Imaging Conductor Pipes in the Gulf of Mexico Using 3-D High-Resolution Seismic Data: Containing One of the Largest Oil Spills in US History

Mississippi Canyon Block 20 (MC-20) was Taylor Energy's oil platform in the Gulf of Mexico, located approximately 19 km (12 mi) from the mouth of the Mississippi River. In 2004, Hurricane Ivan generated an underwater mudslide that overturned the production platform and displaced it approximately 152m (500ft) downslope, leading to a significant oil spill. During the mudslide, the conductor pipes were disturbed and buried in sediment up to 57m (187ft) over the top of the wellhead. Since then, this oil spill has reportedly become the longest running in the history of the United States and one of the largest to date. To assist with remediation efforts, precise detection and visualization of the buried conductor pipes was required. In May 2022, Kraken Robotic Systems (formerly PanGeo Subsea, a subsidiary of Kraken Robotic Systems) was contracted by Couvillion Group to conduct a sub-bottom/below mudline (BML) survey of the MC-20 site using their specialized, high-resolution Acoustic Corer™ (AC) technology. The AC comprises collocated transmitters, low and high-frequency chirps, and a parametric source that covers a frequency range of 1.5kHz to 12.5kHz using a fixed landed survey platform. The acoustics are designed to penetrate the sub-seabed to obtain a 14m (46ft) diameter volumetric “acoustic core” down to 60m (197ft) below the seafloor. To image and interpret the conductor pipes within the MC-20 site, 63 AC surveys were acquired throughout the 205m (673ft) x 60m (197ft) survey area. The AC data processing followed standard seismic procedures using ZoomSpace™ in-house software. Rather than mosaicking the individual acoustic cores, the pre-processed data sets were merged and migrated into a single unified volume which was statically corrected to the same processing datum. This resulted in enhanced resolution and coherency for accurately identifying and representing the conductor pipes. After processing and interpreting the acquired data, the full extent of the conductor pipes was identified, and the locations of all structural and geological features were digitized within the sub-seabed. The upper sub-seabed was dominated by unconsolidated sediments intermixed with blocky clay and the conductor pipes were observed to be reposing onto a highly consolidated basement layer. Specifically, 18 smooth and continuous linear conductor pipes were identified, presenting as a collective bundle, constricting at its center and splaying outward as they continue from the collection dome towards the well bay. A region of acoustic blanking was observed within the survey area northwest of Row 11, near the well bay. The combined application of merging high-resolution seismic data into a unified volumetric data set, as applied in this study, enabled a detailed representation and characterization of the conductor pipes for the first time.