Texas GulfLink is the only proposed offshore crude oil export terminal whose design complies with all current safe maneuvering guidelines for VLCCs at an SPM.

Every aspect of the Texas GulfLink deepwater port has been thoughtfully designed by professionals and engineers with decades of relevant experience. Industry regulations, standards, and guidelines concerning engineering an offshore platform or pipeline pump station have existed for decades. Until recently, the same could not be said for how a deepwater port with integrated single-point mooring buoys (SPMs) was to be laid out. The offshore environment is dynamic and unpredictable, and oil tankers have gotten larger. That is why it is critical that any offshore installation be designed, constructed, and operated with the utmost care and consideration of the risks posed to the health and safety of the environment and the personnel involved.

Texas GulfLink’s team has significant experience operating offshore deepwater ports and have firsthand knowledge of those risks, including those associated with the navigation of VLCCs into and around the terminal. Texas GulfLink’s Director of Marine Operations, Captain Dan Harris, is one of the few licensed Mooring Masters in the U.S. who has considerable experience with SPM mooring and unmooring VLCCs at a deepwater port, having done so safely and without incident for over 18 years at Louisiana Offshore Oil Port (Loop).  

With an increase in deepwater port applications to obtain a license, industry associations, international classification societies, and certifying entities have begun to develop guidelines for the design specifications around deepwater ports relative to the overall layout, particularly in unprotected offshore waters. Considering the complexities involved in safely operating a 1,100 ft long vessel laden with 2,000,000 barrels of crude oil around fixed offshore objects (like manned platforms), well-informed safe operation guidelines and their operational compliance are critical.

As originally conceived, Texas GulfLink developed its “Safe Port Design”, which includes installing its two SPMs at a distance of 1.25 nautical miles (1.5 miles) from its manned platform and 1.32 nautical miles apart from each other. This distance provides sufficient clearance for the VLCC not only as it weathervanes around the SPM during loading (its “swing circle”), but also during departure from the SPM when the VLCC is laden and slow to react, gain steerage, headway, and counter the forces acting on the massive underwater hull.

The “maneuvering area” is the area through which a vessel is to maneuver in making an approach to or a departure from the SPM. A radius extending outward from the center of the SPM is used to indicate the distance measurement of the maneuvering area. When designing the layout of a deepwater port with SPMs and other fixed structures, the importance of getting the maneuvering area right cannot be overstated. The “minimum maneuvering area” (MMA) for an SPM port design is dependent on environmental conditions and vessel class. For example, SPMs that will service VLCC Class Tankers (1,100 ft) need more clearance (and thus will have a bigger MMA) than SPMs that will service Aframax class tankers (735 ft). For that reason, industry guidance includes a multiplier on the length of the largest mooring vessel when calculating MMA.

Texas GulfLink’s navigation team, led by Captain Harris, has devoted countless hours and resources to ensuring that its deepwater port design was sufficiently safe and compliant with all current guidelines, including commissioning maneuvering studies and simulations, consulting with multiple senior Master Mariners, obtaining a Lloyd’s Register full port assessment, reviewing other existing Deepwater Port SPMs, and closely reviewing all Class, OCIMF, and PIANC guidance documentation and updates. Texas GulfLink ultimately settled on a 1.25 nautical mile distance between its platform and its SPM, which was determined to be beyond the calculated MMA for Texas GulfLink’s proposed location in the Northwest Gulf of Mexico.

U.S. Coast Guard regulations define “exposed waters” as more than 20 nautical miles offshore and which presents special hazards due to weather or other circumstances. Within the industry, exposed waters are also referred to as unprotected waters or waters exposed to extreme sea conditions. In those environments, breakaways at SPM deepwater ports will occur from time to time and port designs must account for this and other upset events. LOOP experienced one in April 2021 from a sudden unforeseen severe weather event when a VLCC broke away. In 1989, Exxon Houston broke away from the Barber’s Point, HI SPM terminal as well.

As proposed, Texas GulfLink’s 1.25 nautical mile distance between its platform and SPMs puts its manned platform well outside the 1.1 nm MMA calculated using all applicable guidelines and industry standards for loading VLCCs at Texas GulfLink’s location. Below is a summary of those guidelines and standards:

American Bureau of Shipping (ABS) Rules for Building and Classing Single Point Moorings – Rule 3.5 Maneuvering Area (2023)
(Please see Part 3, Chapter 1, Section 2, Page 19)

ABS’s rule on maneuvering area distance was amended effective January 1, 2023, to provide that the maneuvering area (previously 3x the length of largest vessel, plus hawser length and maximum buoy offset) is to be “increased substantially to account for an additional safety allowance necessary for safe vessel maneuvering” when SPM is used in offshore exposed waters. For deepwater ports proposing to load VLCCs in protected waters, the MMA is approximately 0.65 nautical miles; however, deepwater ports in unprotected offshore environments should be increased substantially beyond 0.65 nautical miles taking into account potential extreme weather and sea conditions. Rule 3.5 further makes clear that “Fixed obstacles such as platforms or buoys, other than the mooring, are not to be anywhere within the maneuvering area.” Texas GulfLink’s 1.25 nautical mile platform-to-SPM distance complies with the new ABS rule.

ABS is a global leader in providing classification services for marine and offshore assets and is one of the leading certifying entities for the U.S. Coast Guard.

PIANC WG-200 Report - Recommendations for the Designs and Assessment of Single-Point (SPM) and Multi-Point Mooring (MPM) Facilities (2023) (purchase the full report here)

On March 1, 2023, PIANC, The World Association of Waterborne Transport Infrastructure, published a Working Group report (WG-200) to provide guidance on good “industry practice” and a uniform set of recommendations for the design, analysis, and maintenance of SPMs. The PIANC Report provides that “in nearshore and protected waters, the radius of the maneuvering area (and distance to danger line) is recommended to be at least four times the length of the operating tanker.” In offshore locations in exposed waters (>20 nm), the radius of the maneuvering area should be “significantly increased” beyond the MMA. Further, PIANC reports that “some operators will typically consider 1.2 nautical miles as the maneuvering area or greater to incorporate a safety margin factor into the maneuvering area radius.” Texas GulfLink’s 1.25 nautical mile platform-to-SPM distance complies with the new PIANC recommendation.

PIANC is a global organization providing guidance and technical advice for sustainable waterborne transport infrastructure to ports, marinas, and waterways, similar to the OCIMF.

Lloyd’s Register Port Assessment Report 2023

In 2023, Texas GulfLink consulted with Lloyd’s Register for a compliance review and safety audit of not only its safe port design but to provide an expert determination about the MMA for deepwater ports in offshore exposed waters of the Gulf of Mexico. Lloyd’s Register opined that under the applicable rules (ABS SPM Rules, PIANC WG200, and OCIMF SMOG), the MMA for a facility located in a similar Gulf of Mexico location as Texas GulfLink would be 1.1 nautical miles. Texas GulfLink’s 1.25 nautical mile platform-to-SPM distance complies with Lloyd’s Register’s guidance.

Lloyd’s Register is a global professional services company specializing in engineering and technology for the maritime industry and is one of the leading certifying entities for the U.S. Coast Guard.

Glosten – Northern Gulf of Mexico Deepwater Port Shallow Water Ship Simulation

In 2021, Texas GulfLink retained Glosten to model and simulate the movement of a VLCC with engine failure at a facility located in a similar Gulf of Mexico location as Texas GulfLink using the MMA calculated by ABS’s then-existing Rule 3.5 (0.65 nautical miles) for protected waters. Glosten’s simulations resulted in a conclusion that a 0.65 nautical mile maneuvering area was an unsafe distance in extreme sea conditions in an offshore environment and that the VLCC would strike the fixed platform under those conditions. Note: The reference to “shallow water” refers to the ratio of water depth to vessel draft. Glosten’s simulations support the need for a substantial increase in the maneuvering area distance beyond 0.65 nautical miles in offshore exposed waters.

Glosten is a worldwide full-service naval architecture and marine engineering consultancy recognized and respected throughout the maritime industry.