Steam injection is a major oil recovery method in Venezuela, with some three trillion barrels of oil possibly recoverable by this technique. As a result, alongside the progress in steam injection technology, the development of a series of numerical simulators has been proceeding at an accelerated pace in Venezuela.
This paper describes three of the steam injection simulators developed over the past five years, and their applicationto two major heavy oil reservoirs. These simulators describe three phase, non isothermal multi component flow, comprising four, three and two components, respectively, in three dimensions. The implicitness of the simulators increases in the order of decreasing number of components. It is shown, however, that for a variety of problems the less implicit but more efficientsimulators are adequate. The finite difference methods used for each simulator ere outlined. These, as well as the computational performance, are compared with the existing simulators. The application of the simulators to two major reservoirs in Venezuela-Morichal and M-6-is described and compared. Effects of such factors as spacing, injection rate, and gravity segregation are examined. It is shown that the oil recovery in the large M-6 steamflood would be 7 to 9% of the oil in place, well below the expected value, and considerably below the 15 – 26% recovery predicted for the Morichal Field by the simulators. Results also show that the oil-steam ratio is not always a reliable economic index.
Steam injection is the most widely applied and promising enhanced oil recovery process for exploiting some of the vast deposits of heavy oil in Venezuela. The oil reservoirs in the Orinoco Petroleum Belt and the Bolivar Coast fields contain most of these heavy oils. The large M-6 and Morichal steam injection projects are representative of the future development of these oilfields.
Several small field tests have been carried out in the Orinoco Petroleum Belt reservoirs. Waterflooding, gas injection, in situ combustion and cyclic steam injection have been tested on commercial scale. Several other processes have also been investigated in small pilot tests. In particular, cyclic steam injection has been extensively applied in the Bolivar Coast heavy oil reservoirs. A large scale steamflood is currently being conducted under the M-6 project. An in situ combustion pilot was also conducted in one of these reservoirs.
Numerical simulation is a powerful tool in the management of reservoirs where steam injection is the recovery method. Efforts have been made to develop techniques for simulating steam injection into oil reservoirs, however, it was only in the last decade when definite advances in numerical models were realized. Shutler(1,2) rand Abdalla and Coats(3) described two-dimensional, three-phase flow numerical models for steam injection processes. Weinstein et al. (4) described a one-dimensional model that accounted for steam distillation of oil. Coats et al. (5) reported a three-dimensional steamflood model for a dead oil. Coats(6) presented a numerical model that included steam distillation of oil, release of solution gas, temperature dependence of relative permeability and a more implicit treatment of capillary pressure and transmissibilities in the fluid saturation calculations.
