Study On The Influence Law Of Temperature Effect On Wellhead Growth In Deep Water High Temperature And High Pressure Well

With the increasing demand for energy,deep-sea oil and gas development has become an inevitable trend.In deep-water high temperature and high pressure wells,the temperature at the bottom mudline is low,and the temperature of the produced fluid is high.When the fluid migrates up the production casing,the huge ambient temperature difference causes thermal deformation of the casing string,and the annular fluid is heated to generate annular pressure.As a result,the wellhead is uplifted,and the wellhead growth causes serious harm to the underwater manifold and the Christmas tree,which cannot be repaired,affects the safe production of oil and gas development.Therefore,it is of theoretical value and engineering significance to carry out research on the influence of temperature effect on wellhead growth in deep-water high temperature and high pressure wells.Aiming at the characteristics of multi-layered wellbore structure and subsea wellhead structure of deepwater high temperature and high pressure wells,combined with the basic theory of heat transfer,the temperature field distribution of deepwater high temperature and high pressure wells is analyzed in stages,including the wellbore center to the cement sheath,the cement sheath to the formation and heat transfer in seawater.Considering the thermal stress of casing,annular pressure,frictional resistance of cement sheath and equipment gravity,a wellhead growth model of deepwater high temperature and high pressure well is established.According to the established model,carry out simulation experiments.While verifying the accuracy of the model,the factors causing the wellhead growth are analyzed.By analyzing the factors that cause the wellhead growth,it is found that the growth of the casing string is obviously affected by the temperature,and the temperature and the casing elongation basically increase linearly.The annular pressure has a significant effect on the growth.Under the pressure of 15 MPa,the growth of the inner layer increases by 23.44% compared with which has no annulus pressure.After 60% of the casing length is injected with cement,the average growth of the casing string is reduced by 19.44%.Comparing the effects of annular pressure and free casing length,the effect of free casing length is greater than that of annular pressure.According to the wellhead growth prediction model of deep water high temperature and high pressure wells,the deep water high temperature and high pressure wellhead growth prediction software is compiled by computer language,and through the input of relevant parameters,the prediction of the wellbore temperature distribution model and the wellhead growth height prediction are realized.The readability is strong,and the forecast data can provide data reference for the formulation of wellhead growth prevention and control plans on site.Taking a deepwater high temperature and high pressure well in the South China Sea as an example,the case analysis is carried out.According to the basic parameters,the temperature profile of the deepwater high temperature and high pressure well is calculated,the top load of the wellhead is analyzed,and the wellhead growth is predicted,which is basically consistent with the actual situation.The example verifies the adaptability of the model and can provide some guidance for the formulation of on-site management plans.