When cement is bullheaded into the annulus to displace mud, the differential pressure between the cement and the formation fluid can lead to a significant loss of cement filtrate into the formation. If, however, large volumes of cement filtrate invade the rock, the possibility of formation damage exists. As the cement filtrate invades the formation and reacts with the formation minerals, its pH is reduced from 12 to a pH buffered by the formation minerals. This rapid change in pH can result in the formation of inorganic precipitates such calcium carbonate and calcium sulfate. Evidence of formation damage induced by cement filtrates has been clearly demonstrated in experimental studies presented in Cunningham and Smithand Jones, et al..