Temperature Distribution of Shallow Medium during Deepwater Drilling

Abstract

Abstract Since depth of shallow layers in the deep water is general 1500 ft or more, the temperature is approaching the freezing point of water at this depth. Moreover, Drilling Fluid always has a high temperature which can lead the originally stable gas hydrate, shallow flow and shallow gas to disorders, for example, corrosion and deformation of drilling strings, blowout and pipeline jam can be induced by shallow flow, shallow gas and natural gas hydrate respectively. This paper conclude a new method to describe the complex temperature gradient in the shallow layers. A new model of heat transmission about shallow layers including shallow flow, shallow gas and wellbore is established. Thermodynamics and heat transfer are used in this paper either. Meanwhile, assuming the heat transfer among surface casing, formation and shallow flow is stable, whereas the transfer among drilling fluid, drilling strings and casing is unstable, a temperature simulation in the shallow could be done. Furthermore, this paper adopts an infinitesimal control body as a research object and establishes nonlinear partial differential systems. A fully implicit finite volume method is adopted to discrete the control equations. Then through the equation integral in the control domain, the discrete equations of conservation are obtained. Meanwhile, the alternating direction method is used in order to improve the solution efficiency, stability, and convergence. This paper also cities a well data in South China Sea as an example. Through the analysis of different displacement, wellbore and shallow water distance, the new model calculation results are accurate compared with the classical model validation. It can be concluded that the drilling fluid temperature has a great influence on the shallow. The greater heat transfer coefficient of shallow flow, the faster the temperature rises. Some new solutions to solve geological hazards are obtained in the shallow in which the special temperature profile can trigger natural hazards. Safety becomes the biggest concern during drilling in the shallow of deep water. This paper mainly focus on the temperature prediction in the shallow. On one hand, the complex temperature changes can cause numerous geological hazards during drilling or cementing process. On the other hand, the narrow density window of safe drilling fluid demands high standard of techniques. So the accurate temperature distribution of shallow layers in deep water has great significance in drilling works.