Integrating Seismic Data and Seafloor Geochemical Sampling Technologies to De-Risk Deepwater Colombia

Abstract

Abstract

Source rock presence and charge are critical risks when exploring deepwater blocks offshore Colombia. In this uncalibrated frontier setting, geochemical seafloor sampling via piston cores is a low cost de-risking method when properly executed. Through subsequent seafloor sampling programs, the impact of integrating various forms of data for effectively designing piston core programs can be demonstrated.

Piston core programs were executed in 2012 and 2015. In 2012, fifty cores were collected solely on sparse 2D seismic. Two limitations of relying only on 2D are 1) significant areas of the sea floor are not covered by data hence seafloor expulsion features (e.g. mud volcanoes) are overlooked and 2) incomplete view of the subsurface limits identifying those features most likely connected to deep stratigraphy. None of the 2012 cores were interpreted to access an active seep.

The 2015 program was executed with additional 2D/3D seismic, multibeam echo sounder (MBES) bathymetry, and seafloor and water column backscatter. The MBES and backscatter data allowed for identification of significantly more expulsion features than in 2012. In addition, this data provided a mechanism for characterizing likely areas of recent activity (e.g. areas of high backscatter and/or anomalies in the water column indicating gas bubbles from active seeps). Finally, features were characterized based upon association with to the 2D/3D seismic structure.

Expulsion features were catalogued based on their association with subsurface structures of interest in exploration (e.g. deep faults, 4-way closures). Features were prioritized to sample a range of subsurface structures connected to deep stratigraphy, while targeted core locations on the features were chosen using the backscatter and water column data. Cores from these expulsion features were interpreted to have sampled active seeps.

Integrating seismic with bathymetry and backscatter data allows for a comprehensive view of the connection between the seafloor and the subsurface. The availability of 2D seismic is necessary, but not sufficient, for properly designing a piston coring campaign; MBES is also required. Conversely, 3D data may not be necessary if MBES data of sufficient quality is available for detailed targeting. Although this approach requires data upfront, the value added can be measured by the success of coring active seeps and maximizing the effectiveness of piston coring as a de-risking mechanism.

AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016