COUNTERMEASURE FOR PROTECTING WELLBORE STABILITY WHILE GAS-LIQUID TRANSFORMATION DURING DRILLING

According to the complex situations in the process of gas drilling that have influence on the safety of well drilling such as layer watering out, excessive torque and friction or making a trip hard etc., gas drilling had to be converted to conventional mud drilling. This article analyzed the effects of working fluid on sidewall stability during gas and fluid conversion, thereby the requests to drilling mud performance were put forward for transformation. It is thought that when transformation, it should take use of the lower density drilling fluid at first, after the mud cake formed in the wellface, the density of the drilling fluid was increased to balance the layer fluid. And used water base drilling fluid would select the strongly inhibited and emulsified anti-sloughing drilling fluid, non-penetrative drilling fluid, polysilicic alcohol fluid, designer fluid, MEG drilling fluid and polymer asphaltum drilling fluid.