Research On Several Key Technologies Of Jack-up Platform With Oil Storage Mat

Accelerating the development of offshore petroleum resources is the urgentdemand for economic development, which has an important strategic significance inChina. Safe and efficient exploitation of offshore petroleum resources mainlydepends on the cognition of the ocean environmental conditions and thedevelopment and improvement of marine engineering equipment technology. Theoffshore platform is not only an important equipment to exploit petroleum resources,but also the foundation of offshore production and life. Although offshore andshallow sea oil exploitation has been maturely developed, new deepwater platform isimminent as the depth of oil exploitation increases. The Mat jack-up platform is amodern production system, which has oil storage function, and can simultaneouslyachieve the drilling, production and storage. Therefore, it is necessary to study thesurrounding environmental conditions and several key technologies of mat jack-upplatforms, such as platform hydrodynamic performance, platform foundationstability and heat preservation technologies of underwater oil storage andtransportation.The proposed platform is equipped with large-scale oil storage mat, whichtypically differs to general jack-up platforms. Therefore, the influence of large-scalemat on jack-up platform plays an important role in the analytical technology ofoverall performance. Based on interactive verification and analysis between threedimensional potential flow theory and model tests, useful conclusions have beendrawn for the hydrodynamic performance when the mat drops down. The matjack-up platform can meet the requirements of up-and-down process because of itsgood stability and hydrodynamic performance. The mat will not collide with the seabed repeatedly when the mat is contacting with the sea bed because of heave motion,which will avoid the damage of mat structures. Heave motion response and rotational response of the platform tend to reduce gradually as the mat drops down.However, sway and surge responses tend to increase first and then decrease. Thelargest translational response and rotational response are sway and rolling responserespectively. The range of motion is acceptable and the mooring chain can meetoperational requirements. Therefore, the up-and-down operations of the mat jack-upplatform are feasible under sea condition at level3or less.The finite element software ABAQUS is used to calculate the mat upliftadsorption force considering two cases: the first case is that overall shear failureoccurs in the foundation soil, and the second is that the pore water seepage results ina separation between the bottom of the mat and the surface of the foundation.Mohr-Coulomb elastic-plastic model is utilized to calculate the mat uplift adsorptionforce. Then the influence of both soil parameters and time length of pulling on thelimit of adsorption force is analyzed qualitatively. Study on sand liquefaction placesemphasis on the establishment of elastic-plastic dynamic constitutive model andnumerical analysis method. The overturning stability and sliding stability ofplatforms are calculated through changing the spacing of spud legs, the main size ofthe mat, and the penetration depth of the primary mat jack-up platform. Study resultsshow that the overturning stability and sliding stability is closely related to thestructural size.One of the key technologies in deepwater oil exploitation is to keep the oil in astate of fluidity. Heat preservation is an effective strategy to keep oil flowing. It isimportant to study underwater heat preservation materials and heat preservationtechnologies. Foam glass brick is filled between the inner and outer walls as the heatpreservation material, based on the researches on domestic and overseas underwaterheat preservation materials. The heating technology of oil-water separation mat tankis studied based on theoretical calculation. The loop heating system is applied towarm-up the crude oil. Physical modeling experiment is conducted to study the matoil loading and unloading system and heating system. How wave force influencesthe underwater diaphragm is studied. The influences of the diaphragm motion andthe distribution schemes of inlet and outlet pipes on oil loading and unloading process are also analyzed to verify the rationality of oil loading and unloadingschemes. Meanwhile, the model tank is used to study the temperature variation inthe tank. Study results indicate that foam glass brick meets requirements of heatpreservation of the mat.