Summary
The Tahe-fractured reservoir has very special cavities and fractures. There
is no flow in the rock matrix; and cavities provide the main storage space and
even have the scale of meters. Consequently, the reservoir cannot be considered
as a traditional continuous porous medium. Instead of a dual-porosity flow
model, a Darcy-Stokes compound single-porosity model is developed with the
whole flow area divided into a Darcy-flow region, which obeys Darcy’s Law, and
a free-flow region, which satisfies a Navier-Stokes flow.
Through a Tahe real reservoir case, it is found that a cavity-fracture
dual-porosity model is unable to reflect the rapid bottom-water breakthrough,
and that finite difference method has a hard time getting convergence in the
strong heterogeneous reservoir. On the other hand, streamline simulation with a
Darcy-Stokes model developed in this paper successfully demonstrates flow
behavior of bottom- and edge-water flowing into the wellbore through the
cavity: water advances fast, water breakthrough happens in a short time, and
water cut rises rapidly.
In application, a streamline numerical model for Darcy-Stokes flow is built
by combining two-phase Navier-Stokes streamline modeling and streamline-based
simulation of Darcy flow. Examples show that both a Darcy-Stokes model and
conventional Darcy model give the similar simulation results of saturation and
pressure distributions in the Darcy-flow region. However, fluid flow behaviors
from these two models differ in the free-flow region. Such a difference lies in
the different treatment of velocities: our Darcy-Stokes model considers the
fluid velocity difference caused by a shear stress effect; and the Darcy model
only uses the average velocity of the fluid in the cavity, which means the
fluid almost moves at the same speed in the free-flow zone and does not agree
with the reality.
© 2009. Society of Petroleum Engineers
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History
- Original manuscript received:
2 March 2007
- Meeting paper published:
11 June 2007
- Revised manuscript received:
11 January 2009
- Manuscript approved:
14 January 2009
- Published online:
20 August 2009
- Version of record:
28 September 2009
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