Technology And Application Of Subsea Base Plate Using Jack-up Drilling Platform

In the development of offshore oil and gas,in order to maximize the use of existing platforms and resources,reduce development costs,and improve the development benefits of marginal oil fields,oil and gas field development can be carried out using a wellhead with recyclable function.The position of the jacket platform in the original wellhead location is more likely to damage the original reserved wellhead.Therefore,the original well position is filled to the base plate first,and then the jacket is in place.In order to ensure the safety of filling the base plate,it is necessary to study the structural strength and seating error of the underwater base plate during the operation of replenishing base plate.In this paper,the oscillation characteristics of the underwater base plate under the current load and the wave load were analyzed,and the collision effect between the underwater base plate and the jacket during the running process of the underwater base plate was simulated by the marine engineering simulation software.Based on the field conditions of A gas field and the load of marine environment,an underwater base plate suitable for the gas field was designed.Based on the basic theory of structural elastoplastic analysis,a mechanical analysis model of underwater base plate was established,and the structural strength of the underwater base plate under extreme sea conditions and working sea conditions were checked.According to the results of underwater foundation strength check,the size of the positioning pile was designed and optimized.According to the interaction between pile and cohesive soil,sandy soil and layered soil,the calculation model of ultimate bearing capacity of the pile was established,and the minimum driving depth of the pile was calculated to meet the vertical impact force and lateral impact force.Based on the soil parameters and the underwater base plate parameters of the A gas field,the minimum driving depth of the piles that meet the stability requirements was confirmed.A finite element model is used to simulate the installation error of subsea base plate.The simulation results showed:The Lateral impact force is 1432.17 kN under the extreme working condition.According to the calculation of 1568kN horizontal collision force generated by the installation jacket,the positioning accuracy of underwater base plate meets the requirements when the ship's shaking is less than 3 degrees under the installation condition.According to the structural strength analysis of the underwater base plate,the strength of the underwater base plate of A oil field under the extreme sea conditions and working sea conditions meets the operational requirements.According to the optimization results,the stress of the positioning pile with the diameter of 42in and the wall thickness of 1.5in positioning pile is 228.1MPa,which can meet the requirements of underwater base installation.When the horizontal impact is 1568kN,the minimum driving depth of the positioning pile is 27.9m.Considering the influence of lateral and vertical impact forces,it is recommended that the minimum driving depth of the underwater base plate positioning pile of the A gas field is 27.9m.The research results provide theoretical basis and technical support for the rational design and accurate positioning of the underwater base plate.