大直径瓦斯抽采钻孔非凝固膏体材料封孔技术及设备研究

针对大直径瓦斯抽采钻孔密封方法采用固体材料封孔初期密封效果好,但随着时间推移,存在封孔变形破坏后的钻孔抽采瓦斯浓度急速衰减的问题,提出了一种大直径瓦斯抽采钻孔非凝固膏体材料封孔技术。该技术利用膨胀水泥与非凝固膏体材料配合形成多段"固、液、固"结构,利用膨胀水泥材料形成三段固体封孔段,然后在不同抽采时间段在固体封孔段中注入非凝固膏体材料,实现了钻孔抽采全过程的有效密封及抽采不同时间段的二次、多次封孔。基于大直径钻孔孔周裂隙半径的理论分析结果,对最佳注浆压力和黏度的关系进行了数值模拟,研究了非凝固膏体材料封孔的相关技术参数,得到最佳注浆压力为1.2 MPa,最佳黏度为0.001~0.03 Pa·s。根据研究得到的注浆压力和黏度研制了一种封孔设备,设备利用"固、液、固"技术原理形成多段封孔结构,实现了固封液、液封气的抽采封孔模式。现场工业试验结果表明,大直径瓦斯抽采钻孔非凝固膏体材料封孔技术利用膏体材料具有随钻孔时空变化的特征,能有效解决固体材料封孔因钻孔变形而形成新裂隙,造成封孔失败、抽放浓度衰减过快的难题,且二次补浆后抽采体积分数能提升10%左右,有效提高了瓦斯抽采率。

Study on sealing technology and equipment of non-solidified paste materials for large diameter gas extraction boreholes

For large diameter gas extraction boreholes,the solid material sealing method has a good sealing effect at the beginning.However the gas concentration of the extracted gas from the borehole decreases rapidly after the deformation and destruction of the sealing borehole over time.In order to solve these problems,a non-solidified paste material sealing technology for large diameter gas extraction boreholes is proposed.This technology uses expanded cement and non-solidified paste material to form a multi-segment"solid,liquid,solid"structure,uses expanded cement material to form three solid sealing segments,and then injects non-solidified paste material into the solid sealing segments during different extraction time.Hence the technology realizes the effective sealing of the whole process of extraction and the secondary and multiple sealing of the borehole during different extraction time.Based on the theoretical analysis of the fracture radius around the large diameter borehole,the relationship between the optimal grouting pressure and viscosity is numerically simulated.The technical parameters related to the sealing of non-solidified paste material are studied.The optimal grouting pressure is 1.2 MPa and the optimal viscosity is 0.001-0.03 Pa·s.A borehole sealing equipment is developed based on the grouting pressure and viscosity obtained from the research,which utilizes the principle of"solid,liquid,solid"technology to form a multi-segment borehole sealing structure,and realizes the extraction sealing mode of solid sealing liquid and liquid sealing gas.The results of field industrial tests show that the sealing technology of non-solidified paste material in large diameter gas extraction boreholes,combining the characteristics of the paste material changing with the time and space of the extraction,can solve the problems of sealing failure and rapid decay of extraction concentration,which caused by new fracture formed by the solid material sealing due to borehole deformation.Furthermore,the volume fraction of extraction can be increased by about 10%after secondary grouting which can improve the gas extraction rate effectively.