Publications

Sisi Nubi is a gas field within the Mahakam PSC operated by Total E&P Indonésie. The field is compartmentalized by a number of faults, which subdivide the field into seven main panels. Reservoirs in Western panel are generally supported by a very active aquifer, while the Central panel generally has depletion drive mechanism. Properly quantifying aquifer strength is one of the main challenges to accurately determine reserves. A gas reservoir with transient aquifer support can plot as a near straight line on a P/Z plot, masking the existence of an active aquifer, and causing significant overestimation in gas reserves. Cole Plot is useful to distinguish aquifer support effect in CGIP estimation by including water entry effect in the material balance. In addition to the given complex context, each well in this field is producing in commingle from multiple reservoirs. The majority of Sisi Nubi production is coming from fluvial channel sand reservoirs (Fresh Water Sand interval), with good lateral connectivity and excellent petrophysical properties. This production mode gives rise to many interference effects between wells (laterally), and/or between reservoirs within the well (vertically), which will affect CGIP calculation dynamically over production time in each well. This study is the first application of Cole Plot to measure interference effect in a complex mature field with a commingle multi layer production, and lateral connectivity. This method also enabled us to quantify the aquifer effect bias in estimating the CGIP value, with a simple tool in a relatively short period of time.