Geohazard Detection in Deepwater Clastics Basins Using a Seismic Technique Guided by Geology and Rock Physics Model: Methodology and Examples

摘要

Detection of hazardous zones, associated with high-pressuredrnfluids in unconsolidated sands and shales, prior to drilling, isrnessential for environmental as well as health and safety.rnDrilling for deepwater targets is associated with high cost andrnrisk, while margins of commercial operations are small.rnTherefore, it is imperative to control cost through accuraternwell planning and reliable anticipation of geohazards.rnThis paper deals with a novel seismic approach that usesrnthe full bandwidth and the entire offset range of the conventionalrn3D seismic data to detect the presence of hazardousrnzones. Both in shallow and deeper zones, P- and S-velocitiesrnare determined using seismic full waveform prestack inversion.rnShallow water flow (SWF) layers in the deepwater arernidentified through the associated high ratios of P- to Svelocities.rnA new, rock model-based approach especiallyrnsuited for deepwater pore pressure imaging was appliedrnto predict the presence of both shallow and deeperrnover-pressured zones.rnThis paper covers the essential elements of the workflow –rna “five-step process” for hazard identification that integrates arnspecial data processing flow with prestack and full waveformrninversion of 3D seismic data with geology and rock modelsrnappropriate for shallow water flow, gas hydrates and deeperrngeohazards. Real data examples from deepwater elucidaternthe approach.