Ocean Bottom Node Seismic and Full Waveform Inversion Towards Better Imaging Over a Complex Sub-Salt Field in Deepwater Gulf of Mexico

Abstract

Abstract The Stampede Field is a sub-salt Miocene field in the deepwater Gulf of Mexico. Although it is a generally well imaged structure, development and production requirements warranted an improved image over the field. A variety of seismic data such as Narrow Azimuth (NAz), Wide Azimuth (WAz), and Dual Coil (i.e., Full Azimuth or FAz) have been used at various stages in the past. Imaging the field is complicated by the presence of up to 15,000 ft of salt which includes overhangs, inclusions, sutures, steeply dipping flanks, and a rugose base. Successful imaging of the northwest portion of the field has consistently been a challenge, regardless of the vintage or technique used in acquisition and processing. Recently, Ocean Bottom Nodes (OBN) seismic acquisition technology has become popular due to its long offset and low frequency content, which are essential to address complex imaging issues. In 2018, Hess engaged Fairfield Nodal to acquire OBN seismic over the Stampede Field, which recently started production. Acquisition design was based on an OBN modeling study. Nodes were placed over 238 sq km with shots over an 888 sq km area. The survey was safely executed without any incident or lost time. The data recovery was excellent. Data was processed with technologies including Full Waveform Inversion (FWI) for velocity model building and Least Squares Reverse-Time Migration (LSRTM). Dual coil and WAz data were used along with OBN to produce a superior image of the field. In this paper, we will discuss (1) the logistics of node acquisition over a producing field with infrastructure on the seabed and rigs at work and (2) the image uplift from processing the data using cutting edge technologies like FWI and LSRTM.