Study On The Hydrodynamics Performance And Concept Design Of FDPSO

With the increasing demand and rising price for global energy, and the graduallyexhausting resources and energy on land, oil and gas exploration and development isturning to the ocean, and transforming from shallow water, semi-shallow water todeep water. China own more than300million square kilometers of sea area, which isrich in oil and gas. At present, offshore oil and gas exploitation has reached a certainscale. Deep sea oil field hasn't to be developed. The breakthrough of deep sea oilexploration technology is the key factor in long-term strategic of deep sea exploration.Conventional deep-water oil exploitation needs at least two floating units,drilling unit and the producing unit, the cost of which is heavy. Moreover, reducingthe lead-time to first oil is becoming one of the main motivation in the high-profitdeep-water market. FDPSO is a multifunction floating platform, which has the integral function ofdrilling, production, storage and offloading. The concept of FDPSO, combining the FPSOwith a drilling unit, was proposed in1990s. For FDPSO not only reduces the up-frontcost, but also produces early, many oil companies are particularly interested in it.After ten years of research, there have been many innovations and two FDPSO havebeen put into use. The first FDPSO, which was converted from a VLCC class tanker,was used in Azurite field by Murphy West Africa Ltd in August2009. The SecondFDPSO, SEVEN DRILLER, was applied in the Brazil, in Feburary2010.The hydrodynamic performance and concept design study of FDPSO is theadvanced subject in worldwide ocean engineering field. It is also an important issue inthe deep water oil and gas exploration in the South China Sea. The hydrodynamicperformance of FDPSO hull, position performance, coupled hydrodynamicperformance of the hull and the drilling equipment, the concept decision and so on arestudied by numerical simulation and model test method.3-D frequency potential flow theory is adopted to carry out the frequencyanalysis hydrodynamic performance of FDPSO hull and the hydrodynamicperformance of FDPSO hull is studied. The response amplitude operator for six degree of freedom (DOF) motion are calculated. The effect of moonpool on thehydrodynamic performance of FDPSO is great. The hydrodynamic coefficients, firstorder wave exciting force, second order wave drift force of FDPSO hull with differentmoonpool size and different draft have been calculated, and the relation between thehydrodynamic performance and the moonpool size and draft has been studied.Based on the Cummins theory, the hull/mooring time domain analysis isperformed by indirect time domain method. The motion characteristics of FDPSO hull,with spreading mooring system and single point mooring system respectively, in theSouth China Sea state are obtained. And the position performance of FDPSO withspreading mooring system and single point mooring system are also researched. Theeffect of different diameter, unite weight and axis stiffness of mooring line on themotion character of the hull and the dynamic performance of mooring line have beenstudied.In order to verify the numerical method and studied the hydrodynamicperformance of the MPF1000and the position performance of mooring system, modeltest have been carried out. The tests are composed of decay test, white noise test andwind, wave and current test. Decay tests are performed in still water for heave, rolland pitch of the hull to obtain the nature period and the damping coefficients for thesemotions. The RAOs for six degree of freedom motion of FDPSO hull with differentwave directions are achieved by white noise test. The hydrodynamic performance ofFDPSO with spreading mooring system and single point mooring system in operatingcondition and extreme condition of the South China Sea are studied by irregular wavetest.The floating drilling platform requires heave compensator to provide the tensionof the riser and compensate the relative motion between the riser and the hull. In thisway, the heave motion of drill stern is restrained. At present, the hydraulic heavecompensation system are widely used in the floating drilling platform. But with oiland gas exploration moving to deep water, traditional hydraulic heave compensatorcannot meet the needs of drilling operation in deep water. Two different manners areused in FDPSO to compensate the heave motion of the hull, such as sheltered riservessel (SRV) and tension leg deck (TLD).Model tests are designed and carried out to study the coupled hydrodynamicperformance of FDPSO hull and SRV. White noise tests and irregular tests areinvolved in the tests. The RAOs of FDPSO hull and SRV are achieved by white noisetest. One-year return period sea state of the South China Sea is used to simulate the irregular wave test. The time series for the motion response are measured in irregularto investigate the motion character of the hull and the SRV. The feasibility of SRVconcept in South China Sea is investigated. CFD method is adopted to study thecoupled hydrodynamic performance of the hull and the SRV. The compensationperformance of the SRV is researched and the coupled fluid field characteristics ofFDPSO hull and the SRV is analysed.The mathematics model to calculate the coupled hydrodynamic performance ofFDPSO hull and TLD is established. And the program to compute the RAO of the hull,deck and weight is developed. The effects of weight, stiffness of riser and cable on theheave motion of FDPSO hull and TLD have been also studied by the program. Thenumerical model to do the hull/TLD/mooring time domain coupled analysis is set up.The6-DOF motion character of the hull and the TLD, mooring force and riser forceare calculated with the environment condition of the South China Sea. Model tests,including white noise test and irregular tests, are carried out. The RAOs of FDPSOhull and TLD are achieved by white noise test. The results of white noise teat arecompared with the results from frequency domain analysis to verify the mathematicsmodel. One-year return period sea state of the South China Sea is used to simulate theirregular wave test. The time series for the motion response are measured in irregularto investigate the motion character of the hull and the TLD. The results of irregulartest are compared with the results from time domain coupled analysis. Thecompensation character of TLD and the feasibility of SRV concept in South ChinaSea are investigated.A multi-column semi-submersible FDPSO concept, used in the South China Sea,is proposed. Basing on the stability checking on the FDPSO concept, thehydrodynamic performance and the position performance of the concept are studiedby model test and numerical method. White noise tests and irregular tests are involvedin the model tests. White noise tests are used to measure the RAO of FDPSO hullwith the wave direction of180degree,135degree and90degree. Irregular wave testsmeasure the time series for6DOF motion of the hull. The environment conditions areone-year and a-hundred-year return period sea state of the South China Sea. Thehydrodynamic coefficients, first order wave exciting force, second order wave driftforce and RAO of the concept are calculated by frequency domain method. Thehull/mooring time domain analysis is performed by time domain analysis. Thenumerical results are compared with the test results to verify the numerical methodand the hydrodynamic performance of FDPSO concept with spreading mooring system in South China Sea is studied.In summary, the hydrodynamic performance of FDPSO hull, positioningperformance, coupled hydrodynamic performance of the hull and the drillingequipment and concept design et al are studied in this thesis. The reasonable methodsfeasible model tests are proposed. The hydrodynamic performance and the positionperformance of FDPSO in the South China Sea are obtained. The coupledhydrodynamic performance of the hull and the SRV, and the hull and TLD areresearched. The new FDPSO concept is proposed. Several important conclusions aredrawn, which will be very useful to the deepwater oil and gas exploitation in thefuture.