Lateral Buckling of Pump Barrel and Rod String Stability in Pumping Wells.pdf
Creators: name: Vagapov, Samat
name: Vagapov, Shamil
Publisher: name: figshare
Year: 2019
Subjects: subject: 91406 Petroleum and Reservoir Engineering
subject: FOS: Environmental engineering
subject: FOS: Environmental engineering

description: p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 12.0px 'Times New Roman'; min-height: 15.0px} p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; font: 9.0px 'Times New Roman'} span.s1 {font: 12.0px 'Times New Roman'} table.t1 {border-collapse: collapse} td.td1 {padding: 0.0px 5.0px 0.0px 5.0px} <br> It is our view that the influence of a fluid column inside the tubing on the design of a sucker rod pumping system could be far greater than previously thought. The fluid column inside the tubing is an active participant in the buckling behavior not only the tubing, but also the buckling behavior of the rod string and the pump barrel. Using such an approach one may discover quite unexpected phenomena. The column of fluid inside the tubing exerts a buckling effect on the barrel for the tubing pump and the top anchor rod pump. If the pressure is large enough, the straight form of equilibrium becomes unstable and the pump barrel buckles and straightens in succession during the pumping cycle. During pump upstroke the pump barrel, tubing and rod string are buckled simultaneously in most instances. If the pump is installed in the deep wells with low fluid levels, the designer will need to be alert to buckling behavior of pump barrel. We must consider the barrel buckling phenomenon for the determination of the maximum allowable pump setting depth. The column of fluid inside the tubing exerts a straightening effect on the barrel for the bottom anchor rod pumps. During pump upstroke the tubing and the rod string are buckled simultaneously, but the pump barrel remains straight. The straightening effect of pressure results in an increase the ability of the pump barrel to resist bending and keeps the barrel in straight position. Probably the straightening effect of the pressure reduces the plunger-barrel frictional force. The bottom location of seating assembly allows us to not only prevent the barrel buckling but also use the pressure as a way to increase the ability of the pump barrel to resist bending. The straightening effect of pressure adds another argument supporting the use of the bottom anchor rod pump in deep wells. During pump upstroke, the column of fluid inside the tubing increases the rod string stability in two ways: first, the weight of the fluid column exerts a real tensile force and second, the pressure exerts a fictitious tensile force. The fictitious tensile force does not exist when the rod string is straight. The axial tension due to fictitious tensile force will be developed in rod string when the rod string is disturbed from its straight position. We must take into account this phenomenon in the analysis of the buckling behavior of the tubing and the rod string in pumping well. This different point of view will enable us to improve understanding the role of the fluid column in rod pumping system and explain the rod pump failures in a different way.