Author(s)

H. Hawez, Z. Ahmed

Abstract

The majority of carbonate reservoirs have low porosity and permeability in general because of having a high amount of matrixes that make a heterogeneous reservoir, however high permeable layers are fractured. This study shows the effect of carbon dioxide injection on the oil recovery factor using an ECLIPSE 300 compositional reservoir simulator for 3D modelling and the change of carbonate components reaction during CO₂ injection in experimental work. In addition, a high recovery factor has been recorded during miscible CO₂ injection compared to immiscible injection. Water alternative gas (WAG) has been used as an enhanced oil recovery (EOR) method to overcome an unfavourable mobility ratio of CO₂ flooding. Miscible CO₂ injection with the aid of WAG has also had a great impact on the dissolution of carbonate components in dissolving calcite and dolomite components. Consequently, CO₂ flooding has a relatively low recovery factor without any EOR techniques such as gravity stable displacement, WAG or mobility control. CO₂ injection below minimum miscibility pressure (MMP) reduces CO₂ emission, while it takes too long time to maintain reservoir pressure. On the other hand, CO₂ flooding above MMP improves pressure maintenance; causes oil swelling, and increases the oil density.

Keywords

miscibility, MMP, CO₂ and WAG injections, carbonate reactivity