Drag Reducing Performance of a Nanomodified Material in Water Based Drilling Fluids

The flow of water based drilling fluids in slim holes fluctuate significantly and the interface resistance between the drilling fluids and the wellbore/drilling tools is high, resulting in high flow energy loss and high equivalent circulation density (ECD) which in turn cause mud losses and stuck pipe to happen. A drag reducer DRA-1 for water based drilling fluids was synthesized with nano silica as the raw material through graft-modification, and its performance was studied. In laboratory experiment, it was found that a base mud treated with 3% DRA-1 has its flow index increased by 366.7% to 0.5064, the consistency coefficient reduced by 90.6% to 0.4847 Pa·sⁿ, and the extreme pressure coefficient of friction reduced by 81.82%. After hot rolling at 120℃ for 16 hours, the extreme pressure coefficient of friction was further reduced, indicating that DRA-1 is resistant to high temperature. When the DRA-1 treated base mud was flowing under the same conditions on a self-made steel plate and a polytetrafluoroethylene plate respectively, DRA-1 performed much better than the same type of field additives in improving the flow behavior of the mud. Operation data obtained from the well A showed that by adding 1% DRA-1 in the water based drilling fluid, the pressure loss along the circulation system was reduced by 1.937 MPa, a reduction rate of 21.61%, and lower ECD was obtained in the whole drilling operation, indicating that DRA-1 helped increase the drilling efficiency and safety, and this is very important to the increase of economic benefits and the avoidance or drilling accidents.