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Research on Composite Directional Drilling and Mud Pulse Wireless Measurement While Drilling Technology in Coal Mine
Release time:
2021-04-19
Author:
Source:
Gas drainage is not only one of the main ways of coal mine gas control, but also the basis of comprehensive utilization of gas (coalbed methane). Underground directional drilling is an effective way to carry out coal mine gas drainage because of its advantages such as controllable drilling trajectory, long effective drainage distance, multi-branch holes and advanced regional centralized drainage, which plays an important role in ensuring coal mine safety production. However, with the increase of the depth and aperture of the directional drilling hole and the complex diversity of the drilling formation, the inherent limitations of the existing sliding directional trajectory control technology and the wired drilling measurement technology gradually appear. In this paper, large diameter/super long near horizontal directional hole and complex formation near horizontal
Gas drainage is not only one of the main ways of coal mine gas control, but also the basis of comprehensive utilization of gas (coalbed methane). Underground directional drilling is an effective way to carry out coal mine gas drainage because of its advantages such as controllable drilling trajectory, long effective drainage distance, multi-branch holes and advanced regional centralized drainage, which plays an important role in ensuring coal mine safety production. However, with the increase of the depth and aperture of the directional drilling hole and the complex diversity of the drilling formation, the inherent limitations of the existing sliding directional trajectory control technology and the wired drilling measurement technology gradually appear. In this paper, in view of the large diameter/super long near horizontal directional hole and complex formation near horizontal directional hole drilling construction problems, the system of coal mine underground composite directional drilling technology, revealing the composite directional mode of trajectory control mechanism, quantitative analysis of the composite directional mode of drilling tool force characteristics, designed to adapt to the composite directional drilling mud pulse wireless measurement while drilling device, improve the ability of underground directional drilling technology and equipment level, in order to ensure the safety of coal mine production provides favorable technical support.
Firstly, the principle of composite directional drilling technology is studied, the drilling process is formulated with the drilling trajectory control as the core, and its characteristics are analyzed from three aspects: drilling efficiency, drilling safety and deep hole drilling. Based on the drilling tool combination of single bend and unstable near horizontal drilling, a compound drilling trajectory prediction model is established. Using simulation calculation, the variation law of drilling lateral force and hole inclination trend angle with screw motor bending angle, bit lateral cutting force, bit pressure, hole diameter expansion rate, power head speed and drilling inclination angle under compound drilling conditions is analyzed and obtained. Through law research, it is concluded that the 1.25 degree screw motor is used in compound drilling at bit pressure of 15kN, when the drilling expansion rate is more than 10%, the composite drilling trajectory control is in a stable and fast drilling state.
By establishing a three-dimensional simulation model of composite drilling, the vibration mode of the drill string is extracted, and the rock cutting process of the drill bit-drill pipe system is simulated and analyzed. Based on Abaqus/Explicit explicit center difference algorithm, the transient analysis of the rock breaking process of drill bit is carried out, and the resonance phenomenon of bottom hole assembly will not occur under the condition of compound drilling in small diameter near horizontal drilling in coal mine is obtained. At the same time, the periodic stress and strain state between the bottom hole assembly and the formation in the process of compound drilling is quantitatively analyzed to provide reference for the selection of drilling process parameters and drilling tool assembly.
Secondly, according to the special construction environment and drilling technical requirements of coal mine underground, a set of wireless measurement while drilling device suitable for coal mine underground conditions is designed. The pulse generator and 73mm outer tube are designed into an integrated structure, and the proportional pilot control technology is adopted to realize the stable output of pulse signal under the condition of 96L/min small displacement. Application of pressure pulse amplitude calculation and analysis method, the change trend of pulse pressure amplitude increases with the increase of valve head radius, pump pressure, mud displacement and drill pipe inner diameter, and the optimal valve head diameter of coal mine mud pulse transmission is obtained by combining the parameters of coal mine underground pump. It provides reference for the setting of working parameters and the selection of drilling parameters in the application of mud pulse measurement while drilling device in coal mine.
Finally, combined with the three typical sites of medium-hard coal seam, soft and hard interbedded coal seam and roof complex formation, the field test research of composite directional drilling technology and mud pulse wireless drilling measurement device is carried out. The research results on composite directional drilling and supporting mud pulse wireless drilling technology are verified. The research and related conclusions of composite directional drilling and mud pulse wireless measurement while drilling technology carried out in this paper can be used to guide the engineering practice of gas drainage drilling on site, and have certain reference value for further research and application in related fields.
Key words:
Composite, drilling, directional, underground, borehole, pulse, coal mine, technology, mud
