Stress field simulation analysis of combination drilling expansion downhole

Speed boost and synergia have became the central task of oil and gas drilling and rock breaking is the key to speed boost. So the research about the new methods aboutbreaking rock efficiently is the primary problem which must be solved at current. Conventional downhole model and stair downhole model are established through carrying out stress field simulation analysis of combination drilling expansion downhole, toreasearch the differences about stress field and displacement field between the conventional downhole and the stair downhole. Moreover various mechanical models on stair downhole are set up through adopting computer simulation in order to study the effect rules about the stress field and displacement field caused by different drilling expansion ratios Researching the effect rules about the stress field and displacement field caused by different relative locations. The results show that, firstly, the stair downhole has better stability than conventional downhole. Secondly, combination drilling expansion has better effect than the direct use of larger size drill. Thirdly, drilling expansion ratios and relative distance between drilling and expanding body have optimal range for the drilling efficiency of combination drilling expansion.