ANALYZE THE POTENTIAL OF OFFSHORE TIGHT GAS CARBONATE RESERVOIR USING MULTI LAYER RATE TRASIENT ANALYSIS

Abstract

X field is an offshore gas field located in North of Bali. X field is currently developed by 1 subsea deviated well with open hole gravel pack and consist of two reservoir layers. Based on static model, this reservoir has OGIP ratio of around 59% in Layer A and 41% in Layer B and now has recovered 8.6 % of total OGIP. Layer A is known as tight carbonate reservoir with net pay 98–103 ft, and based on core data permeability ranging from 0.2–30 md, meanwhile layer B has better quality of reservoir properties with net pay 53-75 ft, and permeability ranging from 27–1066 md. DST result from exploration well Z-1 indicated that there is small flow from layer A. However, since well Z-1 is commingled, it is difficult to estimate the contribution of each layer properly.

To analyze the gas potential of this tight reservoir layer, Rate Transient Analysis (RTA) is applied in this study. By using this method, production data can be utilized to get estimates of OGIP, production allocation and reservoir properties (skin and permeability) for each layer. Various RTA techniques are used as a default workflow which are Flowing Material Balance, Type-curve analysis, and History matching at multi-well multi-layer model. Result from this study will be used for further development plan of X field.