Fractures Detection and Characterization for the Jurassic Carbonate Reservoirs Using 3-D P-Wave Pre-Stack Seismic Data in Saudi Arabia
Abdulfattah A. Al-Dajani
Pressure well data have indicated a communication between two hydrocarbon-producing Jurassic Carbonate reservoirs: Arab D and Hanifa, in an oil field in eastern Saudi Arabia. Detecting and characterizing the existing fracture system(s) in our area-of-interest (AOI) using 3-D P-wave pre-stack seismic data is the main objective of this azimuthal anisotropy study. A relatively wide-azimuth full-offset 3-D P-wave seismic survey has been acquired over the oil field. The 3-D pre-stack P-wave seismic data has been analyzed to investigate the azimuthal variations of the normal-move-out (NMO) velocities and amplitude-variation-with-offset-and-azimuth (AVOA) as they pertain to the presence of fractures in the Arab D and Hanifa reservoirs in addition to upper Fadhili reservoir. The azimuthal pre-stack seismic anisotropy analysis for the target reservoirs suggests the existence of two dominant orthogonal anisotropy (i.e. fractures) orientations trending in general NE (c. 50–70o from N) and SE (c. 140–160o from N). AVOA anisotropy also suggests that the NE-trending anisotropy (c. 65–70o from N) is the most dominant fractures orientation at the reservoirs levels, which is consistent with the results obtained from borehole image logs. The NMO velocity and AVOA ellipticity maps provided insights about the fractures net-work and their intensities, offering a tool to assist in optimizing well planning and reservoir development. These conclusions are consistent with pressure data. Further enhancements can still be achieved by optimizing our data acquisition and processing techniques. This is the first successful published application of 3-D P-wave pre-stack seismic azimuthal anisot-ropy analysis for fracture detection and characterization in a carbonate reservoirs in Saudi Aramco.
AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain