钻井液侵蚀样品的数值模拟与参数影响分析

Numerical simulation and parameter influence analysis of drilling fluid erosion on samples

摘要:

在岩土工程勘察中，通过钻探获取高质量的原状土样至关重要，其核心在于最大程度减少对样品的扰动。本文针对钻进取样过程中钻井液对土样的侵蚀扰动问题，基于取心钻头孔底模型，采用Fluent软件进行了数值模拟研究。研究表明，钻井液对土样的侵蚀随时间呈阶梯式扩散，其范围自样品上部向底部逐步扩展，并可划分为三个典型侵蚀区域。在不同钻井液黏度和流速条件下，样品上部与底部的侵蚀程度均明显大于中部。具体而言，上部侵蚀范围随黏度和流速的增大而向中部扩展；而底部侵蚀范围随流速增大而增大，却随黏度增大而减小。总体来看，土样渗透率的增大、钻井液黏度的降低以及流速的提高，均会显著增强侵蚀作用，且侵蚀在样品底部最为剧烈。本研究揭示了钻井液与土体相互作用的多参数耦合侵蚀机制，为优化钻井液性能和钻进工艺提供了定量依据，对提升原状土取样质量与工程勘察数据的可靠性具有重要意义。

Abstract:

In geotechnical engineering investigations， obtaining high-quality undisturbed soil samples through drilling is crucial， with the core objective being to minimize sample disturbance. This study addresses the issue of drilling fluid erosion and disturbance on soil samples during the drilling and sampling process. Based on a bottom-hole model of a core bit， numerical simulations were conducted using Fluent software. The research reveals that the erosion of soil samples by drilling fluid advances in a stepwise manner over time， extending from the upper part of the sample toward the bottom， and can be divided into three typical erosion zones. Under varying drilling fluid viscosities and flow rates， the degree of erosion at both the upper and bottom parts of the sample is significantly greater than that in the middle section. Specifically， the erosion range at the upper part expands toward the middle as viscosity and flow rate increase， while the erosion range at the bottom increases with higher flow rates but decreases with higher viscosity. Overall， an increase in soil sample permeability， a reduction in drilling fluid viscosity， and an elevation in flow rate all significantly enhance the erosion effect， with the most severe erosion occurring at the bottom of the sample. This study elucidates the multi-parameter coupled erosion mechanism of the interaction between drilling fluid and soil， providing a quantitative basis for optimizing drilling fluid properties and drilling techniques， which is of great significance for improving the quality of undisturbed soil sampling and the reliability of engineering investigation data.