Water Hammer Modeling in Extended Reach Wells

Abstract

Abstract Water hammer tools (WHTs) are used in coiled tubing (CT) operations for postponing a potential helical lock-up and running deeper into the hole. By rapidly opening and closing a valve in the tool, pressure pulses are created and the axial vibrating force is overcoming the friction between the CT and the wellbore. The pressure pulses depend on the CT parameters (size and material), WHT parameters (size and valve frequency), pumping rate, and downhole pressure. Although the effect of the water hammer pulses on the axial and radial vibrations has been investigated before, the coupling between water hammer pulses and the axial and radial vibrations for CT operations is not currently understood. Radial vibrations may be important as they may reduce the normal and thus the frictional forces between the CT and the wellbore and increase the reach in long horizontal wells. In this paper the effect of the water hammer pulses on the radial vibrations is investigated. A numerical model was developed to simulate the water hammer pulses and vibrations of the CT and WHT assembly. The model was validated against lab data for the case of a single WHT located at the end of a CT. Then the model was used to investigate the optimal performance of the WHT. Several scenarios, such as a WHT located between two CTs and two WHTs working in tandem, were also investigated. It is concluded that the radial vibrations which appear due to the water hammer pulses when two WHTs are used in tandem may be beneficial in reducing the friction forces between the CT and the wellbore. When two WHTs are used, a relationship between the additional pumping pressure and the distance between the two tools is also proposed.