This paper analyses and discusses five means of forecasting petroleum drilling cycle in the world, including historical level method, typical cases method, learning curve method, procedure work-hour method and cyclic rating method.

According to the technical problems existence in many deep wells and consulting relative data, this paper analysed the drilling technologies on lost circulation, hole sloughing, drill pipe sticking, deviation controlling and so on, and proposd out some suggestions for shortening the drilling cycle and improving the drilling r.

Due to the poor drillability,low rate of penetration(ROP),long drilling cycle of the Lower Carboniferous formation,the natural gas exploration and development is seriously restricted in Ludong area of the Junggar Basin.

The study results show that the utilization of reservoir protecting technique can reduce the drilling period and discover and protect petroleum reservoirs without delay,.