Which organic species are most commonly responsible for formation damage?

• A. Heavy metals and salts
• B. Light hydrocarbons
• C. Waxes(paraffins) and asphaltenes
• D. Bacteria

Answer: (C)

Formation damage from organics occurs when certain components in the oil precipitate or crystallize inside the rock’s pore spaces, clogging pores and reducing flow. The organic species most commonly responsible are waxes and asphaltenes. Waxes, mainly paraffins, drop out and crystallize when oil temperature falls below the wax appearance temperature, forming a solid network that blocks pore throats and lowers permeability, especially in tight rocks or near the wellbore. Asphaltenes can precipitate when the oil is diluted by lighter ends or subjected to pressure and temperature changes, coating rock surfaces or aggregating in pores and further hindering flow. This differs from inorganic scale caused by heavy metals and salts, and from bacterial effects, which are other forms of damage but not the typical organic deposition discussed here. Light hydrocarbons are fluids and do not cause the solid deposition that leads to formation damage.