Hydraulic Installation Method and Apparatus for Installing a Submersible Pump

Abstract

Aspects of this invention include a method for deploying a small diameter submersible pump in a deviated wellbore. The submersible pump is first lowered into the production tubing under the influence of gravity. The pump includes a sealing member deployed thereabout which provides a releasable seal with an interior surface of the production tubing. The pump is then forced deeper into the production tubing (e.g., into a deviated section of the wellbore). This is accomplished via introducing a column of liquid (such as water) into the production tubing above the pump. The liquid exerts a force on the pump and sealing member so as to force the pump deeper into the well, thereby drawing one or more power lines into the wellbore with the pump. The invention advantageously enables a small diameter submersible pump to be economically deployed in a highly deviated wellbore. The invention also advantageously enables deployment into partially obstructed and/or damaged tubing.

Description

FIELD OF THE INVENTION

The present invention relates generally to downhole submersible pumping systems. More particularly, the invention relates to a method and apparatus for hydraulically installing a submersible pump used in artificial lift applications in hydrocarbon producing wells.

BACKGROUND OF THE INVENTION

Hydrocarbons, and other fluids, are often contained within subterranean formations at elevated pressures. Wells drilled into these formations allow the elevated pressure within the formation to force the fluids to the surface. However, in low pressure formations, or when the formation pressure has diminished, the formation pressure may be insufficient to force the fluids to the surface. In these cases, a pump may be installed to provide the required pressure to produce the fluids.

The volume of well fluids produced from a low pressure well is often limited, thus limiting the potential income generated by the well. For wells that require pumping systems, the installation and operating costs of these systems often determine whether a pumping system is installed to enable production or the well is abandoned. Among the more significant costs associated with pumping systems are the costs for installing, maintaining, and powering the system. Reducing these costs may allow more wells to be produced economically and increase the efficiency of wells already having pumping systems.

In recent years, the deployment of small diameter pumps in the production tubing has often provided for economic recovery of well bore fluids. One example of such a small diameter pump is disclosed in commonly invented and commonly assigned U.S. Pat. No. 7,252,148. Commercially available small diameter pumps are commonly powered via hydraulic actuation and are therefore connected to the surface via one or more hydraulic lines. Flexible hydraulic tubing is often preferred due to its low cost. Those of skill in the art will appreciate that electrical and mechanical actuation of downhole pumping systems is also known.

In service, the production tubing is typically first deployed in a cased wellbore. The small diameter pump is then typically lowered into the well under of the influence of the Earth's gravitational field. The hydraulic (or electric) power lines are dragged behind until the pump reaches the bottom of the well and is seated in an appropriate connector (e.g., a nipple deployed at the bottom or somewhere along the length of the production tubing).

Deviated wells are commonly utilized to improve production. Wellbores including vertical, doglegged, and horizontal sections are now common. In such deviated wellbores, deployment of a small diameter pump into the production tubing can be problematic. Gravitational force alone is usually not sufficient to drag the pump around the dogleg or along the horizontal section of the well. To overcome this problem, the pump may be rigidly mounted in the production tubing and forced downhole with the production tubing. However, this results in a “permanent” deployment of the pump and necessitates the removal of the production tubing should the pump fail or merely require routine service. As will be appreciated by those of ordinary skill in the art, such removal of the production tubing is time consuming and therefore expensive. The use of rigid hydraulic lines (or rigid power lines) by which the pump may be forced down the well has also been contemplated. However, rigid hydraulic lines are prone to buckling under compression and are therefore not typically suitable for forcing a pump through a highly deviated section of a wellbore (or through a section having a high dogleg severity). Moreover, this approach adds significant cost to the operation (due to the increased cost of the rigid power lines).

Therefore, a need remains for a method for deploying a small diameter pump in a deviated borehole and a small diameter pump or small diameter pumping system suitable for such deployment.

SUMMARY OF THE INVENTION

The present invention addresses one or more of the above-described drawbacks of the prior art. One aspect of the invention includes a method for deploying a small diameter submersible pump in a deviated wellbore. Methods in accordance with the present invention include at least a two-stage deployment of the pump in the deviated wellbore. In a first stage, the submersible pump is lowered into the production tubing under the influence of gravity. During this first stage the pump is typically supported by at least one power line (e.g., a hydraulic line) that extends from the pump to the surface. The pump includes a sealing member deployed thereabout which provides a releasable seal with an interior surface of the production tubing. In a second stage, the pump is forced deeper into the production tubing (e.g., into a highly deviated section of the wellbore). This is accomplished via introducing a column of liquid (such as water) into the production tubing above the pump. The liquid exerts the necessary force on the pump and sealing member so as to force the pump deeper into the well. The pump preferably includes at least one power line that extends to the surface and is drawn into the wellbore during the first and second stages of the deployment.

Exemplary embodiments of the present invention advantageously provide several technical advantages. For example, the present invention enables a small diameter submersible pump to be economically deployed in a highly deviated wellbore (e.g., a wellbore including an extended reach horizontal section). The invention also allows the deployment of pumps into tubing that is partially obstructed by solids such as paraffin or scale, and allows pumps to pass by tight spots caused by mechanical tubing damage. Moreover, the invention does not require the use of rigid power lines. Nor is it necessary to mount the pump in the production tubing prior to deployment. The invention also advantageously enables simple and economic removal of the pump from the wellbore.

In one aspect the present invention includes a method for installing a small diameter submersible pump in production tubing. The method includes providing a length of production tubing deployed in a deviated wellbore, the production tubing including a sealing device deployed therein at a predetermined measured depth. The method further includes providing a small diameter pump having a fluid inlet and a fluid outlet. The pump further includes a sealing member deployed about an outer surface of the pump, the sealing member deployed axially between the fluid inlet and the fluid outlet. At least one power line is coupled to the pump. The pump is lowered into the production tubing with gravitational force drawing the pump into the tubing. The sealing member contacts and provides a releasable seal with an inner surface of the production tubing. The power line extends upward from the pump out an upper end of the production tubing. The method still further includes forcing the pump deeper into the production tubing by introducing a liquid into the production tubing above the pump. The liquid provides a downward force on the sealing member and the pump, the downward force being sufficient to force the pump deeper into the wellbore through a deviated section of the production tubing and into engagement with the sealing device.

In another aspect, this invention includes a method for installing a small diameter submersible pump in production tubing, the production tubing being deployed in a deviated wellbore. The method includes lowering a small diameter submersible pump into the production tubing, gravitational force drawing the pump into the production tubing. The pump includes a sealing member deployed about an outer surface thereof, the sealing member being deployed axially between a fluid inlet and a fluid outlet. At least one power line is coupled to the pump and extends upward to a surface location. The method further includes forcing the pump deeper into the production tubing by introducing a liquid into the production tubing above the pump. The weight (and/or pressure) of the liquid provides a downward force on the sealing member and the pump, the downward force being sufficient to force the pump deeper into the wellbore and into engagement with a seating nipple deployed in the production tubing.

In still another aspect, the invention includes a submersible pumping system. The pumping system includes a submersible pump deployed in a length of production tubing, the production tubing deployed in a deviated subterranean wellbore. The submersible pump includes a pump body having a fluid inlet and a fluid outlet. A releasable sealing member is deployed about an outer surface of the pump body axially between the fluid inlet and the fluid outlet. The sealing member contacts and forms a releasable seal with an inner surface of the production tubing. The pump further includes at least one power line connected thereto, the power line extending upwards through the production tubing to a surface location.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIG. 1 depicts a prior art arrangement in which a submersible pump is deployed in production tubing in a vertical wellbore.

FIG. 2 depicts one exemplary embodiment of the present invention in flow chart form.

FIG. 3 depicts a semisubmersible pump partially deployed in a deviated wellbore.

FIG. 4 depicts the semisubmersible pump depicted on FIG. 3 fully deployed in the deviated wellbore.

DETAILED DESCRIPTION

With reference now to FIG. 1, a prior art pumping system 100 includes a small diameter submersible pump 120 operatively connected with surface equipment 150. The pump 120 is deployed in production tubing 140 in a cased wellbore 32. The production tubing 140 forms a flowbore that extends upward to surface equipment 150 and carries wellbore fluid from the submersible pump 120 to the surface. Submersible pump 120 is connected to surface equipment 150 via power lines 122. The surface equipment 150 may include various pumping equipment, valves, piping, power sources, and the like, for example, including a gas-over-liquid scheme to develop the necessary hydraulic pressure needed to drive the submersible pump 120.

As is known to those of ordinary skill in the art, the operation of the submersible pump 120 draws wellbore fluid from the wellbore 32 into the pump 120 via a fluid inlet 124. The fluid is pressurized by the pump 120 and pumped out through fluid outlet 126 to the surface as depicted at 130. As depicted, pump 120 is engaged with a sealing device 142 (e.g., a seating nipple) deployed at the bottom of the production tubing 140. Such engagement enables wellbore fluids in the wellbore to enter the pump via inlet 124.

In operation, submersible pump 120 may be lowered into the production tubing 140 under the influence of gravity. During this operation, the pump is typically supported by the power lines 122 (e.g., by hydraulic or electrical power lines). The weight of the pump provides the necessary force for the above-described engagement with the sealing device 142. This practice is well established in vertical (or near vertical) wells. However, in deviated wellbores such gravity assisted deployment can be problematic as the gravitational force is not sufficient to move the pump through the deviated section of the wellbore. Deployment of submersible pumps is particularly problematic in wellbores having horizontal or near horizontal sections (e.g., having an inclination greater than about 75 degrees).

With reference now to FIGS. 2 through 4, one exemplary method embodiment 200 in accordance with the present invention is described in more detail. In FIG. 2, the invention is depicted in flowchart form. An exemplary submersible pump 320 in accordance with the present invention is depicted in a deviated wellbore 42 both before (FIG. 3) and after (FIG. 4) step 208 in method 200.

At 202, a length of production tubing 140 is provided in a deviated wellbore 42. The production tubing 140 includes a sealing device 142 (e.g., a seating nipple) deployed at a predetermined depth in the well (e.g., at the lower end of the tubing as depicted in FIGS. 3 and 4). The production tubing may optionally further include a stripper 148 deployed at the surface for sealingly engaging power line(s) extending upward from a pump. The production tubing typically also includes one or more ports 144 located at the surface.

A small diameter submersible pump 320 is provided at 204. The pump 320 includes a fluid inlet 324 and a fluid outlet 326. The fluid inlet 324 is typically on a lower end of the pump 320 and the fluid outlet 326 on an upper end of the pump 320, although the invention is not limited in this regard. The pump 320 further includes a sealing member 328 deployed about an outer surface 329 of the pump, the sealing member 328 being located axially between the fluid inlet 324 and outlet 326. In a preferred embodiment of the invention, the sealing member includes a conventional sand seal, for example, a Flexite® ring available from Harbison-Fisher Mfg. Co., Fort Worth, Tex. At least one power line 322, e.g., one or more hydraulic lines, is further coupled to an upper end of the pump 320.

At 206, the semisubmersible pump 320 is lowered into the deviated wellbore 42 under the influence of gravity (i.e., gravity draws the pump 320 down into the well). As shown on FIG. 3, sealing member 328 contacts an inner surface 145 of the production tubing 140 forming a releasable seal (which may also be referred to as a partial seal) therewith. As the pump 320 is lowered into the well 42, the power line(s) 322 (e.g., the hydraulic lines) are typically used to support the pump 320 and are drawn down into the well with the pump 320. In a preferred embodiment of the invention (and as depicted on FIG. 3), the power line(s) 322 may be pulled through a conventional stripper 148, which is deployed atop the production tubing 140 and which sealingly engages the power line(s) 322. The pump 320 is typically lowered at step 206 until it can't be lowered any further by gravitational force alone. As depicted on FIG. 3, the pump is often lowered until it reaches a deviated section of the well (e.g., having an inclination greater than about 45 degrees) or a section of the well having a high dogleg severity.

At 208, a liquid (preferably water or an aqueous based liquid) is introduced into the production tubing 140 via a port 144 at the surface. The weight of the liquid in the tubing 140 provides a downward force (depicted at 360 on FIG. 4) on the sealing member 328 and on an upper surface of the pump 320 which forces the pump 320 deeper into the well, e.g., through the deviated section of the wellbore 42 and into engagement with the sealing device 142 in the production tubing 140 as depicted on FIG. 4. In certain embodiments it may be advantageous to pressurize the liquid so as to increase the downward force 360 on the pump 320. Such pressurization is sometimes necessary in wellbores 42 having a high dogleg severity section and/or an extended reach horizontal section. Pressurization may also be advantageous when forcing the pump 320 through a mechanically damaged section of the tubing 140. Notwithstanding, the invention is not limited in these regards as the weight of the liquid alone is often sufficient to force the pump 320 into engagement with the seating nipple 142.

As is known to those of ordinary skill in the art, submersible pumps can fail unexpectedly or can simply wear out over time depending on the particular submersible pump and the conditions in the well. This requires removal of the pump from the well since the well ceases to produce once the submersible pump fails. Other reasons for removing the pump from the well are also know (e.g., including a failed installation). Thus, with continued reference to FIG. 2, methods in accordance with the invention may optionally further include removing the pump 320 from the wellbore 42. This may be accomplished, for example, via exerting an upward force on the power line(s) 322 at 210 to disengage the pump 320 from the sealing device 142 (e.g., the seating nipple) and to release (break) the releasable seal between the sealing member 328 and the production tubing 140. The pump 320 may then be pulled out of the production tubing 140 (and out the well 42) by the power line(s) 322 at 212.

As described above, the submersible pump 320 is equipped with a sealing member 328 deployed about an outer surface 329 of the pump 320. Upon deployment of the pump 320 in the wellbore 42, the sealing member 328 sealingly engages an inner surface 145 of the production tubing 140 (as depicted on FIGS. 3 and 4). In preferred embodiments of the invention, the sealing member 328 forms a releasable seal with the production tubing when deployed therein. By releasable it is meant that the seal between the pump 320 and the production tubing 140 is of moderate strength. On the one hand, the seal must be sufficiently strong so as to support the pressure exerted by the column of liquid in the production tubing at step 208. On the other hand, it is important that the seal not be so strong as to significantly resist the movement of the pump 320 down into the wellbore (either under the influence of gravity at step 206 or under the influence of the downward force 360 provided at step 208). Moreover, it is also important that the seal not be so strong so as to prevent the removal of the pump 320 from the wellbore as described above at steps 210 and 212 (FIG. 2). A seal that is too strong, may render it impossible (or overly difficult) to remove the pump 320 via pulling upward on the power line(s) 322 or may cause the power lines 322 to be damaged during removal of the pump 320. This can result in the need for expensive fishing operations or in extreme cases, the need to remove the production tubing 140 from the wellbore 42 (if the pump 320 is stuck) or replacement of the power lines 322 ( if they are damaged). It has been found that a hard, self-lubricating, plastic ring (such as a Flexite® ring sand seal available from Harbison-Fischer) provides a seal having a suitable strength for use in embodiments of the present invention. The ring advantageously expands against the production tubing to form the seal between the pump and the tubing. Moreover the ring tends not to swell in service, which advantageously enables the pump to be pulled out of the wellbore.

In a preferred embodiment of the invention, the pump 320 includes a hydraulically driven diaphragm pump and includes first and second flexible hydraulic lines connected thereto. Preferred embodiments of the pump may employ substantially any known hydraulic actuation mechanism, and may therefore include, for example, one or more pressure intensifiers such as disclosed in commonly invented and commonly assigned U.S. Pat. No. 7,252,148. Furthermore, the pump 320 preferably has a sufficiently small diameter (e.g., less than or equal to 2.5 inch) so as to be deployable in conventional 2⅞ inch production tubing.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alternations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A method for installing a small diameter submersible pump in production tubing, the production tubing being deployed in a deviated wellbore, the method comprising:

(a) providing a length of production tubing deployed in a deviated wellbore, the production tubing including a sealing device deployed therein at a predetermined measured depth;

(b) providing a small diameter pump having a fluid inlet and a fluid outlet, the pump further including a sealing member deployed about an outer surface of the pump, the sealing member deployed axially between the fluid inlet and the fluid outlet, the pump further including at least one power line coupled thereto;

(c) lowering the pump into the production tubing, a gravitational force drawing the pump into the tubing, the sealing member contacting and providing a releasable seal with an inner surface of the production tubing, the at least one power line extending upward from the pump out an upper end of the production tubing; and

(d) forcing the pump deeper into the production tubing by introducing a liquid into the production tubing above the pump, the liquid providing a downward force on the sealing member and the pump, said downward force sufficient to force the pump deeper into the wellbore through a deviated section of the production tubing into engagement with the sealing device.

2. The method of claim 1, further comprising:

(e) exerting an upward force on the at least one power line to: (i) disengage the pump from the sealing device and (ii) release the releasable seal between the sealing member and the production tubing; and

(f) removing the pump from the production tubing via pulling upwards on the at least one power line.

3. The method of claim 1, wherein the deviated section of the production tubing includes a substantially horizontal section.

4. The method of claim 1, wherein the sealing device comprises a sealing nipple deployed at a lower end of the production tubing.

5. The method of claim 1, wherein:

the production tubing further includes a stripper deployed at an upper end thereof, the at least one power line being sealingly engaged with the stripper; and

the at least one power line being drawn into the production tubing through the stripper in both (c) and (d).

6. The method of claim 1, wherein the liquid is water.

7. The method of claim 1, wherein the liquid is pressurized.

8. The method of claim 1, wherein the sealing member comprises a sand seal.

9. The method of claim 1, wherein the pump is lowered in (c) until the gravitational force is unable to draw it deeper into the wellbore.

10. A method for installing a small diameter submersible pump in production tubing, the production tubing being deployed in a deviated wellbore, the method comprising:

(a) lowering a small diameter submersible pump into a length of production tubing, the production tubing deployed in a deviated wellbore, a gravitational force drawing the pump into the production tubing, the pump including a sealing member deployed about an outer surface thereof, the sealing member deployed axially between a fluid inlet and a fluid outlet, the pump further including at least one power line coupled thereto and extending upward to a surface location; and

(b) forcing the pump deeper into the production tubing by introducing a liquid into the production tubing above the pump, the liquid providing a downward force on the sealing member and the pump, said downward force sufficient to force the pump deeper into the wellbore and into engagement with a seating nipple deployed in the production tubing.

11. The method of claim 10, further comprising:

(c) exerting an upward force on the at least one power line to: (i) disengage the pump from the seating nipple and (ii) release the releasable seal between the sealing member and the production tubing; and

(d) removing the pump from the production tubing via pulling upwards on the at least one power line.

12. The method of claim 10, wherein:

the production tubing further includes a stripper deployed at an upper end thereof, the at least one power line being sealingly engaged with the stripper; and

the at least one power line being drawn into the production tubing through the stripper in both (a) and (b).

13. The method of claim 10, wherein the liquid is water.

14. The method of claim 10, wherein the liquid is pressurized.

15. The method of claim 10, wherein the sealing member comprises a sand seal.

16. The method of claim 10, wherein the pump is lowered in (a) until the gravitational force is unable to draw it deeper into the wellbore.

17. A submersible pumping system comprising:

a submersible pump deployed in a length of production tubing, the production tubing deployed in a deviated subterranean wellbore;

the submersible pump comprising a pump body having a fluid inlet and a fluid outlet, a releasable sealing member deployed about an outer surface of the pump body axially between the fluid inlet and the fluid outlet, the sealing member contacting and forming a releasable seal with an inner surface of the production tubing, the pump further including at least one power line connected thereto, the power line extending upwards through the production tubing to a surface location.

18. The submersible pumping system of claim 17, wherein the sealing member comprises a sand seal.

19. The submersible pumping system of claim 17, wherein the at least one power line passed through a stripper deployed on an upper end of the production tubing.

20. The submersible pumping system of claim 17, wherein the production tubing is deployed in deviated wellbore having a substantially horizontal section.