Chapter 11: Drilling Operations

This chapter addresses several heat-transfer topics that originate from well drilling, meaning in openhole situations. In most cases, simple analytical expressions derived from governing differential equations enable estimation of fluid and/or formation temperatures. These topics include (1) fluid circulation temperature under various boundary conditions, both at the surface and downhole; and (2) static formation temperature in the open and cased-hole situations. Thereafter, we present coupled wellbore/reservoir models for estimating flow rates and cumulative fluid loss in an uncontrolled well involving both oil and gas wells.

In drilling operations, the knowledge of accurate temperature with circulating time has a direct bearing on drilling fluid density and rheology. Beyond the design of drilling fluids itself, temperature plays a significant role in many aspects of the well and related engineering. Some of these relevant areas include determination of thermal stresses on tubulars, particularly in permafrost or high-temperature regions; design of cementing programs; logging-tool design; and log interpretation. The estimation of fluid temperature becomes critical for high-temperature and geothermal reservoirs, in which significant heat exchange occurs. In these reservoirs, problems compound when dealing with temperature-sensitive fluid properties such as a non-Newtonian fluid.