--> Abstract: Sandstone Reservoir Property Modeling to Define Flow Unit for Secondary Recovery Project: Layer Z-600 Rantau Field Case Study, Indonesia, by Vena F. Eveline, Yedi Hartono, Bob Wikan H. Adibrata, and Ibnu Suhartanto; #90078 (2008)

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Sandstone Reservoir Property Modeling to Define Flow Unit for Secondary Recovery Project: Layer Z-600 Rantau Field Case Study, Indonesia

Vena F. Eveline1, Yedi Hartono1, Bob Wikan H. Adibrata1, and Ibnu Suhartanto2
1Geology-EOR Project, PT Pertamina EP, Jakarta, Indonesia
2Geology-Region Sumatera, PT Pertamina EP, Prabumulih, Indonesia

Rantau field is an old, depleted oil field. It has been producing oil from several sandstone units since 1930’s. Z-600 is one of reservoirs in the field which still has promising potency. Peak production from this layer reached 5400 bopd in 1966 and now its production rate is 200 bopd on average. Since 1984, peripheral water injection has been conducted into this layer. Today's recovery has reached approximately 34%. To improve oil production from the layer, it is planned to optimize water flooding pattern. This paper is focus on an effort to remodel sandstone reservoir properties of layer Z-600 and to refine flow unit definition to optimize the secondary recovery planning.

Among 570 wells had been drilled, only 409 wells penetrated layer Z-600. Petrophysical analysis to characterize volume of shale, total and effective porosity is performed on wells which have GR-SP-Resistivity-Density-Neutron wireline logs. Then core-log calibration is conducted. Many old wells have only SP, ILD and SN logs. For these wells, neural-network model have been run by using SP logs after careful normalization performed to estimate their petrophysical properties. Based on regional study, core description and electric-facies analysis, Z-600 is modeled as distributary channel, mouth bar, offshore distal bar and prodelta shale deposits. It can be divided into several sublayers separated by shale. Distributary channel and mouth bar facies found as the best reservoir. Offshore distal bar still can take into account as reservoir however gave insignificant contribution. Geostatistical modeling is run to distribute properties all over the field.

The study shows that Z-600 sandbody consists of several flow units. Water flooding pattern should be planned carefully consider to these flow units hence oil can be swept effectively.

 

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas