Research On Casing Safety And Reliability Of Deep Water HTHP Exploration Well LS^*-*-*

As large amount of early investment and high technical risk,the high temperature and high pressure working environment for deep-water drilling which puts forward higher requirements for the design of casing strength.For the problem of the heat carried by oil transfer from the wellbore to earth heating the annulus and building the annulus pressure,there is no reliable way to deal with annulus pressure.Therefore,the research on annulus pressure management,prediction of annular pressure and Countermeasures should be carried out,which to guide the selection,design and construction of pipe string,rationally select the height of cement ring,and effectively prevent or mitigate annulus pressure.Firstly,by investigating the basic measures for maintaining wellbore integrity in HTHP and deep-water wells,combined with the situation of LS^*-*-* well,the annulus trap pressure calculation model of LS^*-*-* well is established,and the wellbore and annulus temperature field under different conditions is calculated.The influence of annulus pressure on casing safety factor is studied,and the mechanical calculation of casing cement ring interaction caused by downhole operation under high temperature and the failure mechanism of cement ring are revealed the formation mechanism.Secondly,this paper investigates the prevention of annulus pressure appear annulus technical measures and technical measures for reducing the risk of the shaft safety pressure,on the model of the heat transfer mechanism of shaft,considering the tubing,casing,formation and the effect of heat transfer,water temperature and pressure coupling relationship and other factors,set up the mining process transient wellbore temperature field and pressure field prediction model.The calculation model of annular band pressure is established.The relative error between the measured value of the annular pressure and the predicted value is within 10%.Thirdly,The relationship between wellbore temperature field,annulus mean temperature difference and well depth and output is discussed for two kinds of well structure under LS^*-*-*.The relationship between annulus thermal expansion pressure and annulus temperature difference under different thermal expansion coefficients is also discussed.The influence of the two well structure schemes on the wellbore temperature field under LS^*-*-* well is revealed.The annulus pressure prediction is carried out,and the relationship between the temperature difference of the annulus,the pressure and the output is compared.Finally,The results show that when the thermal expansion coefficient remains constant,the thermal expansion pressure of the annulus increases with the increase of temperature.At the same temperature,the expansion pressure of high expansion coefficient is larger than that of low expansion coefficient.For the same production condition,the pressure of annulus increases with the increase of expansion coefficient.For the same expansion coefficient,the annulus pressure of high yield is higher than that of low yield.