Summary
Inflow performance in some heavy-oil reservoirs is not well understood
because the fluid properties differ from conventional behavior. In this work,
we develop an expression for inflow performance as a function of properties of
foamy oils (e.g., density, viscosity, solution gas/oil ratio, and formation
volume factor). We define two parameters, the endpoint entrained-gas fraction
and the apparent bubblepoint, adapted from previous studies, to account for the
extent of entrained-gas fraction in the liquid. The fluid properties are
modified to account for the entrained gas and then incorporated in the
equations describing flow from a reservoir at pseudosteady state.
The results of our study show that the entrained gas and the apparent
bubblepoint impact the fluid properties and, therefore, the inflow performance
at the bottomhole conditions. In the presence of entrained gas, the density of
the fluid decreases and the formation volume factor increases. Both these
properties show an inflection below the bubblepoint pressure, and the solution
gas/oil ratio shows a constant value until the apparent bubblepoint is reached.
The inflow-performance curve, therefore, displays an inflection as opposed to
the monotonically changing curve normally observed with conventional oils. The
outflow-performance curve is lowered when the effect of entrained gas is
included, caused by lower density; hence, the nodal systems analysis predicts a
greater production rate for a foamy-oil reservoir compared with a conventional
reservoir.
© 2012. Society of Petroleum Engineers
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History
- Original manuscript received:
15 February 2011
- Meeting paper published:
20 October 2008
- Revised manuscript received:
4 August 2011
- Manuscript approved:
10 October 2011
- Version of record:
28 February 2012
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