Abstract

Sandstones of the Q Layer are the best producing reservoirs in the Sangatta Field which is located in East Kalimantan. The maximum thickness of net sands in this reservoir can be as high as 58 m ranging in porosity from 10% to 30%. More than 120 wells have been drilled in this field. The Q Layers are encountered between 1130 m - 1300 m. However, only 30% (40 wells) are proven to be hydrocarbon bearing.

Analyses of facies, porosity, and permeability from well data, indicate that the productive Q layer sandstones are predominately distributary channels and incised valley fills deposited in a delta plain environment. This condition is responsible for the limited distribution of productive Q Layers in Sangatta Field.

Seismic amplitude and inversion, employing workstation techniques, were used as tools to predict the lateral distribution of productive Q Layer reservoirs. Prior to any analysis, 2D seismic land data had to be corrected for misties between different vintages. This included time shifting and phase corrections. Seismic data was then correlated to the well seismic VSP (Vertical Seismic Profile/synthetic seismogram).

The boundary of deltaic facies elements like distributary channels, distributary mouth bars, prodelta shelves, incised valleys, and barrier bars can be predicted using this method. The result of the interpretation shows that the delta prograded in a northwest to the southeast direction.