Innovative Design and Execution Lead to Successful Grand Banks Platform Operations

Abstract

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 28803, “Hebron Platform: Innovative Design and Efficient Execution,” by Widianto, Justin Chichester, Adel Younan, and Jameel Khalifa, ExxonMobil; Krishna Komperla, WorleyParsons; and Knut Bidne, Kvaerner, prepared for the 2018 Offshore Technology Conference, Houston, 30 April–3 May. The paper has not been peer reviewed. Copyright 2018 Offshore Technology Conference. Reproduced by permission. The Hebron platform was successfully installed on the Grand Banks offshore Newfoundland and Labrador in June 2017. It consists of a single-shaft concrete gravity-based structure (GBS) supporting an integrated drilling and production topsides. The design of the platform was challenged by sub-Arctic and extreme metocean conditions that required innovative design and layout approaches for many elements considered routine for typical platforms. This complete paper highlights the underlying technologies, analytical and design methods, and capital-efficient execution strategies employed. Introduction The Hebron platform comprises a GBS and topsides installed in 93-m water depth. Produced crude oil is stored in storage cells and pumped to shuttle tankers by an offshore loading system. The topsides facilities (operating weight 65,000 tonnes) include the following major modules: Utilities and process module (UPM) Derrick equipment set (DES) Drilling support module (DSM) Ancillaries (flare boom, east and west liftboat stations) Living quarters (LQ) designed to accommodate 220 personnel during steady-state operations The total height of the platform with GBS is approximately 235 m, topsides length is approximately 183 m, and the width is approximately 75 m. The GBS concept includes a single shaft supporting the topsides and encompasses all wells in the initial development. It is designed to withstand sea ice, icebergs, and other meteorological and oceanographic conditions at the offshore Hebron site. The GBS is designed for an in-service life of 50 or more years to support future developments. The lower portion of the GBS up to an elevation of approximately 27 m was constructed in a drydock created by building a bund wall and dewatering the site behind it. Subsequently, the dock was flooded, the bund wall was removed, and the GBS base was towed approximately 3 km to a deepwater site. The floating GBS was held in place with mooring lines while the remaining construction was completed. All walls were constructed using the slip-forming technique. The topsides structure was fabricated in modules at various locations in Newfoundland and Labrador and South Korea. Two of the topsides modules, UPM and DES, were fabricated in South Korea using block/pancake construction methods (Fig. 1). After UPM and DES fabrication was completed, the modules were loaded out separately to heavy vessels for transportation to Bull Arm, Newfoundland and Labrador. All other topsides modules were integrated with the main UPM module at the finger pier in Bull Arm and the completed topsides structure was mated with the GBS while floating at the deepwater site. The mated platform then was towed offshore and installed at the final offshore location.