Virtual Simulation Of Jetting Drilling Of Surface Conductor In Deepwater

Since features like low temperature and loose soil bodies are common in deepwater seabed,risks like both poor quality and stability of cementing and wellhead are existing in conventional drilling technologies.To solve these problems,the technology of running surface conductor by jetting was proposed and extended in worldwide deepwater wells.During conductor jetting process,high-pressure jet impacts shallow soil to form a slightly smaller hole than the outside diameter of the pipe.After the pipe is in place,the friction force gradually recovered between the surface pipe and the surrounding soil is used to support the weight of the pipe and the wellhead equipment.Based on the theory of water jet,this paper deduces the quantitative relationship between displacement and hole enlargement diameter.On this basis,the displacement design is carried out to meet the requirements of rock breaking and rock carrying.According to the principle of drilling pressure design,the calculation of in-place drilling pressure of conduit is analyzed.Based on string mechanics and previous research results,the theoretical formulas for calculating the initial bearing capacity,ultimate bearing capacity,real-time bearing capacity,pipe axial load at the stage of releasing and feeding tool and surface casing hanging wellhead cementing are summarized,and the flow chart for determining the minimum pipe depth and the analysis of the ultimate pipe depth considering the time effect of bearing capacity are drawn.Based on the principle of effective stress and the law of saturated clay migration,ABAQUS,a virtual simulation software of mechanical dynamics,is used to model the process of pipe jet drilling.Initial contact pressure coefficient m and contact pressure recovery coefficient n are introduced into the model to adjust and modify the model.The model can independently determine the depth of conduit entry,and is verified by an example well in the South China Sea.The results match well.The vertical bearing capacity of pipes with suction anchor is evaluated.ABAQUS software is used to establish the interaction model between suction anchor and soil.According to the allowable settlement displacement of suction anchor,the influence of the radius and depth of suction anchor cap on its vertical bearing capacity is discussed,and the function of suction anchor is analyzed by calculation and comparison.The model is of great significance to the operation of ducts under jet method in complex seabed environment and unprocessed sea area.