The Dynamics of Reservoir Fluids and their Substantial Systematic Variations
- Oliver C. Mullins (Schlumberger-Doll Research) | Julian Y. Zuo (Schlumberger HPS) | Kang Wang (Schlumberger BGC) | Paul S. Hammond (Schlumberger-Gould Research) | Ilaria De Santo (Schlumberger Geoservices) | Hadrien Dumont (Schlumberger NAO) | Vinay K. Mishra (Schlumberger NAO) | Li Chen (Schlumberger NAO) | Andrew E. Pomerantz (Schlumberger-Doll Research) | Chengli Dong (Shell Exploration and Production Co.) | Hani Elshahawi (Shell Exploration and Production Co.) | Douglas J. Seifert (Saudi Aramco)
- Document ID
- Society of Petrophysicists and Well-Log Analysts
- Publication Date
- April 2014
- Document Type
- Journal Paper
- 96 - 112
- 2014. Society of Petrophysicists & Well Log Analysts
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- 260 since 2007
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Downhole fluid analysis (DFA) is used to characterize compositional fluid gradients, and equations of state (EoS) models are used for analysis to delineate reservoir fluid variations, connectivity and other complexities. A series of reservoirs is examined to assess the state of the contained fluids in terms of thermodynamic equilibrium in the reservoir. Substantial, systematic fluid variations are found using DFA. The cubic EoS is used for gas-liquid analysis, and the Flory-Huggins-Zuo EoS and the Yen-Mullins model of asphaltenes are used for analysis of dissolved solid-solution equilibria of reservoir crude oils. ‘Young’ reservoirs exhibit large, nonmonotonic variations of fluids (and solids), moderately aged reservoirs exhibit monotonic, yet disequilibrium properties and ‘aged’ reservoirs are fully equilibrated even when in massive scale. Nevertheless, these old reservoirs retain significant fluid and organic solid variations as a result of sequential fluid-related processes in geologic time.
The dynamic behaviors of fluids within reservoirs that account for these variations are obtained by linking a fundamental understanding of petroleum with basic concepts from fluid mechanics. In particular, the location of tar deposition within reservoirs is clarified when formed due to asphaltene instability upon a secondary reservoir fluid charge. Tar deposition can be formed upstructure for rapid gas charge, as is regularly seen in young reservoirs, or can be formed at the oil-water contact for a slower gas charge, as seen in many older reservoirs. The state of the reservoir fluids within the context of geologic time is shown to be tightly coupled to key reservoir concerns for production. Thus, understanding the context of the reservoir within the overall geology and petroleum system can be used to optimize reservoir evaluation. The expanding capabilities of DFA, plus major advances in asphaltene science, have revealed dramatic systematic variations of reservoir fluids and are becoming indispensable for optimization of production.
|File Size||9 MB||Number of Pages||17|