Illuminating Linapacan Limestone Fracture Sweetspots Through a Combination of Seismic Inversion and Ant Tracking

The West Linapacan field is situated some 60 kilometers offshore Palawan Island, The Philippines. This field, of Upper Eocene to Lower Miocene age fractured limestone, was discovered in 1990, with some production during a 3 year period. The planned redevelopment of the West Linapacan field requires that a better understanding of the Linapacan limestone, in terms of reservoir fracture intensity distribution, and, along with it a need to understand the fracture orientation sets within the limestone for further well trajectory planning. 3D recently reprocessed seismic data covered the West Linapacan field. The angle sub-stack seismic were used in the simultaneous seismic inversion technique over the field, computing for multiple rock physics data cubes, such as acoustic impedance, shear impedance and density. The shear-rich data thus obtained was used as input in the Ant Tracking process to image fracture clusters and fracture azimuth sets within the limestone reservoir. The calibrated density data cube was also used to delineate the lower density areas, indicative of higher fracture zones. The two prong method showed a good convergence whereby the low density zones also showed up as more intensely fractured zones, together with the illuminated fracture azimuth sets.