Publications

Although mature oil and gas field, already covered by 3D streamer seismic in 1994, the BEKAPAI field remains with some G&G knowledge uncertainties mainly due to :  poor signal to noise ratio due to the seismic quality and fold at shallow objectives,  some strong seismic artifact such as fault shadowing/push-downs  seismic signal absorption due to a so called “gas cloud” presence,  missing data because of surface obstructions such as platform in central area . For all the reasons listed above, an OBC 4C seismic was carefully designed with:  high fold coverage (1200)  high lateral sampling rate (small binning: 12.5mx 25m)  wide azimuth (4000m IL/2800m XL)  GI guns to optimize frequency content and minimize noise in shallow water area. Instead of shooting cross spread, the shooting lines were parallel to receiving lines due to limitation in depths in the northern shallow part of the survey * TOTAL E&P INDONÉSIE ** TOTAL AS –MTG/AS+INNO (<4m depth) and geographical constraints. For the first time in TEPI this original parallel geometry was specially designed after feasibility study and successfully implemented on site by seismic Contractor who used two vessels shooting in flip flop mode on different shooting lines. Operationally speaking parallel acquisition proved to be particularly advantageous in comparison with orthogonal acquisition:  Shorter Line change for Shooting vessel (50m only between sailed line and sailed line 12 km long)  Cable lay out, is the most time consuming operation in OBC therefore it should be minimized as it is easier to increase density of SP than density of receiving points. For this parallel design shot density is 2000 shot /km2 and receiver density is 200 receivers/km2. This ratio (10) was optimum and shooting was never delayed by cable lay out.  Cable roll is 1 only, for Parallel (instead of 4 for equivalent Orthogonal geometry) optimizing the use of receivers (more time to record less time for moving cables).  Higher fold (for bin 12.5x25 m – fold 1120 for Parallel vs 480 for Orthogonal) Bekapai OBC 4C survey was acquired in Q3 of 2012, over obstructed area with all production facilities and crossed by intense maritime traffic. Commercial traffic mainly consisted in cargo vessels, fishing boats & coal barges. Procedures to regulate the traffic were specially developed with support of local authorities: NAVY Patrol Boat, ADPEL Boat (Samarinda Port Authority) and other Chasing Boat. An innovative approach was developed to analyze and control the huge volume of seismic data acquired on a day to day basis.(Max production rate could be over 5000 SPs/day x 1800 traces). Mainly the QC procedure was based in several steps : 1. Computation of QC attributes (S/N ratio, RMS Noise & RMS Signal) 2. Mapping the QC attributes 3. Interactively visualize anomalous SP or traces The dynamic link between map of attributes and corresponding traces or SP display was very effective to spot and track any anomaly and quickly react to optimize the overall quality of the acquisition.