Publications

Naturally fractured reservoirs have attracted an increased interest of exploration and production in recent years. Fractured “Basement reservoirs provide a challenging environment to properly characterize. The term basement however, defines not just a single homogenous rock type, but a complex interplay of lithologies often genetically very different in origin. Hydrocarbon production from Pre-Tertiary rock is exceptional in Southeast Asia, oil fields in fractured basement are known in Indonesia. Indonesia provides a wide variety of basement reservoir lithologies that range from felsic intrusives to carbonate metasediments. Indonesian basement units are comprised of andesites, granites (granodiorites through monzonites), basaltic dikes, marbles, limestones, quartzites, conglomerates, and phyllites. Granites are dominated by SII intrusives and violent hydrothermal histories have overprinted many of the original “basement rock. Exploitation of these reservoirs requires more then just drilling a basement high. It involves a carefully thought out plan of execution in order to optimize the intersection of breccias and associated fracture sets. Note Breccias are the poorest understood component of fractured reservoirs due to their nature (washouted zones often with drilling losses). Southern Sumatra characterizes the global fractured basement challenges. Understanding fact from fiction is critical in dealing with fractured basement reservoirs. Identifying data that is helpful in understanding these unique reservoirs is important. Force fitting conventional analytical techniques to these reservoirs may result in a gross miss-statement of resources. Structural domains, principle stress (including local stress fields), and mechanical stratigraphy have to be considered in exploration and development of these fields. Data components such as gas shows, gas ratios, mud losses, core, rate of penetration petro-physical and well bore temperature are fundamental to evaluate with a perspective of a fracture reservoir. Outcrop provides significant insight to the problem and solutions with respect to these reservoirs. This paper will focus on the data used to understand the South Sumatra fracture basement reservoirs. Examples of structural domains integrated with lithologies are used to discuss the idiosyncrasies of dealing with fractured reservoir data. Furthermore a brief discussion related to petrophysical schemes related to log data is addressed and finally modeling strategies are summarized for their strengths and weakness.