A Systematic Approach for the Prevention and Treatment of Formation Damage Caused by Asphaltene Deposition

Abstract

Summary Asphaltene plugging is a known cause of near-wellbore formation damage. Deposited asphaltenes can reduce effective hydrocarbon mobility by (1) blocking the pore throats; (2) adsorbing onto the rock, thereby altering the formation wettability from water-wet to oil-wet; and (3) increasing hydrocarbon viscosity by nucleating water-in-oil emulsions. Asphaltene flocculation and deposition can be avoided in some, but not all, cases. Some formation damage resulting from asphaltene plugging is permanent and hence must be prevented rather than treated. Prevention of asphaltene-induced formation damage should be started in the early stages of drilling and well completion, once the oil is known to be asphaltenic. This paper presents a systematic approach to successful diagnosis, prevention, and mitigation of asphaltene problems during recovery of asphaltenic oils. A mechanism of asphaltene flocculation and deposition is proposed and analyzed, and the previously defined concept of asphaltene deposition envelope is further refined. Diagnostic technology is presented that can test the compatibility of drilling and completion fluids with any asphaltenic oil. Important issues that need to be considered in the design of treatments for asphaltene removal are discussed. Finally, the paper presents a methodology for restoring unfavorable wettability changes caused by asphaltene deposition.