WELL KILLING TECHNIQUE BY DIRECT PUMPING IN METHOD

The well killing technique by direct pumping in method is an empty well control method,which is suited to the condition that when the drilling fluid in gas well is blown off,the well can be shut in by wellhead assembly,but the well can not be killed by circulation because there is no drill string in the borehole,and for which,such factors as the wellhead assembly,downhole conditions,formation pressure build up characteristics and dynamic pressure control in the process of killing well,etc.,are comprehensively considered.The key of the method is to understand the relation between the build up rate of the liquid column pressure of the well killing fluid in borehole and that of formation pressure after well is shut in and to determine the turning point of casing pressure change,i.e.maximum casing pressure in well killing operation,and then,taking this as the well killing boundary condition,a rational well killing program can be designed.Through verifying the on site well killing data from three wells,the results of theoretical calculation are basically identical with the practical well killing data,having a good practicability.