Abstract

This paper discusses Mobil Oil Indonesia's experince with an organic acid mixture, used as a stimulation fluid for the Arun carbonate reservoir.

Arun field has been in operation since 1977. Individual wells are capable of producing at flowrates in excess of 150 MMSCF/D. However early in the life of the field it was found that wellbore damage from mud invasion during drilling could drastically reduce well production rates.

Stimulation of the damaged wells with a hydrochloric acid/formic acid mixture was effective in removing the wellbore damage. Unfortunately rapid increase in corrosion rates followed a well stimulation, and these increased corrosion rates took time to return to normal levels. Concern over the corrosion rates prompted a search for a less corrosive stimulation fluid. An acetic acid/formic acid micture was chosen for laboratory and field trails.

The laboratory trials showed that this mixture could achieve production increase approaching those obtained with the hydrochloric acid/formic acid mixture, and that corrosion rates would be substantially reduced. Field trial confirmed the laboratory results both in terms of the increased production rate obtained, and the reduction in the overall corrosion effects due to the stimulation.