Advanced imaging technologies reveal new insights in the mature Neptune field

Seismic imaging in the Gulf of America (GoA) has long been challenged by complex salt geometries. In the early years, limitations in velocity model building (VMB) tools and imaging technologies hindered accurate description of complex overburden salt velocities, restricting reservoir interpretation and field development to simpler geological areas. The Neptune field, like many oil fields in the GoA, has been in production for more than a decade, but most development wells have been confined to regions outboard of salt where conventional manual interpretation based VMB methods provided adequate seismic imaging. Subsalt targets remained undeveloped due to imaging limitations. Recent progresses in full waveform inversion (FWI) and FWI imaging technologies have enabled more accurate salt modeling and improved subsalt imaging, even with suboptimal streamer data. This imaging project leverages cutting-edge technologies including FWI, FWI imaging and elastic FWI to unlock Neptune’s potential. To mitigate streamer data limitations, such as shorter offsets and relatively poor low-frequency S/N, an iterative scenario and FWI VMB workflow was implemented, which incorporated manual scenarios to progressively improve the starting model for next round of FWI and led to substantial improvements in the velocity model. With improved velocities, FWI imaging provided enhanced S/N, improved structural coherency, and sharpened event focusing, particularly in poorly illuminated areas under complex salt. Elastic FWI and elastic FWI imaging further refined the salt model, reducing salt halos and improving S/N at subsalt targets. These improved velocity models and images provided new insights into the mature Neptune field, opening opportunities for future exploration and development.