Abstract
In order to carry out a series of key basic researches, a scientific ultra-deep drilling plan is being undertaken in China. Wellbore temperature is one of the key factors during the drilling process. In this paper, we established a twodimensional transient numerical model to predict the ultra-deep wellbore temperature distributions during circulation and shut-in stages. The simulation results indicate that the cooling effect of drilling fluid circulation is very obvious, especially during the inception phase. Drilling fluid viscosity has great influence on the temperature distributions during circulation stage: the lower the viscosity, the higher the bottomhole temperature. While drilling fluid displacement and inlet temperature have a little effect on the bottomhole temperature. During the shut-in stage, the wellbore temperature recovery is a slow process.
Highlights
Continental scientific drilling is a direct technique to reveal the composition and structure of the continental crust, verify the results of geophysical explorations
KTB-which stands for German Continental Deep Drilling Program completed a 4000.1 m pilot hole and a 9101 m main hole in 1990s, through which lots of achievements have been obtained [3]
The circulation stage can be basically described in three main phases: drilling fluid flows down the drill string, through the bit, and up to the surface (Fig. 1)
Summary
Continental scientific drilling is a direct technique to reveal the composition and structure of the continental crust, verify the results of geophysical explorations It can provide information on the Earth’s natural resources, the global climate and environmental changes and the processes causing earthquakes. Some research has observed that the API method always overestimates circulating fluid temperatures for deep wells [6] This method is originally developed for the oil drilling industry, which differs notably from scientific drilling technology. To solve this problem, two approaches have been emerged to estimate the wellbore temperatures: analytical and numerical. The transient heat transfer model need to be established in order to predict wellbore temperatures during the whole drilling process
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