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Research Papers

Low-Dimensional Modeling of a Pumping Unit to Cope With Multiphase Flow

[+] Author and Article Information
Ala E. Omrani

Department of Mechanical Engineering,
University of Houston,
4726 Calhoun Road,
N285 Engineering Building 1,
Houston, TX 77204
e-mail: ala.omrani@gmail.com

Matthew A. Franchek

Professor
Department of Mechanical Engineering,
University of Houston,
4726 Calhoun Road,
W214 Engineering Building 2,
Houston, TX 77204
e-mail: mfranchek@central.uh.edu

Behrouz Ebrahimi

Department of Mechanical Engineering,
University of Houston,
4726 Calhoun Road,
N285 Engineering Building 1,
Houston, TX 77204
e-mail: ebrahimibz@gmail.com

Mete Mutlu

Department of Mechanical Engineering,
University of Houston,
4726 Calhoun Road,
N285 Engineering Building 1,
Houston, TX 77204
e-mail: mutlumete13@gmail.com

Karolos Grigoriadis

Professor
Department of Mechanical Engineering,
University of Houston,
4726 Calhoun Road,
W212 Engineering Building 2,
Houston, TX 77204
e-mail: karolos@uh.edu

1Corresponding author.

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received May 7, 2016; final manuscript received October 11, 2016; published online February 9, 2017. Assoc. Editor: Shankar Coimbatore Subramanian.

J. Dyn. Sys., Meas., Control 139(4), 041010 (Feb 09, 2017) (11 pages) Paper No: DS-16-1236; doi: 10.1115/1.4035011 History: Received May 07, 2016; Revised October 11, 2016

Pumping unit efficiency is highly disturbed by the presence of gas influx reducing the productivity and inducing unpredictable system response due to the change of its intrinsic properties such as the natural frequency. A poor estimation of those properties may affect the on-field crew and system safety as well as the production rate. The purpose of this paper is to construct a hydromechanical model describing the coupled multiphase flow-pumping unit system dynamics and to develop a procedure to control the pumping speed for safety assurance and oil production maximization. A coupled mechanical-multiphase flow model capturing the interplay between the gas void fraction (GVF) and the driving harmonic force of the pumping unit is developed. Specifically, the predicted downhole pressure is used to determine the sucker rod effective load. Consequently, a reduced-order model, capturing the dynamics of the sucker rod, is used to estimate the saddle bearings axial displacements which are function of polished rod loading. An error-driven adaptation using the difference between presumed bearing displacement with known GVF and the predicted bearing displacement from the proposed multiphysics model is employed to estimate the unknown downhole GVF. The obtained results prove that the adaptation allows an accurate evaluation of the pumped fluid's GVF, thereby circumventing the need for a costly and inaccurate measurement of the two-phase flow gas fraction. Based on this estimation, a control strategy is then proposed to regulate the pump speed while avoiding the resonance frequency of the sucker-rod system.

Copyright © 2017 by ASME
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References

Figures

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Fig. 1

Pumping unit with itemized components [1]

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Fig. 2

Two-phase upward vertical flow pattern map

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Fig. 3

Two-phase upward vertical flow computational flowchart

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Fig. 4

Free-body diagram of the four-bar linkage system of the pumping unit

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Fig. 5

Model of the sucker-rod system

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Fig. 6

The schematic of the saddle bearings system

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Fig. 7

Saddle bearing free-body diagram

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Fig. 9

Downstroke session

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Fig. 10

First saddle bearing displacement with respect to variation in inlet GVF

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Fig. 11

Second saddle bearing displacement with respect to variation in inlet GVF

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Fig. 12

Bearing displacement sensitivity when changing GVF

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Fig. 13

GVF adaptation through the saddle bearing displacement measurements

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Fig. 14

GVF adaptation for fixed inlet GVF

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Fig. 15

GVF estimation flowchart

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Fig. 16

Pumping speed effect on sucker rod productivity

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Fig. 17

Active control of pumping speed

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Fig. 18

Pumping speed optimization to ensure process efficiency and security

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