高频扭转振动对钻井过程破岩特性的影响研究

Experimental study on establishment of a new constitutive model of rock damage

为了研究高频扭转振动钻井对PDC(Polycrystalline Diamond Compact)钻头破岩的影响,基于弹塑性力学和机械振动原理,分别建立切削齿的切削模型和岩石的振动方程,并指出了岩石的响应特点。通过岩石的应力-应变试验,得到了岩石的等效塑性应变率与岩石剥落之间的关系。依据现场试验与分析计算,研究了高频扭转振动频率对钻井机械钻速的影响。研究结果表明:当钻井扭振频率为岩石的共振频率时,岩石的塑性应变率为1.5%,钻井的机械钻速为6.3mm/s。研究方法与结论对于利用高频扭振提高破岩效率研究具有重要的应用意义。

Bohai rock samples are studied in order to speed up oil and gas resource exploitation in Bohai and improve the existing theory system of rock damage constitutive models. According to the test parameters, a new damage constitutive model of rock is established. Firstly, with the test of variable temperature and confining pressure of rock specimens in the three axis test instrument, the whole stress-strain curves of rock samples are obtained, and the Poisson's ratio, elastic modulus and maximum differential stress of the rock are calculated. Secondly, using the graphic method for Mohr stress circle, the cohesive force and internal friction angle of rock samples are determined. Lastly, according to parts of the test data, a new damage constitutive model of rock is built up, which refers to fewer parameters and simple calculation. The calculation results of the model and the whole stress-strain curves of test have verified the accuracy of this rock damage constitutive model. The conclusions of the study provide experimental and theoretical support to improve the rock damage model and the efficient exploitation of petroleum resources on site.