Fundamental Research On Plasma Discharge Rock Breaking Technology

Oil and gas is a kind of strategic resources which is connected with livelihood of the people and safeguarding national energy safety.With oil and gas resources increasingly depleted,the exploration has developed to more complex and deeper formation.In the exploration,rock breaking technology matters most,and the rock breaking efficiency directly determines the drilling speed,cost and economic benefits.Encountered with hard rock,conventional drilling technology is unable to meet the construction requirements for its high energy consumption and low efficiency.Thus,the development of new efficient rock breaking technology is one of the most important subjects in drilling engineering.Plasma discharge rock breaking technology is a novel kind of highly efficient,environmental and economical rock breaking technology developed in recent years.Focused on plasma discharge rock breaking technology,in this paper more thorough research work was conducted and some innovative research results were achieved.Physical model of rock breaking in the process of plasma discharge was established,the Gauss heat source is loaded into the physical model according to heat conduction equation and phase change process to solve the model,and the temperature distribution of electrode and rock was gained.Using temperature field result as the load,combined with the initial conditions,stress field model was established to gain the stress field distribution of rock breaking in plasma drilling.Meanwhile,the effect of different process parameters on the temperature field and stress field of electrode and rock were studied.A set of rock breaking mechanism was designed based on plasma discharge technology,including servo feed mechanism,rotation mechanism,dynamic sealing joints and tool electrode.Servo feed mechanism can determine the processing position accurately.Rotating mechanism achieves the rotation of rock breaking electrode to improve the quality of rock breaking.Dynamic sealing joint achieves sealing of the entire structure and isolation between the cable cores and prevents the unstable pulsation caused by flushing.Meanwhile,a new plasma electrode was designed,internal and external electrode can be replaced to ensure the stability and continuity of the rock breaking process.In order to verify the effect of rock breaking in plasma discharge process,based on self-designed and developed power supply,rock breaking indoor testbed was built to conduct indoor rock breaking experiments.After a preliminary selection of electrode material,electrolyte solution,electrode structure and electrode polarity,single factor experiments were conducted to study how pulse energy,electrode size,electrolyte solution and other process parameters affect the performance of rock breaking and corresponding results were gained.Processing method,parameters,electrode materials and structure have been optimized in the process of rock breaking.