Successful Chemical Water Shut-Off Treatment in an Omani Field Heavy-Oil Well

Abstract

Abstract This paper relates the successful water shut-off treatment of a heavy-oil Omani well combining the use of microgel and gel. As many sandstone reservoir with strong aquifer in Southern Oman, this vertical well faced early water breakthrough along with sand production. Water cut increased dramatically until reaching 100%. The average permeability was around 500 mD but effective permeability ranged from milli Darcy to several Darcy. Due to well characteristics (several perforation intervals, gravel pack, etc…), it was not possible to identify and isolate the water production zones, which oriented the strategy towards the use of RPM products (Relative Permeability Modifiers). The treatment consisted of microgel and gel injections which were bullheaded into the whole open interval. After the treatment, the water cut dropped from 100% to 85% and sand production was stopped over a period of time superior to one year. The treatment was cost effective, producing more than 9000 bbl of extra oil in one year. In this paper, we describe the treatment design methodology combining laboratory study and near wellbore simulations, and the optimization of injection sequences. Finally, the treatment execution is detailed followed by the presentation of the results obtained since the realization of the operations. The results show that combining low-risk approach and low-cost RPM technology is an attractive way to restore productivity of watered out wells, in which conventional water shut-off zone isolation is not feasible.