Adding Value to a Mature Gas Field by Re-analysing and Integrating Old and New Dynamic Data - Immortelle Gas Field, Trinidad and Tobago

Abstract

Abstract The Immortelle gas and condensate field is located in the Columbus Basin,35- 40 miles off the southeast coast of Trinidad in water depths of 235 feet. It is comprised of highly faulted stacked reservoir units. The TP88 reservoir unit, the subject of this paper, was discovered to be gas bearing in 1975 by the exploration well, SEG10.The reservoir pressure is 3505 psi;with a temperature of 162F.This reservoir was developed with two wells. IA11 was the first producer from 1999 to 2002 and was completed as a 3.5 (inches) multizonal completion across 3 reservoir units, but selectively producing via sliding sleeves. IA14 is the second and current producer. It was completed updip to IA11 in the TP88 in 2001 as a cased hole completion with a gravel pack completion in the good quality upper sand lobes with 3.5 (inches) tubing. The TP88 reservoir has historically had close alignment between static and dynamic models. Pressure Transient Analysis and modelling studies in 2010 has resulted in significant misalignment of the static GIIP and the estimated dynamic GIIP. This paper will describe the modelling work flow and discuss the key lessons learnt from analysing and integrating old and new reservoir data that has led to a completely different understanding of the drive mechanism and future reservoir performance. This has resulted in the static model Gas Initially In Place (GIIP) now lagging behind the reservoir simulation model GIIP and has potential implications for the reservoir depletion plan.