US2356769A - Washing gravel out of perforate well casings - Google Patents

Description

L. A. LAYNE 2,356,769 WASHING GRAVEL OUT OF PERFORATE WELL CASINGS Aug. 29, 194-4.

Filed Dec. 4, 1939 3-Sheets-Sheet 1 4/]. L AYNE 4 I .INVE TOR.

MM BY (fun 6. Wm.

A TTORNEYS.

L. A. LAYNE Aug. 29, 1944.

WASHING GRAVEL OUT OF PERFORATE WELL CASINGS Filed Dec. 4, 1939 Patented Aug. 29.1944

WELL CASINGS wasnmG GRAVEL our OF rEaFoaa'rE I Leslie A. Layne, Houston, Tex. Application December 4, 1939, Serial No. 307,467

' 12 Claims.

Theinvention relates to a means and method of washing gravel out of perforated well casings so as to increase the filter pack area to eliminate the entrance of sand and to reduce the rate of flowat the edge of the filter pack.

The present invention finds its greatest advantage in that type of formation where very fine sands are encountered because under such circumstances it is often found that where a ,strainer or screen of a fine enough gaugeto exclude the sandi's used that it is impossible to obtain a suitable production through such a fine screen. On the other hand, if a coarse enough screen is used ,to obtain production, the fine sand will enter the screen and the well becomes sanded up in a very short period of time.

The invention also finds its application in existing wells where the casing is anchored in position by having been cemented in place and perforated, and where the well may have been producing for some time. Under the'secircumstances the sand is usually packed tightly about the outside of the cement and around the casing so that the well has stopped producing. It is impossible to underream a formation of this sort because of the presence of the casing andit is therefore one of the objects of the present invention to wash out the casing and the sand outside of the casing so as to form a .cavity which can be filled with granular material which is deposited in the casing and washed outwardly through the perforations in the casing.

It is one of the objects of the invention to form a granular filter pack on both the inside and outside of a perforated-easing which is anchored in a well bore.

Another object of the invention is to deposit granular material in a perforated casing in a well bore and to wash a quantity of such gran ular material outwardly through the perforations in the casing to replace the sand about the casing.

Another object of theinvention is to agitate or churn a body of granular material in a per-' forated casing in a well bore so as to wash it out- 45 vide a method of procedure and the apparatus 50 for forming a double filter pack outside of a per- Fig. 2 is aside elevation withthe equipment arranged ready to begin the washing out of the gravel. i

Fig.3 isa vertical section illustrating an in-! termediate step in the method, wherein the c'av-j ity outside of the casing has been enlarged and almost filled with granular material.

Fig. 4 isya side elevation partly in section,.-

wherein the washing out string has been rev moved and the strainer is about to be washed in.- to position.

Fig. 5 is aside elevation partly in section showing the filter pack as having been completed both inside and outside of the casing and with the-strainer in position.

In Fig. l the well bore is indicated generally at and has been provided witha casing 3 which is anchored in the formation by the cement 4.

' Thisj cement is usually pumped downwardly through the casing leaving a portion 5 thereof in the bottom of the casing to exclude foreign material.

The perforations I may have been formed in the casing in any desired manner so as to admit;

newly drilled and cased well or it may be a well which has been producing for some time. In

either event, the fine sand ill will be closelyad- Jacent the layer ll of cement around the outside of the casingand if it is an old well which is being re-worked the sand III will be closely packed in position because in all probability the well is being reworked because of the fact that the packing of this sand has cut down the production of the oil, gas, or water as the case may be.

forated casing and inside of the casing around a strainertherein. Other and further objects of the invention will be readily apparent when the. following description is considered in connection with the accompanying drawings, wherein:' 4

Fig. 1 is a vertical elevation partly in section,

\ .of the perforated casing anchored in the well bore with the body of gravel therein.

The upper end of the casing 3 carries acasing head I! and a flow line 13 which may be controlled by a valve l4. The casing headl2 has a tapered bowl It in the inner upper end.

A body of granular material I8 is shown as having been deposited inside of the'casing 3 in a sufficient quantity as may have been estimated to be desirable in forming a suitable filter pack, This body of granular material may have been deposited by shovelling it into the top of the casing or it may have been deposited hydraulically, or otherwise, and it will be noted that the granular material is deposited to an elevation above the uppermost perforations I. v

With the granular material in place the equip ment shown in Fig. 2 will be installed, which in- .cludes a closure head 20 which may beheld in place by the bolts 2| and carries a stufiing boxdischargeof liquid in agitating, churning and maintaining a circulation. It is intended that this circulation of liquid will agitate the granular material l8 and cause it to be suspended in the flowof liquid so that the liquid will tend to pass outwardly through the perforations I.

Thisliquid discharging from the perforations I will tend to form a cavity 30 about the casing 2 by washing away some of the fine sand I which was packed about the casing'as seen in Fig. 1. This sand will be picked up by the circulating liquid and asthewashing out pipe 24 is gradually advanced by lowering it in the casing some of the liquid will return through those perforationswhich have been passed by the bit 21 and this returning liquid will carry some-of the fine sand with it upwardly in the well casing to discharge from the flowline l3. Of course, some of the liquid will pass into the porous formation I insome instances.

If'desired the cavity '30 may have been partially or wholly formed by a washing operation prior to the introduction of the granular material I 8 or due to the fact that the well might have produced considerable sand prior to,the reworking operation which woul have left a cavity about the casing.

In any event, it is the intention to 'wash' the granular material l8 outwardly throu h.the perforations to form a filter pack about the outside of the casing. This is desirable because of the fact that a larger diameter filter pack may be in this manner provided. The larger diameter filter pack is of advantage because the velocity of "flow of the fiuid being produced is materially less in, a geometric. proportion to a diameter of th bore .filled with the granular material. A

In this manner the entrance of sand iselimlnated by the large filter pack. In this manner a double filter pack is formed, part of which is on the outside of the casing and part of which remains inside of the casing.

ably by the circulation of liquid to suspend the.

that the packing of the fine sand restricts the production to such an extent that the well may become unprofitable, while on the other hand if a sumciently coarse strainer is placed inthe well to obtain a practical production then the entrance of sand occurs through the strainer to sand up the well and require a clean-out job.

If afllter pack is formed as has been described it seems obvious that it will exclude this fine to be washed into the granular material within thecasing. This strainer string may be washed into position in any desired manner but prefergranular material as the strainer advances.

Fig. 5 shows the strainer 40 after having been washed into position andthe double filter pack in place both on the inside and outside of the casing.

Under some circumstances the formation may be such. that a sufficientfilter pack may be pro-' vided by merely washing out the granular mate rial to form the filter pack outside of the casing and the granular material will then bridge over the perforations and the granular material remaining inside of the casing maybe removed. The well will'thus produce through the gravel pack outside of the casing and the fluid thus produced removed from the well in any desired man- '5 Under other circumstances the producing formation may be such that the gravel pack will be be desirable to place a screen or strainer" adjacent Fig. '3 shows the washing out pipe advanced almost to the bottom .of the casing and the cavity 30 as having been practically filled with granular material so that the washing out'operation is practically complete.

When it is determined that the desired amount oi granular material has been washed out of the pressure is required to maintain the granular .material' inside of the casing in suspension than casing the washing out pipe may be gradually withdrawn while maintaining circulation so as to leave the granular material settled inside of the I casing. This fact may be determined either by the is required when it is being washed out of the tion is the loosening and washing out of the sand .around the casing and the replacing of this sand with granular material which will in the future filter out the fine sands. This is true because it has been found that where a fine sand is encountered and a strainer of a sumciently fine the top of the. filter pack inside of the casingbut above the perforations. v I I A fourth circumstance may require that the strainer be arranged within the gravel pack inside of the casing as has been described in detail above. v

These various arrangements will be adopted and used depending upon thecircumstances encountered, which may vary with the volume of production, the fineness and condition of packand the character of strainer required. v

Attention is directed to the fact that the circulating of the granular material out through the perforations continues the agitation of the material in the cavity 20 outside of the pipe and .that this agitation loosens the sand to assist in its removal and replacement by the granular material. when the granularmaterial settles or is deposited after the circulation is reduced or discontinued, it may be desirable in some instances to pack it in position and this may be accomplished by restricting the discharge through the flow valve l4 so as to apnlypressure to the granular material and force it into any soft spots or cavities which might be present. This causes ing of the sand, the type of ,fluid being produced I the granular material to also pack the particles thereof together more compactly.

. therein so-that the washing out and agitating of gauge to exclude the sand is placed in the well the gravel and the setting of the strainer maybe accomplishedin a single operation. If this proassa'zco cedure is followed it may be desirable to have a smaller diameter wash pipe incorporated inside of the strainer to conduct the agitating liquid to the bottom of the strainer to be discharged from the shoe thereof. j

Broadly, the invention contemplates a method and apparatus for forming a filter pack by washing granular material out through a perforate casing anchored in a well bore. a

What is claimed is:

1. A method of arranging a granular filter about a perforated casing which is anchored in a well bore which comprises the steps of depositing a body of granular material within the casing, running a washing out string into the casing, pumping liquid through said string while lowering the string into the body of granular material in the casing, agitating or churning the material with the'liquid so that the material will be washed out through the perforations in the casing while some of the liquid may pass into the formation and some return to the casing through those perforations which have been passed by the liquid discharge, maintaining such circulation of liquid until the cavity has been washed out as indicated by the sand returning to the surface and the cavity filled with material, withdrawing the washing out pipe while circulating to leave material in the casing, and washing a string of strainer into the granular material in the casing so as to provide a filter Pack about the strainer in the casing and between the formation and the outside of the casing.

2. A method of forming a filter pack of granue lar material inside and outside of an anchored perforated casing in a well bore which comprises washing the well by circulating liquid so as to loosen. sand packed about the outside of the casing, depositing a body oi granular material within the casing, agitating such material with a liqout through the perforations in the casing into the cavity, and washing a strainer into the material remaining in the casing so as to provide a double filter about the strainer.

3. A method of forming a filter pack of granular material inside and outside of an anchored and carry some of the granular material therewith to form a filter pack both on the inside and the outside of said pipe.

6. A method of excluding sands from wells wherethe sand is too fine to be excluded by a strainer through which production of oil may be 6 the inside to the outside of the casing through the perforations, depositing such material about the pipe as a filter, and discontinuing circulation so as to leave a filter pack of granular material inside of the pipe.

8. A method of providinga filter pack about a perforate pipe anchored in a well bore which comprises circulating a. granular material from the inside to the outside of the casing through the perforations, depositingsuch material about the pipe as a filter, discontinuing circulation so as to leave a filter pack of granular material inside of the pipe, and arranging a strainerpipe closely adjacent the top of the inside filter pack to receive the fluid being produced. 7

9. A method of providing a filter pack about a perforate pipe anchored in a well bore which comprises circulating a granular material from the inside to the outside of the casing through 40 uid circulation so as to wash a portion thereof the perforations, depositing such material about the pipeas a filter. discontinuing circulation so as to leave a filter pack of granular material insidepf the pipe, and arranging a strainer pipe out through the perforations in the casing into the cavity to further enlarge the cavity by replacing some of the sand with granular material,

and washing a strainer into the material remaining in the casing so about the strainer.

4. A method of forming a doublefilter pack of granular material in a well bore having a perforated casing therein which comprises depositing a body of such material inside the casing, washing some of the material outwardly through the perforations with an agitating liquid, and washing a strainer into the granular material inside the ca'sing.

5. In the art of reworking existing oil, gas, or water wells where a sand has packed about a perforated string of pipe anchored in the well bore, the steps of depositing a body of granular material in the perforated pipe, agitating the material with a flow of liquid so that the fiow will pass outwardly through the perforations as to provide a double filter closely adjacent the top of the inside filter pack above the perforations in the pipe to receive the V fluid being produced.

10. A method of providing a, filter pack about a perforate pipe anchored in a well bore which comprises circulating a granular material from the inside to the outside of the-casingthrough the perforations, depositing such material about the pipe as a filter, discontinuing circulation so as to leave a filter pack of granular material in- 1 side of the pipe, and arranging a strainer pipe inside of the filter pack within the casing to receive the fluid being produced.

11.- A method of forming a filter pack about a perforate pipe anchored in a ,well bore which comprises agitating a granular material within tie as a double filter pack on the inside and outsi e or the pipe.

. 2. A method of forming a filter pack about a perforate pipe-anchored in a well bore which comprises agitating a granular material within the pipe and conveying a portion of the material through the perforations to the outside of the pipe so as to form a double filter-pack on the inside and outside of the pipe, and packing the deposited material in position by restricting the return of the conveying liquid so as to apply an added pressure to the granular material,

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