Influence Of Deepwater Development Well Of Wellbore Temperature And Pressure On Casing Strength Reliability

In the deepwater oil and gas development process,the temperature at the sea floor mud line is low,but the formation produced fluid temperature is high.With the high temperature of the produced fluid return,the liquid between the wellbore casing annulus segment will be heating and swells generated higher annulus pressure.The strength of the casing string safety is threaten.Accurate calculation of temperature and pressure distribution within the wellbore,and then study its effect on the reliability of casing strength.It has an extremely important significance on the pre-design of casing strength and the safety of well development.The author of this paper aim at the influence of deepwater oil and gas development well of wellbore temperature and pressure on casing strength reliability problems.Based on the system research of wellbore temperature and annular pressure calculation method and the temperature pressure on casing strength reliability of progress and achievements,constructs the calculation model for deepwater oil and gas development wells of wellbore temperature and pressure.By way of example calculations,analyzed the wellbore temperature and pressure distribution with the liquid producing capacity,geothermal gradient,production time variation.The influence of casing on the casing reliability under different annulus pressure and different temperature is studied and the strength design verification method for casing string suitable for deepwater oil and gas wells considering annular load is presented.The results of the study show that,the temperature and annulus pressure in the wellbore are the most significant increase in speed in the lower and initial fluid production,then gradually stabilized,and with the increase of the geothermal gradient approximation linear increase.Wellbore annulus free period of casing is heated by high temperature fluid produced fluid thermal stress,can lead to wellhead casing elongation on top.It could not be ignored when making the design of casing string.Through the analysis,the technology casing pipe is more sensitive to the thermal stress.Current level of some steel pipes for casing string design can not meet production safety of oil and gas wells,and the control measures should be adopted to deal with the annulus pressure.