Modelling Development of a Thermal Gas/Oil Gravity-Drainage Process in an Extraheavy-Oil Fractured Reservoir
- Eider Niz-Velasquez (Shell Canada) | S. R. Bagheri (Shell Canada) | Johan J. van Dorp (Shell Canada) | Marco L. Verlaan (Shell Canada) | James W. Jennings (Shell International E&P Co.)
- Document ID
- Society of Petroleum Engineers
- Journal of Canadian Petroleum Technology
- Publication Date
- July 2014
- Document Type
- Journal Paper
- 234 - 246
- 2014.Society of Petroleum Engineers
- 4.1.9 Tanks and storage systems, 5.4.6 Thermal Methods, 5.5 Reservoir Simulation, 5.5.3 Scaling Methods, 5.8.7 Carbonate Reservoir, 4.3.3 Aspaltenes, 5.2.1 Phase Behavior and PVT Measurements, 4.1.5 Processing Equipment, 5.8.6 Naturally Fractured Reservoir, 5.5.2 Core Analysis, 5.3.9 Steam Assisted Gravity Drainage, 4.6 Natural Gas, 5.5.8 History Matching, 5.7.2 Recovery Factors, 5.1.2 Faults and Fracture Characterisation, 5.2.2 Fluid Modeling, Equations of State, 2 Well Completion, 5.1 Reservoir Characterisation, 5.6.3 Deterministic Methods, 5.4.7 Chemical Flooding Methods (e.g., Polymer, Solvent, Nitrogen, Immiscible CO2, Surfactant, Vapex), 5.1.1 Exploration, Development, Structural Geology, 5.1.5 Geologic Modeling
- extraheavy oil, steam injection, gas/oil gravity drainage, fractured reservoirs, thermal recovery processes
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Thermal gas/oil gravity drainage (T-GOGD) is an attractive enhanced-oil-recovery method applicable to naturally fractured reservoirs (NFRs). The process is applied successfully in Qarn Alam, a heavy-oil field in Oman. This paper presents a case study featuring dynamic-modelling optimization and uncertainty-analysis workflow for T-GOGD in a bitumen-bearing fractured reservoir on the basis of realistic 3D fracture characterization. In T-GOGD, the fractures are displaced to steam to provide a
(matrix) gravity-drainage potential while heating the reservoir at the same time. One of the recovery mechanisms associated with T-GOGD is thermal expansion, which can result in high initial rates, but may cause plugging of the fracture system in the case of extraheavy oil (bitumen) if the expanded oil cools down before it is being produced. This situation requires short-distance well configurations and/or steam-stimulation cycles to establish communication. In an NFR, steam vapour occupies the fracture system while oil drains through the matrix, increasing the area for heat transfer with respect to the steam-chamber case; the process therefore differs significantly from steam-assisted gravity drainage, and a different production function applies. Shell’s in-house reservoir simulator MoReS with advanced dual-permeability capability is used to model development of T-GOGD in a bitumen reservoir employing 3D element-of-symmetry (EOS) models. A realistic fracture-characterization and -modelling process is described. The geometrical well configuration and operating schedule and strategy are optimized on an economic function for a deterministic subsurface realization. Using an uncertainty-analysis work flow, cumulative distribution functions of recovery and steam/oil ratio (SOR) are generated. Finally, robust optimization is explored by use of an economic objective function. The study concludes that (1) relatively large well spacing is feasible while injector/producer horizontal well offset is necessary to avoid steam channeling to the producer well, (2) live steamproduction control is a robust operating strategy, (3) performance is most sensitive to matrix permeability and oil viscosity, and (4) vertical fracture connectivity plays an important role in the process performance. T-GOGD has significant potential to develop the bitumen resource in naturally fractured carbonates.
|File Size||6 MB||Number of Pages||13|
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