GEOG 4891 Lecture Notes - Lecture 7: Dimensionless Quantity, Overburden, Polyethylene Terephthalate
Document Summary
Pfrac/d = (pob /d pf/d)( /(1- ) + pf /d. Poisson ratio is a dimensionless number, and generally (world wide) takes value in between 0. 225 and 0. 500 by increasing directly with depth. The best way to find out poisson ratio is to run leak off test during drilling. Step 2 complete cementing and wait for cement thickening time (about 24 hour). Step 3 lower drill string and drill the well about 3-5 ft below the casing shoe. Step 4 - stop rotary (rpm=0), release weight on bit (wob=0). Step 5 increase mud pressure, observe the pressure value from mud pressure indicator on the rig up to fracturing the bare formation below casing shoe, and register the pressure when start decreasing. Fracture pressure gradient is calculated by using fracture pressure obtained from leak off test as: Thus, poisson ratio is calculated by using below formula since fracture pressure gradient (pfrac/d) is already obtained from leak off test:
