Method and System for Optimizing Downhole Fluid Production

Abstract

A method and system for pumping unit with an elastic rod system is applied to maximize fluid production. The maximum stroke of the pump and the shortest cycle time are calculated based on all static and dynamic properties of downhole and surface components without a limitation to angular speed of the prime mover. Limitations of structural and fatigue strength are incorporated into the optimization calculation to ensure safe operation while maximizing pumped volume and minimizing energy consumption. Calculated optimal prime mover speed is applied to the sucker rod pump by means of beam pumping, long stroke or hydraulic pumping unit by controlling velocity, acceleration and torque of the electric prime mover or by controlling pressure and flow rate in hydraulically actuated sucker rod pumping system.

Description

FIELD OF THE INVENTION[0001]This invention relates to methods and systems for maximizing downhole fluid pumping using a sucker rod pumping system, and more particularly to methods and systems for maximizing fluid production by optimizing the sucker rod prime mover speed.BACKGROUND OF THE INVENTION[0002]Reciprocating oil pumps are traditionally operated by a beam pumping unit, as illustrated in FIG. 1 and described below, with a sinusoidal characteristic of reciprocating motion of a polished rod as dictated by the fixed speed of an electrical or gas prime mover and the geometry of the beam pumping unit. Conventionally, a constant crank speed is employed in the operation of the beam pumping unit; as a result, the geometry of the beam pumping unit dictates a rod speed which follows a curve which is sinusoidal in nature. Other types of pumping units, such as long stroke or hydraulically actuated pumping units, operate at a first constant speed of the polished rod during upstroke motion ...

AI Technical Summary

Benefits of technology

[0014]The present invention seeks to provide a method and system for optimizing the sucker-rod pump prime mover speed in order to maximize oil production while at the same time reducing operating costs and providing for operation with safe loading factors. The optimization can be performs(for existing pumping systems as well as during the design phase of a new system. The presented optimization process and system focuses on finding and applying the optimal variable speed of the prime mover; however, the resulting optimal prime mover angular speed determines the optimal polished rod linear velocity, therefore—after minor modifications within the competence of a person skilled in the relevant art—the present method can also be applied to optimization of the polished rod velocity instead of the prime mover angular speed.

[0015]The present invention also seeks to provide the ability to automatically monitor, analyze, test, optimize, control, and manage a given well from a remote central location. The proposed system performs kinetic and dynamic analysis of the oil well equipment, and using various experimental data and mathematical modeling is able to optimize the well performance. Additional benefits include monitoring the pumping conditions and detecting unusual, deteriorating or detrimental operating conditions, and changing the pumping parameters in response to the detected changes.

[0047]When optimizing the energy use to achieve the production target the stresses are reduced with respect to the movement with the same cycle period and a constant motor speed.

[0049]When the optimization is performed not on the existing pumping system, but during the design phase, then the design can be further improved based on the power and load requirements resulting from the prime mover speed determined from the optimization process. Making the design changes to improve the performance of the system powered by the prime mover optimal variable speed, e.g. increasing the diameter of the weakest segments of the rod string, will allow for further improvement of the system performance by applying the pumping system design and prime mover speed optimization processes iteratively.

[0051]To overcome the limitations of the prior art, the present invention seeks to analyze current performance and calculate and apply the most advantageous variable speed of the prime mover to maximize fluid production for an existing sucker rod pumping system. Some prior art systems would require system components to be changed to achieve any increase in production volume, or otherwise would have to compromise safety conditions it higher fixed speed of the prime mover were to be attempted. Operating costs would also increase since larger components and higher energy consumption would be necessary.

[0056]The present invention is directed to controlling prime mover speed and, in doing so, polished rod motion so that the downhole pump is reciprocated with any stroke length required to maximize production within the fatigue load limits of the sucker rod. In addition, any desired speed of the downhole pump and behaviour pattern can be controlled to overcome excessive friction, gas lock, or other detrimental downhole conditions.

Problems solved by technology

The interaction of the movable and stationary elements of the well and dynamic interaction with fluids present in the well creates a complicated mechanical system that requires precise design and control to be able to work in an efficient way.

While trying to improve the design of a new pumping system or improve the operation of an existing system, there was no attempt to optimize its performance by optimizing the stroke period and the variation of the prime mover speed within a stroke.

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