Experimental Study of the Impact of Drilling Fluid Contamination on the Integrity of Cement-Formation Interface

Flood experiments were conducted over 30-day periods at 14.48 MPa (2100 psi) confining pressure and temperature of 22 degrees C (72 degrees F) with cement-sandstone composite cores and brine at a flow rate of 1 ml/min. Higher pH values were observed in the effluent brine from the 10% mud contaminated core than the 0% mud contaminated core due to increased dissolution of cement. Microtomography revealed higher porosity at the interface zone of the 10% mud contaminated core. These show that mud contamination has a deleterious effect on the cement-sandstone interface and may create pathways for interzonal communication as well as sustained casing pressure.