An Innovative Acid Stimulation Technique for Reviving Dead Wells in the Ghawar Field of Saudi Arabia - A Holistic Approach

摘要

The Uthmaniyah field is one of the biggest sub fields and older producing sections in the giant Ghawar structure. A few wells have been dead for sometimes due to high water cut (60 to 80%). In all cases the target interval was only 5'-10' at the top of the dominating water producing zones. There was no scope of water shut-off and artificial lifting. The pilot stimulation comprised of trials in a number of such wells with similar reservoir producing conditions. Isolation of bottom intervals by conventional gel-plug method was not very suitable here because of very marginal target interval. Even slightest inaccuracy of the coil tubing depth meter or depth correlation could be detrimental due to very close water producing interval. The treatment involving the use of high viscous visco-elastic surfactant (VES) diverter technology and controlled bullheading placement was designed to achieve effective acid diversion during acid stimulation. Stages of high viscous VES was pumped as a diverter to temporarily plug the dominating water zones, followed by considerably low strength HCl acid to achieve shallow wormhole growth. All the wells responded to the treatment with sustained oil gain. Although water cut remained high, the well head pressure increased substantially to flow the well naturally. This paper discusses the planning and design processes leading to the successful implementation of the technique, the experience during the stimulation treatment execution and the excellent post-stimulation results. Considering no cases of matrix acid stimulation in high water cut wells in the field, this technique promises to deliver in similar wells here and elsewhere. The significance of the new well stimulation technique is to revive dead wells with very high water cut and also to enhance oil recovery from these wells in a cheaper, easier and effective way.