Optimization of perforation design at Oseberg South with regards to perforation clean-up and productivity

Abstract

The Oseberg South field, originally estimated to contain 93.4 Sm3 oil equivalent of recoverable reserves, has been producing since 1985. Recent reports estimate remaining reserves to be approximately 25.1 Sm3 oil equivalents. Despite the reservoir being highly depleted, some uncertain still exists about the presence of isolated high-pressure pockets in the reservoir. Traditionally Oseberg South has been perforated on pipe with highly overbalanced well pressure with a kill pill along the reservoir. The main research task described by this report has been to evaluate the best perforation techniques for the depleted Oseberg South field with specific emphasis on perforation cleanup and cost. Experimental work and simulations have been conducted to quantify expected perforation characteristics and predict associated productivity. The experimental work was performed at the Jet Research Center in Texas at downhole conditions, with simulation studies carried out with industry software.