Fracture Basement Imaging, Identification, and Characterization Through Separated Wave Field Processing Strategies – A Case Study From Offshore Indonesia

Abstract

As fractured basement characterization has become very critical in Vietnam, Indonesia, Yemen, the United Kingdom, and Malaysia, the focus of our industry has been to improve the imaging technologies related to faults and fractures within the basement. This abstract showcases a sequential and systematic strategy to resolve all imaging challenges from the surface to the pre-basement zones on a dataset from offshore Indonesia. As the overburden is very complex, containing varying sizes of carbonate bodies in a shallow water environment, the image of the basement in the vintage data was very poor and not easily identifiable. With very focused efforts, including the latest available processing technologies in reprocessing, we were able to obtain accurate velocities. This was possible through extensive application of refined denoise, deghosting, and demultiple providing continuous, well-imaged top-basement images that showed good correlation with well data. Most of the efforts in fracture characterization have been concentrating on reviewing, analyzing, and improving seismic attribute performance applied to the seismic data. The performance of the attributes very much depends on the accuracy of the seismic images. With the past successes of fracture basement discoveries, accurate imaging of fractures has been an important objective in seismic data processing. The accuracy of imaging fractures in the pre-basement zone depends on the technologies and their accuracies in resolving the imaging challenges of the overburden geology. In the past, lots of efforts have been made to effectively image, analyze, delineate, and study fractures in basements. The carbonate presence and thick clastic section above the basement have generated strong surface and interbed multiples, and one of the steps that have significant impact on reconstructing the weaker pre-basement signals is effective estimation and subtraction of these. In addition to the specialized workflow for imaging the total wavefield, we extended the workflows to image the separated wave fields of specular reflections and diffraction energy. Imaging diffraction energy provides accurate imaging of faults and basement fractures, and with the integration of the various analyses and attributes, fracture characterization can be optimized.