极地深部冰层取心钻探孔壁水压致裂研究

Research on Hydraulic Fracturing in Deep Ice Core Drilling Borehole Wall

为了维护极地深部冰层取心钻探工作中钻孔的稳定,避免孔内事故的发生,冰层孔壁的水压致裂问题是亟待解决的重要科学问题之一。本文在深入分析国内外冰层钻探资料的基础上,结合冰盖动力学相关理论,计算得出了钻孔所在区域冰层的密度、温度及内部应力随深度的变化规律。在此基础上,结合油气资源勘探水力压裂技术与冰层钻进钻井液等相关理论,建立了合理的孔壁压差计算方法,深入探讨了适用于深部冰层钻探孔壁水压致裂机理。研制了冰层钻孔水压致裂模拟实验装置,可分析研究不同围压条件下冰样的脆性变形机理。结合我国Dome A深冰心钻探工程实际,提出钻孔可能发生水压致裂的深度区域及孔壁所需的起始裂纹长度判定,以期为后续的安全高效冰层钻进提供重要的理论依据。

In order to maintain the stability of deep ice core drilling borehole wall and avoid the occurrence of in-hole accidents,the hydraulic fracture become one of the important scientific problem which need to be solved urgently.On the basis of deep analysis of the ice drilling data,and combining the ice sheet dynamics related theory,we calculated the change rules of ice density,temperature and internal stress with depth.Then,combining the hydraulic fracturing technology in oil and gas resources exploration drilling and ice drilling fluid theory,we established a reasonable differential pressure calculation method of ice borehole wall and discusses the mechanism of hydraulic fracturing for deep ice drilling deeply.By developing a true-triaxial hydraulic fracturing equipment,we obtained the brittle deformation mechanism of ice borehole under different confining pressures.Combining the actual deep ice core drilling in Dome A,we obtained the depth interval and necessary initial fracture length of occurring potential hydraulic fracture in this borehole.This method provides an important theoretical basis for subsequent safe and efficient in future ice drilling engineering.