复杂地层钻井液漏失诊断技术系统构建

井漏不仅是最严重的储层损害方式,而且是钻井工程中长期悬而未决的重大理论和技术难题。诊断并有效控制井漏,要从根本上认识并准确描述井漏三要素:位置、类型及强度。漏失机理及类型诊断是制定科学合理的漏失控制技术的前提。综合利用钻前、随钻、钻后信息资料,描述和表征漏失层性质及参数,进行潜在漏失层预测。建立了钻井液漏失诊断技术系统框架,提出了漏失诊断具体方法,综合室内实验和数值模拟开展裂缝、孔洞的应力敏感性和裂缝传播机制研究,预测漏失通道变形程度和漏失强度,为优选堵漏材料提供理论依据;基于钻时、岩屑、钻井液等工程参数对井漏的异常特征响应来识别井漏,利用实时录井参数来监测并描述井漏状态,提前预测井漏发展趋势;建立了基于漏失发生机理的漏失压力模型,从漏失压力的角度诊断了漏失类型。针对井漏演化过程的认识,初步建立了井漏诊断技术框架,为漏失控制技术提供理论支持。

Diagnosis System for Characterizing Lost Circulation in Troublesome Formations

Lost circulation imposes the most serious damage to reservoir and is an arduous technological problem remained unsolved.To diagnose and control lost circulation, three elements to lost circulation, i.e., location in which mud is lost, type of lost circulation, and rate of mud loss, should be fundamentally understood.The mechanism and type of lost circulation are the prerequisite for selecting/making the reasonable lost circulation control technology.In lost circulation prediction, drilling data and geological data are the most important.Series of laboratory studies have been conducted to find a method for lost circulation diagnosis.Studies were conducted on the stress sensitivity of fractures and vugs, and the propagation mechanism of fractures.The deformation of channels into which mud is lost and the rate of mud loss can be predicted for the choice of best lost circulation materials.When lost circulation occurs, drilling parameters such as penetration rate and drill cuttings change correspondingly, and real-time mud logging data can be used to predict the status of lost circulation.In the diagnostic model developed, the type of lost circulation is diagnosed using circulating pressure when lost circulation occurs.Based on the understanding of the changing course of lost circulation, a preliminary diagnostic system for lost circulation is developed, providing theoretical support for lost circulation control.