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OTC 20237
Developments in Deepwater Spar Installation
R. Narold, 0. Willemse,.iand C. Brenninkmeijer, Heerema Marine Contractors
Copynght 2009, Offshore Technology Conference
This paper was prepared for presentation at the 2009 Offshore Technology Conference held in Houston, Texas, USA, 4-7 May 2009
This paper was selected for presentation by an OTC program committee following review of information contained ie an abstract submitted by the author(s). Contents ofthe paper have not been reviewed by the Offshore Technology Conference and are subject to correction by the author(s). The material does ext necessarily reflect any position of the Offshore Technology Conference, its officers, nr members. Electronic reproduction, distribution, or storage of aey part of this paper withost the written consent of the Offshore Technology Conference is prohibited. Perrnisvnn to
reprcduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgmentof OTC copyright.
Abstract
During the last seven years Heerema Marine Contractors (HMC) has installed more than halfofall Spars in the deep waters of
the Gulf of Mexico. The dual crane deepwater construction vessels have proven repeatedly that a complete Spar installation,
from piles to hull, topsides and SCR (Steel Catenary Riser), can be performed very efficiently with a single vessel.
Since the first Spar was insta'led, significant challenges have been overcome throughout every phase of the Spar
installation. Spar anchor piles for example have included installation ofboth driven piles in water depths of up to 4,900 ft, and ofsuction piles in 8,600 ft ofwater. Another good example is a recent industry first, where the VIV strakes on the belly side of a Spar were installed offshore. This offshore installation eliminates the need to compromise in the design ofthese VIV strakes, which will be beneficial for the Spar during the rest ofits operational life.The advantages of using installation vessels with large deck space and with dual cranes with a high lifting capacity, is demonstrated in almost all phases of the Spar installation. A large deck area with dual cranes allows for easy handling and
upending of items such as piles and Aircans. At the same time it is also possible to store several mooring lines on the deck at
once, allowing for flexibility in the order in which these lines are installed. An additional advantage of the Deepwater
Construction Vessel (DCV) Balder is that it has installed both Spiral Strand Wire and Polyester mooring lines with the 10.6 m
diameter Mooring Line Deployment (MLD) winch. The Semi Submersible Crane Vessel (SSCV) Thialf has recently been
outfitted with a similar capability.
HMC is best known for its heavy lifting capacity, which is reflected by the installation of Spar topsides with modules ofup
to 8,695 st. The large weight allows significant savings in cost by outfitting most topsides components onshore at a yard.
A specific example of tools used in order to obtain flexibility is given by means of the in-house developed Mooring Line Hook-up software. This software allows greater insight in the various forces acting on the Spar and the installation vessel. Software such as this allows making offshore decisions for the best route forward during the installation of mooring lines,
while reducing overall risks and downtime. lt is shown that especially during the installation of polyester mooring lines, where the forces are less well known in advance due to fabrication tolerances, an adjustable procedure has its advantages.
In 2008 HMC introduced the Incident and Injury Free (11F) program. This program aims to change the mindset from one of "accidents happen" to one where working incident and injury free all the time is achievable for everybody.
In conclusion this paper shows that all three of HMC's installation vessels have proven that they are capable of deepwater
Spar installation HMC has the advantage of having two vessels with similar deepwater capability, providing considerable
savings on mobilization, mode change and weather downtime and allowing greater schedule flexibility.
Introduction
One may question the necessity of using a large heavy lift vessel for the installation of deep water floatingstructures in the Gulf of Mexico. At face value, most installation work for Spars can in principle be carried out with the "smaller" assets, which have been introduced by many contractors operating in the deep waters of the Gulf.
In reality however, there are many factors which have made the deep water Operators decide that for the installation ofa
deep water Spar, for example, the unique equipment offered by a contractor like Heerema Marine Contractors defmitely adds value to their developments. As a result of this, Heerema Marine Contractors, (HMC) has been involved in the installation of more than half of all deep water Spars in the Gulf of Mexico. Although some of these were partial installations, where HMC offered an urgently needed helping hand, in most cases it involved an integrated transport and installation service.
HMC's track record includes the deepest development to date; the Shell-operated Perdido Spar in 7,817 ftwater depth in the Alaminos Canyon area, but also includes the successful installation of a number of Spars in the infamous loopcurrents and eddies of areas like Green Canyon and Atwater Valley.
2 OTC 20237
HMC has proven repeatedly that Spars can be installed very efficiently using our dual crane deepwater construction vessels. These vessels are adapted for deep water pipelay in J-lay mode for the installation of steel catenary risers and
flowlines and the use of a unique mooring line deployment winch for the safe deployment of all known types of mooring lines. The installation equipment offered by HMC has been instrumental in ensuring the Spar hull reaches storm safe status in the
shortest amount of time. This also provides the assurance of completing the installation of the entire facility in the shortest
possible window thereby protecting the delivery date for first oil.
Installation periods differ per project and in some cases have taken place right in the middle of the hurricane season. These situations require meticulous planning of the logistics phase and close interface with all involved parties including a number of regulatory bodies.
HMC increased its vessels' capital value by investing heavily in Dynamic Positioning power, allowing us to continue work in hostile loop currents and eddies.
Computer software has been developed specifically for offshore use allowing offshore rescheduling of mooring operations depending on the direction of the daily current situation (in loops and eddies), also made possible by marshalling all mooring components on deck, rather than on the beach.
We are flexible in scheduling the installation of platform components like moorings and SCRs, since these can either be
pre-laid or build-up in situ, using i-lay equipment with high top tension capabilities. This flexibility is why operations based on multifunctional installation vessels like l-IMC's Balder and Thialf have been a preferred solution by a number of Operators.
In this paper we explain how our methods are being engineered to deliver the highest level of safety and reliability we
require to protect our personnel and equipment according to the Incident and Injury Free (11F) standard we practice.
HMC's track record
The starting point for this paper is HMC's track record of successful Spar installations in the deepwater Gulf of Mexico. This track record goes back to Horn Mountain for BP in 2002 up until most recently Shell's Perdido hub. At the time of
writing, the piles, moorings and hull of Perdido have been successfully installed by DCV Balder in 2008. The 9,500 st topsides will be installed end of February 2009 with the Semi Submersible Crane Vessel (SSCV) Thialf. Upon completion, Perdido will be the deepest Spar in the Gulf of Mexico, installed at a water depth of 7,817 ft. This installation also includes the record for the deepest permanent suction anchor pile at 8,600 ft. An overview of the particulars of each Spar installation by HMC is given in Table 1.
In 2005 a paper was presented at the OTC [ref 1] in which the first of these Spar installations were described. Since then
HMC has installed Kerr-McGee's Constitution and CVX's Tahiti Spar in the Green Canyon (blocks 680 and 640) and Shell's Perdido in the Alaminos Canyon (block 857) of the Gulf of Mexico.
Both DCV Balder and SSCV Thialf are DP class Ill installation vessels that have large diameter mooring line deployment
winches and capabilities for ultra deep water installations due to their large capacity Abandonment and Recovery winches.
Their similar capabilities allows for a great flexibility in schedule. This flexibility showed when the Tahiti Spar Hull
installation, which was planned for the Thialf in 2007, had to be delayed due to unforeseen circumstances. The Spar was
eventually installed by DCV Balder early 2008. Another example of this flexibility is that both vessels have been used in BP's Thunderhorse PLET re-installation in 2008. Table 2 provides an overview of HMC's installation vessels main characteristics.
Evolution of the installation procedure
Compared to the 2005 paper [ref. 1], many changes have taken place in the way Spars are installed. Greater insight has
been gained in, for instance, polyester mooring line installation in large water depths, requiring unique challenges compared to
spiral strand wire. Most of these changes are a form
of
evolution due to the experience gained and the technology developed.This evolution is mainly aimed at reducing the time required to install a Spar to storm safe condition, the most critical phase of the hull installation. A Spar is considered storm safe when it can withstand for example a 10-year winter storm or even a
one-year hurricane. Most commonly storm safe is reached when one line of each cluster [Table 1] of mooring lines hasbeen installed. The installation procedure after storm safe has also increased in both flexibility and duration, allowing a company to reach the all important first oil on target.
A look at some specific steps of the Spar installation will show how the installation procedure has evolved to where we are now and to what may lie ahead of us in the future.
Anchor pile installation
All HMC's installation vessels have vast experience in installing both driven and suction anchor piles at a wide range of
water depths. The advantages of having a large deck area and the option of dual crane upending and overboarding hardly needs
explanation. Storing multiple piles on the installation vessel's deck reduces the weather sensitive operation of (unmooring
barges. Dual crane upending followed by lowering of a pile vertically through the splash zone can also be performed at higher sea states compared to having to lower a pile through the splash zone almost horizontally.
The large capacity of the cranes allows for ultra deep water installation of large anchor piles. Constitution has proven that
driving piles at a water depth of 4,900 ft is a very feasible option, with the proven possibility of using driven piles in even deeper water. Suction anchor piles of 185 t have been installed in water depths of 8,600 ft. currently the deepest permanent
Spar tow
After arrival in the Gulf of Mexico, usually by means of submersible transport vessel, a Spar is towed out to sea by tow
tugs. Increases in Spar size and restrictions in water depth along the tow route have lead to some challenging solutions to limit
the draft of the Spar. For Holstein and Mad Dog the VIV strakes on the belly side of the Spar were omitted on the bellyside
and the Spar was left with missing sections. For Perdido the strakes on the belly side were partially trimmed to ensure the
bottom clearance during wet tow, while for Tahiti an industry first was performed by installing the missing part of the Spar's
VIV strakes offshore. A separate paper on this subject will be presented at the OTC '09 conference [ref. 2]. This offshore installation, which was performed by DCV Balder, shows that smart solutions mean that no compromise is necessary to
achieve the optimal design.
Spar upending
tJpending a Spar, from its horizontal tow position to its vertical operational position, generally consists of two phases, Soft Tank flooding and Hard Tank ballasting [fig. I]. Soft Tank flooding is most commonly designed to induce a roll of the Spar in
a predetermined direction. A designed roll ensures that pre-installed components, such as the Motor Control Centre and
Hydraulic Power Units do not submerge during Soft Tank [fig. 23.
The second phase, hard tank ballasting, has been optimized to be performed as quickly as possible, without losing track of the stability requirements of the Spar. HMC's installation vessels are generally able to provide higher water ballast flow rates
then allowed by the designer. This is a difficult cost consideration since higher flow rates require higher grade and larger
diameter piping. This piping is not used daring the remaining lifetime of the Spar. On Constitution and Perdido tanks high up in the hard tank had to be used for wet tow stability, heel and trim requirements. In both cases, a draining system was installed to drain the water from these high tanks to the lower tanks in the hard tank. This saves critical time since it prevents that water
that is already in the Spar needs to be pumped in again offshore. Moving water ballast from high to low tanks is also a quick
win in stability during upending of the Spar.
The ballast plan is optimized to ensure that the minimum amount of ballast has to be added in critical time, with measures
taken to add water ballast later in non-critical time. A good example of added value of this particular solution was present
when a Spar had to be abandoned for a hurricane. All nine mooring lines were already installed at this point and preparations
for fixed ballast were underway. In order to limit impact of fatigue life of the strakes of the Spar, it was decided by the designer, the client and HMC, to add additional water ballast to the Spar and increase the draft to a point where the strakes
were fully submerged.
Mooring line installation
Both Balder and Thialf are capable of installing both polyester and spiral strand wire mooring lines. DCV Balder has, at the time of commissioning, in 2001, the largest Mooring Deployment winch in the world with a drum diameter of 10.5 meters and a width of 14.2 meters, which has a proven track record of over a hundred kilometer of spiral strand and polyester mooring line successfully installed [fig. 3].
Some of the advantages of this large winch are:
The large diameter drum allows for low sheathing pressure
The 14.2 m width allows for large segments to be spooled single layer, reducing the risk for sheathing damage 275 t SWL line pull allowing 12% dynamics
Maximum lowering speed of 40 rn/mm
Protruding outboard, for obstacle free handling of the wire Suitable for both SSW and polyester types.
An additional feature on both the Thialf and the Balder is the unique equalizer system. During the installation of a Spar mooring line, this system allows the vessel to transfer the horizontal component of the pulling force of the mooring line
directly to the Spar. This allows for greater workability, because there is no need to usc DP powcr to pullthe mooring line to
the Spar. All available thrust can therefore be used for station keeping purposes.
Polyester mooring line installation has proven to need some additional consideration, due to unknown stiffness and length
properties of the line and stricter installation criteria compared to Spiral Strand Wire. At the moment the MMS requires that the polyester mooring line does not touch the seabed at any time during or after the installation. The additional flexibility
required to deal with the installation of polyester mooring lines will be discussed in a separate chapter.
The sequence in which the mooring lines are installed is dependent on the environmental conditions and is determined
offshore. The large deck space of the installation vessels allows for storage of multiple mooring lines. This allows the decision for the next mooring line in the sequence to be postponed to a very late stage, allowing the order of the lines to change along with the weather.
4 OTC 20237
Fixed ballast installation
One of the last steps of Spar hull installation is the installation of fixed ballast in the soft tank. Fixed ballast usually consists of a type of inert metal, similar to hematite. This material is pumped from a (hopper) barge over the installation vessel's deck
to the top of the Spar in the form of dense slurry. The piping is routed over a fixed ballast boom, supported by one of the installation vessel' s cranes. From the top of the Spar separate piping is routed to each of the soft tank compartments.
The piping is routed over the deck of the installation vessel to limit the motion sensitivity of the procedure. SSCVs are
known for their excellent motion characteristics. Routing the piping over a fixed ballast boom allows for a higher access point to the Spar, making weathervaning easier for the installation vessel [fig 4]. The motions of both the barge and the SSCV can thus be limited by choosing the optimal environmental heading.
Accuracy is of the utmost importance for this part of the installation. The amount and distribution of fixed ballast
determines the stability of the Spar during its operational life and therefore the payload of the Topsides. HMC tries to apply the KISS. principle to the fixed ballast installation. The basic philosophy is that there are three vertical forces acting on the Spar:Gravity: the combination of the weight of the Spar, the water ballast and the amount of added fixed ballast Buoyancy: due to the displaced water, taken from the hydrostatic tables
Mooring lines: the vertical component of the installed mooring lines.
By measuring the draft along the centre line of the Spar, the buoyancy can be derived from the hydrostatic tables. The
change in buoyancy is equal to the installed amount of fixed ballast. This amount has to be corrected for the change in tension of the mooring lines. As the Spar draft increases, the tension in the lines decreases. The decrease in tension has to be added to the increase in buoyancy to derive the actual amount of fixed ballast installed. Although this seems straight forward, in case of polyester mooring lines, with some uncertainty in the properties, especially this last step requires great attention.
SCR installation
The challenge with hanging off SCRs to a Spar is to have enough crane capacity at Soft Tank level. The other challenge is
to have enough horizontal capacity to pull-in the SCR into its designated porch. On several Spars, HMC has combined
equipment for the pull-in of both mooring lines and SCRs. This reduces the amount of equipment needed and the preparation time on top of the Spar. A linear winch placed on the Spar deck together with a set of sheaves and a spooler winch is used to
pull-in both the mooring lines and the SCRs. Advantage of SCR hang-off with a SSCV is that the relative motions between
Spar and vessel are minimal, which increases workability during the critical hang-off of the flexjoint into its porch.
As mentioned in the introduction there is a great flexibility of the installation sequence of the Spar hull and SCRs, since the SCRs can either be pre-laid or build-up in situ, using J-lay equipment with high top tension capabilities. Another advantage of having a multifunctional vessel is that switching between installation and pipelay can be done in a short time, without having
to (de-)mobilize expensive equipment. During one of the last installations performed the Balder changed from mooring line
installation mode to pipelay mode within one day.
Installation of Aircans
Various Spar installations have included the installation of Aircans, or other types of top tensioned risers. A good example of such an installation is described in the 2003 OTC paper concerning the Horn Mountain Spar installation [ref. 4]. The latest
air can installation was performed during the Constitution Spar installation in 2005. The great lifting height of the cranes of
HMC's installation vessels allows for a relative easy installation of long sections, with the same added advantage as with the piles of a large available deck space and dual crane upending possibilities.
Spar Topside installation
HMC is best known for its heavy lifting capabilities. This capability greatly enhances the feasibility of the Spar concept.
Offshore commissioning time is expensive, and therefore it is of great importance to allow as much pre-outfitting as possible
to take place at the yard. Table 2 shows the current capacity of HMC's crane vessels, which are still the largest in the world
when it comes to heavy lifting. Both Thialf and Balder allow full DP-Ill capability for heavy topside lifts. The DP upgrades
described in the 2005 paper [ref 1] have proven their worth in countering any instability and performing installations in eddy currents.
Polyester Mooring Line installation
As has been said before, the most important first steps of the Spar installation procedure are aimed at getting a Spar storm
safe as early as possible. However, the quickest path to storm safe is not always clear in advance. The
environmentalconditions that act on the Spar, the tugs holding the Spar in place and the installation vessel can determine what the best order for installation of the mooring lines is at that particular time and what the best procedure is. This section is aimed at showing how these decisions are made and what the additional complexity is that polyester mooring lines bring to the equation of the
Forces on polyester mooring lines
The variables that determine the forces acting on the installation vessel and the Spar during hook-up of mooring lines need
to be determined first. We can split the force acting on the mooring line in two components; i.e. the weight acting in the vertical direction and the catenary acting in the horizontal direction. For spiral strand wire, both are quite well defined. The
stiffness of the system is given based on the properties of the steel. With polyester this is not as straight forward. The length of
the polyester is known within a certain fabrication tolerance, usually +1- 0.5% of the length. For ultra deep water, this can amount to a length deviation of 100 ft. This variation can mean a difference between 110 t or 22% of the in line tensions,
which may lead to some components possibly being loaded beyond their allowable safe working loads.
The same unknowii applies to the stiffness. The paper in reference 3 discusses the detail of the installation of polyester mooring lines for the Mad Dog Spar. Most of the same issues described there are still valid. However the understanding of which variables are there and the size of these unknowns has already led to improvements in the polyester mooring line installation procedure. For every type of mooring line installed by HMC, DNV has performed tests to determine the load-elongation characteristic throughout the life of the polyester. In the beginning of its life however it remains very unclear to
where on the cycle the polyester actually is during the installation and specifically during each phase of the installation. Again this difference is in the range of 75 t, or 15% of the total in-line tension. Now we can examine the influence of these unknowns on the force in the mooring line. The weight of the mooring line is the sum of the polyester and the amount of ground chain not lying on the bottom of the seabed. This amount increases for a shorter or stiffer mooring line. The catenary of the line is also determined by the weight and stretch of the line.
In recent developments we have seen shorter ground chain lengths to reduce total mooring line weights and production costs. This however increases the difficulty of the mooring line installation. A shorter ground chain length decreases the
clearance of the polyester mooring line with the seafloor significantly. This especially makes the mooring line deployment and the transfer of the mooring line to the Spar more complex. lt also must be taken into account that due to the low stiffness of the polyester mooring line during installation and a possible Spar offset, caused by for example the 1oop current, the chance that mooring lines will touch the seabed will also increase significantly. HMC's procedures and software are specifically designed to take these scenarios into account.
Mooring line installation software
HMC has developed software in-house that is used widely within the company for catenary calculations. This software has been certified by DNV in the past. During the installation of the Perdido and Tahiti Spars new Mooring Line Hook-up (MLH)
software was developed which is a shell programmed around the certified catenary software, enabling a click-and-play calculation of each step of the installation procedure. This software was the result of a process started during the installation of
BP's Mad Dog Spar and Enterprise's Independence Hub. The basic steps of a typical mooring line installation can be
summarized as follows [figures 5 through 7]:
Mooring Line deployment (using smart buoy procedure)
Equalizer system connected to Spar hull (or choose to install on DP only) Transfer of platform chain inc. mooring line from installation vessel to Spar Mooring line pull-in, messenger chain removal and mooring line connection.
The main goal of this software is to provide accurate answers, without the need for time consuming calculations.
Additionally, it always helps to have a clear graphical interface showing the relevant forces acting on each vessel when havingdiscussions with all parties involved such as the Captain, Superintendent, the Client and Marine Warranty Surveyor. This
software can be used for both Spar and semi submersible installations.
The sequence in which the mooring lines are attached to the Spar is determined by the sum of all forces acting on the Spar. Since station keeping of the spar for the first set of lines is performed by tugs, the sequence is determined by the least amount of thrust required by the installation vessel, taking into account a conservative estimate of the behavior of the mooring lines. If the environmental conditions are favorable enough, the use of the equalizer option can be omitted in order to save some time.
The extreme scenarios are taken into account in order to optimize the installation sequence. On the one hand, if the stiffness turns out to be low and the polyester segment length is long, the clearance between the polyester and the seabed
becomes critical. On the other hand, if the stiffness is high and the polyester segment length short, the installation vessel will need most of its DP power to sail to the Spar and has less left to counter the environmental conditions.
The in-house developed mooring line hook-up software can quickly determine the sum of the forces acting on the Spar caused by the environment and the tugs, so all possible installation sequences can be easily evaluated and themost optimal
installation sequence can be determined on the spot. It can also be used to determine maximum conditions in which the
operation can proceed if eddies or heavy storms are nearby [fig. 8].
Once the optimum sequence has been established the MLH-software is used to determine the envelope in which the tugs have to position the Spar during hook-up of the mooring line. The limits are determined by the thrust the installation vessel needs to deliver and the clearance of the polyester mooring line with the seafloor once it has been attached to the Spar. The
limits are calculated as a distance from the pile of the mooring line in question, thus leading to an envelope for station keeping
6 OEÍC 20237
showing the distances to sail, for both the tug and installation vessel and the lowering distance for the link held up by the tug acting as the buoy [fig 10]. The smart buoy procedure is aimed at keeping the polyester mooring lines clear of the seabed when the mooring line is being deployed from the installation vessels winch and the vessel is sailing towards the Spar.
Once the first set of mooring lines is installed to the Spar, the tugs are either released or idle. The MLH-software can now be used to determine the optimal sequence of the next mooring lines. Additionally it can be used to determine whether or not to reposition the Spar with chain jack operations in order to help lower the forces for installing the next mooring line. If the Spar is closer to the anchor pile of the next mooring line to be installed, this reduces the tension in the mooring line making it easier to install without losing out on DP capacity and therefore workability. However this will decrease the clearance of the mooring
line to the seabed during installation. The software will show directly what the impact is on the polyester mooring line
clearance with the seafloor in this situation.
The software presented here is under continuous development to offer more flexibility and quick calculation of more
difficult equations if required.
Safety Mindset: incident and Injury Free
Along with improvements to the technical side of Spar installation, other aspects such as safety and management are all
integral parts of any excellent installation. It is therefore important to mention that after years of improving safety statistics, the
last few years the amount of incidents and injuries within HMC has seemed to level off to a certain stable minimum. Since
every incident is still considered one too many by HMC and by modern day industry standards, HMC has adopted a program aimed at changing the mindset of its employees with respect to safety. In 2008 HMC introduced the Incident and Injury Free (11F) program. This program is aimed at changing the mindset from one of "accidents happen" to one where working incident
and injury free all the time is achievable for everybody. At this point the program has been implemented at all HMC offices
and vessels worldwide. HMC also includes its subcontractors in the training program.
Conclusion
HMC's vast experience with Spar installation in the Gulf of Mexico has led to a great evolution of the possibilities for Spars and Spar installation. HMC has proven in practice that with the right equipment, the right tools and the right mindset the critical windows available to install a Spar can be reduced to a minimum. A flexible approach leads to a problem solving attitude which does not compromise safety in any way, but actually strengthens the safety mindset by allowing adjustments based on the actual situation. Ali three of HMC's vessels have proven that they are capable of Spar installations, with the
added advantage that two of those vesels have similar deepwater capability, providing considerable savings on mobilization, mode change and weather downtime and allowing greater schedule flexibility.
As illustrated by the described mooring line hook-up software, HMC is still striving to improve its installation capability and flexibility by introducing new tools and techniques that help to reach an optimal installation procedure and minimize risks.
Whether a Spar requires installation of suction or driven anchor piles, spiral strand wire or fiber rope, including SCRs of different sizes, HMC's vessels are eminently suited for the job. They have a proven track record of delivering qualrty and
safety, with the boundaries of their capability far from being reached.
References
I. 0TC2005-175l6, "Spar Installation in Deep Water - A Developing Technology", M. Hendriks & F. Lange, HMC,
May 2005, Houston, TX, USA
0TC2009-l9878, "Fabrication and Installation of Tahiti Truss Spar Belly Side Strakes", P.E. Griffin, H.T. Jones,
Chevron;A.Cattell, Consultant, M. Schcffer, HMC, S. Miller, Technip, May 2009, Houston, TX, USA
D0T2004 23-3, "Mad Dog polyester mooring system installation and operation", David Petruska, Hugh Wylie, Jeff
Geyer, BP America Inc.; Saskia Rijtema, Heerema Marine Contractors, Nov 2004, New Orleans, USA
0TC2003-l5367, "Installation of the Horn Mountain Spar Using the Enhanced DCV Balder", Cees Dijkhuizen, Ton
"planned at moment of publication "not installed by HMC
Table 1:Deepwater spar installation by HMC in the Gulf of Mexico
Tab e 2: Overview of HMC's installation vessels
Project information
Oil company BP Kerr-McGee BP BP Kerr-McGee CVX Shell Project Horn Mountain Gunnison Holstein Mad Dog Constitution Tahiti Perdido
Installation Installation Period March/June 2002 August / September 2003 October 2003 & April / May 2004 February / March / April / July 2004 March September I November 2005 March 2007 / March-May July 2008 F ebruary / August / Septeni ber 2008 & March 2009 HMC Instatlatron Balder Balder, Herniod Balder, Thialf Balder, Thiaif Balder, Thialf Balder, Thialf Balder, Thiatf
Water Depth (ft)
5400 -3150 -4340 -4500 -4970 -3995 -7800 Hull Characteristics
Type Truss-spar Truss-spar Truss-spar Truss-spar Truss-spar Truss-spar Truss-spar
Diameter (ft) 106 98 149 128 98 128 118
Centrewetl (ft) 52x52 42x42 75x75 60x60 42x42 50x50 46x46
Overall Length (ft) 555 549 745 555 554 555 555
Weight (Sh.T) 15,000 13,800 35,350 21,250 15,000 23.900 19,524
Topside Characteristics
No. of Major lifts (s 1000 Sh.T)
1 major lift, dual crane
i major lift, dual
crune
4 major lifts, dual
crane
2 major lifts, dual crane
I major lift, dual
crane
3 major lifts, dual
crane 2 major lifts, 1 dual crane" ""ajor Lift(s): Weight )Sh.T) 4387 5754 4120, 4400, 5315, 8340 7640, 4050, 1300 6,400 2460, 8695, 5760 9500, 14CC" Topsides Malor
Lift(s) Production Deck Production Deck
MSF, N-Module, S-Module. DR
Production Deck,
Drill Rig, LO Production Deck
MSF, Production Module, UM
Production Deck, LO
Mooring Wire Characteristics
Nos. 9off 3 clusters ol 3 R4 Studless 9off 3 clusters of 3 K4 Studless 160ff 4 clusters of 4 R4 Studless 110ff 3 clusters R4 Studless 9off 3 clusters R4 Studless l3off 3 clusters R4 Studtess 9off 3 clusters R5 Studless Configuration
Platform Chain Type
Diameter 5.75" 5.6" 6.7" 5.75" 5.59" 6.18" 5.28"
Length)ft) 800/930 850/1030 900 950 800-850 1000-1325 1060-1170
Submerged Weight 375 356 509 372 365.6 513 327
Intermediate Wire Type 55W SSW SSW PR SSW PR PR Diamnieter (sheath) 5.0")0.5") 5.0"(0.5") 5.8(0.5") 10.63" 4.92")0.43") 9.69" 9.69"
Total Length
per line (ft) 7000 4300-5100 6600' 4800-6390 6400-6550 6795-7435 10200-11300
Submerged Weight 66 66 90 12 60.3 11.8 10.1
Ground Chain Type R4 Studloss K4 Studiosa R4 Studless R4 Studless R4 StudIosa R4 Studless R5 Studless
Diameter 5.75" 5.6" 6.7" 5.75" 5.59" 6.18" 528" Total Length (fI) 250 236 250-650 245-272 186.9 90 175-225
Submerged Weight 375 356 509 372 365.6 513 327
Foundation Piles
Type Suction Driven"" Suction Suction Driven Driven Suction
Outside Diameter 18 9(84") 18 18-25 7.0 7 18
Length (5) 90 -95 220 129 52-88 I 50-57 228.0 254 87-103
Penetration )ft) 86 - 91 205 126 49-85 / 47-54 214 239
Weight (Sh.T) 194-200 138 282 147-264 162.0 203 203-249
Steel Catenary Risers yes yes
No. of SCR's
instatled 2 2 2 2 2 0 3
Diameter (inch) 10 / 12 16 / 18 16/24 16/24 2x14 n/a 10.75 + 2x16
Air Cans
Installed by HMC yes yes no yes yes j no no
Vessel DCV Balder SSCV Thialf SSCV Hermod
Year Constructed 1978 (Converted 2001) 1985 1978 Operating Draft 22 m (72 ft) 26.6 m (87 ft) 25 m (82 ft) Ljght Wejght 48,690 mT 154m (505 ft) 69,531 mT 202 m (663 ft) 56,251 mT 154m (505 ft) Length Overall Breadth 137 m (450 ft) mcl Tower Support Module 88 m (270 ft) 86 m (282 ft) OP Power 42.9 MW 42 MW N.A. Thrusters 7 x 3,5 MW 6 x 5.5 MW N.A. Lift Capability 3000+ 4000 st 2x7100 mT 4000 + 5000 sT
8
Figure 1: Typical spar nomenclature
Fig
Figure 2: Simulation and actual roll of pre-defined roll during soft tank flooding
Figure 3: Mooring Line Deployment Winch on DCV Balder
ure 4: Typical example of weather va-"-g range during fixed ballast installation with SSCV.
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Figure 5: Typical steps of smart-buoy mooring line deployment procedure
STEP 10
Figure 6: Typical example of equalizer connection and mooring line transfer to spar
Figure 7: Typical example of mooring line load transfer from installation vessel to spar A48191 otO 909V i i r
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