Abstract
Multiphase flow through fractures is important not only for naturally
fractured petroleum reservoirs but also for underground disposal of radioactive
waste and geothermal hydrotransport, cap rock integrity, as well as underground
water and aquifer flow. For instance, naturally fractured reservoirs located in
Northern Alberta contain large quantities of heavy oil and bitumen. It still
remains unclear how multiple phases flow in fractures and how to determine the
relative permeability of each phase that can be used in reservoir simulators.
In typical practice, simulation of fractured reservoirs uses, in general, very
crude and unproven hypotheses such as linear relative permeability curves.
However, by using inaccurate relative permeability curves, large errors of the
predicted oil recovery can result. In this work, a relatively simple flow model
is derived to determine analytic functions for the relative permeability curves
versus phase saturation in a single fracture. The results show that relative
permeability is not just a function of the fluid saturations but also of the
fluid properties and flow pattern within the fracture itself. The analysis
reveals that at certain viscosity ratios and flow pattern conditions, the
relative permeability of one phase can exceed unity owing to lubrication
effects. The available experimental data confirms the validity of the proposed
model.
Introduction
Fracture-dominated flow is not only important for naturally fractured
petroleum reservoirs but also for underground disposal of radioactive waste,
geothermal hydrotransport, cap rock integrity, and underground water and
aquifer flow. In naturally fractured reservoirs, fractures are highly
conductive flow pathways that dominate fluid transport throughout the
reservoir. To examine flow of multiphase flow in fractures, many different
experimental(1–12), theoretical(13–18) and numerical studies(19–26) have been
done. However, flow structure and momentum transfer between flowing phases in
fractures are not yet well understood(4, 27, 28). Transport parameters such as
relative flow rates of phases and the relationship between fracture geometry
and flow remain unclear. The relative permeability concept can be used to
describe behaviour of multiple phases flowing together through porous media,
interfering and aiding each other to move under the action of a pressure
gradient. Despite the importance of relative permeability in fracture flows,
still there is no unique and consistent theory which provides an easy, yet
computationally inexpensive, method to calculate relative permeability curves
in fractures.
© 2010. Society of Petroleum Engineers
View full textPDF
(
1,895 KB
)
History
- Original manuscript received:
10 February 2009
- Meeting paper published:
17 June 2008
- Revised manuscript received:
22 September 2009
- Manuscript approved:
2 January 2010
View Cart
