Massive mud shale cuttings will adhere to cutters and bit body when PDC bit bailing occurs, which affects rock breaking rate. To clarify PDC bit balling mechanism is the prerequisite for summing up influence factors and studying the methods and measures of preventing and eliminating bailing．In view of this, from a collection of the relevant literatures at home and abroad. We summarized new achievements, methodologies and trends in the research of prevention and mitigation of PDC bit balling in four aspects. Including drilling fluid type and property, bit structure, bit hydraulic parameters and other processing of PDC, on thc basis of bit balling mechanism, countermeasures and application. On this basis, the following research directions in this field were propsed. It will be a trend to research the adhesion mechanism between the shale cuttings and bit from the microscopic point of view and to establish the quantitative relationship between the downhole flow field and bit bailing. The method will be considered available ill letting the water base drilling fluid present the oil base drilling fluid¢s property by adding sonic chemical additives. Massive experinlents will be necessary to determine the bit structure parameters and bit hydraulic parameters for the prediction of bit balling. 

reference: http://news.gasshow.com/News/SimpleNews.aspx?newsid=354446