Simulation Study Of Wellbore Temperature And Pressure During Gas Intrusion In Deep Water Drilling

As the recovery of the world's economies, countries of fossil energy demands have been increasing. Humans began to march to deep water area to meet the increasing demands, which makes the deep water drilling technology to be the hot issues in recent years. In the process of deep water drilling, the impact on the wellbore pressure and temperature distribution during drilling construction are manifold, especially when the gas kick happened. Therefore, the distribution of temperature and pressure accurately for the safety of deep water drilling fast has very important practical significance and application prospect.Based on the seepage theory, the multiphase flow theory, fluid mechanics and heat transfer theory, the wellbore temperature and pressure model with high precision has been optimized according to the present situation. So the paper deduced the mathematical model that made circulation fluid as the research object, considering the coupling relations of well bottom-hole pressure and gas and the coupling relationship of wellbore temperature and pressure. Furthermore, the simulation software is compiled and the comparison with the finite element value has been carried.The rule of gas has been revealed after the gas cut. As the growth of the kick time, gas is also increased after gas kick while drilling. As the increasing rate of drilling, at the same time the drilling depth increased, the gas of the wellbore will increased. When the permeability increases, at the same time the wellbore gas will be more.The influence factors of the annulus temperature have been analyzed. The annulus circulating temperature was influenced in the process of gas cut mainly by formation temperature gradient, the coefficient of thermal conductivity, sea depth, drilling discharge and the inlet temperature of drilling fluid. The amount of gas has less effect on the temperature of the annulus.Based on the finite element software called WORKBENCH, wellbore temperature and pressure simulation has been carried and the related results are analyzed:the deviation value of the pressure distribution in the drill string at 1%, compared with the measured values and deviation value of Fluent simulation at 5%; Compared with the model values, the deviation value of annulus temperature simulation value is around 6%; The deviation value of air volume fraction is about 3%.The influence law on the wellbore temperature and pressure has been revealed. The greater the gas, the lower the temperature of the annulus, but the change is very small. The greater the gas, bottom hole pressure drop of the faster. Gas cut the longer the time, the lower the annulus pressure.The expansion rule of the gas into the wellbore in annulus has been revealed. The volume expansion ratio of gas in the process of formation increased slowly before the bubbles move into the riser. The volume increased only two times. When the gas moved to the riser, the volume expansion ratio increases fast. The volume increased about 18 times. The greater the drilling fluid density, the smaller the gas volume expansion ratio is. When the drilling fluid density increased 1.46 times, gas volume expansion ratio decreased 11 times.