Publications

Carbonate reservoirs are often considered as less significant than clastic reservoirs, however large accumulations of hydrocarbons can be found in carbonate rocks. The challenges faced in exploitation of carbonate reservoirs are far more complex than those in clastics. The Early Miocene carbonate reservoirs in the Ujung Pangkah Field offshore East Java Indonesia possess very complex reservoir properties. Petrophysical challenges the subsurface team has to deal with include how to establish reliable porosity, water saturation and permeability models used in generating representative geological and reservoir modeling. Further complexity is presented by how to develop a thin oil-rim with a long transition zone in fractured and vuggy reservoirs. The data collected from appraisal wells provides only partial information of the field that has led to planning and development decisions in some cases found unrepresentative of the actual subsurface conditions encountered during development, fractures were not commonly seen in the appraisal wells: most of these were vertical wells, seismic resolution was not at level to define fractures, and only limited cores were taken. More information about the field was obtained during development, fractures were intersected by horizontal wells, and tendency of oil-wet reservoirs was revealed from new cores. Integrated Petrophysics is one of the keys to the future Pangkah development strategy. The integration includes how to incorporate more recent data including sedimentological study, various special core analyses, such as capillary pressure data, relative permeability analysis, wettability and Core NMR, advanced wireline logs, image logs and NMR logs. In addition how to deal with the high degree of heterogeneity demonstrated by very large variations in both log response and core measurements such as saturation exponents that cause problematic water saturation estimation. Hydraulic Flow Unit generation to characterizeporosity, water saturation and permeability, fracture characterization from image log and transition zone thickness identification also are parts of this rigorous integration effort to not only provide inputs for a new 3D geological model, reservoir simulation and volumetric estimate, but also to give feedback for mitigation strategies such as well placement and completion type.