摘要
PDC钻头已成为开发深部资源的主体钻头,但在钻井过程中产生的热损伤是影响钻进效率及钻头寿命的重要因素之一.该文针对PDC钻头切削齿热损伤问题,开展基于不同影响因素的井底流固耦合环境下切削齿冷却仿真实验.建立了 PDC钻头井底冷却流固耦合模型,结合实际钻井工况制定了数值仿真方案,根据仿真实验结果分析了井底流固耦合环境中不同影响因素下钻头切削齿的温度变化规律,并通过正交试验对钻头冷却效果与各影响因素间的敏感性进行了评价.切削齿冷却敏感因素从大到小依次为:钻井液排量＞钻井机械参数、钻井液温度＞地层温度.研究成果为探索井底工况下钻头破岩过程中切削齿热损伤问题和优化PDC钻头设计提供了理论依据.
Abstract
[Objective]Polycrystalline diamond compact(PDC)drill bits have become the primary choice for developing deep resources.However,thermal damage during drilling considerably influences the drilling efficiency and drill bit lifespan.Owing to the complex bottom-hole environment,conducting indoor experimental research on the cooling of PDC drill-bit cutting teeth is challenging.[Methods]Therefore,this study utilized computational fluid dynamics to simulate cutting tooth cooling in a bottom-hole fluid-structure coupling environment,considering various influencing factors.This study targeted the thermal damage issue of a PDC drill-bit cutting teeth.A PDC bit simulation model was established using an 8-1/2"six-blade PDC bit as the basis.The wellbore rock,PDC bit,and wellbore flow field models were integrated to create a PDC bit bottom-hole cooling fluid-structure coupling model.Owing to the complexity and irregular shape of the PDC drill-bit and bottom-hole flow field model,an unstructured tetrahedral mesh with high applicability was selected across the computational domain.An expansion mesh was placed at the interface between the PDC drill bit and the fluid,and the mesh around the cutting teeth of the PDC drill bit was refined.Based on the actual drilling conditions,four simulation schemes were designed using experimental methods to control the variables.Simulation experiments were conducted on parameters such as the drilling fluid displacement,drilling fluid temperature,cutting tooth heating power,and formation heating power.[Results]The simulation experiment results were analyzed to observe the temperature changes in the cutting teeth at different positions of the drill bit under the influence of various factors in the bottom-hole fluid-structure coupling environment.To explore the sensitivity of cutting teeth cooling under the bottom-hole fluid-structure coupling environment to four influencing factors—drilling fluid displacement,drilling fluid temperature,drilling machinery parameters,and formation temperature—a four-factor,five-level orthogonal experimental design scheme was adopted.Simulation experiments were conducted,experimental data were extracted,and range and variance analyses were performed on orthogonal experimental results.The sensitivity factors affecting cutting tooth cooling were as follows:drilling fluid displacement had the greatest impact on the cooling of the drill-bit cutting teeth,followed by drilling mechanical parameters and drilling fluid temperature.The influence of the formation temperature on cooling was relatively insignificant.[Conclusions]A comparison of the cooling effects of cutting teeth at different positions on each blade revealed uneven cooling,and cutting teeth directly flushed by the drilling fluid at the nozzle had better cooling effects.In the design of the drill-bit structure,the number of cutting teeth directly flushed by the nozzle jet should be maximized.The research results provide a theoretical basis for exploring the thermal damage problem of cutting teeth during the rock-breaking process of drill bits under bottom-hole fluid-structure coupling conditions and for optimizing the design of PDC drill bits.
基金项目
国家重点研发计划项目(政府间重点专项)(2021YFE0111400)
教育部产学合作协同育人项目(220506517103435)
NETL
NSTL
万方数据