Modern Rheological Analysis of Drilling Fluids

Rheological analysis provides a good comprehension of the deformation and flow of substances under different stress conditions. The complex composition of the drilling fluid and the versatile functions makes rheological studies here indispensable as well as in other scientific fields like the food industry and material science. In spite of adding many high-quality additives to the drilling fluids, problems still occur, such as barite-sag, lost circulation, change of mud properties (particularly at high and very low temperature), solids transport. Others are often mentioned as reasons for increasing the cost of wells. The areas in which rheology plays an important role in drilling technology will be highlighted in this article. The reason, why the characterization with the Fann-viscometer alone is not enough for a detailed view on rheology will be focused on. In addition, measuring methods which are able to provide detailed information about gel strength, consistency, gel destruction, gel build up process and yield point have been investigated. A short overview of the basics of rheology is given. In this article, novel procedures will be shown on the basis of flow curve, hysteresis loops, amplitude sweep and 3-interval-thixotropy-test (3ITT). With these procedures, deeper knowledge about the drilling fluid system can be obtained. Implementing these procedures and considering their results in hydraulic calculation programs or taking them into account by the design of drilling fluids, can reduce costs and lead to safer drilling process in general.