  This paper introduces the model, numerical methods, algorithms and parallel
implementation of a thermal reservoir simulator that designed for numerical
simulations of thermal reservoir with multiple components in three dimensional
domain using distributed-memory parallel computers. Its full mathematical model
is introduced with correlations for important properties and well modeling.
Various well constraints, such as fixed bottom hole pressure, fixed oil, water,
gas and liquid rates, constant heat transfer model, convective heat transfer
model, heater model (temperature control, rate control, dual rate/temperature
control), and subcool (steam trap), are introduced in details, including their
mathematical models and methods. Efficient numerical methods and parallel
computing technologies are presented. The simulator is designed for giant
models with billions or even trillions of grid blocks using hundreds of
thousands of CPUs. Numerical experiments show that our results match commercial
simulators, which confirms the correctness of our methods and implementations.
SAGD simulation with 15106 well pairs is also presented to study the
effectiveness of our numerical methods. Scalability testings demonstrate that
our simulator can handle giant models with over 200 billion grid blocks using
100,800 CPU cores and the simulator has good scalability.
