Establishment of bore hole cleaning and monitoring technology andits application in Dagang oilfield（）

Bore hole cleaning is one of the key technologies of extended reach well drilling, with the law of annulus cutting transport as the core. With the technological development of extended reach wells and complex structural wells, the bore hole cleaning and monitoring technology faces new difficulties and challenges. The problems urgent to be resolved are how to monitor the cutting transport under complex geological condition and in complex structural well, and how to predict the time of cuttings forming bed, in order to help judge and solve the downhole problems. Based on the law of cutting transport and the forming mechanism of cutting bed, the multilayer cutting transport model is adopted, the ECD curve to monitor the conditions of bore hole cleaning is established, considering the effect of cuttings on annular pressure lost and the transformational relation between annular pressure lost and equivalent circulation density. It is used in Well ES-H6 of Dagang oilfield, and the application shows that the ECD curve is an important criterion for measuring the bore hole cleaning condition, and it should be controlled within a reasonable range. Besides, the ECD is related to such factors as annular loads, annular velocity, mud property, and so on. Reasonable control of mud property and rotational speed is beneficial to bore hole cleaning of extended reach wells.