冰层回转钻进钻头切削具温度理论计算分析

Theoretical calculation and analysis on cutting heat with drilling fluid in ice core drilling

摘要:

极地冰盖底部暖冰层冰的脆性小而粘弹性大，且温度和压力较高，可钻性差。回转钻进时产生的切削热量极易使冰屑处于熔融或半融状态，致使冰屑相互聚结成团，甚至会在钻具局部位置再次冻结，导致孔内事故频发。为了解冰层回转钻进时切削具的温度变化规律，本文对切削具的受力特性和传热规律进行了理论研究，建立了钻井液循环条件下切削具温度计算理论模型，对切削具的温度变化及影响因素进行了深入分析。结果表明，回转速度、切削深度、冰与切削具间的摩擦系数、切削具刃前角及冰的抗剪强度等参数对切削温度均有重要影响，而低温钻井液虽有良好的冷却、降温效果，但仍可使切削具温度升温2～5 ℃，为暖冰层钻进带来不利影响，需深入优化钻进参数组合。

Abstract:

The warm ice at the bottom of polar ice sheet has small brittleness, high viscoelasticity, high temperature and pressure, and poor drillability. The cutting heat generated during rotary drilling can easily cause the ice chips to be in melting or semi-melting state; as a result, the ice chips will gather together and even freeze again locally over the drilling tool, resulting in frequent accidents in the hole. In order to understand the temperature change law of cutting tools during ice rotary drilling, theoretical study is conducted on the mechanical characteristics and heat transfer law of cutting tools, and then the theoretical model for cutting tool temperature calculation under drilling fluid circulation is established. The result shows that rotation speed of the drilling bit, cutting depth, friction coefficient, cutting edge angle and ice shearing strength et al. are all have important impact on cutting temperature. Although the low-temperature drilling fluid has good cooling and cooling performance, it can still make the cutting tool temperature rise by 2 to 5℃, adversely affecting warm ice drilling. In-depth optimization should also be made for the combination of drilling parameter.