Frac Plug

Abstract

A plug apparatus, also called the frac cup, includes an interior body with conical surface, a top wedge, a slip, and seal system that limits fluid movement around the interior body while fracking The seal system can be of the cup type, expandable pad type, labyrinth seal type, or other device that limits fluid flow. A method, where a plug is conveyed into the well on electric line and a Baker type power charge setting tool, where pump fluid acts on a cup thereby propelling the plug to a preselected position in a horizontal wellbore. The plug provides a barrier to applied frac slurries in order to force the frac slurries into a formation. After the frac, the plug allows flow past an internal ball seat from the bottom side or the plug can be milled out using coiled tubing methods.

Description

BACKGROUND OF INVENTION

1. Field of the Invention

This invention relates to downhole tools for oil and gas wells and similar applications and more particularly to improve multizone frac plugs and methods.

2. Description of Related Art

Well plugs are used to form a barrier within well tubing or casing, to create fluid barriers, or plugs, within tubing or casing. Plugs may be used to temporarily direct acid and frac slurries into formations to increase flow of hydrocarbons.

Typical well plugs consist of a plug body. Radially mounted on the body are a locking mechanism, a packing element system, and a slip system. These plugs tend to be 2 feet or longer depending on the plug design. The packing system is typically an elastomeric packing element with various types of backup devices. The packing system is typically expanded outward to contact the I.D. of the casing by a longitudinal compression force generated by a setting tool or hydraulic piston. This force expands the elastomer and backups to create a seal between the plug body and casing I.D. This same longitudinal force acts through the sealing system and acts on the slip system. The slip system is typically an upper and lower cone that slides under slip segments and expands the slip segments outwardly until teeth on the O.D. of a series of slip segments engage the I.D. of the casing. Teeth or buttons on the O.D. of the slip segments penetrate the I.D. of the casing, to secure the plug in the casing, so the plug will not move up or down as pressure above or below the plug is applied. A locking system typically secures the seal and slip systems in there outward engaged position in order to maintain compression force in the elastomer and, in turn, compression force on the slip system.

Disadvantages with prior art plugs can be the excessive length of the plugs since all of the above combined systems require length. It would advantageous to have a plug that is much shorter in that reduced material would certainly lower material and manufacturing costs. It would be advantageous to have a very short plug, so if plug removal is required, milling time would be greatly reduced. Some of the drillable frac plugs on the market are the Halliburton “Obsidian Frac Plug”, the Smith Services “D2 Bridge Plug”, the Owen Type “A” Frac Plug, the Weatherford “FracGuard”, and the BJ Services “Phython”. By comparison, all of these plug designs are very long in comparison to the current invention.

Historically packer cups have been used on various types of downhole service tools. Typical packer cups are furnished by companies such as Oil States Industries, Inc. and are molded from a durable oil, gas and abrasion resistant rubber compound that withstands wear and tear. Molded into the packer cups are metal supports such as wires to add toughness to the cups. Specially designed packer cups are also made by companies who specialize in the area of downhole seals. The term service tool typically means that the tool is run into the well on either pipe or coiled tubing, pumping or pressure operations are performed, and then the tool is retrieved to the surface by pulling the pipe or coiled tubing. The present invention allows a permanent set plug that is not retrieved with pipe, as in the case of service tools, to be run into horizontal wellbores with the utilization of faster and more economical wireline or electric line. Normally it is not possible to use wireline in horizontal wells because wireline tools are gravity assisted and in horizontal wells, gravity will not move the tools out into the horizontal section of the well. The present invention allows pumping of fluids against the cup to provide a force that propels the plug, setting tool, and wireline all the way to the toe of the horizontal well. A multiple number of plugs can be positioned and set along the length of the horizontal wellbore to allow a “plug and perf” approach to multizone fracking In this invention, a single cup or series of cups, are used for both pumping the plug to the proper location in the horizontal wellbore and creating a fluid barrier as to force frac fluids into the formation. The plug has a simple anchoring device used in combination with a cup which is coupled to a Baker type electric line setting tool, and with this combination provides an economical method to completing wells.

The current invention utilizes a typical packer cup on a frac plug. The advantage being is that the cup can be used to pump the plug, setting tool, electric perforating guns if desired, and electric line through highly deviated portions of the wellbore. Once the plug is in position, the same packer cup also creates a fluid barrier in the I.D. of the casing thus eliminating the need for a more expensive expandable packing element system on the plug. It should also be understood that the cup holds pressure from above and does not hold pressure from below.

Applied pump pressure from the surface acts on the cup from above thus creating the fluid barrier for fracking It should also be understood that the cup may not create the prefect seal that is desired with expandable type packing elements so the cup acts primarily as a fluid diverter where very small fluids leaks may occur past the sealing edges of the cup. In high volume fracs, the small fluid loss around the cup is undetectable at the surface.

BRIEF SUMMARY OF THE INVENTION

This invention provides an improved plug for cased wells. A very short and simple plug that can be pumped though horizontal wellbores. This plug can be anchored using standard electric wireline or with hydraulic setting tools conveyed on jointed pipe or coiled tubing.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic view of the present invention in the “running position”.

FIG. 2 is a schematic view of the present invention in the “set position”.

FIG. 3 is a schematic of the present invention in the “running position” with the setting tool attached shown inside of a section of casing where pump fluid is acting on the plugs cup to propel the string of tools through the horizontal well.

FIG. 4 is a schematic of the present invention with the plug set and the setting tool released from the plug. After releasing from the plug, perforating guns are moved to a position above the plug. The casing is then perforated before removing the setting tool and expended guns from the well while leaving the cup plug permanently set in the horizontal well.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, a schematic of the present invention shows a 180 degree cross-section of the plug 25. A mandrel 4 has an o-ring 6 positioned in a groove. The o-ring 6 seals on the inside of the cup 5. A Pin 9 fits into slots at the lower end of the cup 5 to prevent spinning of the cup relative to mandrel 4. A thimble 8 threads onto the lower end of the mandrel 4 to trap the cup 5 onto mandrel 4. The thimble 8 has a thin malleable lip 7 that is deformable outwardly as to support the cup 5 when pressure differential is applied from above. An expandable slip system 3 slides over mandrel 4 where the slip system has sharp teeth that can engage and penetrate the I.D. of casing. A lock ring 2 threads onto the mandrel 4 and threads inside of the wedge 1. A ball 10 is shown at the upper inside of the plug 25. FIG. 1 shows the plug 25 in the running position with the slips 3 retracted.

FIG. 2 shows the plug 25 in the “set position” inside of casing 11. A setting tool 26 (shown in FIG. 3) attaches to the plug 25 in FIG. 2. The setting tool 26 attaches to plug 25 with a shear screw 13 and shear screw 12. The setting tool 26 holds the mandrel 4 stationary with screw 12 while pushing downward against surface 23. The downward force against surface 23 moves wedge 1 downward (to the right side of the schematic). Lock ring 2 is threadably 16 engaged to wedge 1 and moves along with wedge 1 while ratcheting along thread 15 on mandrel 4. Surface 17 of wedge 1 pushes on slip 3 and slip 3 travels outwardly up conical surface 24 until teeth 18 engage the inside of casing 11. The teeth 18 anchor the plug 25 to the casing 11. The cup 5 contacts the inside of casing 11 at location 21 to block movement of fluid downward past the cup 5. Pressure applied from above the cup 5 forces surface 22 to act on lip 7 outwardly to contain the elastomer of cup 5, and prevent movement of cup elastomer over thimble 8. Ball 10 lands on seat 14 to prevent fluid from traveling through bore 20. With the plug 25 in the set position the plug prevents fluid movement past the plug.

FIG. 3 shows a view of the plug 25 attached to setting tool 26 located inside of casing 11. An electric or wireline connection 27 is shown at the top of the schematic. The plug 25 is in the “run-in” position with the cup 5 making contact with the inside of the casing 11. Pump pressure applied from the surface of the well acts on the cup 5 thus propelling the plug 25 and setting tool 26 through the horizontal wellbore.

FIG. 4 shows the plug 25 in the set position inside of casing 11. The setting tool 26 shears off and separates from plug 25. Upward movement of the wireline 30 pulls the setting tool 26 away from plug 25 a preplanned distance away from plug 25 in order to locate perforating guns 28 inside of casing 11 relative to the oil bearing formation. The perforating guns 28 are detonated to create perforations 29 in casing 11. The guns 28 and setting tool 26 are retrieved to the surface by retrieving the wireline or electric line. The well is treated by pumping frac fluids down the casing from the surface, through the perforations in the casing wall, so that frac fluids cannot pass plug 25 but instead are forced through the perforations and out into the formation in order to stimulate the formation for improved oil or gas production. The ball 10 can be flowed back to the surface or left in place for mill out with the plug at a later point in time.

Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.

Claims

1. A well plug comprising: a mandrel having an exterior surface,a cup positioned on the exterior surface of the mandrel,an expandable seal positioned on an exterior surface of the mandrel,a plurality of anchoring elements surrounding the mandrel; andmeans for moving the plurality of anchoring elements radially outwardly to engage an inner surface of a tubular within the well.

2. The well plug of claim 1 wherein the means for moving the plurality of anchoring elements comprises a wedge and an inclined surface on the mandrel.

3. The well plug of claim 2 wherein the anchoring elements are slips.

4. The well plug of claim 2 further including a locking ring between the mandrel and the wedge.

5. The well plug of claim 1 further including a thimble secured to the mandrel downhole of the cup, the thimble engaging a downhole protion of the cup.

6. The well plug of claim 5 wherein the thimble includes a thin malleable lip that is deformed outwardly so as to support the cup when pressure is applied from above.

7. The well plug of claim 1 wherein a central fluid passageway is provided in the mandrel.

8. The well plug of claim 7 further including a valve member blocking flow through the central fluid passageway.

9. The well plug as claimed in claim 1 further including means for attaching the well plug to a setting tool.

10. A method of treating a well having a casing comprising: providing a completion tool including a perforating gun, a setting tool and a frac plug, the frac plug including a cup member adapted to slideably engage an interior surface of a well casing;pumping the completion tool into the well to a predetermined location;setting the frac plug within the well at the predetermined location; andperforating the well casing using the perforating gun portion of the completion tool.

11. The method of claim 10 further including the step of removing the completion tool absent the plug from the well using coiled tubing, wire line or electric line.

12. The method of claim 11 further including the steps of attaching a second frac plug to the completion tool and running in the completion tool to a second predetermined position uphole of the first predetermined position.

13. The method of claim 12 further including the steps of setting the second frac plug in the well and perforating the well casing a second time with the perforating gun.

14. The well plug of claim 1 wherein the plug is made of a millable material.

15. The well plug of claim 1 wherein the cup expands outwardly to form a seal on an inside of the casing when pressure is applied to the cup.

16. The method of claim 10 further including the step of pumping a frac fluid into the well after the casing has been perforated.