Seismic surveying is a vital part for the oil and gas exploration and is normally the primary method for structural interpretation. Unfortunately, the remote location and complex geology are most often degrading the seismic quality. In this circumstances, borehole seismic data can be acquired with multiple fixed offset position (MOVSP) to improve the structural image away from wellbore. On top of that, borehole dip data can be used to provide a high definition 3D near wellbore structural modeling. This paper presents a case study on the "BHG" development wells campaign, where these two techniques were integrated to provide an enhanced structural information.
The interpretation workflow of this study started with the structural interpretation of single well borehole dips. Shale dips which were deposited with a horizontal or near horizontal attitude provides the best input for structural analysis. In all "BHG" wells, the shale dips shows high magnitude and demonstrate dipping to different direction, indicating the structural deformation. In order to validate this single well interpretation, multi wells structural modeling was performed. The resulted model shows two structural features, anticline at the bottom which overlain by the monocline structure. The structure model was then integrated to the velocity model, ended up with a CDP image that correlated well with the dip information from the borehole image log, and allowed for a good model validation of the key events in the up-going wavefield, hence also validating the 3D near well structural modeling.
This technique has shown that it can greatly enhance the structural interpretation, velocity control and subsequent imaging, which provides invaluable to the oil and gas operator and can provide significant savings, HSE control and to avoid unexpected events during drilling, especially in development campaign where the reservoir structure has not been properly appraised.
