Sensitivity analysis of multicomponent seismic attributes to fluid content and pore pressure

Abstract

We analyzed the sensitivity of multicomponent (MC) seismic (P-P, P-SV, and SH-SH) reflection coefficients (RCs) and traveltimes to water saturation and pore pressure by taking the appropriate partial derivatives. Applying this approach to a poorly consolidated sandstone reservoir partially saturated with light oil and brine, demonstrates that P-P traveltimes have the largest sensitivity to water saturation, but the least sensitivity to pore pressure. In contrast, SH-SH traveltimes have the least sensitivity to water saturation, and the most sensitivity to pressure. P-SV traveltimes have intermediate sensitivities to pressure and saturation, but are more affected by saturation than pressure. By analyzing the sensitivity of MC seismic RCs to water saturation at the reservoir top, i.e., shale over oilsaturated sandstone, and at the oil-water contact (OWC), i.e., oil-saturated sandstone over brine-saturated sandstone, we found that the absolute value of amplitudes at all angles is greatest for P-P, smallest for P-SV, and intermediate for SH-SH. In addition, the absolute values of AVO (amplitude variation vs. offset) gradients at the reservoir top and OWC can be organized in descending order as (P-SV, SH-SH, PP) and (P-P, P-SV, SH-SH), respectively. For the sensitivity of both interfaces to pressure (the reservoir top and OWC), angle-dependent relations are extracted.