NUMERICAL SIMULATION ON CHARACTERISTICS OF THERMAL JET IMPACT FLOW FIELD
This paper combines high pressure jet and thermal spallation drilling methods together and presents a new thermal jet drilling method. It means striking the rock and conducting heat to it in the meantime. Cooling water is injected with the thermal jet because of the high temperature of jet. Therefore, two cooling plans (lateral plan and downward plan) are designed and analyzed numerically. In this work, the downward cooling plan is taken for example. Four variables are studied about the impact on the bottom hole jet field. They are jet velocity, cooling water velocity, jet temperature and length. Results are analyzed from four aspects which are axial temperature, axial velocity, bottom hole temperature and bottom hole pressure field. In addition, if a potential core of jet is assumed to exist, there is a positive relationship between potential cores of jet and the maximum axial velocity. Moreover, it is better to control the ratio of jet velocity and cooling water velocity when drilling. Finally, two plans are compared from annular temperature and annular return velocity aspects. Results show that it is better to use the lateral cooling plan when reaming is needed. It is better to use the downward cooling plan when normal drilling is needed.