Can We Ignore Asphaltenes in a Gas Injection Project for Light-Oils?

Abstract

When light-oil reservoirs are considered for miscible gas injection processes (with CO2 or hydrocarbon gases), more often the potential of asphaltene precipitation is either overlooked or not anticipated for two seemingly compelling reasons: first, the asphaltene content in most light-oil reservoirs where gas injection is implemented could be minute, and second, the reservoir has had no prior experience of asphaltene precipitation during its primary production phase. As a consequence, the potential of asphaltene precipitation occurring during gas injection does not get the careful attention it deserves. Operators are often confounded and taken by surprise when they experience a manifestation of serious asphaltene precipitation soon after the gas injection starts. Once the asphaltene precipitation occurs, it causes severe permeability reduction and wettability alteration in the reservoir, and plugging in the wellbore and surface facilities. Remedial measures, which are expensive and disruptive, usually include chemical treatments and workover operations are often disruptive and expensive. Therefore, one must investigate the possibility of asphaltene precipitation prior to implementing a gas injection scheme.