SHALLOW HAZARD ASSESSMENT AND INTERPRETATION USING GEOELECTRICAL DATA: BUNGAMAS PSC STUDY CASE, ONSHORE SOUTH SUMATRA AREA

摘要

The Bungamas PSC is located onshore South Sumatra. A total of 725 km of new 2D seismic data have been acquired in 2008 and 2010, and six new exploration wells have been drilled since 2010. A critical risk during drilling operations is the possibility of shallow hazards. This risk was assessed carefully by geoelectrical acquisition, data processing and interpretation; because shallow resolution was not clearly imaged on the migrated and angle stacks data of the 2D seismic data. There is no high resolution seismic data acquired in Bungamas PSC. The geoelectrical survey for shallow hazards assessment was designed with sounding point intervals of 50 m and 200 m, and with 3,000 m of AB length. The data was then processed using the Inversion Vertical Electric Logging (IVEL) technique, which generated a resistivity section across the proposed exploration wells and associated seismic lines. Shallow exploration wells were used to calibrate the tie between resistivity measurements and well data. The result of this assessment was used to assist drilling operation in assessing the shallow hazards potential and defining the casing program, especially for the shallow section. Geoelectrical processed data showed several high and isolated resistivity spikes in the shallow section of the proposed deep well, which were interpreted as potential porous sand with no hazards. Based on that information, the most suitable position for the 20” casing shoe was determined. This potential shallow hazard interpretation wa s confirmed by the actual drilling operation and has successfully helped achieve a more efficient and safe drilling campaign.