Innovative Approach Using Geostatistical Inversion for Carbonate Reservoir Characterization in Sopa Field, South Sumatra, Indonesia

Raguwanti, Rusalida, Artini Sukotjo, Bob Wikan H. Adebrata, Pertamina Upstream, Jakarta, Indonesia

The declining production performance in Sopa field, South Sumatra Basin during few years were caused by many aspects. One of which is reservoir thickness of Baturaja Formation that are below seismic resolution. That limitation raised a problem in reservoir characterization being applied to the 3D seismic data at that time.

Geostatistical Inversion is applied to overcome this problem whereas Sparse Spike Inversion is not sufficient to do it. However, Sparse Spike Inversion which invert 3D seismic to an acoustic impedance volume with well constrain is used as a preliminary data in geo­statistical inversion. The advantage of using Geostatistical Inversion is to produce a set of reservoir property and reduce the uncertainty.

3D property models generated in Sopa field using well and amplitude data also support the inversion result. These particular model was generated using carbonate facies distribu­tion derived from Neural Network, as a control in reservoir properties propagation.

Controlled by acoustic impedance and property model analysis, two upside potential were found as structural trap at the north and central part of Sopa area. The north prospect was succesfully drilled and proven to be hydrocarbon oil bearing with 600 bopd which is significantly increasing the production performance.The second prospect is proposed to be drilled afterwards.

Geostatistical inversion provide better integration of well, seismic and geological data which produce better spatial distribution and the connectivity in carbonate reservoir. Uncertainty can be quantified through multiple realizations output of this methods. This approach will enhance confidence level in finding new prospects within this field.