水合物开采喷射破碎工具自锁式压控机理

Self-locking pressure-controlled mechanism of jet crushing tool for hydrate exploitation

喷射破碎工具是天然气水合物开采中用于水合物矿体储层破碎造腔的关键工具。本文旨在解决现有类似工具存在的喷头开关状态不可控、井眼钻进与破碎扩径作业不可自动切换等问题。首先,设计了一种带自锁式压控滑芯的喷射破碎工具,可以通过控制滑芯入口钻井液流量来改变滑芯的位置,实现喷头的开启与关闭及滑芯的自锁与解锁;其次,采用数值模拟方法研究了结构尺寸对滑芯内部压降及轴向力的影响,得到了滑芯内部的最优结构参数。最后,加工了实验样机,实验验证工具的工作性能。研究结果表明:当滑芯入口直径为45 mm、入口角度为30°、出口与直管段直径为30 mm、入口流量为470 L/min时,效果最佳;在常规井眼钻进流量下,喷头不会开启;当入口流量为453 L/min时,喷头完全开启且滑芯实现自锁;当入口流量为253 L/min时,滑芯实现解锁且喷头逐渐关闭;工具自锁流量与设计流量(470 L/min)的最大相对误差为3.62%,在可被认同的误差范围内。因此,在所设计的钻井液流量下,自锁式压控滑芯喷射破碎工具的射流喷头可以正常开启与关闭,滑芯能完成自锁与解锁。

The jet crushing tool is key for crushing and cavity formation of hydrate reservoirs in gas hydrate exploitation.The study aims to solve the problems of similar tools,such as uncontrollable nozzle switching state,and non-automatic switching between borehole drilling and jet crushing expansion.Firstly,a jet-crushing tool with a self-locking pressure-controlled sliding core was designed,which can change the position of the sliding core by controlling the flow rate of drilling fluid at the sliding core inlet,and realize the opening and closing of the nozzle and the self-locking and unlocking of the sliding core.Secondly,numerical simulation methods were employed to study the effects of structural dimensions on the pressure drop and axial force inside the sliding core,and the optimal structural parameters inside the sliding core were obtained.Finally,an experimental prototype was machined to verify the tool's performance.The results show that when the inlet diameter of the sliding core is 45 mm,the inlet angle is 30°,the diameter of the outlet and the straight pipe section is 30 mm,and the inlet flow rate is 470 L/min,the effect is the best.The jet nozzle will not be opened at the conventional borehole drilling flow rate.When the inlet flow rate is 453 L/min,the nozzle is fully opened and the sliding core is self-locked.When the inlet flow rate is 253 L/min,the sliding core is unlocked and the nozzle is closed gradually.The maximum relative error between the tool's self-locking flow rate and the design flow rate(470 L/min)is 3.62%,which is within an agreeable error range.Therefore,under the designed drilling fluid flow rate,the jet nozzle of the self-locking pressure-controlled sliding core jet crushing tool can be opened and closed normally,and the sliding core can complete self-locking and unlocking.