Abstract
Heavy oil is particularly known for the difficulty it presents in obtaining
accurate fluid property measurements. The uncertainty of heavy oil fluid
property measurements affects the quality of fluid property data which in turn
affecting the accuracy of production forecast. In our investigation, we
included the impact from certain heavy oil fluid property uncertainties,
including live oil viscosity and saturation pressure [or the initial gas-oil
ratio (GOR)]. The reservoir simulations were performed for case studies with a
9°API reservoir fluid and geology similar to those typically found in the Faja
region in Venezuela. Two base cases and the underlying process mechanisms were
established, one assuming primary production process and one assuming
steam-assisted gravity drainage process (SAGD). We then performed sensitivity
studies of the different fluid property variations to determine the effect on
the process performances. We found that the process mechanism dictated the
magnitude of the sensitivity to different fluid properties. The uncertainties
of the recovery prediction obtained from a reservoir simulator confirmed
importance of selecting accurate fluid property data on the dynamic simulation
prediction.
Introduction
In upfront reservoir engineering study, the reservoir and fluid properties
are very important input data for the dynamic reservoir simulation as they
dictate the accuracy of the simulation prediction. The uncertainties of the
reservoir properties, such as the geologic and petrophysic data, are often
given more attention than the uncertainties of the fluid properties, such as
oil viscosity and initial GOR.
It is well known that there are uncertainties in fluid property data,
especially for heavy oil, because accurate measurements of heavy oil properties
are quite difficult to obtain. For example, it has been observed that a large
variation exists in the heavy oil viscosity measured from different
laboratories using different measuring techniques. In addition to the
inconsistency from the measurements, fluid sampling is another main source
contributing to the accuracy of fluid property data. Therefore, it is essential
to study the effect of the variation in fluid properties, such as oil viscosity
and oil saturated pressure (or initial GOR), to predict the heavy oil recovery
performance by means of dynamic reservoir simulation.
© 2010. Society of Petroleum Engineers
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History
- Original manuscript received:
8 April 2008
- Meeting paper published:
17 June 2008
- Revised manuscript received:
6 April 2009
- Manuscript approved:
14 December 2009
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