Method and apparatus for removing debris from cased wells

March 17, 1970 j. l. burba, jr„ etal 3,500,933

METHOD AND APPARATUS FOR REMOVING DEBRIS FROM CASED WELLS

Filed Aug. 16, 1968

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JOHN L. BURBA, JR. ROBERT 3. RUWYAW

United States Patent Office

3,500,933

Patented Mar. 17, 1970

3,500,933

METHOD AND APPARATUS FOR REMOVING DEBRIS FROM CASED WELLS

John L. Burba, Jr., Monahans, and Robert S. Runyan, Odessa, Tex., assignors to Gulf Oil Corporation, Pitts- 5 burgh, Pa., a corporation of Pennsylvania

Filed Aug. 16,1968, Ser. No. 753,180

Int. Cl. E21b 37/00

U.S. Cl. 166—311 7 Claims

ABSTRACT OF THE DISCLOSURE

A junk catcher for use in completing cased wells to be run on drill pipe comprising a pair of wiper cups to remove clinging particles from the casing wall, and an an- 15 nular junk accumulation space between an inner mud upflow member and an outer cage member.

This invention relates to oil field equipment, and in particular it pertains to method and apparatus for removing debris from fluid filled wells, particularly oil and gas wells, prior to performing other operations in such wells.

During the course of drilling deep wells to petroliferous _2gdeposits, debris, “junk” as it is known in the art, accumulates in the well. As is known, petroleum wells are at all times full of fluid, usually some substance known as “drilling mud” which comprises a wide range of relatively heavy slurries designed to provide a hydrostatic head ₃θ above the pressurized formations which are encountered, lubricate the bit during drilling, carry the cuttings to the surface, and the like.

The junk with which the invention is concerned comprises bits of cement or concrete resulting from destruc- 35 tion by drilling of floats that may have been put in the well for other purposes or from spillage from cementing operations, bits of various kinds of metal resulting from expendable tools and other items left in the well and subsequently ground to pieces, other foreign matter which 40 may have fallen into the well, and other miscellaneous and sundry debris which may have found its way into the well by happenstance.

The pressence of this debris is harmful during completion operations, and other operations requiring that pack- 45 ers be set in the well. The debris described, and particularly the smaller particles, cling to the inside surface of the well casing. Such particles and other accumulated debris interfere with the motion and setting of well packers, resulting in such packers being set prematurely, not 50 setting properly, or being set at an incorrect height, or the like, resulting in a faulty completion possibly requiring that the packers be drilled out of the well.

The present invention comprises a positive action wiper junk catcher which is run on drill pipe or drill tubing. ⁵⁵Prior junk catchers, or junk baskets as they are known in the art, are usually run on a wire line. Generically, wire line operation is preferred to operation on drill pipe or tubing because it is easier to simply drop the wire line or rope into the well than to “make a trip” with tubular ⁶⁰goods. However, it is not possible to push on a wire or rope, and such prior debris or junk catchers suffer from the disadvantage that they cannot positively wipe the inside of well casing to push the junk downwardly so that it is either collected or pushed to the bottom of the well. ⁶⁵By the step of running the apparatus of the invention on tubular goods a positive wiping action in addition to collection of the junk is possible. The increased cost of running the apparatus of the invention on drill pipe rather than on wire line is deemed “bargain price insurance” for 7° a trouble-free completion following the cleaning operation.

Thus, it is an object of the invention to provide a junk basket of the character described which comprises wiping means to clean clinging debris from the casing wall and an annular junk accumulation space surrounding an inner upflow cage member which accomplishes a separation of the junk and the well fluid at its upper end.

In the accompanying drawing forming a part of this disclosure the sole figure is a cross-sectional elevational view of an apparatus embodying the invention shown in place in a fluid and debris filled well.

Referring now in detail to the drawing, 10 designates a petroleum well which has already been cased by well casing 12 in the usual manner. As is known to those skilled in the art, petroliferous wells are lined or cased with metal pipe known as well casing . The casing serves the function of preventing cave-ins of incompetent formations that the well may have been drilled through, and facilitates completion of wells since, by perforating the casing, a high degree of control of the amount of product that will be produced is obtained. In any event, the method and apparatus of the invention is suitable for use with cased wells only, and not with the so-called “open hole” completions wherein the formation is so firm and other conditions are just right that casing is not required.

The entire length of the inside of casing 12 is filled with a fluid 14, which is usually drilling mud. Partly entrained in mud 14 and partly adhered to the inside surface of casing 12 are a plurality of particles 16 which constitute the debris which is to be removed. These particles may be bits of formation, bits of metal, bits of cement or concrete, and other sundry foreign matter. Located in the well is a casing wiping and junk accumulating apparatus or tool 18 embodying the invention.

lunk catcher 18 is mounted and moved up and down in the well on the lower end of a string of well tubular goods 20 which may comprise drill pipe, drill tubing, or other well tubular goods, dependent upon the diameter required and other factors known to those skilled in the art.

Junk catcher 18 comprises a top adapter or sub 22 comprising a top end internal thread 24 which cooperates with the male thread or pin at the lower end of the drill pipe 20. At its lower end, top member 22 comprises a depending flange 26 formed with external threads which cooperate with mating internal threads on an outer cage member 28.

Outer cage 28 makes up the bulk of the length of junk catcher 18. For example, in a tool sized for 4½ to 7 inch I.D. (inside diameter) casing, the overall length of the tool will be about 13 feet, 7 inches and the length of the outer cage will be about 10 feet. In a tool sized for 7¾ to 13¾ inch I.D. casing, the overall length of the tool will be about 14 feet 5 inches and the length of the outer cage will be about 10 feet.

At spaced locations along the length of outer cage 28 the wall thereof is formed with a plurality of sets of slots 30 each having a width which is predetermined to allow free passage of the drilling mud and to restrain passage of debris 16 therethrough. At its lower end, cage 28 is formed with internal threads 32 which mesh with mating external threads on the upper end of a mandrel member 34. Mandrel 34 comprises a top block portion 36 formed with an upstanding annular flange 38, which on its outside surface has threads cooperating with threads 32 and which on its inside surface is formed with threads 40 which cooperate with mating threads formed on the lower end of a trap valve pipe assembly 42, described below. The lower end of top block 36 is formed with a shoulder 44, at the radial inside portion of which is a depending mandrel sleeve 46 formed with external threads 48 at its lower end. Threadedly mounted on threads 48 is a hollow nose piece 50, which serves to guide the tool.

Means are provided to wipe the debris which clings

3,500,933 ³ :o the inside of casing 12 off of the casing and into the frilling mud 14, and to cause the mud carrying this loosened debris and the remaining debris 16 already suspended in the mud into the inside of tool 18. To this :nd. a wiper assembly is mounted on mandrel sleeve 46 md is held in place thereon between shoulder 44 and ;he top of nose piece 50. The wiper means comprises a jauge ring 52 seated on the top surface of the nose piece which serves to check the casing size for later packer □perations. Seated on the upper surface of ring 52 and plosely fitting about mandrel sleeve 46 is a lower spacer sleeve 54 having an upper thinned neck portion 56. The inside diameter of sleeve 54 is dimensioned so that it fits snugly about the outside diameter of sleeve 46. Mounted □n lower spacer sleeve neck 56 is a lower wiper cup 58 which is held in position on the slight shoulder formed petween neck 56 and the body of spacer 54 by a lower viper cup mounting thimble 60. Mounted above lower :himble 60 is an upper spacer sleeve 62 formed with an jpper thinned neck 64. In a manner similar to the lower sup described above, an upper wiper cup 66 is held in place on the upper neck 64 by means of an upper thimble 58.

The wiper cups 58 and 66 are instrumental in achievng the advantages of the invention in that, as the tool is pushed downwardly through casing 12 the lower edges if said cups clean the clinging debris off of the casing. Additionally, the use of such cups impart substantial /ersatility to a tool embodying the invention in that, vithin ranges, by using differing sized cups the same tool pan be used for different sized casing. The cups are commercially available items, one supplier being Guiberson Division of Dresser Industries, Inc., which supplies the pups under the name of “packer cups,” their type GW. The cups are made of wire and rubber. Another advan;age is that the cups are relatively inexpensive items, are easily replaced and they absorb most of the abuse that :he tool is subjected to in cleaning a well. By removal of :he nose piece 50, the two spacer sleeves and the two humbles, the cups are quickly and easily renewed at minimal cost, thus renewing the entire tool.

Means are provided to permit passage of the drilling fuid through the tool while trapping the debris which inters through the bottom open end of the mandrel sleeve 46. To this end, the lower end of valve pipe assembly 42, briefly mentioned above, fits into the inside hreaded opening on upstanding flange 38 of mandrel 34 within outer cage 28 to a height thereon spaced somewhat below the upper end of said cage. The lower end □f the trap valve assembly is formed with threads which cooperate with threads 40, and with an upset shoulder 70 to butt against the bottom of the mandrel flange. The main body 72 of trap valve 42 is formed with one or more sets of elongated slots 74 each having a width, similar to slots 30, which will permit passage of the well fluid therethrough while small enough to not permit passage of debris therethrough. In one of the successfully built embodiments of the invention designed for use in 4½ to 7 inch I.D. casing, slots 30 had a width of about y_in of an inch and slots 74 had a width of about Vs of an inch, with 3 sets of 6 slots each being provided in the □uter cage 28 and 1 set of 6 slots being provided in the trap valve body 72. At its upper end, valve body 72 is formed with a thickened end 76 comprising an upstanding bifurcated lug 78 to which is hingedly mounted a flapper valve 80 by means of a hinge pin 82.

OPERATION

Tool 18 is first mounted on the drill string 20 at the surface in the normal manner. Tool 18 is then run into the fluid and debris filled well as additional lengths or stands of drill pipe are added to make up the string of drill pipe or other tubular goods. As the tool 18 moves downwardly into the well under the influence of the weight of the string of tubular goods, the outer edges of the two cups 58 and 66 wipe the entire inside of the casing and urge the debris that was clinging thereto downwardly. All the fluid in the well with the loosened and entrained debris 16 therein will enter the bottom open end of the mandrel sleeve 46 and pass upwardly therethrough, taking a path through the entire length of the mandrel 34 and then through the entire length of the trap valve assembly 42. The speed of passage of the mud with the entrained junk upwardly through the trap valve 42 will be substantially greater than the downward speed of passage of the tool 18 through the well because of the decreased cross-sectional area of the trap valve body 72 with respect to the substantially larger cross-sectional area of both the outer cage 28 and the casing 12. This increased speed of flow through the innermost part of the tool tends to keep the particles 16 in suspension in the mud. The mud flowing through the tool finally flows upwardly out of the top thickened end 76 of the trap valve, lifting the flapper valve 80 upwardly by its momentum. Upon exiting from said upper end 76, the speed of the debris laden fluid is suddenly decreased because it suddenly encounters a larger cross-sectional area, namely the inside of the outer cage 28. This sudden decrease in velocity, coupled with the relatively high upward velocity of the debris laden fluid which is about to pass by the flapper valve, causes the debris 16 to fall downwardly under the combined influence of gravity and the overall downward velocity of the tool through the well. The debris collects in the annular space between the outer cage 28 and the trap valve body 72 starting at the top of the upstanding flange 38 of the mandrel 34. Another advantage is that substantially only debris collects in the annular space. Thus, the well fluid does not have to filter through the accumulated debris which could cause clogging of the tool and difficult operation. A separation occurs at flapper valve 80, the debris dropping into the annular space and the bulk of the well fluid continuing upwardly in the outer cage 28, out through the slots therein, and back to the well.

During this entire stage of debris collection, the well fluid 14 only, and not the debris, was able to flow out of the nested members 42 and 28 through the sets of slots 74 and 30 so as to not create excessive back pressures within the tool during its downward passage. Thus, the slots serve as a pressure equalizer of fluid above and below the moving sealing means 58 and 66.

After the tool has been lowered to a depth well below the depth at which the well is to be perforated or otherwise completed, it is simply removed from the well by taking apart the string of tubular goods in a normal manner, thereby pulling the tool upwardly outwardly. During this upward passage through the well, the now cleansed well fluid will pass rapidly through the sets of slots 30 and 74 and through the tool, thus equalizing pressure from above to below the moving sealing means 66 and 58.

After a cleaning operation is completed, and the tool is back on the surface, the accumulated debris is removed by simply opening the threaded connection between the lower end of the outer cage 28 and the outside of the upstanding mandrel flange 38. In the event a great deal of relatively sharp debris was removed and a visual inspection indicates that cup renewal is required, the operator simply removes nose piece 5® and gauge ring 52, the two spacers, the two thimbles, and the worn wiper cups, renews the wiper cups and re-assembles. As is obvious, the entire cleaning, and even the renewal operation if necessary, can be simply carried out on site by relatively unskilled persons.

While the invention has been described in some detail above, it? is to be understood that this detailed description is by way of example only, and the protection granted is to be limited only within the spirit of the invention and the scope of the following claims.

3,500,933