Abstract

Paraffins and asphalt in crude oil are major factors in promoting formation damage. Temperature and pressure reductions accompanying flow of crude oil which contains a large amount of paraffinic or asphaltic material may reduce formation permeability by blocking pore spaces or by causing the formation to become oil wet.

Sandstone formations are usually more susceptible to damage caused by oil wetting, emulsion blocks, and water blocks than limestone formations. Depletion drive wells are more susceptible than high pressure wells to plugging with paraffin.

A number of types of formation damage can be prevented or alleviated with surfactants and solvents. Wells producing high pour point crude oil and containing appreciable quantities of paraffinic material are the most likely to be associated with formation damage that is amenable to surfactant and solvent stimulation.

All producing wells in the Lirik Field, Central Sumatra are old, depletion drive sandstone wells. The goals of stimulation jobs in Lirik are to eliminate paraffin from the sand face, to lower surface and interfacial tension, to change wettability, and to prevent emulsion blocking and water blocking. To increase the success ratio after stimulation jobs and to reach the optimal production index, the production rate is optimized.

In 1990 - 1991, ten wells were stimulated at Lirik with paraffin solvent and surfactant, resulting in a 155.40 % success relative to the target.