Improvement of Thermal Heavy-Oil Recovery in Sandstone and Carbonate Reservoir Using Hydrocarbon Solvents
Abstract
This thesis introduces a new approach for heavy-oil recovery from fractured reservoirs: Steam-Over-Solvent Injection in Fractured Reservoirs (SOS-FR). The SOS FR technique is a new technology proposed as an alternative method to the sole injection of steam or solvent and consists of three phases; Phase 1 produces heavy oil by thermal expansion and conditions the oil for Phase 2, which is solvent injection, and Phase 3 is applied mainly to retrieve the solvent.
Extensive experimental evidence and analysis were provided through static and dynamic laboratory scale experiments. Static experiments were conducted to test four parameters: (1) Matrix wettability, (2) solvent type, (3) initial water saturation, and (4) matrix boundary conditions and size. This was followed by dynamic experiments to test the effect of solvent injection rate on the process. Experiments were conducted using heavy-crude oil samples obtained from a field in Alberta on either wettability-treated sandstone (to mimic oil-wet behavior), or cleaned carbonate cores.
Visualization experiments were also performed on 2.5 cmx7.5 cm Hele-Shaw cells with different boundary conditions to gain an insight into fluid-fluid interaction between oil in the matrix and solvent in the surrounding fracture. Interaction between oil saturated 2-D models and the hydrocarbon solvent surrounding it was analyzed qualitatively. Two new dimensionless numbers were introduced as functions of fluidproperties (viscosity, density, and diffusion coefficient) and matrix boundary conditions, and the numbers were correlated to oil recovery rate.
Finally, numerical simulations were conducted using a commercial software package for two main purposes; (1) history matching and obtaining an insight into the upscaling procedure from lab to larger scales, and (2) examining the efficiency of the process at the field scale (mainly large matrix sizes).
The importance of this work is that it provides a novel perspective on the interaction between steam/solvent and heavy oil in the matrix, and presents an alternative technique for heavy-oil recovery from deep natural fractured reservoirs with tight and oil-wet matrix.
