Asphaltene Flow Assurance Risks: How Are Pitfalls Brought into the Open?

Abstract

Asphaltene flow assurance is a critical subject during oil production and transportation in the upstream oil industry. Solid asphaltenes are precipitated and grown into aggregates that plug the pore throat of a rock formation, production tubing, surface flowlines and/or further downstream. These organic types of flow restriction are used to cause formation damage or production loss which require costly remedial measures. When the problem area is a reservoir rock surface, the issue is not only one of simple flow restriction but also of ultimate oil recovery deterioration owing to wettability alteration. Furthermore, solid asphaltene particles as nuclei can assist in forming tight emulsions that reduce oil-water separation efficiency and oil quality from the perspective of water content. The accumulation of asphaltene deposits in the surface oil-water separator is another factor that reduces separation efficiency because of periodic shut-down to remove sludge. Chemical treatment and/or facility design modification can be applied to mitigate such issues. Gas injection is a promising technique of enhanced oil recovery (EOR) that changes the composition of reservoir fluid by mixing with injection gas, which can enhance asphaltene precipitation. The risks associated with asphaltene precipitation must therefore be carefully evaluated as a part of potential gas injection application. Indeed, the increase of asphaltene risks related to gas injection is widely recognized1)~11). Because of its importance in securing asphaltene flow assurance, the author and associated research teams have conducted various asphaltene analyses12)~15). This work consistently requires some novel contrivance to understand the underlying mechanics of asphaltene behavior whereas apparent contradictions are often encountered. For example, the asphaltene onset pressure (AOP) is detectable at some locations but not others14),15), and some asphaltene deposits observed in the field have not been detected from experimental predictions13). This article is therefore motivated by the need to summarize the practical lessons learned with regards to asphaltene issues in industry. [Review Paper]