a 15 24 cm 6 inch long by 2 54 cm 1 inch diameter berea sandstone core 2 about 10 50 md was mounted in a sleeve 4 in a hassler cell 6 equipped with multiple pressure taps 8 it was saturated with 5 nh 4 cl solution and then the core in the cell was loaded into the formation response tester and heated to 93 u00b0 c 200 u00b0 f a 6 9 mpa 1000 psi back pressure controlled by back pressure regulator 10 and 13 8 mpa 2000 psi confining pressure source and mode not shown were applied fluid injection was from a storage vessel 12 by a pump 14 controlled by a computer 16 the system also had an inlet pressure gauge 18 and a differential pressure gauge 20 tubing additional storage vessels valves etc used to switch between fluids and select the pumping direction are not shown 5 nh 4 cl was injected in the production direction right to left in the figure at 5 cc min to obtain the initial permeability a fluid containing 10 by volume of one or the other scale inhibitor concentrate was injected for 15 pore volumes in the injection direction left to right in the figure an effluent sample was collected for icp inductively coupled plasma elemental analysis after every pore volume 5 nh 4 cl was again injected in the production direction for 400 pore volumes pv effluent samples were then collected for every 3 pv during the first 20 pv.