Development of a reproducible method of formulating and testing drilling fluids

Previous work has indicated that is very difficult to obtain consistent and reproducible test data on drilling fluids of identical composition mixed in similar equipment. The present work is an attempt to determine the causes of the divergent results and to point the way towards a method which avoids them. Drilling fluids are prepared in the laboratory to determine their suitability to meet specific drilling requirements or to serve as a base fluid to evaluate the effectiveness of thinners, dispersants or other additives. Their preparation normally consists of adding together measured quantities of the constituents, stirring for a short time in a low speed device to obtain a uniform mixture and hydrate clays, and then to agitate in a higher speed mixer such as the Hamilton Beach mixer or the Waring blender to disperse the clay particles more thoroughly. In this work, it is shown that: 1. The properties of the muds after the above procedure are changing rapidly, and are extremely sensitive to the duration and violence of agitation. 2. The increase in temperature associated with the agitation causes substantial and variable loss of water by evaporation, leading to a gelling of the mud before its properties reach constant values. It is not feasible to protect mud in these devices against loss by evaporation. ..