1. n. 
A laboratory test used to determine if a drilling fluid blocks movement of filtrate through pore spaces of a shale sample. The PPT device monitors the increase in pore pressure in a shale when exposed to a drilling fluid over a period of time. Shale cores from 1 to 3-inches long are fitted into a modified Hassler cell that has sensitive pressure transducers in reservoirs on each end of the cell.
Reference: Van Oort E, Hale AH, Mody FK and Roy S: "Transport in Shales and the Design of Improved Water-Based Shale Drilling Fluids," in SPE Drilling and Completion 11, no. 3 (September 1996): 137-146.
Alternate Form: PPT