Research on the Mechanism of Hole Deviation in Gas Drilling

Deviation control was difficult in gas drilling.The mechanism of hole deviation in gas drilling was not clarified.The comparative analysis between the deflecting characteristics of formation in gas drilling and mud drilling was carried out by means of BHA(Bottom Hole Assembly) analysis method and rock-bit interaction model.The result shows that formation deflecting force and bit side force in gas drilling are both bigger than that of mud drilling.But the difference of formation deflecting force between gas drilling and mud drilling is bigger than that of bit side force.Therefore,the main reason of the gas drilling has more deviation tendency than that of mud drilling.Therefore,in the gas drilling technique for vertical hole section,bit side force should be enhanced properly by means of selecting BHA and the adjustment of drilling parameter to improve wellbore quality.