The productivity of the perforated wells is controlled by several perforating parameters; perforation length, perforation diameter, degree of the damage around the perforation tunnels, shot density, and perforation phasing angle. In a new well, once the well is perforated and the production is tested, the well is then killed and completed. Even with the used of non-aggressive kill fluid and non-damaging completion fluid, some degree of formation and perforations damages are induced during well killing and completion operations. Reduction of well productivity post completion compared to pre-completion is often observed.
The well productivity can be restored by stimulation treatment which is commonly successful practice in carbonate oil reservoirs but this option can be complicated when it comes to sandstone and gas reservoirs. Production enhancement through matrix stimulation on sandstone and gas wells has much lower success rate. This option is even more difficult in cases where reservoir information is limited. Restoring the gas well productivity to the initial pre-completion condition is challenging and most gas wells unable to deliver the expected production.
This paper describes a case history of a gas well in sandstone reservoir, where productivity falls dramatically after completion. Proper investigations were carried out through well test evaluations and comparisons to pre-completion tests which showed high degree of formation and perforation damages. Potential root causes from completion activities which contributed to the damages were identified. Several productivity enhancement options were evaluated in order to restore the well productivity. Re-perforation option was selected as the best option with lowest risk to induced further damage to the formation as well as being the most economical option available. Re-perforation was carried out on the same interval as the original perforations using reactive liner perforating technology. Reactive liner perforating technology was used as it is independent of rock properties and wellbore conditions. The technology also has successful track record especially in tight sandstone reservoirs. Post re-perforation well tests indicated significant production rates improvement as a result from successful re-perforation. In addition, the paper summarizes the key learning’s that will assist operators when attempting to enhance gas well productivity through re-perforation.