基于气体钻井工艺参数的钻具冲蚀模型

An erosion model of drill string based on process parameters of gas drilling

针对气体钻井中钻具冲蚀磨损严重而造成钻具过早降级和报废的问题,基于微切削理论,建立了钻井环空中钻具的冲蚀模型,并依据该模型推导出了气体钻井中钻具冲蚀强度的数学模型,该数学模型把气体钻井中钻具的冲蚀强度同井下状态参数、钻具材料、井身结构,以及注气量、机械钻速等钻井工艺参数联系起来。通过钻具冲蚀模拟实验确定了数学模型中的常数,并对数学模型进行了修正,为气体钻井作业中合理选择钻井工艺参数和预测钻具的冲蚀磨损提供了依据。利用该数学模型分析表明,气体钻井中的注气量应以保持排屑顺畅即可,过分加大注气量,不仅会造成能源浪费,而且会加剧钻具的冲蚀磨损,导致钻具过早降级或报废。

Based on the micro-cutting theory, we established an erosion model of drilling string in wellbore annulus to solve drilling-string premature degradation and abandonment problems caused by severe erosion wornout in gas drilling. In addition, a mathematical model for computing the erosion strength of drilling string in gas drilling was derived from the erosion model, and this mathematical model closely combines the erosion strength of drilling string in gas drilling with various underground status, drilling-string material, hole structure, and drilling process parameters of gas drilling, such as, amount of gas injection and the penetration rate. Through erosion simulation experiments of drilling string, constants of the mathematical model were determined and the mathematical model was modified as well, which can provide a basis for the rational selection of drilling process parameters and the erosion wornout prediction of drilling string in gas drilling practice. The analysis with this mathematical model showed that the amount of gas injection in gas drilling should be controlled just to keep the cuttings discharge smooth, the excess amount of gas injection would cause not only energy waste but also accelerate the erosion wornout of drilling string and result in drilling-string premature degradation and abandonment.