Experimental Study On Single - Tooth Impact Rock Breaking Under Bottom Hole Pressure

Raising penetration rate is one of the main technical bottlenecks that we should s olve for exploration and development of deep hydrocarbon resources. In recent years, dynamic-static coupling tools, like air hammer, torsion impacter and hydraulic impactor are showing a remarkable technical advantage in drilling engineering of deep formati on. However, the damage behavior of rock in the complex stresses environments is ve ry complicated due to rock is a strain-rate sensitive material. So it is necessary to kn ow the mechanism of rock cracking under the complex stresses environments. And thi s is the foundation of seeking the new theory and technology to raise penetration rate in drilling engineering.This thesis is aimed at the tight sandstone in Sichuan Xujiahe group. Static rock mechanics experiments, SHPB dynamic rock mechanics experiments and ANSYS-AUT ODYN dynamic simulations are carried out to analyze the damage behavior of sandsto ne impacted by a single tooth under the simulated formation stresses environments. As a result, rock fragment characteristics, crack growth, energy conversion and dissipatio n have been achieved. By accomplishing the above research, a set of quantitative eval uation technique for rock fragmentation process shall be formed. The main research co ntent of this thesis is followed as below:(1) The parameters of Johnson-Holmquist damage constitutive model have been achieved by static rock mechanics experiments and SHPB dynamic rock mechanics experiments, which establishes the foundation of tight sandstone as a dynamic simulation material in ANSYS-AUTODYN.(2) Experiments that sandstone impacted by a single tooth has been conducted. The characteristics of rock fragment are analyzed based on the fractal theory. Furthermore, the energy conversion and dissipation theory model of this progress are developed based on elastic mechanics theory, which establishes the theoretical foundation of analyzing the later simulation data.(3) The feasibility and optimization of parameters of Johnson-Holmquist damage constitutive model are verified by the simulation of SHPB dynamic rock mechanics experiments using ANSYS-AUTODYN. What’s more, SHPB dynamic rock mechanics experiments under the high confining pressure are conducted by ANSYS-AUTODYN, and a series statistical empirical models of dynamic-static rock mechanics parameters related to well logging data are founded.(4) The simulation of sandstone impacted by a single tooth is conducted by ANSYS-AUTODYN. The law of sandstone crack extension, crushing volume, crushing ratio, energy conversion and dissipation are analyzed emphatically. Some key parameters including impacting velocity, confining pressure, hydrostatic pressure of the fluid column and static load are taken into consideration in the simulation. As a result, a serious of statistical models related to those parameters are established. All of the researches above contribute to the foundation of failure mechanism of tight sandstone when impacted by the dynamic-static coupling tool. And which provids a theoretical support for improving and optimizing method to raise penetration rate in drilling engineering.