| In recent years,the petroleum exploration extends to the complex formation constantly,and the windows between pore pressure and fracture pressure of complex formation is usually narrow.Improper control of Bottom hole pressure can cause drilling problems such as kick,leakage,leakage of harmful gases,card drill and excessive time of going in and pulling out.Managed pressure drilling(MPD)is an effective technology of solving the complicated situation mentioned,and reducing the time of operation.In MPD,estimation of bottom hole pressure includes wellhead back pressure,well bore static fluid column pressure,drilling circulating pressure loss and pressure fluctuation,so annulus dynamic simulation is very important to estimate the pressure of bottom hole pressure in MPD.Firstly,based on flow pattern identification of gas-liquid two-phase flow and mechanism modeling,the annulus dynamic mechanism model is established.which is coupling with the formation of non-Darcy flow model.A differential method is presented to get numerical solutions of partial differential equations.And,the accuracy of the model is well verified by the data of the actual engineering well.Secondly,the Non Darcy percolation model of gas kick while drilling is established.The annulus dynamic mechanism is analyzed,and the qualitative analysis of well bore gas ratio change rules under gas cut,distribution of vapor density in the annulus,annulus flow state analysis under gas cut,influence of wellhead back pressure on gas holdup,changing tendency of bottom hole pressure under constant drilling speed,influence of gas cut on bottom hole pressure,and influence of wellhead back pressure on bottom hole pressure are given.It provides guidance for engineering design of MPD.Thirdly,a MPD annulus dynamic simulation and analysis software is created using MATLAB GUI tool.This software has the characteristics of simple operation and highly precision,as a result,it can provide effective guidance to the field operation. |
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