Abstract
Three Kinds of experiments on formation damage are carried out at simulated in-situ geothermal conditions. The most severe test conditions are of Temperature of 250°C and pressure of 8.1MPa. Bentonite and sepiolite muds are used throughout the tests. The first test is measurement of mud properties at room conditions after aging for 24hours. The second test is measurement of rheological properties by a capillary tube. Rapid gelation of both muds is observed above 200°C. The third test is measurement of permeability recoveries of models invaded by muds. As simulated formation models, slits packed with sand grains and Berea sandstone cores are used. Permeability impairment of the models are measured after aging for 24 hours. Formation damage appears above 150°C in some cases. Severe cases of permeability recoveries below 10% of original values are observed above 200°C.
