US3381755A

US3381755A - Sand retainer plug

Info

Publication number: US3381755A
Application number: US535410A
Authority: US
Inventors: Lige T Morrison
Original assignee: Exxon Production Research Co
Current assignee: ExxonMobil Upstream Research Co
Priority date: 1966-03-18
Filing date: 1966-03-18
Publication date: 1968-05-07
Anticipated expiration: 1985-05-07

Description

Filed March 18, 1966 LIGE T. MORRISON INVENTOR- ATTORNEY United States Patent 3,381,755 SAND RETAINER PLUG Lige T. Morrison, Tia Juana, Venezuela, assignor to Esso Production Research Company, a corporation of Delaware Filed Mar. 18, 1966, Ser. No. 535,410 6 Claims. (Cl. 166-191) ABSTRACT OF THE DISCLOSURE Apparatus for gravel packing a well including a perforated liner extending below a packer, a tubular mandrel mounted in fixed position at the lower end of the liner, a cup packer axially slidable on the mandrel, and means f r limiting the axial movement of the cup packer with respect to the mandrel.

The present invention relates to the completion of oil and gas wells and is particularly concerned with an improved completion system for plugging back open casing below gravel packed liners.

Oil and gas wells are often completed by installing a string of casing through the producing interval and then perforating the casing opposite the oil-bearing formation. The production of formation sand with the oil flowing through the perforations is often a problem in such wells. This sand incursion can be curtailed by installing a slotted liner inside the casing adjacent the perforations. The conventional liner is held in place at the top by a hanger and packer and is closed at the bottom. Sand or gravel of a predetermined size is then placed in the annular space between the casing and liner so that the oil produced must pass through the perforations, the packed sand or gravel, and the liner slots. Any formation sand entrained in the inflowing oil will thus generally be screened out by the sand pack and not carried into the liner itself.

The installation of a liner of the type referred to above requires that some provision be made to retain the sand pack between the casing and liner. Otherwise, the sand or gravel may fall into the open casing below the liner during the sand packing operation or may bridge over the liner shoe and then collapse into the open casing when the oil is produced. In either case, the benefits of the sand or gravel pack are lost. Present procedures for avoiding this involve the use of formation fill above the casing float valve, the placement of sand or gravel as a filler below the liner, or the installation of a bridge plug near the lower end of the liner and below the bottom perforation. All of these methods have disadvantages.

The most common of the methods referred to above requires that the formation fill be cleaned out of the well to a depth of about feet below the producing interval, that the liner be installed, and that the gravel or sand pack then be placed on top of the fill. This dictates that the liner extend well below the perforations and hence increases liner costs. Any sloughing of sand while pulling the cleanout bit or running the liner may fill the 15 foot interval and partially plug the producing zone, requiring additional cleanout and liner runs. Produced sand or fines may pack inside the liner and thus require still further cleanout operations. In cases where suflicient formation fill to reach to within about 15 feet of the bottom perforation is unavailable, a bridge plug or sand fill may be placed below and as close to the perforations as normal practice allows. The setting of such a bridge plug or the introduction of the additional sand or gravel required is time consuming and expensive. If a bridge plug is used, it may be diflicult to drill out during later workover operations. These and related difficulties are encountered in a high percentage of the wells completed in the conventional manner.

The present invention provides an improved system for plugging back open casing below the perforations to facilitate the installation of sand and gravel packs about slotted liners. This system involves the use of liner fitted at its lower end with a movable packer cup which supports the sand or gravel injected into the annular space surrounding the liner. The use of such apparatus reduces the total length of liner required, provides a plugback at a predetermined depth, permits accurate determination n the amount of sand or gravel required for the completion operation, and eliminates fill across the producing interval due to the sloughing of formation sand. Any sand which does slough from the formation while pulling the cleanout bit and running the liner can fall into the open casing below the producing interval and hence bit and liner runs which might otherwise be necessary can be avoided. The system also eliminates the necessity for setting bridge plugs in the casing prior to installation of the liner, provides a means for catching junk which may be dropped into the well during the completion operation, permits disposal to the open casing below the liner of produced sand which might otherwise pack in the liner and shorten the well life, and expedites the installation of sand and gravel packs so that the danger of losing the well due to escape of the control fluid is reduced. Such a system permits substantial savings in the installation of sand and gravel packed liners and the workover of wells containing such liners.

The nature and objects of the invention can best be understood by referring to the following detailed description of apparatus embodying it and to the accompanying drawing, in which:

FIGURE 1 is a schematic view of a well containing the slotted liner of the invention prior to the installation of a gravel pack; and

FIGURE 2 is a schematic view of the same well following completion of the gravel pack.

The apparatus shown in FIGURE 1 of the drawing includes a pipe string 11 which extends downwardly in wellbore 12 and is connected to a liner hanger and packer assembly 13 of conventional design. The liner hanger at the top of the assembly includes slips 14 for anchoring the apparatus to the inner wall of casing 15. Passageway 16 extends through the assembly from an opening in the upper end thereof to a.lower port 17. This permits the passage of fluids from the pipe string above the assembly into the annular space surrounding the lower part of the apparatus. Port 17 can be opened and closed by rotating the pipe string from the surface after the assembly has been set in place. Passageway 18 extends from the lower end of the assembly to a lateral port 19 near the upper end of the apparatus shown. This makes possible the transmission of fluid from within the apparatus to the annular space above it. Packer 20 is located on the outer surface of the liner hanger and packer assembly below slips 14 and is actuated by manipulating the pipe string in the conventional manner. It will be understood that the invention is not restricted to the particular liner hanger and packer assembly shown and that a crossover, setting tool and liner hanger or other apparatus which functions in a similar manner to that depicted may be employed.

A tubular liner 21 containing slots or similar openings 21 is connected to the lower end of liner hanger and packer assembly 13. The liner extends downwardly in the wellbore adjacent perforations 23. The cement behind the casing and the producing formation are not shown. Although the invention will generally be employed in wells containing casing adjacent the producing zone, it may also be used in open hole completions where no casing is present.

In the apparatus shown, a sand retainer plug mandrel 24 is connected to the lower end of liner 21 by means of collar 25. In lieu of this, a mandrel integral with the liner may be used. If a separate mandrel is employed, it may be imperforate or may contain slots or other openings similar to those in the liner. A push ring is welded or otherwise attached to the outer surface of the mandrel near its upper end. Near the lower end of the mandrel is a sand retainer cup 27 of rubber or similar resilient, oilresistant material. The cup includes an internal collar 28 on which the rubber element is mounted. The internal diameter of collar 28 will normally be about of an inch greater than the outside diameter of the mandrel. The cup assembly is supported on the mandrel by a shear pin 29 which extends through opposed openings in the mandrel wall or by similar means which will permit dis engagement of the mandrel from the cup assembly. Inside the mandrel, the shear pin passes through a tubular shear pin stabilizer 30 and is held in place by a cotter pin or similar fastener 31. The fastener extends through holes in both the pin and stabilizer. To avoid vertical movement of cup 27, the length of the mandrel between the push ring 26 and the shear pin 29 should be greater than the distance through which the pipe string must be lifted in order to pull the slips out of the rotary bushing. Tubing 32 extends downwardly through the liner and into the mandrel for use in placing the gravel pack.

In utilizing the apparatus of the invention, the assembly is first lowered into the wellbore to a point adjacent the formation as shown. As the apparatus is lowered, push ring 26 will bear against collar 28 and thus force the packer cup 27 downwardly. After the apparatus has been positioned at the desired depth, the slips 14 and packer 20 are set by manipulating the pipe string from the Surface in the conventional manner. If broken slips and springs or other junk should be dropped into the hole during the setting procedure, the packer cup will act as a junk catcher. If the liner has to be pulled out of the h Ie prior to the gravel packing operation, the force exerted on the shear pin 29 will be insufiicient to cause the pin to fail. The entire apparatus can thus be retrieved without difficulty.

Following installation of the apparatus in the position shown in FIGURE 1, a slurry containing the sand, grave] or other particulate material to be employed for gravel packing purposes is injected into pipe string 11 at the surface. This slurry flows downwardly through the liner hanger and the packer assembly 13 and emerges into the annular space below the packer through port 17. The fiuid constituents of the slurry pass through the slots 01' other openings in the liner and are withdrawn to the surface through tubing 32, passageway 18, port 19 and an nular space 12 above the liner and packer assembly. The particulate materials accumulate in the annular space be tween packer 20 and packer cup 27. After the annular space has been substantially filled with the particulate material, injection of the slurry is halted. The pipe string is then rotated from the surface to close port 17. Tubing 32 and the internal structure of the liner hanger and packer assembly are disconnected from the apparatus by further rotation of the string and are withdrawn with the pipe string to the surface. The completed gravel pack and liner assembly are shown in FIGURE 2 of the drawing.

The well may now be placed on production. Sand grains entrained by the producing fluids will be screened out on the gravel pack so that difficulties due to subsidence and other problems are avoided. Any sand particles which pass through the gravel pack into the liner settle through the fluid into the open casing below the producing zone. This reduces the frequency with which the liner must be cleaned out and thus promotes longer well life. If it should be necessary to pull the liner at any time, the shear pin will fail as the liner is pulled, leaving the cup in the hole. The gravel or other particulate material can then be circulated out of the hole with fluid injected at the surface.

It would be apparent from the foregoing that the invention has advantages over methods conventionally employed for the installation of inside gravel packs. Ex perience has shown that the use of the apparatus described is considerably less expensive than the installation of a bridge plug or the use of sand to plug back the well below the producing interval. Difiiculties due to premature bridge plug setting, problems encountered in determining the actual amount of particulate materials required, difficulties due to fill across the producing interval due to sloughing formation sand and similar problems with conversion installation methods are substantially eliminated.

What is claimed is:

1. In apparatus for the installation of a gravel pack in a wellbore including a perforated liner extending below a packer, said liner including perforations for fiow through the gravel pack into said liner, the improvement which comprises:

a tubular mandrel mounted in a fixed position at the lower end of said perforated liner;

a cup packer axially slidable on said mandrel below said liner;

means near the upper end of said mandrel for limiting the upward movement of said cup packer with respect to the mandrel and liner; and

means near the lower end of said mandrel for retaining said cup packer on the mandrel, said means permitting disengagement of said mandrel from said cup packer.

2. Apparatus as defined by claim 1 wherein said mandrel is a separate member attached to the lower end of said liner.

3. Apparatus as defined by claim 1 wherein said means for retaining said cup packer on said mandrel includes a shear pin against which the packer seats in its lowermost position on the mandrel.

4. Apparatus as defined by claim 1 wherein the wall of said mandrel is perforated.

5. Apparatus as defined by claim 1 wherein said cup packer is mounted on a sleeve which slides on said man: drel.

6. Apparatus as defined by claim 1 wherein said mandrel is an integral part of said liner.

References Cited UNITED STATES PATENTS 1,534,960 4/1925 Jones 166--228 2,897,897 8/1959 Breukelman 166-202 3,145,778 8/1964 Grekel et al. 166- 236 3,316,971 5/1967 Brown 166-202 JAMES A. LEPPINK, Primary Examiner.