Seismic Prediction for Clastic Thin Reservoir Along Slope Zone of Orient Basin in South America

Abstract

Orient basin of Ecuador locates in the north of sub-Andes foreland basin chain in South America. The major target for oil and gas exploration in its eastern slope zone are M1, U and T formations of Cretaceous Napo group which characterizes thin clastic reservoir with average thickness of sandstone reservoir 8.5 feet. Reservoir distribution is difficult to be predicted due to low seismic resolution in 3D data with conventional processing which restricts oil and gas exploration in this area. Here sparse-layer reflectivity inversion technology has been introduced. Both effective seismic bandwidth and dominant frequency can be broadened and increased through frequency band recovery to improve seismic resolution resulting in the promotion of seismic vertical resolution from λ/4 to the range of λ/8–λ/16. The unique advantage has been illustrated for interpretation and discrimination of thin reservoir through high resolution results processed by frequency band recovery technique which has proven with higher fidelity and reliability based on analysis of different aspects. Top and bottom interfaces of reservoirs can be discriminated from seismic section after reprocessing of 3D post-stack data by such kind of technology in T block of Orient basin, which has broken through the extremity thickness of Chalk reservoir through method of conventional seismic interpretation and inversion. The real drilling result in T block demonstrates that forecast accuracy of thin reservoir with thickness above 10 feet reaches to 80%. Two new discoveries have been discovered in the west of T block after application of this technology, and several newly drilled exploration wells succeed.