To enhance oil productivity in its Alkhalij field offshore Qatar in 1997, Elf Petroleum Qatar took the decision to complete the carbonated Mishrif reservoir through horizontal cemented perforated liners. The vertical or subvertical wells in this field produced an average of 3000bbl/day per well. The last 5 horizontal wells were put on stream at a more than of 8000bbl /day flow rate.

To achieve maximum productivity from the horizontal drains, complete entry exposure had to be established along the entire length of the horizontal section. To meet this objective the perforated sections of the drain were stimulated in two stages as follows:

  • by opening the perforations in the toe of the horizontal section by pumping acid through coiled tubing and then

  • by performing the main acid job by bull heading, through the DST string, a retarded triphase acid system (emulsified acid diesel solution with nitrogen) with ball sealers as the diverting agent.

This paper documents the engineering methodology and the operational techniques employed on 5 horizontal wells to selective stimulate producing intervals of between 600m. and 1,200m. length.

Case histories are presented to illustrate procedures, treatment designs and productivity results.

You can access this article if you purchase or spend a download.