Gas Chimneys Identification for Shallow Hazards Assessment Using Seismic Attributes

Abstract

Summary Gas chimneys and shallow gas are important shallow hazards during drilling operations because they can jeopardize drilling operations, putting in risk human lives and causing important economic and environmental loses. The seismic is the most relevant data to assess these shallow hazards because it gives a wide coverage vertical and horizontal to identify and to characterize and these hazards. The seismic attributes as chaos, semblance, coherence, etc. help to identify gas chimneys because they represent higher values of discontinuity on seismic data. On the contrary, reflection strength, acoustic impedance, etc. permit to map shallow gas because they highlight anomalous amplitude values This work presents an example of shallow hazards assessment to identify gas chimneys using seismic attributes onshore Indonesia. Seismic amplitude and coherence attribute identified a gas chimney after artisanal well blowout. The gas chimney is located below the blowout and it was mapped deeper to see its origin. Other potential gas chimneys were identified to complete the assessment and to guarantee safety drilling operations. New well was drilled at 700m at NW of blowout without incidents because well trajectory avoided any shallow hazards after this rigorous assessment using 3D seismic data.