Prediction model of casing wear for extended reach wells considering buckling of drill string

Key words:  casing wear  extended reach well  drill string buckling  drill string footage

Abstract:

The tubular string is vulnerable for buckling during downhole string loading operation due to many factors, such as long well depth, large dog-leg severity and high drag and torque. Buckling of the drill string can significantly increase its slide and footage, which aggravates casing wear. In this paper, the change of drill string footage due to bucking was coupled into a conventional casing wear prediction model, in which a new case wear model was established appropriating for extended reach wells. Referring to the caliper test data from well W1 in South China Sea, the casing wear prediction of the adjacent well W2 was conducted. The results indicate that, when the buckling of drill string is not considered, the predicted value of the casing wear at depth of 2144 m can be underestimated by 16.9%. When the change of drill string footage caused by buckling is ignored, the predicted value of the casing wear at the same depth can be underestimated by 10%. The new casing wear prediction model presented in this paper can accurately predict the casing wear in extended reach wells.