The tubing flowing pressure (Ptf) is open to atmosphere. You are tasked to calculate the annulus injection pressure at the surface (Psurf) to reverse out muds at 6 bbl/min. The well is 5000 ft deep and has an inclination or deviation angle of 60 degrees. The reservoir pressure is 2500 psi. The drilling mud and completion fluids are incompressible and have the same density. Fortunately, the previous summer intern had determined the friction pressure for the annulus (Fann) and tubing (Ftub) at the pump rate of 6 bbl/min. The result is a ratio of Ftub over Fann of 1.5, i.e., (Ftub/Fann)=1.5. derive the equation that describes this reverse circulating operation, i.e., express Psurf in terms of Ptf, hydrostatic and friction pressures in the annulus (HPann,Fann) and tubing (HPtub and Ftub). hint, find the relation betwenn BHP and Psurf and between BHP and Ptf. From these 2 relations you can establish the relationship between Psurf and Ptf. Note, there is no numerical calcualtions for this