Integrated Log Analysis and Porosity Mapping in the “ITS” Field, East Java Sea, Indonesia: A Case Study

Dedy Kurniawan Santoso
Institut Teknologi Sepuluh Nopember Surabaya (ITS), N/A, Indonesia

Evaluation and log analysis of several wells in the East Java Sea was conducted to determine the gas reserves of the Paciran Formation. Well ITS-1 is the wildcat discovery, and the others are delineation wells. Geological data and a time structure map show that the reservoir in all of the wells is located on the same anticlinal structure. The gas zone in ITS-1 is 162 ft in thickness, Early-Late Pliocene in age, and dominated by claystones. Well ITS-2 is located to the Northeast of ITS-1 and has a gas zone 292 ft in thickness. This consists of the Upper Paciran Sandstone formation, dominated by sandstone intercalated with siltstones (shaly sand). Well ITS-3 is located in 3.7 km East of ITS-1 and 1.8 km Southeast of ITS-2; it has 47 ft of gas zone thickness in Paciran Carbonate and Upper Paciran Sandstone formations in a section dominated by claystones. Log analysis indicates porosity in ITS-1 of 30.95% and water saturation 28.56%. In ITS-2, porosity is 35.82% and water saturation 56.35%. ITS-3 has porosity of 31.67%, water saturation 32.27%. The top of the reservoir in the three wells is: ITS-1 – 2188 ft; ITS-2 – 2088 ft; and ITS-3 – 2324 ft.

Petrophysics analysis, well correlation, and time structure mapping indicates that the area North of ITS-2 has the greatest potential for further field development. Additional mapping of porosity and water saturation and integration with seismic hydrocarbon indicators can be used to construct more detailed reservoir maps.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005