James P. DiSiena

Fracture detection using offsetP‐wave andS‐wave VSP

Multioffset VSPs were used to investigate azimuthal anisotropy in a deep well where fractures were observed with televiewer log data. Orthogonally polarized shear-wave VSPs and P-wave VSPs at far offsets both north and west of the well were analyzed. Interval velocities measured from shear waves polarized parallel to fracture trends (SH to north and SV to west) are 5% to 10% higher than shear waves polarized orthogonal to fractures. Also, P-wave interval velocities to the north appear to be 2% to 5% higher than to the west. These results are consistent with nonvertica oriented fractures. Reflection images of these offset VSPs show that the west SH VSP has an increasing delay with depth of 10 ms per 1000 ft compared to the north SH VSP. P-wave reflection images show a similar relationship of several ms per 1000 ft. Although the signal of the north SV VSP polarized oblique to the fractures is poor, it appears that these reflection images are to the west SV VSP. delayed with respect

Two-term Inversion From AVO to Detect Combined Effect of Porosity And Gas In a Cretaceous Sand Reservoir

2. applying a recursive inversion method to independently generate estimates of acoustic impedance from NI and Poisson ratio from PR; and 3. utilizing a crossplot method to simultaneously display and as a color-coded section portraying variations in lithology, porosity and pore fluid. This approach overcomes limitations in stack seismic inversion to discriminate porosity from lithology. It also extends application of AVO to sands with exceeding shale