METHOD FOR IDENTIFICATION OF SHALLOW WATER FLOW HAZARDS USING MARINE SEISMIC DATA

摘要

The problem of detecting sedimentary formations having an abnormally highfluid pressure that are underneath arelatively impermeable formation, (118), having normal fluid pressures isaddressed. At shallow depths, a formation with abnormallyhigh fluid pressure has a shear velocity that is close to zero, (134), and isthus significantly different from the shear velocity ofoverlying sediments, (118). The high shear wave-velocity contrast is detectedby measuring, (116), a change in the amplitude ofseismic waves reflected from the top of the abnormally pressured formation,(130). This may be done by an amplitude versus offset(AVO) analysis of the reflected amplitudes of compressional or shearreflections. Measurements of the amplitude of reflected shearwaves from a formation, (118), at some depth below the anomalous zone are mayalso be used to detect the presence of abnormallypressured intervals with low shear velocity, (138), and high shear waveattenuation.