TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractProgressive Cavity Pump (PCP) performance has been traditionally modeled as a composition of Couette flow and Poiseuille flow, represented by pump displacement and internal slip respectively. Pump displacement can be easily calculated from pump components geometry, but calculating internal slip is not a trivial problem. Previous studies have proposed to use Hagen-Poiseuille equation for modeling internal slip flow, assuming a constant interference value. In these studies slippage gap area is not clearly defined, so great results have not been reached.This study introduces a new approach for modeling single lobe PCP performance. Slip flow is modeled as the result of two components, one of them due to the movement of the rotor and the other one due to the differential pressure between cavities, assuming that slippage gap area depends on the stator material. This assumption is based on the analysis of metallic, elastomer and PTFE stator PCP characteristic curves, obtained from experimental data of previous works.The existence of a strong relationship between slippage gap area and differential pressure, related to mechanical properties of stator material, is demonstrated. Thus, internal deformation of stator is identified as the main parameter to be understood before predicting PCP performance. For a polymer stator PCP this relationship approximates to a quadratic form, while in a metallic stator PCP a constant gap area can be assumed.Although the proposed model is not able to fit data for any PCP models, its results agree with the ideas proposed above and documented PCP performance theory. In order to obtain a definitive model, future investigation is needed to improve expressions for calculating friction factor inside the pump and also to define a procedure for obtaining gap area relationships for any type of stator material.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractProgressive cavity pump metal to metal has its two elements, rotor and stator, made from a metallic material. It has been demonstrated that this pump can reach an acceptable volumetric efficiency with high viscosity fluids. However, the performance of the pump with two-phase flow has never been investigated. There are not field or experimental tests which provide tools to predict the behavior of the pump in such applications. If progressive cavity pump metal to metal were able to handle high viscosity fluids with gas void fractions, as well as conventional progressive cavity pumps, it could be found a range of application for using this pump in heavy oil production. Its advantages would be valious, since it doesn't have the problems due to the use of elastomer stators.In this research the progressive cavity pump metal to metal performance has been studied. Characteristic curves and instantaneous pressure profiles along the pump with singlephase and two-phase flow have been obtained experimentally. The results show that the internal slip with two-phase flow is a function of gas void fraction, differential pressure and rotational speed. Under some conditions an increase in volumetric efficiency occurs when the gas void fraction is increased. Instantaneous pressure profiles explain the changes of internal sealing lines when gas void fraction changes, also show that longitudinal pressure distribution along the pump have a linear behavior for single-phase and twophase pumping.The knowledges acquired with this research are useful for understanding the progressive cavity pump metal to metal performance in two-phase pumping applications and also can be used in the future for theorical modeling of the pump.

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