Solid reservoir bitumen is a reservoir-altering cement (Lomando,
1992). Within the porosity of oil and gas reservoirs, it occurs as
droplets, grain coatings, or as honeycomb or finger-like bodies.
Solid reservoir bitumen may be finely dispersed throughout the
porosity or may be localized in a particular interval, potentially
creating a fluid barrier (e.g., a tar mat). If solid reservoir
bitumens are present in the reservoir, they typically reduce
permeability significantly even when found in only moderate amounts
(Lomando, 1992).
Since solid bitumen may be formed by different processes, it
will vary in chemistry. Some varieties contain predominately
saturate-rich hydrocarbons soluble in organic solvents, while other
solid bitumens may contain predominantly solvent-insoluble
asphaltenes and resins (Hwang et al., 1998). The various types and
chemical compositions of solid bitumen will also differentially
impact the producibility of the associated fluids in the
reservoir.
Solid reservoir bitumens are reported as porosity by routine log
suites; consequently, their presence affects reserves calculations,
recovery factors, and secondary recovery programs. Thus all phases
of oil field exploitation, including exploration,
development,
and production
are impacted by the presence of solid reservoir bitumens.
For an accurate assessment of the impact of solid reservoir
bitumen on the production of fluids from the reservoir, OilTracers
LLC recommends resolution of the following properties:
- Reservoir bitumen type
- Bitumen solubility
- Formation mechanism
- Volume of bitumen in the reservoir,
- Distribution of solid bitumen in the reservoir.
The study of solid bitumen requires examination and analysis of
conventional or sidewall core and analysis of associated
hydrocarbon fluids. Geochemical analyses may include: high
resolution gas chromatography, separation of compound class
fractions (saturated hydrocarbons, aromatic hydrocarbons,
asphaltenes, and resins), biomarker
analysis, total organic carbon (TOC), Rock-Eval pyrolysis, and
microscopic/reflectance analysis. In order to determine the
quantity of solid bitumen, and its distribution in the reservoir,
routine core analysis and thin section modal analysis are typically
required.
For more information on solid reservoir bitumen or to discuss a
specific project, e-mail us at info@oiltracers.com, or call
us at (214) 548-9169.
References
Huc A. Y., P. Nederlof, R. Debarre, B. Carpentier, M. Boussafir,
F. Laggoun-Defarge, A. Lenail-Chouteau, and N. B. L. Floch, 2000,
Pyrobitumen occurrences and formation in a Cambro-Ordovician
sandstone reservoir, Fahud Salt Basin, North Oman: Chemical
Geology, v. 168, p.99-112.
Hwang, R. S., S. Teerman, and R. Carlson, 1998, Geochemical
comparison of reservoir solid bitumens with diverse origins:
Organic Geochemistry, v.29, p.505-518.
Littke, R. F., J. Brauckmann, M. Radke, and R. G. Schaefer,
1996, Solid bitumen in Rotliegend gas reservoirs in northern
Germany: Implications for their thermal and filling history:
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Lomando, A. J., 1992, The influence of solid reservoir bitumen
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Preliminary Reservoir Geochemistry Study of oil and Bitumens from
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Sassen, R. 1986, Biodegradation of crude oil and bitumen
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Formation (Abstracts and Programs): Society of Organic Petrology,
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Wavrek, D. A., D. M. Jarvie, and J. D. Burgess, 1999,
Characterization of solid reservoir bitumen: Insights to formation
mechanism, timing, and correlation (abstract): TSOP Abstracts and
Program: v. 16, p.7-10.