vertical well and a newtonian fluid this can be expressed as follows where p1 and p2 line pressure readings from the two pressure transducers 30 and 31 respectively h hydrostatic head caused by fluid weight between two points p1 and p2 by recording and plotting the pressure readings p1 and p2 on the uphole recorder and plotter 32 in the form of the plot as shown in fig3 the difference between the p1 and p2 curves can be used directly as an accurate diagnostic tool to describe the downhole system behavior including fracture opening and closing whenever the fracture is extending or is still open a pressure difference between p1 and p2 exists indicating that fluid is still flowing in the injection lines and q in eq 1 is greater than zero upon shut in the fracture closes and fluid flow in the injection line is stopped q o and the difference between p1 and p2 is equal to the hydrostatic pressure only i e fluid density u00d7 distance fig3 illustrates two pressure profiles recorded during a hydraulic fracture test fig3 encompasses four stages during the test in which the minimum stress applied is 800 psi the four time periods t f t c t p and t d correspond to t f time it takes to fill the tubing two transducers p1 and p2 show different readings t c time it takes for fluid in wellbore to compres very slow fluid motion no friction and fluid flow only for wellbore leakoff t p fracture propagation period transducers p1 and p2 show different readings due to fluid flow and t d fracture closure and pressure decline period pressure.