Water reduction techniques were applied in the openhole gravel pack (OHGP) completions of four wells in Field C. Field C is operated by BP Trinidad and Tobago LLC (bpTT) and is located offshore Trinidad in the Columbus Basin. During the first phase of field development, six wells encountered economically recoverable reserves and first gas was achieved in 2007. The field produced at peak rates from December 2009 to April 2011. Between October 2010 and March 2013, four wells became liquid loaded due to aquifer influx, and production declined by ~ 80%.

The second phase of field development was scheduled to commence in 2016, and hence the bpTT field team began to investigate ways to revive the four liquid loaded wells and return them to production. Using experiences from BP Global Operations, and based on the assumption that the reservoir drive mechanism was bottom and/or edge water drive, the team decided to install zonal isolation devices. Also known as water shut off plugs; these devices are usually used in oil well casing applications and had never before been tested in gas well openhole gravel packs in Trinidad and Tobago. Each plug was set within an interbedded shale in the reservoir and screen joint of the completion to provide a vertical flow barrier. Due to uncertainty on the lateral extent of the shale and its ability to act as a barrier to water encroachment, an additional step of dynamic wellbore modelling was implemented. This was used to modify well bean up in order to minimize drawdown while maintaining the critical rate.

The well intervention campaign to install the plugs began in December 2013 and was executed using both slickline and e-line tools. One of the key considerations during job execution was depth control, to prevent setting the plugs too high in the wellbore and isolating gas bearing sands. This was achieved by correlating the gamma ray (GR) and Casing Collar Locator (CCL) logs with the original openhole logs. The plugs were installed by July 2014 and 75% of the wells were successfully offloaded with an average reduced WGR of 40%. This prolonged the producing life of the wells and improved the recovery factor by an average of 2%.

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