Design and experimental study of a new hydraulic tool for lost-circulation materials (LCM) plugging while drilling.

Big Data Analysis from the worldwide field shows that lost circulation is a common phenomenon in drilling and the success ratio of remedial treatment for lost circulation is low. It is not only because of these complexities of the formation, but also because of the poor performances of the lost-circulation materials (LCM) and technologies. This paper proposes a new method in plugging, which is based on a particular physical method for lost circulation controlling and plugging while drilling. This method is different from these traditional treatments, which only use chemical methods. When pore-permeable and fractured leakage formations are encountered while drilling, We can use this new hydraulic tool, the drilling fluid will have a diffluence at a constant rate from the jet of the hydraulic tool which is installed on the drilling pipe and the fluid laden with particles can be injected into the natural or induced fractures of the borehole wall which may lead to lost circulation. Combined with the corresponding drilling fluids which have been tested in the laboratory, the additives such as ground marble, ground nutshells, and graphite in the drilling fluid are quickly pushed into the fractures because of the differential pressure provide by the hydraulic tool, then form a firm seal at the mouth of the fractures which could isolate fluid pressure in the wellbore and prevent effective pressure communication to interfere the extension of the fracture. What's more, according to the stress cage theory, when these sealing particles which prop the fracture open, act as wedges to compress the rock around the wellbore, the hoop stress could be increased, so that the wellbore pressure containment (WPC) could be improved. Since the annular flow may have some interference with the side nozzle jet, this paper also numerically simulates the flow field of the annular air section through the fluid simulation software Fluent, and the simulation results show that the interference of the annular flow on the jet is very weak and basically has no effect. In addition, through the oilfield field test, it is known that this new physical plugging method has good plugging effect, and it can obviously improve the pressure-bearing capacity of the formation, which has great popularization value.