Experimental study of tip screenout fracturing by using CT scanner

In hydraulic fracturing, a rapid rise in the pump pressure sometimes occurs late in the job after proppant is added in the injection fluid. One of the possible reasons is the formation of tip screenout (TSO), but it has not been verified clearly yet. In this study, we attempted to reproduce TSO in laboratory experiments. A new test vessel was developed, which allows us to do fracturing experiments in a cylindrical specimen of φ168 mm x 150 mm subjected to tri-axial compression, and observe inside the specimen in real time using the X-ray CT scanner. The experiments were carried out on conditions that a fracturing fluid was switched on the way of fluid injection to a slurry containing fine solid particles. As a result, it was clearly seen from CT images that soon after the slurry injection, the particles reached fracture tip and accumulated there with time. These results show that TSO is a really existing phenomenon, and it surely causes the rapid rise in injection pressure.