自激振荡钻具振荡力计算及影响因素分析

OSCILLATION FORCE COMPUTATION AND INFLUENTIAL FACTORS ANALYSIS OF SELF-EXCITED OSCILLATION DRILLING TOOL

自激振荡钻具是利用自激振荡原理,将连续的高压钻井液转化为间歇周期性的脉冲射流,以增强钻头冲击力和减少岩屑重复破碎,进而提高机械钻速的井下工具。该工具以其结构简单、无密封件和工作可靠等优势得到广泛应用。然而由于自激振荡钻具的振荡力使用解析法难以计算,使得其结构优化和现场应用受到限制。文章基于大涡模型理论,对自激振荡钻具内部流场进行模拟,进而计算出工具振荡力的大小,并计算分析了钻井液密度、钻井液排量和工具最小水眼尺寸变化对振荡力的量化影响,指出钻井液密度和钻井液排量是影响工具振荡力的主要因素,同时现场应根据实际许用节流压降选用合适的最小水眼尺寸。文章的研究工作为工具内部结构的优化提供方法,同时也为现场合理使用该工具提供依据。

The self-excited oscillation drilling tool could convert the high pressure drilling fluid into intermittent cycle pulsed jet by using the self-oscillation principle to increase the impact force of drill bit and reduce the rock repeated crushing,and then increase the drilling rate.The tool was widely applied by reason of the advantages of simple structure,no sealing element and work reliability.However,the oscillation force of the tool was hard to be computed,and the structure optimization and field application were limited.Based on the theory of Large Eddy model,the flow field of the tool was simulated,and the oscillation force was calculated.And the affections of drilling fluid density,drilling fluid displacement and minimum holes diameter on oscillation force change were analyzed,the main factors influencing oscillation force were drilling fluid density and displacement.The research in this paper provided optimization method for the tool structure,and a basis for reasonable using the tool.