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Integrated Shallow Gas Imaging using Fiber Optics DAS VSP and OBNNormal access

Authors: M.D.D. Muhammed, M.F.A. Rahim and A.R. Ghazali
Event name: 81st EAGE Conference and Exhibition 2019
Session: Borehole Seismic Methods I
Publication date: 03 June 2019
DOI: 10.3997/2214-4609.201901251
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 713.23Kb )
Price: € 20

Summary:
Fiber optics distributed acoustic sensing (DAS) allows vertical seismic profile (VSP) data to be acquired across the entire wellbore trajectory without any costly well intervention or safety issues. The utilisation of fiber optics receivers also allows for better spatial sampling compared to conventional wireline VSP. This paper investigates the possibility of improved imaging beneath the shallow overburden gas cloud region of Malaysia's Bokor field through the utilisation of DAS VSP with ocean bottom node (OBN) seismic while the well is still producing. This paper discusses the denoising techniques implemented to suppress the heavy production noise observed and the OBN-DAS integrated imaging method. F-x filters with varying frequency ranges were utilised to suppress production noise while f-k filter was utilised to suppress residual impulsive noise. The denoised shot gathers were then separated into the upgoing and downgoing wave field to obtain reverse time migration (RTM) stack and reverse time migration with multiples (RTMM) stack respectively. The RTM, RTMM and OBN stack were then integrated into a single stack to retrieve reflector information in the gas cloud washout zone while improving lateral continuity.


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