Method and System for Optimizing Downhole Fluid Production

a technology of fluid pumping and downhole, applied in the direction of pump parameters, borehole/well accessories, survey, etc., can solve the problems of no attempt to optimize the performance of the mechanical system, complicated mechanical system that requires precise design, etc., to achieve safe loading factor operation, reduce operating costs, and maximize oil production

US20080240930A1Inactive Publication Date: 2008-10-02PUMPWELL SOLUTIONS
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Patent Information

Authority / Receiving Office
US · United States
Patent Type
Applications(United States)
Current Assignee / Owner
Publication Date
2008-10-02
Estimated Expiration
Not applicable · inactive patent

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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.
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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 ...

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Optimization Method

[0065]Referring now to the summary of the present invention set out above. the optimization problem (I) is defined as finding the VFD input angular speed profile Ω(s) that maximizes the average fluid volume pumped per unit time. The volume pumped during one stroke as a result of the imposed VFD input speed Ω(s) is equal to:

where[0066]Ap—plunger cross-sectional area[0067]η—pumping efficiency coefficient[0068]UP(Ω)—plunger stroke length (the product ηUP is called an effective stroke length).

[0069]Therefore. the optimization goal of maximizing the production per unit time can be mathematically defined as finding the VFD input speed profile Ω(s) that maximizes the following functional V(Ω), while satisfying the constraints (A-C):

V(Ω)=Vol(Ω)T(Ω)=ApηUP(Ω)T(Ω)=Maximum(Ω)(1)[0070]where T(Ω) is the stroke period resulting from applying the input velocity Ω(s).

[0071]Similarly, the optimization problem (II) can be defined as finding the VFD input speed profile Ω(s) that mini...