Time-Lapse Shear Wave Splitting Analysis at Ekofisk Field, North Sea

G046 TIME-LAPSE SHEAR WAVE SPLITTING ANALYSIS AT EKOFISK FIELD NORTH SEA Summary 1 The ability to detect and measure shear-wave (S-wave) birefringence or shear splitting using modeconverted (PS) waves is well understood and is demonstrated in several recent studies. In September 2002 a 4-component (4C) test line was acquired at the Ekofisk Field to investigate the application of PS-waves. Analysis of the PS-wave data indicated the presence of significant S-wave birefringence in the near surface. This phenomenon has been correlated to the local sea floor subsidence that is induced by the compaction within the underlying chalk reservoir at a depth