Publications

The giant Tunu field was discovered in 1977 and reached its peak production in November 1999 at an average of 1.8 Bcf/d of wellhead gas. The cumulative production at end of 2013 was approximately 8.5 Tcf of gas and 183 MMstb of condensate. Higher than anticipated production decline was observed in 2011 and 2012, however as a result of an increase in the perforation activity, combined with several different production optimization efforts, and the continuation of the intensive new well drilling activity, the gas production in the field has stabilized at an average rate of 750 MMscf/d since the second half of 2012 up to now (February 2014). Perforation activity remains one of the key activities to fight against the production. Additional perforations in existing and new wells contribute to approximately 45% of the yearly production potential. Due to the nature of multilayer reservoirs and the risk of unexpectedly producing water, a general bottom-up perforation strategy is applied in Tunu Main Zone, which allows maximizing the reserves and optimum reservoir management. In 2013 alone, approximately 700 perforation jobs were conducted over almost 1900 meters of net pay sand, giving an average instantaneous gain close to 0.7 MMscf/d per perforated meter of net pay. Concomitantly on a yearly basis, around 80 wells have been drilled on average in the Tunu field over the past four years. New wells continuously provide additional net pay sand to be perforated in the future and at the current rate of perforation jobs, these new wells allow to replace the consumed perforation portfolio till the current optimum level of 13 to 14 perforations per week. Additionally, production optimization efforts such as water shut-off (WSO) interventions, sand production management, foam assisted lift (FAL) via installation of capillary strings (CS), along with very intense well monitoring and an integrated highly developed data management system and tools, provide the key to positive results observed in the Tunu field production.