting in rapid GOR and water-cut increase after 3 years of production. The high stakes (both reserves and facility investments) and the reservoir's complexities, make an effective reservoir management scheme critical. For this reason an integrated geological, geophysical and engineering description was carried out to provide a 3-D Reservoir Simulation Model to evaluate development options. Geologically, the Oligo-Miocene age Batu Raja Limestone was deposited on the Seribu Platform, a basement-controlled, fault- bounded structure. The Upper Batu Raja carbonate build-up is thickest on the structurally highest parts of the platform where the rock comprises a series of "cleaning upwards" cycles (muddy deposits overlain by progressively more grain-rich sediments). A Lower Miocene drop in sea-level caused subaerial exposure of much of the platform and leaching by meteoric fluids. This diagenetic event resulted in contrasts in the reservoir quality (porosity, permeability, fluid saturations) at various intervals of the Upper Batu Raja. Based on these dissimilarities, the reservoir was zoned into 6 model layers. Once zonation was established, well logs could be calibrated to whole and sidewall core. A dense grid of seismic data were used to map the Batu Raja structure. From these data, color seismic inversion sections were produced and calibrated to the well logs. The calibrated seismic data were then used to map the top of structure, the carbonate build-up's edges, the total thickness of the Upper Batu Raja (needed to control aquifer size in the model) and the thickness of the main pay zone (layers 1-3). Engineering reservoir description began with a detailed compilation of capillary pressure, relative permeability, production and DST data. The 3-D simulation model required special treatments, including varying the GOC depths to honor separate gas cap closures; making permeability pressure dependent in poorly-consolidated zones; and setting up horizontal well completion treatments. Results suggest that water injection into the oil rim and gas cap is an effective approach toward maximizing recoveries and minimizing gas cap resaturation. However, waterflood reserves are sensitive to injection timing. The synergistic approach of geological, engineering and geophysical input into the Bima reservoir study has had impact by delivering a reservoir management tool that can evaluate future development expansion and possible gas sales. The simulation model can also track fluid migration during the field's producing life. The geological/geophysical model led to an enhanced understanding of Batu Raja depositional and diagenetic processes that has potential in regional exploration strategies.