Float over topside installation has become a cost effective alternative for offshore construction over the past 25-30 years, as ever-increasing integrated topside weight constantly exceeds the lifting capacity of installation vessel cranes.
The basic concept of float over installation is to transport the topside on a vessel in one piece, position the vessel over the substructure, and lower the topside onto the substructure while maintaining the position of the vessel.
While this basic principle of loadout and transportation remains the same, methods and systems used to execute the concept vary significantly, and pose numerous technical and operational challenges.
PETRONAS Carigali Sdn. Bhd. (PCSB) undertook the development of BARDEGG-2 and Baronia EOR project located offshore Sarawak, Malaysia within South China Sea. Baronia B Central Processing Platform (BNCPP-B) was installed in May 2017 and was the first PCSB's float over installation by a portable Dynamic Positioning 2 (DP2) vessel.
A Deck Transportation Vessel (DTV) was upgraded with DP2 capability by adding two portable azimuth thrusters to allow safe and efficient installation of the topside. Sea trials and annual DP trials were conducted in ensuring DP functionality and performance in compliance to Class requirement. Float over engineering was performed including float over design criteria, hydrodynamic analysis and mating analysis. All outfitting, secondary steel works and grillage structures were installed on the vessel before mobilization for transportation and installation of BNCPP-B Topside.
The operation required high precision engineering and execution considering the close proximity between BNCPP-B Topside and existing BNQ-B platform during the vessel approach towards BNCPP-B Jacket. Additional control measures were taken for safe execution. DP checks were conducted at certain intervals while approaching the jacket. BNCPP-B Topside installation commenced at first daylight on 22 May 2017 and successfully completed by noon.
It has again proven that float over installation by portable DP2 vessel was technically feasible and would be an example for future projects undertaking the same approach. Having a vessel with portable DP2 system will help to optimize the vessel utilization and improve overall project cost.
This paper aims to highlight the float over methodology for BNCPP-B topside using portable DP2 vessel and the technical challenges for offshore execution. The activities during the float over operation, analysis and simulation methods are also presented in this document.
This paper should be an interest to those who will perform the offshore installation via float over method utilizing Portable DP Vessel.
Pan Malaysia Maintenance, Construction and Modification (PM-MCM) Contract 2018 – 2023 is a PETRONAS-led initiative in collaboration with Malaysian Oil & Gas Operators, which are also known as Petroleum Arrangement Contractors (PAC), aimed at cost optimization through the technical standardization of offshore Hook-up and Commissioning (HUC) and Topsides Major Maintenance (TMM) works. The initiative was participated by ten (10) Petroleum Arrangement Contractors (PACs) operating in Malaysia (redundant).
The initiative competitiveness relied heavily on the number participating PACs in order to accumulate and integrate sufficient volume of work through sharing of their long-term offshore work plan over a period of 5 years with active contribution on lessons learned, best practices, and challenges. Leveraging on high volume of work per region will generate the economics of scale thus drive cost reduction.
The technical standardization is achieved through the identification of minimum requirements for each work (HUC and TMM) by operators, and where applicable, common specifications are accordingly derived. This simplifies the requirements and accordingly reduces the number of specifications to be complied across the region, thus, effectively allows the HUC/TMM Contractors to competitively quote the best price for the services.
Apart from the technical standardization and optimization above, the initiative is further supplemented through the standardization of the Contract Terms and Conditions among the PACs. However, landing to an agreement amongst the ten (10) established Oil & Gas Companies was crucial and considered as a major challenge, as each company had operated differently under their own set of Terms & Conditions. Despite this, consensus achieved towards standardization.
In assisting the tender evaluation and aligning with PETRONAS’ effort towards Digitalization of its Busines Operation, digital tools were deployed. Online eAuction and digital bid price analyzer were extensively used to commercially evaluate and to identify best value for PETRONAS and PACs, respectively.
In conclusion, the PM-MCM contract was successfully awarded with a significant cost reduction against the original estimated cost by approximately 40%. In comparison to previous contracts, Pan Malaysia MCM also recorded significant reduction in most of the unit rates of similar services rendered. Market feedbacks obtained by participating bidderss indicated that the standardization had indeed helped the participants to lower their prices.
Pan Malaysia Maintenance, Construction and Modification Contract has brought forward industry players into one crucial objective of cost optimization. The collaboration between PETRONAS and PAC which resulting for greater impact and value to all players involved through productivity improvement and cost reduction.
Kvaerner, in a joint venture with KBR, signed a contract with Statoil to provide the topside for the utility and living quarter platform at the Johan Sverdrup field in the North Sea. The agreement is worth approximately USD 875 million and includes an option for commissioning assistance and offshore hook-up for the platform. Detailed engineering has already begun and fabrication is expected to begin next spring. Kvaerner holds a 51% interest in the project and KBR holds the remaining 49%.
The Caspian Sea is the largest landlocked sea between Asia and Europe with its own pros and cons. The enormous reserves in Caspian has created great opportunities for Oil and Gas operators and their partners (Service and EPIC Contractors). The design and installation of offshore structures have been always inspiring for structural designers and naval architects. In the past decade, various installations have been successfully completed using different techniques based on the availability of marine vessels & cost dynamics. This paper provides insights about challenging techniques used for various installations including Topside float over keeping focus on Safety, various technical aspects and cost effectiveness right from detailed engineering to installation phase. Considering availability of marine heavy lift vessels in the region and their day rates considering the constraints with the Volga-Don Canal size, the following methods/Designs were developed and implemented: 1. The jacket was divided into two parts (lower and upper). Each portion weighing approximately 400 mt (metric ton) were installed one above the other with locator mechanism to maintain lower CAPEX. This was mainly due to non-availability of heavy lift vessels.
Fixed Offshore Platforms (FOP) in shallow water depths for wellhead-cum-production operations are frequently installed by float-over deck technique to reduce offshore tie-in and commissioning time. Generally, float-over deck installation method is justified for a medium to reasonably large topside involving many equipment (related to process, electrical, instrumentation, utilities and HSE) and piping that can be pre-commissioned onshore to a large extent before sail-off. A high CAPEX for construction and installation of such platforms may be justified for a proven field in which reserve may last for several years with 8 or more numbers of drilled wells. However, when the reservoir volume and pressure is uncertain, the investment risk is too high to make a commercial decision for a medium to large sized offshore platform.
Whatever be the installation technique, structural design of an FOP is greatly influenced by the topsides requirements in terms of space and weights of various equipment/facilities to be supported and the construction/installation methods to be adopted. In the present study, structural design of an offshore wellhead-cum-production platform in 26m water depth is carried out considering a conventional but two-phase installation approach for the structure as well as the topside facilities. This approach for an oil production platform is suggested to reduce the high initial CAPEX when the expected success of drilling outcome is uncertain. The first phase will consist of only essential facilities such as power generation/supply unit, equipment for well testing, separation of water & gas from oil, heating unit in case of high viscosity crude and critical safety related equipment before sending the crude to onshore through pipeline. In case of successful drilling outcome and proven reserve, the offshore platform can be further extended (Phase-2) by installing remaining facilities such as installation of low pressure system, sand handling unit, artificial lift equipment, produced water treatment plant.
A comparison of structural weight and cost has been made between the proposed platform and an actual float-over platform of similar deck space. The advantages of the proposed design are (i) significant reduction of investment risk by lowering the initial cost and (ii) significant reduction of the overall structural weight resulting in cost saving for structural material and fabrication.
In spite of two-phase installation approach, the cost of conventional installation will be less than the float-over installation due to the requirement of smaller capacity crane vessel and less marine spread. Based on the results, it is found that a two-phase installation approach may govern the design for certain fields due to low initial cost and reduced overall cost of medium sized FOP's.
Allseas Engineering's giant new offshore construction vessel has a new name, prior to its first job. What was once the Pieter Schelte is now the Pioneering Spirit. The change occurred in early February after Jewish groups protested that the original namesake, a pioneer in creating the heavy lift offshore business, supported the Nazi war effort by serving in the SS during World War II. The company said the vessel's new name, "reflects what she stands for: a new technological step in platform installation and decommissioning. It also fits the 30-year tradition of Allseas to pioneer and surpass technical boundaries."
Wang, Alan M. (Offshore Oil Engineering Co., Ltd.) | Jin, Xiaojian (Offshore Oil Engineering Co., Ltd.) | Liu, Yiyong (China National Offshore Oil Corporation) | Tao, Fuwen (Offshore Oil Engineering Co., Ltd.) | He, Chen (Offshore Oil Engineering Co., Ltd.) | He, Min (Offshore Oil Engineering Co., Ltd.)
This paper presents the floatover hardware systems and the operation procedures of this innovative low-deck floatover technology, as well as its successful application in the floatover operations for a drilling and production (DPP) platform in South China Sea. Great lessons were learned from the first failure attempt. A combination of conventional low-deck floatover scheme and strand-jack lifting technology is adopted to rectify previous serious defects. Various field measurements, including a barge motion monitoring system, an environmental monitoring system, a visual monitoring system, and a strain gauge stress monitoring system, etc., have been employed to ensure the success of this challenging floatover installation. The advantages and disadvantages of this unique floatover method are also addressed here.
An innovative low-deck floatover technology was developed in combination with a sophisticated strand-jack lifting system to successfully install 12,700Te large integrated topsides onto a preinstalled eight-legged jacket standing in a water depth of 106m in South China Sea in August, 2014. This innovative floatover method can be divided into two phases: first a conventional floatover method with an extremely low-deck position, only 2.7m above the barge deck, is applied to perform the docking, mating, undocking operations and then a strand-jack lifting system with 24 strand jacks installed atop the four outer legs, 6×850Te lifting capacity per leg, is used to raise the topsides up to the final design elevation, including multi-phase leg welding and load distribution onto inner legs during this second phase.
A more complicated strand jack lifting technology was adopted in August 2013 but failed to install the integrated DPP topsides. Initial failure to lower the four outer support legs with smaller strand jacks yielded an unfortunate chain of events, thus yielding a complete failure of the floatover installation never happened in history. A rescue operation was carried out thereafter. It took a great effort to successfully salvage both the topsides and the floatover barge which were stranded for two days inside the jacket slot in extraneous circumstances. The failure events of the first-attempt low-deck floatover technology are briefly reviewed here. Refer to Wang et al. (2014) for details.
This paper presents the nonlinear time-domain mating simulations and their major findings successfully applied in designing the installation devices and selecting the dominant design parameters, thus ensuring the successful execution of the DP floatover installation for the HZ25-8 DPP integrated topsides. It is essential to correctly and accurately model the jacket flexibility, fender gaps, nonlinear fender stiffness, as well as the contact mechanism and high nonlinearities of the elastomeric elements in LMUs and DSUs, etc., and therefore obtain reliable and repeatable design maxima. The analysis of the results meet the design requirements, and successfully completed in May 21, 2014.
Float-over is an offshore installation method which describes the operation of transferring the integrated topside onto a pre-installed jacket by float-over vessel’s ballasting system and tidal change, it’s first introduced in year 1983 and applied on the installation of topside of Phillips Maureen Project. Refer to He et al. (2011) for details. Since then many float-over concepts have been successfully applied on fixed platform even floating platform. DP float-over describes the float-over operation by maneuvering the DP vessel entering the jacket slot and holding station during weight transfer without the aid of moorings. Refer to Brink et al. (2011) for details.
Dynamic positioning float-over technology is a new type of float-over installation technology combined with dynamic positioning system and float-over installation technology. Refer to Johan et al. (2011) for details. It uses barge transport platform topside into the jacket slot installed, implements barge loading adjustment, tide level and other ways to transfer the topside weight during the installation process. In the meantime, it is supplemented by fender components to complete installation technology of topside and jacket docking operation. But the biggest difference is that does not require the mooring system positioning and auxiliary tug traction, which saves costs and preparation time of manufacturing, installation and use of these devices and structures, and it does not need the large floating crane and cooperation of professional personnel when installation. The main advantage of the differences are: (1) DP float-over installation can resist worse offshore work condition and increase weather window of construction operation, which can effectively guarantee the time limit of topside installation schedule requirements. (2) DP float-over installation operation eliminates the arrangement and connection of mooring system, and its cost will not increase with the increase of water depth. (3) The DP vessel in the installation process has good ballasting ability and precise docking ability, which is easier to meet the weather window needed, especially suitable for the South Chinese sea under harsh environmental conditions. (4) The DP vessel has the ability of self-propulsion, which saves the ship sailing days and is higher safety. During the installation process of float-over, there is no need of the assistance of tugboats, which saves the cost of ship. Analysis of DP float-over installation is complex, which needs to design a docking fender system to analyze the DP capability. Refer to Xu et al. (2011) for details.
Jung, S. J. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Kwak, H. U. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Oh, S. H. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Kwon, Y. J. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Nam, B. W. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Kim, N. W. (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Lee, Kangsu (Korea Research Institute of Ships and Ocean Engineering (KRISO)) | Sung, H. G. (Korea Research Institute of Ships and Ocean Engineering (KRISO))
In this study, time-domain mating analyses were carried out to verify safety of float-over operation during various load transfer stages. Water depth of the target field is 130m. Topsides weighing 20,000 ton will be installed on fixed jacket structure by float-over using DTV (Deck Transportation Vessel) with the support of mooring lines. Five (5) operational stages from initial contact to 100% load transfer have been assessed by time domain analysis. For topsides mating analysis, DSUs, DSF Support Points, LMUs, steel-to-steel contacts at LMU points, sway fenders, mooring lines and many parts were modelled to investigate the interactions between the DTV, the topsides and the jacket. The results of analyses have been approved by a MWS.
There are two methods for topside installation at offshore fixed structure. In case of heavy integrated topside, lifting method is limited by allowable lifting weight of crane vessels. Float-over method can handle the heavy topside by DTV's ballast system. If a topside weight is becoming heavier, the Float-over method is preferred. Since the first success of HIDECK float-over integration in 1983, many projects have been carried out with float-over method installation.
Jung et al. (2009) evaluated impact loads occurring at various load transfer during the mating phase by performing frequency domain and time domain analysis. Min He et al. (2011) analyzed the time domain using Moses and applied nonlinear spring to DSU, Fender, and LMU. Kurian et al. (2013) carried out model test and numerical calculations to confirm motion performance of the barge for the float-over installation. Magee et al. (2014) conducted a float-over installation model test. The barge motion response and the dynamic load acting on the LMU were measured and the instrumentation for the model test was described. Kim et al. (2017) carried out float-over model test in various load transfer stages.
This study is a part of research project funded by a Korean government to develop the technologies for offshore topsides installation. The research project is aimed to develop installation design package of float-over method for 20,000 ton class topsides on jacket structure.
Yu, Wentai (Offshore Oil Engineering Co., Ltd.) | Wang, Alan M. (Offshore Oil Engineering Co., Ltd.) | Zhu, Shaohua (Offshore Oil Engineering Co., Ltd.) | Xu, Jingkuo (Offshore Oil Engineering Co., Ltd.) | Wang, Andy (DNV GL Oil & Gas China) | Luo, Hanbing (Tianjin University)
This paper presents the rapid load transfer technology and the hydraulic jacking system, as well as its different applications in floatover installations. The innovative jacking hardware and its central control unit are described in details, as well as the detailed mating operation with the rapid load transfer technique. This load transfer technology which combines slow ballasting and rapid jacking operations will shorten the initial mating and final separation within one minute, thus minimizing the weather exposure period and enabling the floatover installation suitable to the harsh environment conditions such as long-period swells and large-amplitude waves. In addition, the jacking operation will benefit the stability of the floatover vessel during transportation. The advantages and disadvantages of this unique floatover method, especially in combination with dynamic positioning floatover vessels, are also addressed here.
Many different floatover technologies have been developed and successfully applied to offshore installations of large integrated topsides onto various fixed and floating substructures since 1983. Several rapid load transfer technologies have been developed recently to surmount the significant movement of floatover vessels in long-period swell conditions such as West Africa, cyclonic conditions like in Indian Ocean and South East Asia, as well as large-amplitude waves in the high air-gap areas of Canada and Sakhalin Island, and so on. These innovative load transfer technologies enable short-time mating and separation duration of floatover installations and therefore increase installation window and ensure safe installation operation.
The rapid load transfer technique is developed to combine active hydraulic jacking operation and ballasting operation during mating phase to avoid high impact load between the integrated topsides legs and the pre-installed substructure legs. This combined operation of rapid jacking and conventional ballasting can achieve an initial leg mating between topsides and substructure and a final separation with an instant gap between topsides and DSF in a very short duration of approximately one minute. This is very different from the conventional ballasting operation which takes nearly one hour to achieve initial mating or final separation. The active hydraulic jacking system with a central control unit is first used to achieve the docking clearance by jacking up before entering the substructure slot. Upon docking and positioning the floatover vessel inside the substructure, the docking clearance will be closed rapidly and then the initial 20-30% load transfer will be completed by lowering jacks within duration of only one minute. The mating operation will be continued by ballasting down floatover vessel and extending jacks second time until the 70-80% load transfer is completed. A rapid ram retraction is performed again within one minute to complete the 100% load transfer, as well as to achieve an instant gap, about 1.0m, for safe undocking operation. The rapid initial mating and final separation enable floatover installations suitable to the harsh swell conditions up to a significant wave height Hs = 1.2m – 1.5m with a peak period range of 10 seconds – 14 seconds.