METHOD AND APPARATUS FOR TREATING A WELL

Abstract

A tool for forming an obstruction in the production casing of an oil or gas well includes a sleeve adapted to be secured to the casing and having an annular abutting surface that captures a body or a cage having a solid body within the casing thereby forming an obstruction. The tool may be secured within the well either by an expandable sleeve or a collet having resilient fingers. The tool may be used as a plug to prevent flow through the production casing of the well in a well treatment process such as fracing. A process for treating a well using the tool is also presented.

Description

This is a Continuation-in-Part of application Ser. No. 13/605,298 filed on Sep. 6, 2012.

BACKGROUND OF INVENTION

1. Field of the Invention

The invention disclosed and claimed in this application relates to the treatment of oil and/or gas wells. One example of such treatment is commonly referred to as fracturing the formulation around an oil or gas well. Fluid with certain chemical additives and a proppant are injected into the formation surrounding either a vertical or horizontal well to form cracks or passageways in the formation to stimulate the production of the well.

2. Description of Related Art

Currently there are several techniques utilized to stimulate producing of a well by fracing. Typically a packer or plug is utilized to isolate a particular portion of the well and the fracing fluid is injected into the isolated portion under high pressure. Once a given portion of the well is treated in this manner, a second zone uphole of the first zone is isolated by a second packer or plug that cuts off flow to the downhole portion of the well that has been treated.

U.S. Pat. No. 7,322,417 discloses a plurality of vertically spaced production layers 1 and a plurality of valves 14. A ball is captured on a valve seat 94 which will cause an increase in pressure to open valve 14. This allows fracturing fluids to enter the annular region that surrounds the valve. The balls may be formed of a dissolvable or frangible material, which allows the ball to be dissolved or eroded to open up communication upstream through the casing.

U.S. Pat. No. 7,134,505 discloses a similar system in which a plurality of spaced apart packers 20 a-n and a plurality of valve bodies 26 c-n that capture balls of varying diameters to selectively open ports 16 c-e to allow fracturing fluids to flow into the isolated zones.

Stage frac methods include the use of pump down bridge plugs, perforating guns, and sliding sleeves. The current pump down method requires a drill out phase after frac with coiled tubing or jointed pipe. This is an expensive and time consuming process which involves additional risk of the coil tubing getting stuck in the wellbore. This time and operational risk is a significant impact item on the overall economics of oil and gas projects.

Sliding sleeves require that their exact position needs to be known as the casing is run into the well. The number of frac initiation points is limited and the cost is significant for each sleeve. Sleeves may malfunction either during opening or closing. Higher risk comes from incomplete frac distribution and limited reservoir drainage.

BRIEF SUMMARY OF THE INVENTION

The present invention overcomes the difficulties with the prior art as described above by using proven concepts and a simplified approach. An expansible valve seat or stop member that can be run on wireline (pump-down, tractor, tubing or coiled tubing) is positioned at predetermined locations along the production casing and is expanded for example by a shaped charge or with a mandrel extrusion process. A disintegrating or dissolvable ball can be dropped in the valve seat to isolate a portion of the well to allow for fracturing of the isolated portions of the well. The seat may be made of the same material as the ball so that the drill out step is completely eliminated. Alternately, the valve seat may be mechanically captured by the production casing.

The ball and valve seat become the frac plug that would normally be pumped down in a conventional horizontal pump-down process.

The production casing can be perforated as in the pump down method and fracing can be initiated once the ball seals on the valve seat. A dart may be used in lieu of a ball. Balls, darts, seats or sleeves may be soluble, dissolvable or frangible.

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

FIG. 1 is a flow diagram of the process according to an embodiment of the invention.

FIG. 2 is a cross sectional view of expansible sleeve seat according to an embodiment of the invention.

FIG. 3 is a cross sectional view of the sleeve seat deployed within the production casing with the ball.

FIG. 4 is a cross sectional view of a second expansible sleeve seat and a dart.

FIG. 5 is a cross sectional view of a third expansible sleeve seat and a ball.

FIG. 6 is a cross sectional view of a fourth embodiment with an expansible sleeve and separate seat with a dart.

FIG. 7 is a cross sectional view of a fifth embodiment of the invention.

FIG. 8 is an end view of the embodiment of FIG. 7.

FIG. 9 is a cross sectional view of a sixth embodiment of the invention.

FIG. 10 is a cross sectional view of a further embodiment of the invention.

FIG. 11 is a cross sectional view of yet a further embodiment of the invention.

FIG. 12 is a cross sectional view of an embodiment of a connector sub.

DETAILED DESCRIPTION OF THE INVENTION

As described below, the invention of this application is directed to a novel process of fracturing a plurality of zones in the formation surrounding a horizontal or vertical well without the use of multiple bridge plugs or frac plugs that require drill out after the fracturing process is complete prior to the production stage.

This is accomplished in the following manner. After the well has been drilled (81) and the production casing has been fully positioned (82), an expansible sleeve such as shown in FIG. 2 is placed at the desired location within the casing (83). As shown in FIG. 2, the expansible sleeve 10 consists of a relatively thin walled cylindrical tube 11 formed of a high tensile strength material similar to that of the production casing 21. A ring of expansible material 12 may surround a portion of tube 11. A cap 15 is positioned over the downhole end 16 of the tube so that the expansible sleeve 10 may be pumped into the well. The outside diameter of the ring 12 is slightly less that the inside diameter of the casing. Detonation cord 14 is wound about a frangible mandrel 13 positioned within the tube and includes an electrical cord 17 for detonation. Another embodiment of this invention may employ the use of an extrusion process using a mandrel and sleeve to create the seat as shown in FIG. 3. The resultant sleeve or seat installed in the production casing will be the same whether the installation process is expansive or extruded.

Expansible sleeve 10 may be precisely positioned within the production casing by any suitable known technique such as a line counter or collar locator. Once positioned within the desired location of the production casing, the cord is detonated (84) causing the sleeve to expand outwardly against the inner surface of the casing (21). In so doing, the sleeve forms a seat 12 as shown in FIG. 3 which is capable of catching and retaining a ball or dart as shown in FIG. 3 and FIG. 4 that is pumped down (86). The outer surface of tube 11 may be impregnated with a thin strip of no slip high strength metallic material.

Once the tube 11 and seat have been set in place, the production casing and cement (if present) in the first frac zone can be perforated (85) in the conventional way by a perforating gun on the same tool-string as the expansible sleeve. At this point the tool-string can be removed, and the fracing process can be initiated by pumping down (86) a ball or dart to rest against seat 12. This will prevent the fracing fluid from flowing downhole and will cause the fracing fluid under pressure (87) to enter the formation surrounding the perforations in the production casing and thus commence the fracing process.

Once the process is completed for the first zone, a second expansible sleeve can be placed (88) to isolate a second zone and the process can be repeated (88-92) for as many zones as desired as indicated in FIG. 1. The ball, dart, seat or sleeve may be made of a soluble, dissolvable, or frangible material such that it would not be necessary to drillout the sealing mechanism after fracturing. The ball, dart, seat or sleeve would shrink in size or completely dissolve so that the constituents went into solution or were flowed back with the frac load water.

Another embodiment of the expansible sleeve is illustrated in FIG. 5. In this embodiment, a tubular member is shown in an unexpanded condition at 45. Chevron or swellable seals 43 are positioned about an uphole portion 44 of the sleeve 45. Sleeve portion 45 is expanded by a mandrel or shaped charge into the position indicated at 46 against the inner surface of the casing 21. In this embodiment the uphole portion 44 of the sleeve may have a beveled surface (47) against which ball 22 rests when a ball or dart is pumped down into the casing.

An additional embodiment of the expansible sleeve is illustrated in FIG. 6. In this embodiment, a sleeve 11 is expanded in the production casing 21 and used as a stop or no-go for a secondary conical seat 51 that is either simultaneously or subsequently placed on the no-go. The perforations are then added. A ball or dart 32 is then landed on the seat forming the sealing mechanism for the wellbore and the stage is frac'd. Secondary seat 51 may have an elastomeric annular seat 52 that engages a tapered portion 53 of the sleeve 11 to form a seal. This process can be repeated as many times as necessary to adequately stimulate the formation surrounding the wellbore. The ball, dart or seat in this embodiment may also be made of a soluble, dissolvable, or frangible material.

A further embodiment of the invention can be described by reference to FIGS. 7 and 8. As with other embodiments, an expandable sleeve 10 is positioned and expanded within production casing 21 so that cylindrical tube 11 is secured to the casing. A cage member 65 having a ball 66 is then pumped down to a position where it rests on shoulder 53 of tube 11 as shown in FIG. 7. Cage member 65 has a hollow cylindrical portion 62 of slightly less diameter than the internal diameter of casing 21. Cage member also has a hollow frustoconical portion 61 which terminates in an outlet 68.

A perforated disk 64 having perforations 63 closes one end of the cage as shown in FIG. 7. Disk 63 includes an annular wall portion 67 which spaces ball 65 from disk 64. The diameter of ball 63 is smaller than the inside diameter of cylindrical portion 62 of cage 65 so that fluid can flow from right to left, looking at FIG. 7, around ball 65 and through apertures 63. However, cage 65 will prevent fluid flow from left to right as in fracing operations by virtue of ball 66 resting on frustoconical portion 61 of the cage.

As in previous embodiments, the sleeve 11, cage member 62 and ball 66 may be made of a soluble, dissolvable or frangible material so that it would not be necessary to drill out the sealing mechanism after fracing.

Another embodiment of the invention is illustrated in FIG. 9. This embodiment also utilizes a cylindrical tube 11 that has been expanded so to be secured within casing 21. A solid frustoconical plug 71 after being pumped down into the well, rests against shoulder 53 of tube 11 at 72 as shown in FIG. 9 to prevent flow downhole of the plug 71. Plug 71 may also be made of a soluble, dissolvable or frangible material.

The expandable sleeve may be formed of steel for example J-55 or similar steel. The wall thickness may vary from approximately 0.095 inches to about 0.25 inches. The diameter of the sleeve is selected to be slightly smaller than that of the production casing so for example if the casing is 5 ½ inch casing, the sleeve may have an outside diameter of 4.5 inches.

A further embodiment of a tool suitable for use according to the invention is shown in FIG. 10. The tool 100 includes a hollow cone shaped sleeve 103 having an end portion having an outlet 119 formed therein. Sleeve 103 includes an internal converging passageway 110 leading to outlet 119. The uphole end of the tool includes a plurality of radially spaced resilient collet style fingers 108 which each include a tab member 105 of a given width. The tabs 105 are sized to mate with an annular gap 107 formed between two sections of production casing 101. The two sections 101 are secured together by a coupling 104. Tool 100 may be run into the well with a disposable setting sleeve in conjunction with select fire perforating guns. As tabs 105 come into alignment with gap 107 having the same width as the tabs 105, fingers 108 will expand outwardly in a known manner to lock the tool within the production casing. A ball or dart 106 can then be dropped into the production casing and will engage a converging wall section of sleeve 103 to thereby act as a frac plug. Ball or dart 106 may be made from a bio degradable material that dissolves. Sleeve 103 may be made from a degradable fiberglass resin or any other degradable material so that it does not need to be drilled out. This process can be repeated to form plural fracing zones. Each tool or plug 100 will have tabs 105 having a unique width so that the collet fingers will only be captured by a gap between the production casing members having the corresponding width.

A cup shaped member 112 having seals 113 can be positioned on the uphole portion of ball or dart 106 to provide a seal. The internal surface of cup 112 is formed to conform to the spherical surface of ball or dart 106.

FIG. 11 illustrates yet a further embodiment of a tool according to an aspect of the invention. In this embodiment the tool includes an outer collet sleeve 127 that is deployed from inside a setting tool and is run in a wire string in the same manner that a frac plug would be run. Outer collet sleeve 127 includes a plurality of resilient collect fingers 131 having tabs 123 of a given width that mate with a gap 122 formed between adjacent production casing members 111 that are coupled together by a threaded coupler 121 for example. A valve seat 125 having a downhole end 129 is captured within collet sleeve 127 by virtue of complementary converging surfaces on the inside of the collet sleeve 127 and on the outer surface of valve seat 125. Valve seat 125 includes a converging passageway 130 which may be initially filled by a bio-degradable material. Valve seat 125 may be separately carried down to engage collet sleeve 127. Valve seat 125 carries an annular sealing ring 124 which is compressed outwardly against production casing 111 as valve sleeve 125 is forced, for example, by fluid pressure into collet sleeve 127.

After the collet sleeve and valve seat have been positioned within the production casing and the casing has been perforated, a ball or dart can be run in or dropped to engage valve seat 125 to form a plug. At this point, the perforated zone of formation uphole of the plug can now be treated. As in other embodiments the collet sleeve, valve seat and dart or ball can be made of bio-degradable or dissolvable material.

Collet sleeve 127 and valve seat 125 may be run into the production casing separately or loosely attached to each other by an attachment mechanism, for example a shear pin, that can be disengaged by a suitable force applied to the valve seat such as fluid pressure.

As in the embodiment of FIG. 10, each plug will have unique width tabs so as to be selectively placed within the production casing. The gaps between adjacent production casing members will have different widths to selectively capture the collet sleeves. Typically the first tool placed at the end of the production casing will have the widest tabs so as to pass over gaps of a smaller width as the tool is run into the production casing.

The embodiments of FIGS. 10 and 11 could be used in conjunction with a casing profile nipple (CPN). In lieu of having the tabs of the collet fingers being captured in a gap between production casing members, the tabs could be captured by an annular groove provided on the interior of a casing profile nipple which can be connected between adjacent production casing members as is known in the art. A suitable CPN is manufactured by Tesco Corporation. Additionally, a simple connector sub with an interior annular groove could be utilized as the securing mechanism for the embodiments of FIGS. 10 and 11. As shown in FIG. 12, the connector sub 200 has threaded end portions 201, 202 and a cylindrical tubular body portion 203. An annular groove 204 is formed in the interior surface of body portion 203. The groove is sized to accommodate tabs 105 or 123 on the end of the collet fingers 108 or 131.

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 tool for forming an obstruction in production casing of an oil or gas well comprising:

a sleeve adapted to be secured within the production casing;

a cage member having an annular surface adapted to abut against a first end portion of the sleeve; and

the cage member having a solid body that is axially movable to a first position blocking fluid flow through the tool in a first direction and movable to a second position permitting fluid flow through the tool in a direction opposite to the first direction.

2. The tool according to claim 1 wherein the cage member includes a hollow cylindrical portion having a diameter slightly less than that of the production casing and a hollow frustoconical portion extending downstream of the hollow cylindrical portion and terminating in an outlet.

3. The tool according to claim 1 wherein the cage member further includes a perforated disk closing one end of the hollow cylindrical portion of the cage member.

4. The tool according to claim 1 wherein the perforated disk includes an annular wall spacing the solid body from a planar flat portion of the disk.

5. A tool for forming an obstruction in the production casing of an oil or gas well comprising:

an expandable sleeve adopted to be secured within the casing.

a solid body having a frustonical shape and having a surface portion adapted to abut against an annular surface on the sleeve thereby forming an obstruction in the well.

6. A tool for forming an obstruction of an oil or gas well having production casing comprising:

a sleeve having a passageway therethrough;

a plurality of collet fingers on the sleeve adapted to engage a gap between adjacent production casing members; and

a ball or dart adapted to seat on a surface of the sleeve to close the passageway.

7. A tool as claimed in claim 6 further including a cup-shaped member having an interior surface conforming to the exterior surface of the ball or dart and engaging an uphole surface of the ball or dart.

8. A tool as claimed in claim 6 wherein the sleeve includes a valve seat.

9. A method of treating a well having a production casing comprising:

providing a production casing including a plurality of production casing members;

securing a tool having a valve seat and a through passageway at a predetermined position within the production casing;

perforating the production casing uphole of the tool;

closing the through passageway in the tool; and

pumping a treating fluid in the production casing and out through the perforations.

10. The method of claim 9 including:

terminating the pumping of the treating fluid;

positioning a second tool in the production casing upstream of the perforations in the production casing;

perforating the production casing at a second location uphole of the second tool and resuming pumping of the treating fluid in the production casing and through perforations located in the second location.

11. The method of claim 9 wherein the tool includes a collet having a plurality of resilient fingers with tabs, the tabs adapted to be captured by a gap formed between adjacent production casing members.

12. The method of claim 9 wherein the tool includes a collet having a plurality of resilient fingers with tabs, the tabs adapted to be captured by a groove within a connection sub that connects two adjacent production casing members together.