Improved filtration parameters from modified API filter press

Static filtration tests carried out by using the API filter press have been extensively used to assess drilling fluid filtration performance in terms of filter cake design. However, this test does not address many aspects of the filtration process such as the invasion of the particles into the substrate, the time the external filter cake starts forming and the effect of the pore throat size of the substrate. This is because the API filter press is designed to use as substrate filter paper with a pore throat smaller than the solid particles size in the drilling fluid. Here it is shown that by a simple modification of the base cap of the API filter press it is possible to use thick porous disks with pore throats larger than the solid particle size in the drilling fluid. This simple variation allows a better investigation and understanding of the filtration process and drilling fluid performance.