Dual shear gun for efficient drilling fluid shearing : Laboratory experiments

A dual shear gun prototype was produced to provide an efficient, low noise shear gun for rig site shearing of oil-based drilling fluids. At the same time this shear gun shall not produce metallic debris to the drilling fluid as such debris alter logging results. In this shear gun, two opposite directed jets collide inside a silencer chamber. Improved efficiency of the shear gun reduces the need for drilling fluid circulation to maintain drilling fluid properties. Initial series of laboratory experiments are conducted. During the experiments a pumping unit was connected to a fluid tank and a divided flow is lead through a model shear gun device with adjustable nozzles. The viscosity and electric stability were measured as function of time for the mixture. The experiments were conducted in an acrylic model of the planned tool. It is also possible to implement camera recordings of the experiments, including borescope view from the centre of the mixing unit. Within the accuracy of measurements, also following API specifications, the viscosity profile developed rapidly. No significant noise was observed from the shear gun. These two properties are showing that the shear gun will be efficient in practical application. An analysis shows how the dual jet mixing chamber flow appears and how this flow will provide proper mixing.