Delineating Karsts, Small-Scale Faults, and Fractures by Using a Global Stratigraphic Framework to Integrate Conventional Seismic Attributes with Diffraction Imaging in a Giant Offshore Field, Abu Dhabi.

Abstract

Abstract Poor resolution and signal-to-noise ratio have often been key factors impacting an interpreter’s ability to directly delineate subsurface features from seismic data. Improvements in full azimuth, high-density acquisition and in diffraction imaging, have the potential to reveal greater subsurface detail. To date, the application of diffraction imaging has in part been limited by the methods available to parse and analyze that same data. For instance, visualization of diffraction images on time and or depth slices may show patterns, but as these slices can cut through successive seismic reflectors, they tend not to be geologically meaningful. An approach is described that uses machine automation to rapidly incorporate diffraction images into a full-volume 3D seismic interpretation. Delineation of key stratigraphic surfaces is driven by stacking patterns and stratigraphic terminations and performed in both structural and Wheeler domains. Stratal slicing is a highly flexible and rapid method of generating chronostratigraphic surfaces. These chronostratigraphic surfaces can be extracted at sub-sample resolution and therefore accurately matched to well log responses which typically fall well below the resolution of a seismic dataset. The diffraction image is then projected onto a series of chronostratigraphic surfaces, allowing the interpreter to parse through and compare diffraction data directly with conventional seismic attributes at the same chronostratigraphic layer. The novel approach described has been used to demonstrate both the value of diffraction imaging and the importance of using a global full volume 3D seismic interpretation when identifying features such as karsts and small-scale faults and fractures. When applied to a recently processed high-density wide azimuth seismic survey, the workflow was able to seamlessly integrate diffraction images to provide improved confidence in the delineation of karsts and other collapse features that can pose a drilling hazard within the Giant Field, offshore United Arab Emirates.