ELECTROFACIES MODELING IN VOLCANIC RESERVOIR OF THE JATIBARANG FIELD BASED ON OPEN HOLE LOG AND CORE DATA

• Main Author: YUDHA, SYAMSU
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/69614
• Institution: Institut Teknologi Bandung

A classical problem in characterization of volcanic-naturally fractured reservoir of the Jatibarang field is its high heterogeneity and the existence of fractures. Electrofacies modeling has been conducted to characterize the reservoir. This model is built based on log expression on volcanic interval which then compiled with lithologic data from core. Artificial Neural Network method has been used to develop electrofacies model on uncored interval in four key wells. Facies variation in those key wells was then propagated to other wells in the field over the volcanic interval. The result of modeling showed that reservoir can de divided into five electrofacies, i.e. lithic tuff, crystal tuff, vitric tuff, igneous, and sandstone facies. Vitric and crystal tuff facies has been identified as the most prolific facies of oil production among the five-facies. Porosity in vitric and crystal tuff facies was developed by fracture porosity and void spaces that preserved after dissolution of unstable mineral in the rocks. Combination of such porosities formed permeability with the best storage capacity. Lithic tuff facies was also undergone dissolution process of unstable mineral, but probable ineffective fracturing on this facies did not create better permeability than vitric or crystal tuff facies. Igneous facies, characterized by high density and physically dense, is more resistant to deformation than tuff facies. Fractures did not significantly contribute permeability to igneous facies because they did not intensely develop. Most fractures in volcanic reservoir in Jatibarang field are fault associated fractures, except in the central part of the field (central block) are possibly related to development of local folding in that area. Such fractures developed on vitric and cystal tuff facies in that central block, so they still productive although relatively far from fault zones.