Total uses reservoir simulation for history matching and forecasting of
thermal development projects. One of the main targets of its thermal
development activities is the Canadian oil sands, where unconsolidated sand
reservoirs contain very large volumes of extremely viscous bitumen (roughly 1
million cP). The favored process for producing this bitumen is SAGD.
In SAGD, steam is injected through a horizontal well, enabling the development
of a steam chamber within the reservoir. Heated bitumen is produced by gravity
from a parallel horizontal producer below the injector. A SAGD development
requires mapping the steam chamber and bitumen release from the adjacent well
pairs.
SAGD operations
At the start of SAGD operations, individual steam chambers may be
modeled independently. However, SAGD chambers can quickly communicate with each
other because of physical phenomena such as pressure exchanges, gas fingering,
and aquifer interactions. Therefore, after a short period of operation, it is
necessary to include all SAGD pairs in a single model to account for lateral
interactions between SAGD chambers. Such models can be very large (several
million cells). Simulating such large and complex multi-pair SAGD models is not
practical with commercial thermal simulators.
Very large thermal simulation projects
Total participated in the industry initiative to develop the INTERSECT*
next-generation reservoir simulation software, which features improved
numerical techniques and optimal parallel scalability. The application runs
large and heterogeneous models—simulating tens of millions of
cells—very quickly.
INTERSECT software is an unstructured-grid,
parallel, and fully implicit simulator that handles complex physics associated
with heavy oil thermal recovery. It solves component material balance, energy
balance, and mass equilibrium equations for component mole fractions,
saturation, temperature, and pressure. External heat sources and sinks are
included to model the energy interaction with overburden and underburden rocks.
To prove the application's capability to run large-scale SAGD models,
Total partnered with Schlumberger Information Solutions to run INTERSECT
simulation on a typical SAGD model (9 well pairs) in the Canadian oil sands.
The oil was modeled using two oil pseudo-components, one light and
one heavy. The model had over 1.7 million grid blocks with heterogeneous cell
properties. The producers were controlled by steam production rate, maximum
liquid rate, and minimum bottomhole pressure (BHP). The injectors were
controlled by maximum injection rate and maximum BHP. The injected steamquality
was about 90%.
