Abstract

"A" West field is a heavy oil field (17–25 deg API), discovered in 1972 in the South of Oman, with a 200 m thick oil column in Haradh formation. The field development started in 1984 by cold production with vertical and horizontal wells. In 2007, the steam drive concept through 10 acre inverted 7-spot patterns was selected for the full field development. Being part of the concept, two Cyclic Steam Stimulation "CSS" campaigns were executed between 2011 and 2014 to stimulate both the wells and the reservoir using a mobile steaming unit. Throughout the two campaigns, a number of optimizations have been implemented including: the deployment of Vacuum Insulated Tubing "VIT", the extension of the perforated intervals, the adjustment of the injection and production cycle durations and resources management.

The deployment of the 1000 m VIT during the steam injection phase confirmed the predicted oil gain, resulting from a reduction in wellbore heat losses. Along with CSS, a re-perforation campaign has been conducted on wells with low productivity index "PI" to maximize their gross offtake. After steam stimulating the re-perforated wells, it has been observed that higher oil to steam ratio "OSR" is obtained for thicker oil column exposed to steam. In addition, for highly depleted zones in the reservoir, it has been found that producing at the maximum possible rate and right after the end of the soaking period, leads to a better OSR. CSS proved also to have improved the steam conformance within the targeted pattern.

Based on the promising results from the CSS jobs a decision was made to build a permanent CSS capability in all future wells in "A" West. This will also enable a proper management of the lateral steam conformance.

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