Research On The Method Of Wellbore Temperature And Pressure Calculation During Deep-water Drilling

With deep-water exploration gathering pace, it is clear that deep-water drilling is becoming a hotspot in recent years. A precise knowledge of wellbore temperature and pressure is particularly important for the deep-water drilling. However, because of the mechanism of heat exchange with the sea is more complex than for rock formation, the reliability of existing correlation and models is sometimes reduced in deep-water wells. According to the conversation of energy law and basic principals of heat transfer, a wellbore circulating heat transfer model of deep-water drilling has been proposed, which has been solved by termless steady finite difference method. Over-all heat transfer coefficients are used in this model,the predicted results from the new model presented in this paper are satisfactorily close to those from other proven models, so this model was proved to be valid. The sensitivities of parameters to affect the circulating temperature in wellbore have also been analyzed. The new model can be employed to calculate temperature distribution of drilling fluid in the pipe,pipe string, the drilling fluid in the annular. According to the wellbore heat transfer characteristic under static condition,a wellbore static heat transfer model of deep-water drilling has also been proposed, which has been solved by analytical method. The model can predict the wellbore temperature distribution during static period. Take into account the effect of temperature and pressure on density of drilling fluid, a accurate and practical model for predicting densities of drilling fluid has been developed on the analysis of measured data. This density model was used to analyze the variation of drilling fluid density in wellbore at the different conditions during deep-water drilling. According to the theoretical knowledge, a computer program is developed. The program can provide useful technical support for deep-water drilling operations.