--> Design Seismic Acquisition With Illumination Analysis, Gulf Of Thailand

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Design Seismic Acquisition With Illumination Analysis, Gulf Of Thailand


PTTEP acquired 3D seismic data in 1998 covering Arthit field, Gulf of Thailand, designing for facilitate exploration and appraisal campaign since 1999. The survey has configuration dual sources with 6 x 3000 m streamers. However, there were numbers of data issues i.e. Fault shadow and limited bandwidth/ resolution in the reservoir section. PTTEP reprocessed several times with either PSTM or PSDM to resolve this problem but the constraint from survey configuration was met. So PTTEP is looking for possibility for new 3D seismic data which meet the following objectives; 1) Main objectives: Primary reservoir which is aiming for better image, overcome fault shadow issues, accurately position fault planes for Well Planning Purpose and better image channels fairways and pay sands; 2) Secondary objectives: Deeper section which required better penetration but keep resolution at shallow section for Shallow Gas Investigation. PTTEP conducted a survey design study to derive the required acquisition parameters meeting the above objectives, and mainly, to quantify, by seismic modelling/illumination, the effect of varying parameters, especially the shooting direction and streamer configuration, on the actual geological conditions. Marine standard design elements were parameterized from geophysical principals/method before assessing with ray tracing modelling over the detail model. The detailed models were selected and subsequently applying with test geometry/parameters for running with 3D modelling. Quantitative and qualitative on the generated attributes or relative simulated image response which are displayed as illumination, illumination cone and simulated migration amplitude response. The selected geometry and configuration is expected to both being acceptable by illumination result at target horizons but keep operational efficiency. The ray tracing method used for the study is Wave front Construction, duplicating wave propagating through the layered medium. The information from the simulation, including travel times, amplitude and reflection point, were summarized and illustrated as attribute maps. This is also counted as approximate solution of the seismic wave equation valid for high frequencies. The illumination result is then used for survey planning to quickly finding appropriate offset, azimuth and recording time associated to interested area. The main study attributes are illumination hit and angle population displaying as image response. The test geometries were selected with most likely geometry available in the industry varying from number of streamer (8, 10 and 12 streamer), survey direction (strike and dip of the tectonic fabric), and crossline interval for determining crossline bin size (12.5, 18.75 or 25 m). The analysis of multi-source overlap time then conducted to facilitate the possibility of selective small crossline bin size option. The result of the study implies the key recommendations based on technical requirements and operational considerations. The effect of shooting direction to imaging or fault shadow issues or impact from varying survey configuration i.e. number of streamer and crossline bin size were summary and combined with the parameters derived from marine standard design as recommended for proposed survey parameters. The recommended parameters were separated into two options, either for Main objective focusing on primary reservoir or for both objectives including shallower and deeper section. Final decision to be evaluated considering both time and financial constraint.