Proper filtration minimizes formation damage

Methods to predict contamination-related formation damage quantitatively are reviewed in this paper. Recently developed data on core permeability reduction have been combined with actual range of field data on contamination levels and confirm that 2..mu..m filtration is critical to the minimization of formation damage. To provide the required formation protection, the filters employed need to be 99.999% efficient. This corresponds to a ..beta.. value in excess of 5,000, the upper limit of sensitivity for the filter performance test.