Thrust section wear preventor

A thrust section for use above a motor preferably includes a housing, a thrust shaft, a thrust runner connected to the thrust shaft, a thrust bearing connected to the housing, and a motor lead guard. The motor is preferably positioned above a pump assembly. The thrust runner and thrust bearing prevent upward movement of the shaft.

FIELD OF THE INVENTION

This invention relates generally to the field of downhole pumping systems, and more particularly to an apparatus for protecting motors from wear caused by up thrust.

BACKGROUND

Submersible pumping systems are often deployed into wells to recover petroleum fluids from subterranean reservoirs. Typically, a submersible pumping system includes a number of components, including one or more electric motors coupled to one or more pump assemblies. The submersible pumping systems deliver the petroleum fluids from the subterranean reservoir to a storage facility on the surface. Each of the components in a submersible pumping system must be engineered to withstand the inhospitable downhole environment.

Submersible pumping systems can be attached to the end of production tubing or coiled tubing to deliver fluids to the surface. Various configurations of the components in the submersible pumping system may be used based on the type of delivery system and on various well conditions. For example, some submersible pumping systems that use production tubing through which to deliver fluids to the surface employ a pump above the motor (top intake). Conversely, some submersible pumping systems that employ coiled tubing and that utilize well casing to deliver fluids to the surface employ a pump below the motor (bottom intake).

Referring now toFIG. 1, shown therein is a prior art submersible pumping system200in a top intake configuration. The submersible pumping system200is disposed within a well annulus202, and includes a motor assembly204, a seal section206and a pump assembly208. A power cable210extends from the surface through the annulus202and connects to the motor assembly204.

During operation a shaft (not shown) in the motor assembly204rotates and drives a shaft (not shown) in the seal section206, which in turn drives the pump assembly208to propel well fluid through the production tubing212.

It is well known that during startup of a submersible pumping system, the motor shaft tends to rise, an effect known as “up thrust.” In top intake applications this problem is diminished by use of the seal section206between the motor assembly204and the pump assembly208, which not only facilitates motor lubricating oil expansion and contraction, but also prevents upward movement of the motor shaft. However, in bottom intake applications the seal section is positioned below the motor and therefore is unable to prevent the motor shaft from moving upward during startup. This problem is more pronounced in horizontal wells since the effect of gravity is virtually eliminated from holding down the motor shaft.

The rising motor shaft causes wear on various components of the motor and causes excessive wear on motor bearings. Motors are typically fitted with a radial bearing at the upper end of the motor, and these upper bearings frequently take the brunt of the up thrust generated during startup. Excessive wear on the upper bearings can cause the bearings to fail and can ultimately result in failure of the motor.

It is therefore desirable to control the effects of up thrust in a motor, especially in configurations of submersible pumping systems that are susceptible to excessive wear such as bottom intake systems in deviated wells. It is to these and other deficiencies in the prior art that the present invention is directed.

SUMMARY OF THE INVENTION

In a preferred embodiment, the present invention provides a thrust section for use above a motor, which is positioned above a pump assembly. The thrust section preferably includes a thrust shaft and a thrust protector. The thrust protector is connected to the thrust shaft and prevents upward movement of the thrust shaft.

In a preferred use, the thrust section can be used in a submersible pumping system. In another preferred use, the thrust section is used in conjunction with a coiled tubing assembly. In yet another preferred use, the thrust section is used in a bottom intake submersible pumping system. These and various other features and advantages that characterize the present invention will be apparent from the following description, drawings and claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with a preferred embodiment of the present invention,FIG. 2shows an elevational view of a pumping system100attached to coiled tubing102. The pumping system100and coiled tubing102are disposed in a wellbore104, which is drilled for the production of a fluid such as water or petroleum. As used herein, the term “petroleum” refers broadly to all mineral hydrocarbons, such as crude oil, gas and combinations of oil and gas. The coiled tubing102connects the pumping system100to the surface and supplies power to the pumping system100by use of a power cable (not shown) that extends through the coiled tubing102. Although the pumping system100is primarily designed to pump petroleum products, it will be understood that the present invention can also be used to move other fluids. Also, it will be understood that the present invention can be used with production tubing instead of coiled tubing102.

The pumping system100preferably includes some combination of a pump assembly106, a seal section108, and a motor assembly110. The pump assembly106includes an intake112and a discharge114. The seal section108facilitates lubricating oil contraction and expansion in the motor assembly110. Although only one pump assembly106and one motor assembly110are shown, it will be understood that additional pumps and motors can be connected within the submersible pumping system100to meet the requirements of particular applications.

Still referring toFIG. 2, the submersible pumping system100is shown to include a coiled tubing connector116and a motor interface connector118. The coiled tubing connector116and the motor interface connector118provide a means for transitioning the coiled tubing102to other components of the submersible pumping system100.

A packer120is positioned in the wellbore104as shown inFIG. 2to separate zones in the wellbore104. By positioning the packer120in the location shown inFIG. 2, well fluids can be produced from below the packer120. Fluids below the packer120enter the pump assembly106through intake112during operation of the submersible pumping system100and exit at the discharge114above the packer120. The wellbore fluids are therefore moved to the surface through space in the wellbore104, also known as the “annulus.”

As noted above, at startup of the submersible pumping system100the shaft of the motor assembly110tends to rise, causing components of the motor assembly110to wear. To protect against the unwanted wear, the submersible pumping system100of the present invention includes a thrust section122connected between the motor assembly110and the motor interface connector118.

Turning toFIG. 3, shown therein is cutaway view of the thrust section122. Preferably the thrust section122includes a housing124, a thrust shaft126, a thrust bearing128and a thrust runner130. The thrust bearing128and the thrust runner130collectively form a “thrust protector assembly.” The thrust bearing128is preferably affixed to the housing124with fastener131such as a hex head screw or bolt. The thrust runner130is preferably affixed to the thrust shaft126with an anti-rotation key (not shown), a retaining ring132, and a two piece ring133. The thrust shaft126is coupled to the motor assembly110at end134, and the thrust shaft126and the thrust runner130rotate as the shaft of the motor rotates. The thrust bearing128remains stationary with the housing124.

At startup the tendency of the motor shaft to rise is prevented by the thrust bearing128and thrust runner130, which prevent upward axial movement of the thrust shaft126. Because the motor shaft and the thrust shaft126are coupled end-to-end, when the thrust shaft126is held in an axial position the motor shaft is also held in position.

In other preferred embodiments, the thrust section122also includes one or more motor lead connectors136and a motor lead guard138. The motor lead connectors136continue the electrical connection through the thrust section122so that power supplied from the surface can reach the motor assembly110. Three motor lead connectors136are preferably included in the thrust section122, one each for three phase power.

The motor lead guard138is preferably made of aluminum or other metal that surrounds the thrust shaft126and the thrust runner130to protect the motor lead connectors136. Separating the thrust shaft126and the thrust runner130from the motor lead connectors136prevents the rotating thrust shaft126and thrust runner130from causing wear on the motor lead connectors136that could result in the loss of power. It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functions of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. It will be appreciated by those skilled in the art that the teachings of the present invention can be applied to other systems without departing from the scope and spirit of the present invention.