Experimental Study of Freeing Stuck Pipe by Changing in Characterization and Additives of Mud Cake

Differential sticking is one of the most usual and as yet most troublesome problem in drilling. In this paper according to studies on freeing differential sticking by different properties of mud drilling additives, we focused on the impact of water-based mud, bentonite and lignosulfonate. Selecting the appropriate additives are done by mud cake characterization equipment, by measuring the torsional resistance of mud cake with different compositions as the main variable and also measuring secondary variables that consists of mud-weight, mud cake viscosity, Ambient temperature, water loss, mud cake thickness and its physical structure. The results of these tests indicate that in bentonite muds, salt plays role as a destructive factor and PAC as an effective factor in freeing stuck pipe. Lignosulfonate fluid is also effective in freeing differential sticking by its thinner properties. As the main result of this paper, regarding to measurement of torsional resistance in different mud cake, the best method for freeing pipe stuck is low angle rotation of drill string immediately after occurring the pipe stuck.