Spring Summer2004

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Evaluation of an Ext endable

Draft Platform .

Charting the Course: Spring/

Summ er 2004.

Preparing Sakhalin II for Mating.

Flume Tank Aids Study of Vortex

Induced Motions.Evaluation of a Mini Spar Concept.

New Research in Escape, Evacuation

and Rescue.

Researcher Com putes Ice Loads on

Offshore Structures.

Tandem Offloading Vessels and the

Problem of Coordinated Control.

Evaluation of Single PointMoor ing Systems.

Deepwater Moorings.

Researching Vortex Induced Vibratio

Journal Publications and

Conference Papers.

Personnel on National/

International Committees.

MI 22 Meter Flume Tank Facility Specifications.

Inthisissue...

The Extendable D raft Platform (ED P) is a unique concept developed by Technip

that offers the benefit of com plete outfitting at dockside and m inim al assistance

during installation. O ceanic Consulting Corporation recently conducted an

extensive m odel test program to evaluate the overall perform ance of the

platform . Included in the program w ere tests to evaluate the stability and

m otions of the ED P under tow during pre-service transportation, as w ell

as experim ents to investigate vessel response during the 100-year hurricane

and 1-year w inter storm conditions w hen installed on site.

In addition to a seakeeping evaluation, a structural load evaluation w as

conducted to investigate the forces and m om ents at the pontoon/colum nand deck/colum n interfaces.

M easurem ents included m otions and accelerations on the ED P, forces and

m om ents at the colum n/deck and colum n/pontoon interfaces, as w ell as

m ooring and riser tensions. Further seakeeping and structural evaluations o

concept by Technip indicated a very good correlation w ith the m odel test re

The full program w as conducted in the IO T 2 00 M eter Tow ing Tank and

the O ffshore Engineering Basin (O EB). The testing program provided som e

interesting technical challenges. In particular, the requirem ent to accurately

m easure the forces and m om ents at the interfaces of the m ain com ponents

This w as overcom e through the use of som e novel dynam om etry design.

O verall, the program w as a success as Technip obtained valuble and reliable

inform ation that they can now use as they continue to enhance their concepand O ceanic increased its experience w ith novel deepw ater platform s.

Shaw n

shaw n_searle@oceanicco

valuationof anExtendableDraft Platform.

Spring/Summer


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PreparingSakhalinII for Mating.tested in open w ater, and then in place on the

G BS. Results of the tests were then used

to determ ine the correct force vector to

apply to the m odel to sim ulate current

loading during the next phase of testing.

The final and m ost extensive testing phase

w as conducted again in the O EB. The

objective of Phase 4 w as to determ ine

the force interactions betw een the barge,

topsides and G BS structures. The testing

in this phase w as broken into five stages.

The first stage of these tests w as designedto determ ine fender loads at the m ating pull-in

stage. To optim ize the fender design, barge

fenders w ere tested w ith three different

spring rates. Starting at the pull-in stage,

w ith the topsides supported w holly by the

transportation barge and w ith clearance

betw een the topsides and the G BS, the

barge w as ballasted in stages until the

topsides w ere fully supported on the G BS, w ith

clearance betw een the barge and topsides.

An extensive, four phase test program has

been com pleted for the transportation

and float-over installation of a

topsides unit for the Sakhalin II project.

Phase 1 of the test program w as conducted

in the IO T 9 0 M eter Ice/Tow ing Tank to

determ ine drag forces on the transportation

barge. Using O ceanics Planar M otion

M echanism (PM M ), drag on the barge w as

tested in 15increm ents for a full 18 0.

Phase 2 of testing w as conducted in the

IO T O ffshore Engineering Basin (O EB), in

w hich the seakeeping properties of the

transportation barge w ith topsides w as

evaluated in regular and irregular w aves.

After com pletion of the transportation tests,

the next tw o phases of testing focused on

the float-over and installation of the topsides.

Phase 3 of testing w as again conducted in

the IO T 90 M eter Ice/Tow ing Tank to identify

the effect of the G BS on the barge current drag

loading. The drag of the transportation barge w as

The second, third and forth stages of testing

investigated the interactions of the three

bodies at different stages (0% , 50% and 100% )

of load transfer from the barge to the G BS.

At the fifth and final stage of this phase of

testing, the topsides w ere fully supported by

the G BS and there w as clearance betw een the

barge and topsides. A further series of tests were

conducted on the sam e m odels in deeper water.

The G BS structure w as extended upw ards and

tests at tw o of the float-over conditions (pull-in

and 100% load transfer) w ere repeated.

Specialized m echanical devices w ere necessary to

replicate the m echanical properties of the fenderin

support and m ating system s, and to accurately

record force loading. In particular, to m atch the

polym er m aterials of the leg m ating system betw e

the topsides and G BS, a system w as designed w ith

the specified non-linear spring properties.

Tim Mo

tim_moore@oceaniccorp.

Testing of SPA Rs in the M I 22 M eter Flum e Tank

offers several unique opportunities for the study

of Vortex Induced M otions (VIM ). As the Flum e

Tank allow s tests to be conducted for a long

duration, phenom enon such as beat envelops

in the VIM can be observed. In addition, the

underwater view ing gallery of the tank provides

a unique opportunity for flow visualization.

O ceanic Consulting Corporation has recently

com pleted a third set of SPAR V IM tests in the

M I 22 M eter Flum e Tank and the IO T 20 0 M eterTow ing Tank. A control set of test runs was

conducted in both tanks, the results of which

indicated a good correlation betw een the tests

conducted in the tw o facilities.

The Flum e Tank also offers the possibility of creating

sheared flow profiles for testing deep draft vessels

in w ind generated currents. Phase 1 of the testing,

involving the creation of sheared flow profiles,

has show n prom ising results and Phase 2 of

developm ent is scheduled for M arch 2004.

The prim ary focus w ill be to investigate sim ple

m ethods of producing various shear flow profiles.

O nce com pleted, Phase 2 of the shear flow

developm ent should provide O ceanic w ith

sufficient inform ation to produce w ind generated

surface currents w ith relative ease.

A secondary focus for Phase 1 w as placed on

increasing the efficiency of the uniform flum e flow .

Several m inor inefficiencies w ere identified during

this phase of testing and im provem ents were

im plem ented during the regularly scheduled

annual m aintenance.

John M

john _monk@ocean iccor p.c

Tim Mo

tim_moore@oceaniccorp.

FlumeTank Aids Studyof Vortex InducedMotions.


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W ith increased oil and gas activity off the coast of

N ew foundland and Labrador, the risk for collisions

of ships, offshore structures and m arine installations

w ith ice is real. The probability for a severe accident

(w ith significant environm ental, hum an and capital

liabilities) is increased by the fact that the environm ent

off the Canadian East Coast is harsh and hazardous,

w ith heavy sea states, w ind and fog.

D esigning offshore structures and

ships to w ithstand im pact ice forces

is a m ajor concern for structural

engineers and naval architects

in the arctic and sub-arctic

regions. In nature, there are

various discrete ice m asses, such

as bergy bits and grow lers, and

there are various continuous

ice features, such

as sea ice sheets, pack ice and ice ridges. At

som e point all of these interact and contact offshore

structures, m arine installations and ships. The dynam ic

response of a structure to a collision w ith a discrete ice

m ass is considerably different than its response w hen

interacting w ith an ice sheet at low indentation speed.

D r. Ahm ed D erradji of the N RCs Institute for Ocean

Technology has developed w hat he calls the universal

failure theory for ice.The theory w as developed after

analyzing the results of over 50 0 tests on ice involving

sea ice, iceberg ice, fresh w ater ice and laboratory

grow n ice. These test results were obtained from the

open literature and included the w ork of ice

researchers in various laboratories in N orth Am erica

and Europe over the last 30 to 35 years. In a w ay,

D r. D erradjis theory is an extension of the traditional

failure criteria developed for m etals and geo-m aterials

(rocks and soils) over the last 200 years.

Researcher Computes IceLoads onOffshoreStructures.

the tw o vessels. Also required is an im proved

m ethod of analyzing and validating the entirecontrol fram ew ork.

M illan has devised three approaches

to the investigation, beginning

w ith num erical analysis and the

developm ent of softw are tools.

The second is scale-m odel

testing to explore the efficacy

of supervisory control

system s versus independent

controllers. The third

approach is full-scale trials,

now under discussion w ith

offshore operators. Here, data

w ill be collected from ships

operating in m ulti-vessel system s and

then com pared w ith the m odel-scale results

and num erically im plem ented system s.

The research has potential

benefits for a num ber of groups,

M illan says. They include control

equipm ent m anufacturers, vessel

operators and regulatory agencies.

Jim Mi

jim .mi lla n@nr c-cnrc.g

Researcher Jim M illan has been discussing w ith

FPSO operators the problem of controlling tandemoffloading vessels. The difficulty lies w ith m oored,

dynam ically positioned FPSO s offloading to

sim ilarly positioned shuttle tankers. The operation

poses risks due to the close proxim ity of the tw o

large vessels. Any num ber of factors can disrupt

the offloading procedure, including excessive

m otion of the shuttle tanker, dynam ic positioning

operator error and abnorm al interaction betw een

the positioning and pow er m anagem ent system s,

to nam e a few .

The N RCs Institute for O cean Technology researcher

says the consequences of these problem s can

vary from excessive fuel consum ption to incidents

that could endanger life, the environm ent or the

vessels. The solution, he believes, lies in increased

autom ation through the use of a supervisory

controller to coordinate the control system s on

TandemOffloadingVessels andtheProblemof CoordinatedControl.

The universal theory has been im plem ented into

AN SYS, a com m ercially available finite elem ent

analysis code. It has been validated against

m easurem ents of ice loads on the piers of the

Confederation Bridge to PEI and on the Kem i-I

lighthouse in the G ulf of Bothnia, betw een Finland

and Sw eden. In both cases, the capability of the

universal m odel to predict actual ice loads was prov

D r. D erradji has also investigated ship-ice collision

forces and ice ridge im pact forces on a cylindrical G

destined for the w aters around Sakhalin, Russia. He

also involved in an effort to secure collaboration an

funding to study the effects of ice on a proposed fix

link betw een N ew foundland and Labrador.

Ahmed Derr

[email protected]


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95 Bonaventure Ave., Suite 401St. Johns, NewfoundlandA1B 2X5, CanadaPhone: (709) 722-9060

Fax: (709) 722-9064

i @ i i

MI22Meter FlumeTank FacilitySpecifications:

SpecificationSheets areAvailablefor all Major Facilities, Includi IOT Offshore Engineering Basin IOT 200 Meter Wave/Towing Tank

OERC 58 Meter Wave/Towing Tank IOT 90 Meter Ice/Towing Tank

IOT Cavitation Tunnel MI 22 Meter Flume Tank MI Centre for Marine Simulation

Specification sheets can be obtained from the O cean ic w ebsite or by co ntacting ou r office.

Meet us at:

May3-6, 2004OffshoreTechnologyConference(OTC) June2-3, 2004OffshoreNewfoundlandPetrol

Length 22m

Width 8m

Depth 4m

Max. Water Velocity 1m/ sec

at Max. Water Depth

Max. Velocity of 1m/ sec

Moving Ground Plane

W ater Turning Vanes

20m x 3m O bservation W indow

Tank FiltrationSystem

Electric D rive M otors

Im pellers and Diffusers

M oving Belt GroundPlane

Flow Straightening D evices

Flow Straightening ScreenW ave Dam per

Net Loft

4.7 Tonne Crane

Rem otely O perated Towing M asts

Fishing N etUndergoing Testing

Underw ater VideoSystemDebris Screen

Tests Performed:

Flow Visualization of Submerged Bodies

Hydrodynamic Force Measurement

Assessment of Fishing Gear Configuration

Vortex Induced Motions

Directional Stability

Spar Motions

Towed Vessels

Documents

Spring Summer2004