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Abstract Taking PGP-X well located in Northeast Sichuan province as the research object，the rocks have been sampled respectively between depths of 2 140–4 914 m. Laboratory experiments of static and dynamic mechanical properties of the sampled rocks are performed with the split Hopkinson pressure bar(SHPB)and material test system. By using LS-DYNA，piston-drilling bit-rock interaction system model for air hammer bit drilling is established. In the simulation model，H-J-C dynamic constitutive model is adopted for rock. Taking the damage accumulation caused by the repeated impulsive load into consideration，rock intensity at well bottom is modified after being impacted every time. On this foundation，drilling parameters，structure parameters of air hammer，and the relationship between impact energy and crushing work ratio are researched；and the influences of impact energy，final impacting speed，drilling pressure，impact frequency，rotary speed，well depth and lithologic characters on rock crushing efficiency are explored. The analysis results show that the impact energy-crushing work ratio curve has fluctuation zones and stable zones with clear boundary，so that the critical impact energy and critical drilling pressure of air hammer bit drilling can be obtained. Further research indicates that the critical impact energy and critical drilling pressure are closely related with well depth and lithologic character. With the increase of well depth and rock hardness，both critical impact energy and critical drilling pressure have a tendency of gradually declining. After the simulation of air hammer bit drilling in different formations and lithologies，combinations of critical impact energy，critical drilling pressure，the best rotary speed and impact frequency in typical deep formations are recommended. These results can be for references in field practices for air hammer bit drilling.
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Received: 08 August 2011
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2012, Vol. 31 
