Tests under operating conditions of washpipe mechanical seals for drilling application

New boreholes of unconventional oil and gas deposits, located inside impermeable rocks, are usually drilled using the “top drive” technology. This method is characterized by high torque, which minimizes the risk of pipe stuck in horizontal and directional boreholes with a large angle of inclination. The stability of the wellbore wall during drilling is controlled by applying appropriate, high hydrostatic pressure. The washpipe assembly plays an important role and the key aspect for the success of the entire extraction operation is an effective sealing in the area between fixed goose neck and rotating head of the top drive assembly. In order to cool the drill bit and to remove the drill cuttings, the drilling fluid is fed to the drill string under very high pressure, up to 400 bar. Washpipe mechanical seals and, in particular, sealing rings which are their critical elements, work in extremely difficult conditions. They are exposed to continuous, cumulative destructive action of both friction forces, mechanical stresses, thermal stresses and the corrosive action of the drilling fluid. Seals operating under such conditions must be highly reliable and their application in drilling installations should be preceded by tests in an environment simulating actual operating conditions. A new generation of prototypes of washpipe mechanical seals were tested in this work. The tests were carried out under operating conditions on a self-developed platform simulating the actual operating environment of a mechanical seal. The processing fluid was a chemically aggressive potassium-polymer solution of drilling fluid. During the tests, variable working pressure and rotational speeds (up to 220 rpm) were used. Experiments carried out on the test platform under operational conditions simulating the actual operating environment of seals have shown that such tests are extremely difficult and create a number of methodological problems. This is mainly related to the problem of reproducing the real working environment of washpipe assembly, and in particular its individual parameters. The key, and at the same time the greatest research challenge is to maintain the assumed drilling fluid pressure. Tests under operating conditions using chemically aggressive emulsion drilling fluid are more difficult to carry out than with a water. They showed that the drilling fluid solidifies on the sealing surface, which implies additional technical problems. In addition, temperature gradients can cause thermal cracks on the edges of the rings. It was found that their design features also have a significant impact on the durability of the sealing rings. By modifying the shape of the rings and selecting the geometrical features of the sealing hardware itself, the durability of the system can be improved and the life of the seal can be extended. For difficult operating conditions of washpipe mechanical seals, there is currently no viable alternative of making sealing rings from other materials than solid tungsten carbide (WC).