A Study of Temperature Dependent Friction in Wellbore Fluids

Abstract

Abstract Increased well reach is one of the most important developments in modern drilling. Wellbore friction plays a central role here, both related to the drilling and to the completion phases of a well. The oil industry, however, uses the simple one-parameter Coulomb friction model to analyze well friction, without temperature effects. The University of Stavanger has conducted friction research over some years, trying to further understand mechanical, viscous, temperature and material frictional effects. This paper presents some results of this work. Many water and oil based drilling muds from several mud vendors have been measured. The test equipment used includes a heat element to study the temperature effect on friction. The data reported cover a temperature range of 10°– 100°C. As expected, oil based fluids have lower friction coefficient than water based fluids. The coefficient of friction increases with temperature for all fluids, except for one mud which showed nearly constant friction above 50 °C. There is considerable variation between the different fluids. Friction coefficients have been measured with steel on steel, steel on concrete and steel on rocks. Steel on rock exhibit higher friction due to higher surface roughness of the rock material. An equation for temperature dependent coefficient of friction is derived, and it is used in the field example. It is shown that the temperature effect on friction is considerable.