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Heavy oil resources have become a major asset base in the portfolio of many energy companies. Representative sampling and characterization of rock and fluids are essential for efficient and economical development of heavy oil reservoirs. This paper describes the challenges inherent in fluids and rock sampling, PVT and viscosity modeling, and fluid flow property measurements for heavy oil reservoirs. The key elements in obtaining representative bottom-hole fluid samples from an extra-heavy oil reservoir are described in this paper with examples. Special laboratory techniques are presented for obtaining equilibrium PVT and viscosity data on heavy oil samples. A compositional PVT model that captures the unconventional phase behavior and a viscosity model that quantifies the variations of viscosity with pressure, temperature, and GOR are also presented. Customized equipment and special techniques were employed to measure high-quality relative permeability data and to accurately determine the endpoint saturations such as critical gas saturation, remaining oil saturation, and the corresponding relative permeability. Examples of successful measurements of reservoir conditions steady-sate water-oil relative permeability are presented along with the unique equipment and techniques. This paper highlights a systematic approach for rock and fluid characterization of heavy oil reservoirs and identifies new technologies that have lead to its successful application. |
