Application of Pre-Stack Seismic Anisotropy for Fracture Detection in Osell Field Carbonate Reservoir, Seram Island, Eastern Indonesia



The main production layer in Oseil field is carbonate fracture in Manusela Formation, East Indonesia. The main storage and accumulation space of the carbonate is fractured porous media and the reservoir distribution possesses has strong heterogeneity. Studied on reservoir fractures intensity in Oseil field using pre stack 3D seismic data are based on P-wave reflection amplitude, P-wave seismic amplitude exhibiting variable attenuation with difference fracture orientation called it as seismic anisotropy. Vertical aligned fractures generated seismic anisotropy, analyzing seismic anisotropy produced by fracture is the most important application of seismic data for fracture detection. Several steps were used to generate fracture intensity cube from well and 3D seismic data: First performed reserved amplitude processing, well and seismic correlation, rock-physical modeling of fractured reservoir; based on rock physical studies were built to model seismic anisotropy. Then four azimuth seismic data sets were achieved by selecting and combining seismic data set in the range of 0-2000 meters offset and 0-180 degree azimuth; and calculated different azimuth amplitudes and analyzed their azimuth variations. Finally we come up with a spatial distribution of amplitude azimuth ellipse, with represent amplitude decay along different fracture direction, this anisotropy curvature attribute then convert to fracture intensity. Currently all development wells in Oseil field were design and drilled mainly base on fracture intensity distribution map, and as examples were Oseil-12, Oseil-18 and Oseil-2ST, two wells were drilled in year 2010 and one in 2011 and proved that the technology had been working wells for Manusela fracture carbonate reservoir detection.


Author : Anggoro S. Dradjat