Linear electric motor for downhole use

• US 4,687,054 A
• Filed: 03/21/1985
• Issued: 08/18/1987
• Est. Priority Date: 03/21/1985
• Status: Expired due to Fees

• Current Assignee: George W. Russell, Larry B. Underwood
• Original Assignee: George W. Russell, Larry B. Underwood
• Inventors: Russell, George W., Underwood, Larry B.
• Primary Examiner(s): Novosad, Stephen J.
• Assistant Examiner(s): Dang, Hoang C.
• Application Number:
  US06/714,564
• Time in Patent Office: 880 Days
• Field of Search: 417/417, 417/416, 417/554, 318/135, 166/381, 166/386, 166/53, 166/66.4, 166/66.5, 166/68, 166/105, 166/242, 166/107-111
• US Class Current: 166/66.4
• CPC Class Codes: E21B 43/00 Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells applicable only to water E03B
• CPC Class Codes: E21B 43/128 Adaptation of pump systems with down-hole electric drives
• CPC Class Codes: F04B 47/06 having motor-pump units situated at great depth
• CPC Class Codes: H02K 33/14 wherein the alternate energisation and de-energisation of the two coil systems are effected or controlled by movement of the armatures
• CPC Class Codes: H02K 41/02 Linear motors; Sectional motors

Abstract

Apparatus and method for operating a downhole sucker rod pump in which a downhole linear motor is controlled by a surface digital computer. The motor includes a number of coil sections circumfusing and spaced along the length of a non-magnetic tube, and an armature positioned coaxially inside the tube. The armature section includes a central mandrel of a non-magnetic material and a number of laminated armature sections circumfusing and spaced along the length of the mandrel. The tube is sized substantially the same as the production tubing, and the armature is not physically connected to the tube, such that the armature and the attached pump can be removed without removing the tubing. The coils are energized by electric power supplied by three electric conductors running from the surface. The power is selectively applied to each of the conductors in a predetermined sequence by a number of SCR switching devices controlled by the digital computer, such that the field coils are energized in manner to provide the proper attractive and repulsive forces to the armature section to cause it to move in the desired direction. By properly controlling the power switching sequence, the stroke length, speed, and duty cycle can be programmed and controlled.

Claims

1. In a production tubing string:

a tube of non-magnetic material substantially of the same internal diameter as the tubing string;

a plurality of electromagnetic coil assemblies disposed about the tube and equidistantly spaced along the length thereof;

each of said coil assemblies comprising a coil circumfusing said tube, a first annular pole piece circumfusing said tube and positioned above said coil, a second annular pole piece circumfusing said tube and positioned below said coil, and a sleeve of magnetic material positioned about said coil and said first and second pole pieces and coextensive with the combined length thereof, a cylindrical case coextensive with and enclosing said tube and said coil assemblies;

a separate mandrel of a non-magnetic material centrally positioned in said tube and removable therefrom;

said mandrel having a central bore therein to permit the passage of production fluids therethrough;

a plurality of armature sections equidistantly spaced along the mandrel, said spacing being different from the spacing of the coil assemblies along said tube;

said armature sections being formed as a stack of disks of a magnetic material;

a plurality of annular centralizers separating said armature sections;

a fishing neck on said mandrel, whereby said mandrel and the components attached thereto may be removed through the tubing string without removing said tubing and components attached thereto; and

means for energizing said coil assemblies in a predetermined sequence, whereby electromagnetic attractive and repulsive forces are created between said coil assemblies and the armature sections to thereby move said mandrel longitudinally inside said tube.

2. In a production tubing string as described in claim 1 wherein said energizing means comprises a plurality of electrical conductors connected in a predetermined sequence to said coils and means for selectively applying electrical power to said coils.

3. In a production tubing string as described in claim 2 further including means in association with said tube for sensing the position of said armature sections with respect to said coils and means for controlling said energizing means in reponse to said sensing means.

4. In a production tubing string as described in claim 3 wherein said controlling means further includes means for operating said mandrel and the components attached thereto in a reciprocating motion.

5. In a production tubing string as described in claim 4 further including means for controlling the length of travel of said mandrel and components attached thereto in said reciprocating motion.

6. In a production tubing string as described in claim 5 further including means for controlling the speed of travel of said mandrel and components attached thereto in said reciprocating motion.

7. In a production tubing string as described in claim 6 further including means for controlling the timing of the beginning of each cycle of said reciprocating motion of said mandrel and components attached thereto,

8. In a production tubing string as described in claim 2 wherein said applying means comprises a plurality of SCR'"'"'s.