Multi Component Seismic Technology in Exploration and Characterization of Unconventional Reservoirs

Abstract

Multi component seismic data acquisition is an effective process in exploration and reservoir characterization. The technology provides improved and enhanced strata images by reflecting independent subsurfaces, direct lithofacies and hydrocarbon indication compared to only conventional P-wave seismic stratigraphy and will increase discovery of unconventional resources with significant commercial values. Multi-component seismic technology is composed of three independent vector-based seismic wave modes. These wave modes are compressional mode (P), shear modes SV and SH. The three modes are generated using three orthogonal source-displacement vectors and then recorded using three orthogonal vector sensors. The components travel through the earth at differing velocities and directions. The velocities of SH and SV as they travel through the subsurface differ by only a few percent, but the velocities of SV and SH (Vs) are appreciably lower than the P-wave velocity (Vp). The velocity ratio Vp/Vs varies by an order of magnitude in the earth depending on the degree of sedimentary lithification. The multi-component data used in this study were acquired by nine-component (9C) vertical seismic profile (VSP), using three orthogonal vector sources. The 9C vertical seismic profile is capable of generating P-wave mode and the fundamental S-wave mode (SH-SH and SV-SV) directly at the source station and permits the basic components of elastic wavefield (P, SH-SH and SV-SV) to be separated from one another for the purposes of imaging. Analysis and interpretations of data from the study area show that incident full-elastic seismic wavefield is capable of reflecting four different wave modes, P, SH, SV and C which can be utilized to fully understand the architecture and heterogeneities of geologic sequences. The conventional seismic stratigraphy utilizes only reflected P-wave modes. The notation SH mode is the same as SH-SH; SV mode means SV-SV and C mode which is a converted shear wave is a special SV mode and is the same as P-SV. These four wave modes image unique features and at the same time reflect independent stratal surfaces because of the unique orientation of their particle-displacement vectors. As a result, one mode may react to a critical subsurface sequence more than the other. It was also observed that P-wave and S-wave do not always reflect from the same stratal boundaries.

AAPG Datapages/Search and Discovery Article #90189 © 2014 AAPG Annual Convention and Exhibition, Houston, Texas, USA, April 6–9, 2014