Publications

Transition zone seismic surveys acquired over a subsurface reef structure present significant imaging challenges for producing reliable interpretations for reservoir assessment. Extremely variable seafloor, shallow water depth, marsh and near-surface land conditions create severe data quality issues. A 3D surface seismic survey showed considerable lateral image quality degradation from off-shore to onshore, not just in the overburden but unfortunately also in the target region. To mitigate such effects and counteract restricted surface access issues due to environmental, agricultural or maritime conditions, non-traditional data acquisition and processing techniques need to be employed. In order to obtain a better reservoir description in the transition zone, the complete vertical and horizontal borehole trajectory was instrumented with 3C receivers, while simultaneously recording 3C receivers in shallow vertical wells. Even with a limited source layout along a narrow 2D corridor such a source and receiver geometry allows us to extract a multitude of information about the nearsurface and subsurface. While traditional standard imaging is challenging in such a geometry, interferometric processing, imaging and analysis allows us to obtain valuable reservoir information. Considering the geologic setting and data acquisition aspects, we focused on the value of information obtained by using advanced processing flows, such as a 3D depth-tied velocity model construction using nonlinear travel-time tomography, interferometric seismic gather generation and interferometric imaging, as well as * Hess Indonesia Ltd ** SR2020 *** Statoil elastic full wave-form forward modeling to help in the interpretation, analysis and uncertainty estimates. Each of those particular results provides a limited subset of self-consistent information in overlapping subsurface regions. However, when considered together, they each confirm or deny, and ultimately constrain certain structural, stratigraphic geologic aspects or scenarios. Thus, allowing us to more accurately define the location and extent of the reservoir boundary. The careful design and analysis of non-standard transition zone surveys allows us to obtain valuable information of the reservoir.