| Exploration of oil and gas is directed towards high and steep structural zones. But anti-deviation and fast drilling technology is still a technical problem which hasn’t been fundamentally solved. So foreign companies invented automatic vertical drilling tools and put them into commercial applications. Since 1990s, researches on theory and technology of vertical drilling steerable tools have been conducted and new production which can effectively reduce the well deflection has been developed in our country. The restoring mechanism and the control method of AADDS-I developed by our research group have been deeply studied in order to improve the performances of domestic oriented tools in this paper. The mian works are as follows:(1)The performance deficiencies of the original oriented tool based on single-double cylinder hybrid control pattern is proposed, including that the magnitude of restoring force is unadjustable, the restoring force direction and the gravity high side cannot be coincided accurately, and the floating guide sleeve randomly rotates. The restoring working principle of the original oriented tool is analysed to find the reason that the magnitude and the deriction of restoring foce is unadjustable. By calculating, the basal presssure needed by restoring block to keep the guide sleeve and the borehole wall static relatively is abtained. The characteristics of pressure changes in the restoring clinder under the condition of strong vibration is also obtained. And then the results are used to illustrate the phenomenon of random rotation of the guide sleeve;(2)By analyzing the continuous adjustment mechanism of the magnitude and deriction of restoring force, three cylinders proportional controlling guiding pattern is proposed and its working principle is introduced. This pattern uses three restoring cylinders to interlock presssure. So the restoring force direction and the gravity high side can be coincided, the floating guide sleeve is well autocentered, the random rotation of the floating guide sleeve in the case of strong vibration is restrained by the friction torque between the borehole wall and the support block. The basal pressure of the three cylinders proportional controlling guiding pattern is calculated. A dynamic pressure feedback device is proposed to improve the stability of the restoring force and the measure-control precision of the tool while drilling. Theoretical research, numerical optimization, experimental verification are also conducted;(3)The way to implement the three cylinders proportional guidance control based on Pulse Width Modulation is studied. The continuous adjustment of the magnitude and the deriction of restoring force is achieved. For the hydraulic system under special downhole working condition, the relationship between the power pluse width of PWM signal and the target pressure, the influence of power pluse position on pressure oscillation amplitude are studied. Simulating experimental device is utilized to verify the pressure regulation of guide block and the restoring performance, and is compared with the single-double hybrid control pattern. Based on this, the NPWM technology of guiding hydraulic system is further discussed. And the way to make a further improvement on the control accuracy of this method is explored.(4)The way to implement the three cylinders proportional control based on continuous analog signal is researched. The effect on the pressure steady deviation and dynamic characteristics caused by the structural parameter of the straight moving proportional relief valve are analyzed. Its pressure control characteristics in the guiding hydraulic system with dynamic pressure feedback device are studied. These provide another approach of continuous real-time adjustment of restoring force and improve the tool’s adaptability to geology. |
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