AEGIR is a time-domain seakeeping CFD code that uses an advanced, high-order boundary element method (BEM) to solve the three-dimensional potential-flow and has been developed for several years. In this paper, the latest version of AEGIR is used to predict the seakeeping of the Tri-SWACH with and without side hulls in headsea regular waves respectively. The primary objective was to evaluate its accuracy of predicting seakeeping performance of the Tri-SWACH under regular headsea waves in AEGIR. A series of simulated time domain heave and pitch responses for Tri-SWACH with and without side hulls via AEGIR have been compared with corresponding model tests conducted in the high speed towing tank in Davidson Lab, Stevens Institute of Technology. A good agreement in terms of heave and pitch responses between AEGIR numerical predictions and experimental data shows the seakeeping prediction capability of AEGIR for Tri-SWACH Preliminary Design. Also, the simulated seakeeping of a Tri-SWACH is compared with a Tri-SWACH center hull. It is found that the effects of side hulls will increase the transverse stability of the Tri-SWACH without causing additional significant effect on the seakeeping performance of the Tri-SWACH.

A Ship-shaped FPSO is one of most popular hull forms in oil and gas industry. The only alternative hull in operations with minor market shares is the cylindrical FPSO hull. In order to add contractual options and competitions to reduce field development costs, an innovative hull, eco-FPSO, is proposed and presented in this paper. The proposed hull form shall make it possible to utilize the proven technologies and does not need any step-out applications, technologies and qualifications including equipment limitations, fabrication, transportation, installation, and health, safety and environmental (HSE) considerations. The development philosophy is to focus on entire life cycle of the FPSO to reduce the CAPEX, OPEXand development risk. The proposed hull form shall meet the following criteria: Simple hull geometry without any moving parts and/or mechanical jacking system Without scarifying safety with similar ship-shaped FPSO topsides layout and having adequate deck area and separation spaces between topsides modules No turret (Turretless) system and no thruster system No need to disconnect and re-connect even in harsh environmental conditions Low motions and accelerations for, SCRs, Sensitive topsides facilities and utilities Conventional offloading operations Efficient hull and topsides connection and loading transfer Good constructability and easy for pre-assembled topsides modules Good transportability and installability Overview of an eco-FPSO hull is proposed and introduced and a case study with 1MM bbls oil storage in harsh environmental condition is described and highlighted. Preliminary analysis results of motions, moorings and risers are presented and discussed. Brief conclusions on the features of the eco-FPSO hull form are drawn.

For many offshore developments, there is a drive to minimize the required manning and enabling remote operations to reduce personnel exposure and to reduce the overall cost (lighter topsides, simpler hull, less maintenance). This paper considers semisubmersible production facilities and investigates the opportunities and challenges of an unmanned hull from an overall field development perspective. The unmanned hull poses challenges related to typical practice for the frequency of inspections inside the hull and the closed compartments within the hull. In order to achieve a fully unmanned hull, inspections should be minimized, and ideally completely avoided during the intended service life, if possible. The paper highlights key design features required to achieve a hull design with minimal inspections. Opportunities that will be discussed include, minimizing the hull equipment and system requirements (e.g. ballasting operations), implementing sealed compartments, and enhancing the fatigue life of the hull structure to avoid inspection requirements during the lifetime of the unit. The paper discusses several design challenges associated with an unmanned hull. These include addressing Class and Flag requirements, (i.e. Class and shelf state regulations that may be a barrier for unmanned operations), risk of entering the unmanned hull, damage tolerance, and damage response capability.

Through a collaboration between ROWAN COMPANIES PLC, BP and 3DENT TECHNOLOGY LLC, a series of coming off location (CoL) studies were carried out to develop an approach for increasing the weather window during which operations can safely be performed. ROWAN's patent-pending technology (entitled "Multi-Stage Coming Off Location Technology") uses onboard instrumentation with the results of the CoL studies specific to a given jack-up to increase the weather window for CoL operations. In its initial deployment, the technology uses a 3-Stage Approach. For the given site, with known water depth and expected leg penetrations, onboard instrumentation is used to obtain real-time wave and hull response information. Then, based on the results in sequential checks (STAGES), GO/NO-GO decisions are made, based on pre-determined limits. In this paper, the authors present the background that lead to the 3-STAGE approach, key features for a valid CoL analysis and data from the initial (trial) deployments of the system for the calibration of the analytical models.

During coming off location operations for jackups (the transition from the elevated mode to the afloat and then the transit mode), the hull is jacked down into the water to obtain a buoyancy force great enough to retrieve the legs. In locations with soft clays, leg penetrations in excess of 15m are common. When the legs are stuck, it is rare that all legs become unstuck simultaneously, and whether planned or not, single-leg jacking becomes necessary to pull the legs. One effect of single-leg jacking is that the hull inclination relative to the leg induces leg bending moment that gets transferred to the hull as a combination of a vertical couple (i.e., differential chord load on the pinions) and a horizontal couple (i.e., upper and lower guide loads). The magnitude of the loads for a given amount of jacking on a given leg is a function of the leg's effective stiffness, which varies with water depth and soil stiffness. This paper presents the results from a study intended to increase the understanding and quantify the degree of internal leg loads that are developed for a given amount of single-leg jacking in different water depths and with different soil rotational stiffness values. This is done so that these internal loads are properly accounted for when establishing environmental limits for the coming off location operations.

A Tapered Column Deep Draft Semi-submersible (TCDD-Semi) concept has been developed for dry tree drilling and production applications. The new concept features enlarged lower hull geometry with gradually varying column cross-section, in contrast to conventional semi-submersible design with uniform columns. The enlarged lower columns, in combination with properly sized upper columns and pontoons, provide sufficient buoyancy and stability for topside integration at quayside and offshore pre-service operations such as submergence and wet-tow. Most importantly, this new TCDD-Semi concept with tapered columns optimizes the cancelation effect of wave force and is able to reduce the heave motion in harsh environmental condition for dry tree applications with top-tensioned risers. This paper will present the topside and hull configuration, tank arrangement and ballasting system, stability, as well as mooring system, riser system and global performance design, platform global strength analysis and global fatigue analysis, hull vortex induced motion analysis. In addition, platform fabrication and topside integration methods will also be discussed. The design analyses show that the proposed TCDD Semi-submersible platform has advantages in heave motion performance, topside integration flexibility, and transition stability during pontoon submergence. Its excellent heave motion performance enables the application of top-tensioned riser system with 35 feet (10.5 m) stroke limit. The new design also significantly reduces platform VIM compared with conventional deep draft semi-submersible.

Two production semi-submersibles that were based on Exmar Offshore Company's proprietary OPTI& Hull had been successfully constructed and installed in the Gulf of Mexico in the past five years. The OPTI& hull features pontoon lip extending outboard of five-sided columns. The pontoon lip improves heave motion and the five-sided column design has proven effective in Vortex-Induced-Motion (VIM) reduction. This paper presents the methodology and main considerations in the OPTI& hull sizing process. With a set of limiting criteria, an in-house hull sizing program is used to generate thousands of hull configurations and to perform diffraction and radiation analysis. Subsequently, the hull steel weight and heave motion is examined to determine a design front on which a better compromise between hull steel and motion is achieved. A few candidate hulls may be selected with further considerations of constructability, mechanical and electrical equipment arrangement and structural design restrictions. Finally, Client's preference, riser design requirements, installation and operation preferences, and economics are fully considered.

The hull forms of the sanctioned FLNG projects are all ship-shape with either internal or external turret systems. The cylindrical hull for FLNG application without turret system has been studied for years. Recently, Sansom and Ankarsward (2016) presented a six-column rectangular shape Semi for medium FLNG. In this paper, a conceptual study of an alternative, a Paired-Column Semi-Submersible (PC Semi) platform with spread moorings, is presented for a 1.5 MTPA FLNG application in Western Australia. This study is a generic one to design an economical small FLNG which can be achieved through modular topsides layout, robust hull configuration and turret-less mooring arrangement without scarifying safety and operability. The aim of this study was to explore an alternative option within current industry capability to reduce the overall investment, complexity and risk as much as possible. A PC semi has low motion characteristics with eight columns suitable for large storage requirements and can efficiently support large deck area for production facility with gas processing, treatment and liquefaction facilities, offloading facilities and Living Quarter. This conceptual study presents a generic exercise of efficient topsides and hull configuration and layout with considerations of its constructability, transportability, installability and operability. Advantages of a PC Semi vs. a ship-shaped hull are addressed and highlighted. Standardized and phased approach with multiple small FLNG units vs. a single mega FLNG unit is also discussed.

A truss Spar with direct vertical access merit has been designed and installed in ultra-deep water of Gulf of Mexico for a few years. This paper intends to carry out a comparative study of a Paired-Column Semi-submersible (PC-Semi) platform with the same topsides payloads, TTRs tensions, Ram-style tensioners with 28-ft stroke range and same SCRs tensions in the same metocean criteria with same global performance and mooring design criteria. PC-Semi hull form development and evolution for ultra-deep water dry tree applications in central Gulf of Mexico have been undertaken for a few years through RPSEA ultra-deep water program. Extensive and comprehensive model testing including wind tunnel tests, wave basin tests and VIM tests has been completed successfully. Feasibility and advantages of PC-Semi for dry tree application with large topsides payloads in central GoM have been published and established for years. PC-Semi platform Approval in Principal has been awarded by DNV. Application of PC-Semi concept as an alternative to Spar for West GoM with fewer top tension riser counts and less topsides payloads than those in central GoM was carried out in this study to identify advantages of hull form and scalability of PC-Semi concept. PC-Semi hull and mooring configurations are sized and validated through comprehensive global performance analysis consisting of offsets, rotations, vertical motions, minimum airgaps, maximum accelerations and TTR strokes and mooring analysis. After validation analysis, key figures of hull and mooring configurations along with the detailed global performance results of PC-Semi are summarized and discussed. Features of pre-service conditions, such as feasibility of vertical wet tow and quayside integration, of both hull forms are also addressed and highlighted.

The discoveries made in the pre-salt basin offshore Brazil are among the world's most important in the past decade. The pre-salt province comprises large accumulations of excellent quality, high commercial value light oil, however, the new discoveries are located in ultra-deepwater in areas lacking infra-structure, which makes the Floating Production Storage and Offloading (FPSO) vessel the preferred solution. Steel Catenary Risers (SCRs) are the preferred solution in wet-tree applications due to their simplicity, robustness and low CAPEX and OPEX compared to other riser options. However, due to its relatively high dynamic motions, FPSO is not a feasible host for SCRs in most environments. Also, for efficient production from such rich reservoirs, facilities supporting high production rate and large diameter risers are necessary. This makes it more challenging to find a robust and commercially attractive riser solution. In this paper a novel design for an FPSO with the ability to host large diameter SCRs is presented and evaluated for applications in deepwater field developments. The new design, namely, Low Motion FPSO (LM-FPSO), has a hull form with a generally rectangular cross-section. The platform is moored in-place using a conventional mooring system. The LM-FPSO performance is enhanced with the robust low-tech feature, namely, free-hanging Solid Ballast Tank (SBT). The SBT is located at a certain distance below hull keel and connected to the hull through four groups of short tendons. All tendon components are the same as those used in conventional TLPs. Through the mass and added mass of the SBT, the LM-FPSO provides heave, roll and pitch responses better than or comparable to any floating production structure in use today. The paper presents detailed description of this novel design and its in-service performance. A case study is presented where the LM-FPSO is used in persistent swell in ultra deepwater offshore Brazil to support large diameter SCRs. The SCR's feasibility is demonstrated and reported. The identified risks and associated mitigations for the new design compared to the conventional FPSO are investigated and reported. The paper concludes with discussions on the project execution plan, cost and schedule benefits when developing fields using this novel design.

Recent crude oil prices were dropped more than 50% and new norm price may be fluctuated around $40 to $80 per barrel in many years. In addition, metocean criteria have been increased significantly after Hurricane Katrina and Rita which have imposed considerable impacts on field development in GoM, prior to steep declination of crude oil prices. Under multifactorial pressures on economics of field development in deep water of central GoM, it imposes extraordinary difficulty in sanction of deep water projects and calls for innovative solutions to significantly reduce cost and meet challenges. This paper is intended to present one development scenario of TLP concept in response to the market calls. One study scenario has been carried out based on same design basis and topsides payloads for conventional TLP (CTLP) and secondary column enhanced TLP (SCE-TLP) for central GoM in 4,000 ft water depth. Preliminary global performance analysis has been undertaken to ensure satisfaction of design criteria, such as extreme tendon tensions and minimum airgap, etc. In addition, a high level hull structural scantling of SCE-TLP was performed in order to yield reliable hull steel weight estimate. Preliminary comparison of deck/hull structure weights and tendon/foundation weights of CTLP and SCE-TLP is highlighted and major advantages of SCE-TLP are identified and discussed.

Wind tunnel testing is an almost universal practice in the design of floating production installations (FPIs). The results of these tests have been applied to many aspects of design; including mooring and stability analyses. This paper reports on the parametric study of six different FPIs that operate in the Gulf of Mexico and compares the results of the stability analyses based on wind moments determined with wind tunnel tests and wind moments calculated by the conventional Building Block Methodology. The results of this investigation are presented in the form of allowable VCG and relative effect of the topside weight capacity.

In 2013 the Fincantieri Offshore Business Unit started the Concept Design process for a very innovative UDW Drillship with a r-evolutionary drilling designed by Castor Drilling Solution, a Norwegian company part of the Fincantieri galaxy. One important feature of the innovative tower is the efficiency of the operations in terms of time saving and energy recovery, characteristics that are very attractive to a drilling operator. Every tower on board can be associated with one dedicated firing line, which means that the dual activity function, typical of the modern UDW exploration vessels, foresees two independent towers, which can be positioned on board with a relative freedom in order to optimize other important characteristics such as the drillfloor area and its availability. During the development of the design it was discovered that the increase of the distance between the two towers has a positive impact on the entire package: the platform and the drilling system. However, the increased distance between the firing lines has a negative impact on the dimensions of the moonpool and, as a consequence, on the midship structure and the hydrodynamic effects. What appeared to be a problem at the beginning, transformed itself into several opportunities during the development stage of the project. The paper describes the process of integration of the innovative Tower with a drillship platform and its optimization with particular focus on structural and hydrodynamic aspects.

The interaction between a general hull and a Dynamic Positioning (DP) thruster is investigated using a hybrid method which couples a Vortex-Lattice Method (VLM) solver for the thruster and a Reynolds Averaged Navier-Stokes (RANS) solver for the ambient flow and the surrounding boundaries. The simulated flow field is examined so as to assess the significance of the thruster/hull interaction in the dynamic positioning system.

Barge-shaped FPSO (Floating Production, Storage and Offloading) units are the most favored and adopted development choices in the oil and gas development offshore West Africa, and to a less degree offshore Brazil and in South China Sea as witnessed by the recently completed projects over the last several years. To keep the facility in position, either a spread or turret mooring system has to be designed, fabricated and installed. The first step in mooring system design is to size the mooring lines which rely on accurately predicting the current, wind and wave forces. Due to the complexity of topsides and the uncertainty in predicting the forces numerically, physical model tests are most always carried out. In this paper, a simple, elegant and cost-effective numerical approach is presented and validated to predict the current loading. Comparison between previous model test data and numerical results showed excellent agreement for various operating conditions and for transit condition. It is discovered that to correctly assess the yaw moment on a FPSO, the Munk moment on a FPSO has to be properly accounted for in this numerical approach. The accurate way of estimating the Munk moment is discussed. It is concluded that the proposed tool, simple but elegant, is very cost effective in accurately assessing the current loading on a barge-shaped FPSO, and thus, is a valuable tool for PRE-FEED, and/or FEED, or even Detail design phases of a barged-shaped FPSO project.

The first Tension Leg Platform (TLP) was installed in 1984 to develop the Hutton field in the Central North Sea in about 500 ft. of water. It successfully demonstrated the ability of a floating platform tethered to the seabed to drill and produce with surface trees. In the ensuing years, twenty three additional TLPs have been installed and three more sanctioned, in most major deepwater producing regions around the world, in water depths down to 5,200 ft. The TLP today is a mature and proven deepwater production platform and is routinely included as a platform concept building block for many deepwater prospects during field development planning for dry or wet tree scenarios. This paper presents a retrospective of TLP development that includes: An overview and description of TLP hull configurations Basic hull and tendon design considerations A chronology of TLP designs, applications and contracting strategies The evolution of TLP tendon and foundation systems

The U.S. Beaufort Sea may hold the largest undiscovered oil deposits which could account for up to 25% of the world's undiscovered hydrocarbons based on the article of "Science." Therefore, there are strong interests for oil and gas industry to explore these enormous reserves of oil and natural gas in order to meet the long term increasing energy demands. In Beaufort Sea, an averaging water depth is about 800m which is normally called deep waters. An exploratory well typically takes about five to six months for continuously drilling in shallow waters. Beaufort Sea has an average two-month open water window, thus an exploratory well will take two to three years to complete if only seasonal drilling is considered. In deep waters, it is much more complicated and challenging and will take a few times longer than drilling in shallow waters. Seasonal drilling for deep waters is practically and economically prohibited. Year-round drilling capability is a truly required feature. To have year-round drilling ability, hull and mooring has been designed to withstand ice actions of first-year ice, ridge and up to multi-year ridges depending on disconnection criteria. In Beaufort Sea, it is practically impossible to design the floater to stay in-place for 30-year service life for any ice actions. Thus, dis-connectable ability is another desired feature when a sizable iceberg or unmanageable ice feature is approaching. As of today, there are a few dis-connectable concepts had been proposed, such as disconnectable FPSO, non-ship-shaped circular FPSO, arctic Spar and semi-ridge floater. These concepts are either designed for benign ice conditions or intended just for seasonal drilling and production. So far, no floating drilling and production facility has been installed with year-round operation capability in Beaufort Sea. It strongly calls for development of alternative dis-connectable arctic floating platform concept to explore mega reserves in deep waters of cold regions. This paper presents HOE persisting efforts for developing innovative arctic floating platform concept having above mentioned features in past six years. A preliminary disconnection procedure of HOE arctic floater for drilling and production is outlined as an example.

This paper describes the history of human powered submarines designed, built, and raced by ocean engineering students at Texas A&M University. The first submarine was the Aggie Ray that participated in the 1991 ocean races at Riviera Beach in Florida. These submarines are flooded, and the pilot and driver are equipped with SCUBA while operating the submarine during the races. Texas A&M Ocean Engineering students have built 5 different hulls, including one- and two-person configurations, during the period 1991–2012 and some hulls have been used in 4–5 races. The first European International Submarine Race competition was held in Gosport, England in June 2012, and the Texas A&M submarine, Maroon Harpoon, experiences are discussed. The 2013 races are scheduled for the David Taylor Model Basin in Bethesda, MD. The Ocean Engineering students are planning to design and build a two-person submarine which allows two persons to power the submarine. Recent computational fluid dynamics software has been used to assist in designing the hull shape and the results are described. The annual costs of building and participating in the races borne by the team sponsors are described.

Mega oil and gas reservoirs have been discovered in deep and ultra-deep offshore Brazil. These Pre-Salt discoveries are remotely located at water depths ranging from 2200m (~7,200 ft) to 2600 m (~8,500 ft). Offshore Brazil has unique metocean conditions with long swell periods which present challenges on floating platforms such as Spars and Semis. In addition, the remoteness of location and the associated high cost of vessel mobilization add further pressure on economics and risk. Quayside integration is thus a desired feature of the hull concept in order to eliminate offshore mating and the associated risk to cost and schedule. To explore these pre-salt complicated ultra-deepwater reservoirs usually require large drilling rig and drilling variable payload which result in very large topsides in both size and weight. Spars and TLPs are the only two proven dry tree hull forms in deep and ultra-deep waters in the GOM. However the TLP becomes cost prohibitive if the water depth is beyond 1,524 m (5,000 ft). For large payload systems requiring a large drilling rig, a suitable Spar size creates a challenge for transportation and installation. The semi-submersible hull form is known to offer advantages over Spars such as larger deck space and quayside integration which are essential to reducing offshore commissioning time and risk as well as cost and schedule. Maturation of the dry tree semi-submersible solution in GoM ultra-deepwater (2,400m) had been undertaken by RPSEA and dry tree Paired Column Semisubmersible (PC Semi) platform, developed by Houston Offshore Engineering, was selected by the RPSEA committee in 2009. Extensive wind tunnel tests and wave basin model tests including 1,000-year central GoM hurricanes were successfully completed in 2010. PC Semi hull configuration, TTR stroke, the analytical results and simulation tools had been fully validated. This paper presents validation analysis results of a dry tree PC semi developed with conventional RAM style tensioners, in 2,400m ultra-deepwater of Offshore Brazil Pre-Salt carrying same topsides payloads as RPSEA. The validation analysis was performed by the correlated analysis tools and established analysis procedures. The design efficiencies including payload, steel weight and production efficiencies of PC Semis for BPS and central GoM are addressed and discussed. Highly efficient PC Semi for BPS has been developed, validated and became "market ready".

The TLTP (Tension-Leg Turbine Platform) is a floating, permanently moored structure designed to support a utility-scale offshore wind turbine in water depths of 40 meters and greater. This paper discusses the design tools and unique design process used for this novel structure. Reasons for selecting a tension-leg platform (TLP) are discussed. Motivations to apply TLP technology to relatively shallow water depths are explained. The requirements for supporting a wind turbine, which are fundamentally different than the requirements for supporting a typical oil and gas payload, are discussed.