深部煤矿原位保压保瓦斯取芯原理与技术探索

煤矿瓦斯灾害防治是矿井安全生产的重点和难点,其核心是煤层瓦斯含量与压力的精准测定。目前含瓦斯煤层(或煤矿)取样普遍采用开放式或球阀密闭式取芯技术,取芯效率低,且瓦斯容易损失、测量时效性差,难以保证瓦斯含量与压力数据的准确性与有效性,不能有效评估煤层风险特征指标以指导工程实践。首先深入剖析了深部煤层原位压力内涵,阐明了原位保压保瓦斯取芯的基本目标,建议了原位瓦斯压力及含量的测定与计算方法。其次,基于牟合方盖几何原理,提出了保压保瓦斯取芯工具构想,采用多重防转的取芯结构设计和连续导管作业工艺,能够实现煤样低扰动取芯,确保所取样品瓦斯含量与原位煤层一致;设计了5种构型的自触发式保压控制器,基于自主研发的实验室保压特性试验平台开展了保压能力相关参数测试,结果表明随着保压控制器锥形角度的增加,边缘的有效支撑面增大,极限强度增加。同时,开展了连续导管抗扭特性实验,在扭矩、管长、外径一定时,连续导管扭转角随壁厚的增加逐渐变小、抗扭性能增强,岩芯受到的扰动降低。最后,研制了深部煤矿原位保压保瓦斯取芯原理样机,由煤矿坑道钻机、连续导管装备、保压保瓦斯取芯器等组成,基于仿真模拟和室内试验数据,选定了马鞍形...

Principle and technology of coring with in-situ pressure and gas maintaining in deep coal mine

The prevention and control of coal mine gas disaster are both crucial and challenging to mine safe production.The core issue lies in the accurate determination of coal seam gas content and pressure.At present,the open or ball valve sealed coring is widely used to obtain coal samples containing gas.However,these approaches demonstrate a low coring efficiency,poor timeliness,and easy gas loss,making it hard to ensure the test data’s accuracy and effectiveness,and fail to effectively evaluate coal seam risk characteristic index to guide engineering practice.This study begins with an in-depth analysis of the connotation of deep coal seam in-situ pressure,expounds on the primary goals of in-situ pressure and gas retaining coring,and recommends some methods for determining and computing in-situ gas pressure and content.In addition,based on Steinmetz solid’s geometric principle,the concept of pressure and gas retaining coring tool is proposed.The multiple anti-rotation coring structure design and coiled tubing operation technology help to minimize the disturbance of coal sample during the coring process,striving for consistency between the coal seam gas content of the samples obtained and the in-situ gas content.Five types of self-triggering pressure-maintaining controllers are designed,and the relevant parameters of pressure-maintaining capacity are tested on the self-developed indoor pressure retaining characteristic test platform.The results show that as the cone angle of the pressure retaining controller increases,the effective supporting surface of the edge increases as well,and the ultimate strength goes higher.At the same time,the torsion resistance experiment of the coiled tubing is carried out.When the torque,length and outer diameter are fixed,the torsion angle of the coiled tubing gradually decreases with the increase of tube wall thickness,enhancing the torsion resistance,and resulting in reduced disturbance to the core.Finally,a prototype of in-situ pressure and gas retaining deep coal corer is developed.It is composed of a roadway drilling rig,coiled tubing equipment,and pressure and gas retaining coring device.According to the simulation and laboratory test data,the saddle pressure-maintaining controller(the maximum pressure-maintaining capacity can reach 100.9 MPa)and the coiled tubing made of CT90 steel(with a diameter of 38.1 mm,tube thickness of 3.18 mm)have been selected.The technology of in-situ pressure and gas retaining coring has been preliminarily established.The entire system runs smoothly with flexibility during the field test and successfully obtains pressure-maintaining samples.It has been preliminarily verified that the prototype design is reasonable and the assembly is precise and reliable.The coring system comes with excellent pressure-maintaining performance,low disturbance,high efficiency,and logging capability while drilling.It is expected to break through the technical bottleneck of in-situ gas pressure and content determination.