Selection and Optimization of Artificial Lift System in Heavy Oil Fields

Abstract

Abstract Emulsion which occurs in all phases of oil production and processing in heavy oil fields causes several operational problems. Especially, it can preclude performance of artificial lift system and induce malfunctions due to high pressure drop in production string and high shear stress around rod. Existence of rod string in tubing heavily reveals production limitations in artificial lift systems used in deep wells which produce emulsifying heavy oil. Artificial lift systems do not only require power for lifting heavy oil up to the surface, but also they require power for coping with resistance of high viscous fluid during movement of rod string in tubing. Movement of rod string originates shear stress that is very sensitive to viscosity of fluid. In case of using progressing cavity pump, radial shear stress occurs during clockwise rotation of rod string. In contrast, as sucker rod pump is used, axial shear stress takes place on the up and down stroke of rod string. As far as negative effect is concerned, radial shear stress on the progressing cavity pump system is less detrimental than axial shear stress on the plunger pumping system in theoretical and practical aspects. It is also evident that it is possible to decrease negative effect of radial shear stress by selecting large displacement pump and reducing rotation speed of rod string by means of variable speed drive system provided that the same amount of production is received. Moreover, tubing back-off, twist-off caused by reversed movement of rod string and rod being screwed off when being shut down can be avoided owing to decrease in radial shear stress or torque created by high viscous fluid. This paper aims to expatiate that progressing cavity pump is viable choice for particularly deep wells producing emulsifying heavy oil in terms of operation and energy consumption.