US3481402A

US3481402A - Cement placement tool and method

Info

Publication number: US3481402A
Application number: US701603A
Authority: US
Inventors: Joseph K Beckett
Original assignee: Gulf Oil Corp
Current assignee: Chevron USA Inc
Priority date: 1968-01-30
Filing date: 1968-01-30
Publication date: 1969-12-02
Anticipated expiration: 1986-12-02

Description

.2, 1969 J. K. BECKETT CEMENT PLACEMENT TOOL AND METHOD Filed Jan. 30, 1968 n w mum w? m m nw HUI.

M VEIVTOA'. 4055 4 BETA/77 United States Patent 3,481,402 CEMENT PLACEMENT TOOL AND METHOD Joseph K. Beckett, Kern City, Calif., assignor to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Jan. 30, 1968, Ser. No. 701,603 Int. Cl. E21b 33/ 13, 43/00 US. Cl. 166-290 12 Claims ABSTRACT OF THE DISCLOSURE Cement is placed at a desired interval in a well for displacement into the surrounding formation by placing the desired volume of a cement slurry in a tubing string closed at its lower end and lowering the tubing string to the desired level in the well. A closure member is secured to the bottom of the tubing string by means of left-hand This invention relates to a method and apparatus for depositing cement or other sealing or plugging material at a desired interval in a well to prevent flow of undesirable fluids into the well.

Frequently excessive amounts of water are produced with oil produced by an oil well. If the water is flowing into the well from isolated intervals penetrated by the well, the difliculty can be remedied by plugging the formation through those intervals. The usual method of plugging isolated intervals has been to lower a dump bailer containing a liquid plugging material such as a slurry of a hydraulic cement, usually Portland cement, suspended from wire line into the well to the depth of the interval to be plugged. After the dump bailer is at the desired level in the well, the bailer is opened to discharge the cement into the well. The cement is forced through perforations in casing, if the well is cased through the interval producing the undesired fluids, or directly into the formation through the interval if the well has been completed with an open hole.

Some difficulty has been encountered in discharging the cement slurry from the dump bailer. One method of overcoming that difiiculty has been to include within the dump explosive charges which are ignited after the bailer is at the desired level in the well. The explosive forces the cement slurry out of the bailer. One of the disadvantages of dump bailers, both of the explosive-discharging type and the ordinary type which does not use an explosive to discharge the cement, is premature discharging of the cement from the bailer. If a bailer having its lower end closed, for example by having a frangible disc or other mechanism actuated by a blow, strikes a liner or other obstruction in the well, the bailer may be unloaded before it has reached the desired level. Moreover, the limited volume of bailers of a size that can be conveniently used requires repeated trips into the well. Frequently discontinuous plugs are formed through the interval to be plugged because of the intermittent type of operation.

This invention resides in a method and apparatus for plugging a selected interval of a well in which a cement slurry or other fluid capable of being forced into the formation at the selected interval to form the desired plug is delivered to the interval to be plugged in tubing having at its lower end a detachably secured closure mem- "ice her. A column of liquid is in the tubing above the cement slurry. The tubing is then disconnected from the closure member at the level to be plugged to allow flow of the plugging material from the tubing. A swab cup on the tubing string just above the connection of the tubing string to the closure member confines the plugging material to the desired interval. The closure member is suspended from the lower end of the tubing after disconnecting to allow the closure member to be withdrawn from the well.

In the drawings:

FIGURE 1 is a diagrammatic side view, partially in vertical section, of the tool used in the method of this invention.

FIGURE 2 is a diagrammatic view of a well as the tool is lowered into the desired location in the well.

FIGURE 3 is a diagrammatic illustration of the tool in place before the plugging material is discharged from the tool.

FIGURE 4 is a vertical sectional view of the well showing the tool at an intermediate position during the discharge of the plugging material.

Referring to FIGURE 1 of the drawing, the tool is illustrated secured to the lower end of a tubing joint 10 by a coupling 12. Coupling 12 is internally threaded for connection to the tubing joint 10 and to a tubing nipple 14. Coupling 12 is also externally threaded on the lower end to receive a downwardly opening swab cup 16.

A lower coupling 18 is internally threaded at its upper end for connection to the lower end of nipple 14. Lower coupling 18 is threaded at its lower end with left-hand threads 20 to receive left-hand threads on a suitable closure member. In the embodiment of the invention illustrated in the drawing, the closure member is a bull plug 22 having a left-hand threaded pin 24 at its upper end for engagement with internal left-hand threads in the lower end of coupling 18.

A belly spring indicated generall by 30 has an upper collar 32 and a lower collar 34 joined by a plurality of bowed strips 35 adapted to engage the borehole wall if the well is completed open-hole, or to engage the casing of a cased well, to prevent rotation of the belly spring when the drill string is rotated. Upper collar 32 is slidable on nipple 14 between the coupling 18 and swab cup 16. Lower coupling 18 serves as a stop limiting downward movement of collar 32 to permit removal from the well of the closure member after it has been disconnected from the lower coupling 18, as hereinafter described. A pin 26 extends transversely through the bull plug 22 and is secured thereto by any suitable means such as welding or a friction fit. Both ends of pin 26 extend outwardly beyond the bull plug 22 and through holes 28 in lower collar 34. Holes 28 have a diameter slightly larger than the diameter of pin 26 to provide a loose fit aiding in alignment of the lefthand threads as the tool is assembled. Collar 34 can be hinged or constructed in two parts that are secured together after placement over the pin 26.

The method and apparatus of this invention will be described for plugging the formation surrounding perforations 36 in the casing 38 of a well illustrated in FIGURES 2, 3 and 4 of the drawing. The perforations 36 are in an interval through which undesired fluids, ordinarily water, flow into the well. .In many instances the perforations may extend without interruption from the water-bearing formation to be plugged into an overlying oil-bearing formation. The tool and method of this invention can be used for setting a plug through such water-bearing intervals as well as through the entire perforated interval. The formation to be plugged may be at any level in the well, but for successful plugging of undesirable fluids without an adverse elfect on the production of desirable fluids, it is preferred that the formation to be plugged be isolated from the formations producing the desired fluids.

The tool is made up as illustrated in FIGURE 1 and connected to the lower joint of a tubing string indicated by reference numeral 40 in FIGURES 3 and 4. Tubing string 40 has a spring-loaded, downwardly opening check valve 42 mounted therein at a level below the level of liquid in the well at the end of the displacement of cement from the tubing string, as illustrated in FIGURE 3. The amount of cement slurry estimated to be required to plug effectively the water-producing interval is placed in the tubing string. Filling can best be accomplished by making up the tool and tubing string up the check valve 42 and lowering the tool into the well as it is made up. The tubing string is filled with cement slurry, the check valve is installed, and the tubing is made up to a length such that its internal volume is equal to the total volume of cement to be displaced into the well. That length of tubing string is lowered into the well as it is made up and then filled with a cement slurry. Making up of the tubing string is then continued and the tubing string run into the well to fix the level of the tool illustrated in FIGURE 1 at the level of perforations 36, as shown in FIGURE 3 of the drawing.

After the lower end of the tubing string is at the desired level, a water or oil column is placed in the tubing string above the cement to a level such that when the cement is discharged from the tubing string the liquid level within the tubing string will be substantially the same as the liquid level in the annulus between the tubing string and the casing.

With the tool at the level shown in FIGURE 3, the tubing string is rotated to the right. The friction of the belly spring 30 against the casing 38 prevents rotation of the belly spring. Engagement of collar 34 with pin 26 prevents rotation of bull plug 22; hence, the bull plug 22 is unscrewed from lower collar 18 on continued rotation of the tubing string. Bull plug 22 is then suspended from the lower end of tubing string by means of the belly spring 30 and the engagement of collar 32 with lower coupling 18 and of collar 34 with pin 26. Upward fiow of the cement slurry through the annulus surrounding tubing string 40 is prevented by swab 16.

After flow of cement from the tubing string has started, the tool is gradually raised to position the swab cup 16 above the uppermost of perforations 36. The column of liquid in the tubing string above the cement slurry forces the cement slurry outwardly into the borehole and through the perforations 36 into the formation. After the cement has equalized, the tubing string is lowered rapidly to provide a vigorous down-swab action. The swab cup 16 increases the pressure forcing the cement into the formation to be plugged without applying additional pressure on the liquid in the annulus overlying the cement; hence, the overlying liquid is not forced through the perforations 36. Upward displacement of the cement slurry through the tubing string 40 during the lowering of the cup is prevented by spring-loaded check valve 42.

At the end of the operation, the liquid level 44 in the annulus between the casing 38 and tubing string 40 will be substantially the same as the liquid level 46 within the tubing string. If desired, liquid can be introduced into the annulus to wash cement from the upper surface of the swab cup and increase the pressure available to force the cement slurry through the perforations 36 into the formation. The tubing string is then pulled from the Well. Engagement of collar 32 with coupling 18 and attachment of collar 34 to bull plug 26 causes the bull plug to be removed from the well with the tubing string.

If the zone to be plugged is contiguous to a potentially oil-producing zone and the perforations continue into the potentially oil-producing zone, the tubing string 40 is raised only to place the swab cup at the upper limit of the zone to be plugged. The swab cup then prevents flow upwardly into the perforations in the oil-producing zone.

Plugging intervals of a well by this invention allows a substantial reduction in the cost of setting a plug as compared with the conventional dump bailer or explosiveoperated discharge bailer technique. This invention is particularly advantageous when large volumes of plugging materials are required to plug the desired interval. A continuous plug can be laid in the hole without potential skips or cavities that occur between runs of sequential small loads. The disconnection of the closure member to allow flow from the tubing string is much less likely to discharge the plugging material prematurely than frangible discs or slide valves in tubing strings or the explosive dump bailer.

This tool and method also eliminate the shortcoming of pumping small plugs into a well with regular surface cementing pump and equipment where the pressure in the formation will not support the hydrostatic head of liquids the full height of the well casing. Those excessive liquid heads will often squeeze the cement out into the formation well beyond desired limits. This tool can place a slurry in any shallow well with any low liquid level without increasing the hydrostatic level in the well excessively. The actual liquid rise need only be that caused by the liquids that are placed inside the tubing for the purpose of assuring proper equalization of the cement slurry.

I claim:

1. A method of plugging a formation penetrated by a well comprising lowering a tubing string in the well to place the lower end of the tubing string at the level of the formation to be plugged, filling the tubing string with the desired volume of a liquid plugging material, disconnecting the lower end of the tubing string, displacing the liquid plugging material from the tubing string at the level of the formation to be plugged, blocking upward flow around the tubing string to direct the plugging material displaced from the tubing string into said formation, and thereafter withdrawing the tubing string and disconnected lower end from the well.

2. A method as set forth in claim 1 in which the plugging material is a slurry of hydraulic cement.

3. A method as set forth in claim 1 in which pressure is applied to the cement in the borehole of the Well but not to liquid overlying the cement to displace the cement into the formation to be plugged.

4. A method as set forth in claim 1 wherein the closure member is connected to the lower-end of the tubing string by a left-hand thread to permit disconnecting the closure rnember from the tubing string, and a downwardly openmg swab cup counted on the lower end of the tubing strlng above the left-hand thread blocks upward fiow through the annulus surrounding the tubing string.

5. A method as set forth in claim 4 including the steps of engaging the wall of the well with means secured to the closure member and turning the tubing string to unscrew the closure member therefrom.

6. A method of plugging a formation penetrated by a well having liquid standing therein above the level of the formation comprising placing the desired volume of a cement slurry in a tubing string closed at its lower end by a closure member, placing a column of liquid of a height locating the upper surface thereof at substantially the level of the liquid in the well at the end of the plugging operation, lowering the tubing string in the well to place its lower end at the level of the formation to be plugged, disconnecting the closure member from the lower end of the tubing string whereby the column of llqllld in the tubing string discharges the cement slurry therefrom.

7. A method as set forth in claim 6 in which upward flow of liquid around the tubing string after disconnecting the closure member is blocked to direct the cement slurry into the formation.

8. A method as set forth in claim 6 in which the tubing string is moved slowly upwardly through the interval to be plugged to the upper limit of the interval after disconnecting the closure member.

9. Apparatus for plugging a formation penetrated by a well with a fluid plugging material comprising a tubing string, a closure member secured to the lower end of the tubing string by a left-hand thread whereby the closure member can be disconnected from the tubing string on rotation of the tubing string to the right, friction means secured to the closure member and adapted to engage the borehole wall, and means connecting the closure member to the tubing string for limiting movement of the closure member apart from the tubing string on disconnection of the closure member from the tubing string.

10. Apparatus as set forth in claim 9 in which a downwardly opening swab cup is mounted on the tubing string near the lower end thereof but above the connection of the closure member to the tubing string.

11. Apparatus as set forth in claim 10 in which a check valve mounted in the tubing string prevents upward flow therethrough.

12. Apparatus for plugging a selected formation penetrated by the borehole of a well comprising a tubing string, a closure member connected to the lower end of the tubing string by a left-hand thread, a collar vertically slidable on the tubing string above the left-hand thread,

stop means limiting downward movement of the collar on the tubing string, outwardly bowed members adapted to engage the wall of the well secured at their lower ends to the closure member and at their upper ends to the collar, and a downwardly opening swab cup mounted on the tubing string adjacent and above the collar adapted to engage the wall of the well to prevent upward flow through the annulus surrounding the tubing string.

References Cited UNITED STATES PATENTS 1,971,514 8/ 1934 Stone 166-124 2,189,445 2/1940 Dale l661 17 2,191,702 2/ 1940 Yowell 166---27 2,493,962 1/ 1950 Gray 166-27 2,671,511 3/1954 Mater 166-226 JAMES A. LEPPINK, Primary Examiner U.S. Cl. X.R. 166166, 226