A Type of Advanced Mud-Hammer Applied to Oil Drilling

Abstract

Abstract A kind of percussion rotary drilling system applied to oil drilling, which includes a mud-actuated hammer as a key element. The overall goal of this system is to rise up the ROP and to provide significant cost reduction and technical advantage over current drilling practice particularly in deep, medium-to-hard rock formations. This paper describes a new type of efflux mud hammer, its structure principle and latest experiment results in some detail. Introduction According to rock-breaking theories, the percussion rotary drilling technique is one of the most effective ways to drill hard formations. The research work starting in 1992, aims at developing a type of efflux mud hammer applied to oil drilling to rise up the ROP of hard formations. A set of mud hammer prototype and its testing system is developed; a lot of simulated experiments are made. The research of improving the impact energy of hydro-efflux hammer has made a break-through. The final impacting velocity of hammer has reached 5.43m/s. The high-energy hydraulic hammer has been designed. The designing method and calculation formulas of efflux element are established, the computer calculation program is compiled and the computer-aided designing is fulfilled. The series of hammers have been designed, and experimented in the Sichuan, Qinghai, Xinjiang oilfield in the west of China. The hammer's lifetime, stability has been improved. At present, this technique has been gradually used in the oilfield in the west of China. Description of Technology The key element of this mud hammer is an efflux element, which controls piston stroking upward and piston stroking downward. Figure 1 illustrates the basic principle of this hammer system. The high-pressure mud fluid from drill-string inputs into jet nozzle and forms a truss of high-speed jet, which can automatically attach to one side of efflux element. If it attaches left side, the jet flows into the down chamber of piston, and pushes piston move upward to its upper dead center. At this moment, the piston abruptly stops, and the water hammer is produced in the down chamber of the piston. The water hammer wave feedbacks to the left control punch, pushes the jet to attach to the right side of the jet nozzle, jet fluid inputs into the upper chamber of piston and pushes the piston to move down and strikes the anvil. At this moment, the piston abruptly stops moving, the water hammer is produced in the upper chamber of the piston. The water hammer wave feedbacks to the right control punch to push the jet to attach to the left side of the jet nozzle, the next cycle begins. The piston and hammer reciprocates just like this. Features. There are no spring and valve in this kind of mud hammer, so, it has long lifetime; The piston and hammer move in an open system, so this type of mud hammer can be used in deep well. Experiments in Lab Experiments in autoclave. The efflux mud hammer is installed in the autoclave testing system (Fig.2). High pressure is set up in the autoclave by using pump and valve. When the pressure in the autoclave varies from 1.2MPa to 32MPa, the hammer can be operated normally. The experimental results demonstrate that the confining pressure have no influence on the hammer's performance. The testing results are as table 1. Experiments on testing system.A set of mud hammer prototype and its testing system (Fig. 3) is developed in1997. The system can test the hammer's frequency, impact energy and upper pressure or down pressure of piston chamber, and so on. A lot of experiments have been done with this system. The experiment data and results are as followed Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, and Fig. 9.