高压差下冰的蠕变特性对冰孔缩径的影响机理

Borehole closure is a huge problem faced by dry hole drilling in ice sheet when approaching to its depth limitation. Not ony does it influence the drilling efficiency, in some serious senarios also sticking accidents might happen, even cause the inevitable ecnomic lost as bad as abandoning borehole and drill. This project is aimed to research the dry borehole closure mechanism by comfirming the ice sample protocals using in-situ ice core database as standard and carrying out ice creep tests under high differential pressure with singal variable and multi variables ice samples. Through which we can conclude the ice creep curves shifting laws, sensitive factors effecting creep rates and impacting ways of multi variables on ice creep characteristics. Mathematic modelling of creep rate of each stages and dry bolehole closure under different enviromental conditions can be concluded after defining starting points of each creep stage combining ice microstructure evolution druing creep tests, resulting in revealing the dry borehole closeure mechanism and predicting its critical depth for various environmental conditions. This project can prevent sticking accidents scientifically and rationally as well as provide technical and thoretical support to implement rapid access drilling in ice sheet safely and effctively, especially in the cutting edge projects, for instance, 2k array and oldest ice, where 500 m to 1000 m suvey holes are imperative.

冰孔缩径是冰层干孔钻探至极限深度时必然遇到的难题，不仅会影响钻进效率，严重时还会发生卡钻事故，造成钻孔报废和埋钻等不可避免的经济损失。本项目以干冰孔缩径机理为研究目标，根据原位冰芯标准数据库确定冰样制作工艺，开展高压差条件下单一变量和多变量冰的蠕变特性实验，得出高压差下冰的蠕变特性曲线迁移规律、影响蠕变速率的敏感因素和多变量对冰的蠕变特性的组合作用方式。结合冰在蠕变实验中的微观结构演化明确各蠕变阶段的作用起点，建立适合于不同环境条件下各蠕变阶段的蠕变速率数学模型和干冰孔缩径数学模型，揭示适用于不同冰层条件的干冰孔缩径机理，预测不同环境条件下干冰孔钻探的极限深度。本项目旨在为诸如两千年冰芯和最古老冰芯计划等需要钻取500～1000m勘察孔的前沿项目，科学合理的预防孔内卡钻事故、安全高效实施冰层快速干孔钻探提供技术指导和理论依据。

冰孔缩径是冰层干孔钻探至极限深度时必然遇到的难题，不仅会影响钻进效率，严重时还会发生卡钻事故，造成钻孔报废和埋钻等不可避免的经济损失。本项目以干冰孔缩径机理为研究目标，开展了极地原位冰的物理化学性质研究，确定了人工冰样的检验标准；基于压力烧结法，探究了以雪颗粒为原料制备烧结雪冰的工艺参数，对其开展了冰的单抗压强度试验研究，验证了制备的人工冰样满足冰的物理力学性质要求，形成了一套适用于冰蠕变特性试验的小尺寸人工冰样制备工艺；开展了烧结雪冰在高应力条件下的蠕变特性试验研究，探究了应变-时间数据降噪方法、最小蠕变速率求解方法，建立了冰的初级蠕变阶段和第二蠕变阶段蠕变速率数学模型以及达到第二蠕变阶段所需时间的数学模型；结合干冰孔孔周应力分布数学模型，修正了干冰孔缩径数学模型，并将模型用于解释英国南极调查局在2017-2018年南极Little Dome C和2018-2019年南极Sherman Island的干冰孔卡钻事故，仍需进一步开展蠕变实验精细化数学模型，揭示干冰孔缩径机理。研究结果可服务于诸如两千年冰芯计划和最古老冰芯计划等需要钻取500～1000m勘察孔的冰孔结构设计。