Wells – Processes – Producing the well
Reexamination Certificate
2000-10-07
2003-05-06
Bagnell, David (Department: 3672)
Wells
Processes
Producing the well
C166S068500, C166S073000, C166S105000, C417S374000
Reexamination Certificate
active
06557639
ABSTRACT:
FIELD OF INVENTION
The present invention relates to an apparatus and a method for use in pumping fluids in a wellbore, wherein the apparatus and method are for use with a downhole rotary pump. Further, the present invention relates to an apparatus and a method wherein a pipe string defining an interior fluid path for the passage of the fluids therein is used to actuate the downhole rotary pump.
BACKGROUND OF INVENTION
To produce downhole production fluids from a wellbore to the surface, conventional production systems typically include a tubing string extending from a wellhead at the surface through the wellbore to the hydrocarbon producing formation. The downhole end of the tubing string is connected with a downhole pump which typically pumps the production fluids from the formation and to the surface through the tubing string. Further, the pump is actuated by a rotating or reciprocating rod string which extends within the tubing string from the wellhead at the surface to the downhole pump. Similar systems are provided for injecting fluids from the surface downhole through the wellbore to the formation.
For instance, in a conventional downhole rotary pump, commonly referred to as a progressive cavity pump, the rod string is rotated within the tubing string by a motor associated with the wellhead at the surface. Rotation of the rod string actuates a rotor within the downhole pump in order to produce the downhole production fluids to the surface. More particularly, the production fluids are pumped to the surface within the tubing string in the annular space formed between the rod string and the tubing string.
Alternately, in a downhole pump including a reciprocating plunger for pumping the production fluids, the rod string is reciprocated within the tubing string by a walking beam or other pump drive system associated with the wellhead at the surface which vertically lifts or reciprocates the rod string. Reciprocation of the rod string actuates the reciprocating plunger within the downhole pump to produce the downhole production fluids to the surface.
However, actuation of the downhole pump by the rotation or reciprocation of the rod string within the tubing string has not been found to be fully satisfactory for various reasons. For instance, it has been found that the rod string tends to be prone to structural failure. Structural failure of the rod string is particularly prevalent where the rod string is subjected to an amount of torque in order to rotate the rod string and thereby rotate the rotor within the downhole pump.
Further, where a rotating rod string is used to actuate the downhole pump, it has been found that the rod string may not be able to provide a required or desired amount of torque to the rotor of the pump to optimize the operation or functioning of the downhole pump. In other words, the downhole pump may not be able to be used efficiently or to its maximum capacity due to the limitations inherent in the structure of the rod string and the potential for its failure.
As well, the rotation of the rod string to actuate the pump tends to cause wearing of the tubing string and rod string failure as a result of abrasion between the rod string and the inner surface of the tubing string. For instance, the rod string may include a plurality of rods interconnected by rod couplings and may be connected to the downhole rotary pump by a further coupling referred to as a shear coupling located just above the rotary pump. The rod couplings and the shear coupling are larger in diameter than the rods comprising the rod string.
As a result, wearing occurs along the length of the rod string but tends to be greatest at the locations where the rod couplings and the shear coupling contact the inner surface of the tubing string. Wearing of the inner surface of the tubing string can result in a hole developing in the tubing string and a possible loss of production fluids due to leakage. Further, where high concentrations of silt and sand are produced from the wellbore along with the production fluids, the abrasive nature of the silt and sand accelerates the wearing that occurs between the rod string and the inner surface of the tubing. In addition, the wearing is further accelerated when the wellbore being produced is slant, directionally or horizontally drilled.
Various attempts have been made to address these issues by eliminating the need for or the use of the rod string. However, none of these attempts have been fully satisfactory, particularly when using a downhole rotary pump or a progressive cavity pump to produce the production fluids from the formation.
For instance, attempts have been made to eliminate the use of a reciprocating rod string to actuate a downhole reciprocating pump. United States of America U.S. Pat. No. 4,661,052 issued Apr. 28, 1987 to Ruhle describes a downhole reciprocating pump including a pump plunger, which is activated by the axial oscillation or reciprocation of a string of lightweight composite pipe. The string of pipe is axially oscillated from the surface. More particularly, the string of pipe is provided to activate the reciprocating pump by axially oscillating the pump plunger and to transport the production fluids to the surface.
United States of America U.S. Pat. No. 5,351,752 issued Oct. 4, 1994 to Wood et. al. also describes a downhole reciprocating pump including a reciprocating pump plunger. Specifically, a tubing string is connected between a pump drive at the surface, referred to as a jack unit, and the downhole reciprocating pump. The tubing string performs the dual function of reciprocating the pump plunger in response to activation of the pump drive at the surface and transporting production fluids from the formation to the surface.
Further, attempts have been made to eliminate the use of a rotating rod string to actuate a downhole pump. United States of America U.S. Pat. No. 5,220,962 issued Jun. 22, 1993 to Muller et. al. describes the use of a rotating tubing string to activate a particular downhole pump. Specifically, the downhole pump is comprised of a first section, a second section and a third section. The first section of the downhole pump is connected to the downhole end of the tubing string and rotates circumferentially in response to the rotation of the tubing string. The second section of the downhole pump is connected to the first section and reciprocates longitudinally in response to the rotation of the first section. The third section is connected to the second section and receives the production fluids from the wellbore and subsequently pushes the fluids uphole in response to the longitudinal reciprocation of the second section.
United States of America U.S. Pat. No. 5,667,369 issued Sep. 16, 1997 to Cholet describes the use of a continuous tube or continuous length of coil tubing in place of the rod string to activate the downhole rotary pump. Specifically, a tubular column extends from the surface for connection to the downhole rotary pump. The tubular column is described as a “production column” which has as its main role the channeling of the production fluids from the bottom of the wellbore to the surface “via its inner pipe”. The coil tubing extends from the surface through the production column for connection to a rotor of the downhole rotary pump. Thus, rotation of the coil tubing within the production column drives the rotor of the rotary pump.
Thus, there remains a need in the industry for a downhole production system and method which address the disadvantages associated with the conventional use of a rod string to actuate a downhole pump.
SUMMARY OF INVENTION
The present invention relates to an apparatus and a method for use in pumping fluids in a wellbore. Further, the apparatus and method are preferably for use with a downhole rotary pump. More particularly, a pipe string defining an interior fluid path for the passage of the fluids therein actuates the downhole rotary pump in order to pump the fluids. Preferably, the pipe string is comprised of a tubing string rotatably supported within the wellbore. Th
Anaka Jim
Anderson Gary
Deugo Shawn
Matthews Ed
Paton Mel
Bagnell David
Dougherty Jennifer R.
Innovative Production Technologies Ltd.
Kuharchuk Terrence N.
Rodman & Rodman
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