Abstract

As conventional-oil resources are depleted worldwide, vast heavy oil reserves become important as a secure future energy source utilizing thermal or/and non thermal methods. Significant improvements to the effectiveness of these methods can be achieved by developing a basic understanding of the complex displacement mechanisms, developing new techniques, and optimal strategies for in situ characterization of fluid and reservoir characteristics.

Thermal recovery method has been proved as a successful method for heavy oil recovery either cyclic stimulation, steam flooding stimulation or in situ combustion method in order to reduce oil viscosity, increase oil mobility, change the wettabilitiy of the reservoir and also reduce the residual oil saturation. Fracture carbonate reservoirs add more challenge to produce heavy oil, because of dual porosity and severe heterogeneity are occurring in such type of reservoirs.

Steam flooding is preferably applied in low viscosity formation less than 1,000 CP and in shallow depths less than 3,000 ft. Steam zone, hot waterflood zone, cold waterflood zone are formed when steam injected in reservoir consequent mechanisms occurred during steam flooding stimulation are; Gas drive effect of steam displaces the highly mobilized oil in the steam zone, many pore volumes of the steam reduce the oil saturation in the steam zone from initial oil saturation, thermal expansion of oil helps increase its mobility, steam distillation, and also when the temperature increase the relative permeability of oil increases and that to water decreases.

A simulation study has been undertaken to explore the optimum development method of heavy oil recovery in fracture carbonate reservoir with 11.7° API and subjected to steam flooding stimulation which is much like water flooding with arrays of injectors and producers that depend on a pattern size. This is applied on a sector model of 2500 × 2500 ft (Fig. 1) utilize compositional, thermal, and dual porosity options. Different sensitivities have been examined such as well spacing, number of injectors and producers, well completion, sensitize the injection and production parameters, and well type (vertical or horizontal) to evaluate each sensitivity effect on the oil recovery.

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