US2215913A - Method and apparatus for operating wells - Google Patents

Description

Y Sept. 24, y R l. BROWN METHOD AND APPARATUS-.FOR OPERATING WELLS Filed Oct. 4. 1938 393 Hg@ F155 F16 Patented Sept. 24, 1940 UNITED STATES PATENT OFFICE Richard I. Brown, Los Angeles, Calif., assignor to Standard Oil Company of California, San Francisco, Califv, a corporation of Delaware Application October 4, 1938, Serial No. 233,257

21 Claims.

This invention relates to apparatus and method for casing and completing wells, such as oil and gas wells.

In many instances a. well, such as an oil or gas well. penetrates more than one productive zone. One of the major diiculties in-using a single oil well to produce simultaneously from a plurality of productive zones is that the productive zones are usually separated by zones containing water.

It is necessary in such instances to seal such last mentioned zones to prevent the communication of such water to the upper and lower* productive zones. The diiculties of producing from more than one productive zone simultaneously are such that in many instances no eiort is made to produce from other than the lowest productive zone. In such cases, the necessary surface, water and oil strings are placed in the well to the deepest productive zone, and the upper productive and unproductive zones are cemented o.

One method of producing from more than one productive zone is to run casing from the top of the well to its bottom and to endeavor to obtain the necessary water shut-offs by cementing of the string in the well. When such cement jobs have been completed the casing opposite the productive zones is gun-perforated. One of the disadvantages of such'method is that it is difcult thereby to obtain adequate and satisfactoryperforationsV to permit the productive zone to produce in quantities approaching its maximum capacity, by reason of the fact that a large portion of the zones face is blocked by cement or blank portions of the oil string.

'I'his invention comprehends broadly an arrangement of alternate sections of casing, usually of a hard material such as steel at points opposite unproductive zones, and of a softer .drillable material at points opposite the zones 40 from which production is desired, together with a mode of supporting these sections in spaced relation during their introduction and cementing, followed by a selective removal of one cr more of the drillable sections to produce the oil or gas from the desired zones or strata.

It is an object of this invention to provide a simple and expedient apparatus and method for multi-zone production.

Another object of this invention is to provide a convenient method in a multiple zone well of opening the productive zones to the well and blocking the non-productive zones or zones from which production is not desired.

.Another object of this invention is to increase -Y the flow of iiuid from zones from which production is desired.

These and other objects and advantages will be more fully apparent from the following description and from the accompanying drawing which form a part of this specification and illustrate a preferred embodiment of this invention.

In the drawing:

Figure 1 represents a vertical and part sectional `view of a Well showing location of the oil string with respect to various strata.

Figure 2 is a vertical sectional view of the well of Figure 1, wherein the soft or drillable casing has been removed opposite the zones from which production is desired.

Figure 3 is a vertical sectional View of an oil string illustrating a variation of the means for supporting and removing the drillable sections of Figure 1.

Figure 4 is a vertical sectional view of an uncemented oil string illustrating a further variation of the method partially illustrated in Figures 1 and 3, in which the drillable sections are reinforced during their insertion into the well bore.

Figure 5 represents a Vertical sectional View of an uncemented oil string showing a further variation of the general method partially shown in Figures 1 and 3, in which the drillable sections are entirely omitted.

Figure 6 is a vertical sectional view of a cemented oil string with a perforated secondary liner illustrating an advanced stage of the general method illustrated in Figures 1, 3 and 5, especially in combination vwith the stage illustrated in Figure 2.

In the drawing: Figure 1 indicates a fragmentary portion of a string of casing'in an oil or gas well. Such portion, being that which penetrates the producing zones, is known in the art as the oil string, to differentiate it from the upper, water and surface strings. The oil strings shown in Figures l, 2, 3, 4 and 5, being the outer oil strings, will be called primary oil strings to differentiate them from an oil string within such primary oil string, herein called a secondary oil string, as shown in Figure 6.

The well is indicated as passing through si'x different strata, zones, or formations, 2, 3, 4, 5, 6, l. Strata 2, 4 and 6 are non-productive strata, or strata from which production is not desired. Formations 3, 5 and 'l are formations from which production is desired.

The casing is shown to be secured in the hole by the cement 8, which may be introduced by any conventional method. The primary oil string in 55 the drawing is shown to comprise a number of divisions equal to the number of strata. Such divisions of the primary oil string are 9, IU, I I, I2, I3 and I4. Each such division of casing is composed of one or more joints or sections of casing not individually shown in the drawing, suicient to give each division the desired length.

The divisions of the primary oil string, 9, I I', I3, opposite the portions of the well which are nonproductive, are made up of sections of normal oil well casing.

The divisions of the primary oil string, I0, I2 and I4, opposite the portions of the well from which production is desired, are made up of sections of drillable casing, which may be an aluminum alloy or the like as will be discussed in greater detail below.

All the sections of the primary oil string are joined in normal fashion such as by threads or by weldings, not shown in the drawing.

Referring to Figure 1 of the drawing, the location and depth of the productive and non-productive intervals being known, the primary oil string I is run into the well hole in such manner that sections I0, I2 and I4 of such oil string face productive intervals 3, 5 and 1, and sections 9, II and I3 of the oil string face non-productive intervals 2, 4 and 6.

As shown in Figure 1, all lengths of the primary oil string are of the same diameter. However, the sections of such string 9, II and I3, opposite non-productive intervals 2, 4 and 6, are normal casing, but the sections of thev string I0, I2 and I4, opposite productive intervals 3, 5 and 1, are made of softer, drillable casing.

After the primary oilstring has been cemented in the well hole by any desired method, during which the primary oil string may be moved to prevent channeling of the cement, and after the cement has set, the drillable sections of the primary oil string are removed by any desired method. Such removal may be accomplished by van under-reamer, explosives, abrasives, or chemicals, for instance. Wherethe sections of the normal and drillable casing are of the same size as shown in Figure 1, an expansion type drilling tool may be used to drill up the drillable pipe. In that portion of the hole from which the drillable pipe has been removed, the cement, mud and other undesired substances are then also removed, by any desired method, such as wallscraping or under-reaming.

This results in a well having normal casing cemented opposite the sections of the well which are unproductive, or from which it is not desired to produce, and no casing opposite the zones from which it is intended to produce oil or gas or other desired substances.

Figure 2 illustrates the appearance of the well and casing after the well has been completed as described under Figure 1. The drillable sections I0, l2, I4 have been removed and the cement and mud formerly surrounding such drillable Sections have also been removed. The sections of normal casing, 9, II and I3 remain in place, surrounded by cement to hold such sections in place and to prevent flow of undesired substances from the strata 2, 4 and E.

Figure 3 shows a modification of the method and apparatus illustrated in Figures 1 and 2. As shown in Figure 3, the softer drillable sections I5, I6 and I1 of the primary oil string are of smaller diameter than the normal casing 9, II and I3 opposite the intervals desired to be excluded. This reduction of the size of the drillable Casing.

which may be accomplished by any desired method, as by use of drillable reducers, has numerous advantages, the most important of which is that it facilitates the removal of such drillable casing. The method of disposing of the drillable pipe I5, I6 and I1, as illustrated in Figure 3,

may be accomplished by use of a bit small enough, even in its expanded, operable condition, to pass freely through the normal casing sec-1 tions 9, II and I3. When the bit, with a diam eter slightly smaller than the diameter of the normal casing 9, II and I3 strikes, the sections of the smaller-sized drillable casing, its cutting, drilling eect will be operative. Except for the smaller diameter of the drillable casing the method illustrated by Figure 3 operates in much the same manner as that illustrated in Figure 1. When the drillable sections I5, I6 and I1 and the cement surrounding them are removed the appearance of the well, as completed, is similar to that shown in Figure 2.

Figure 4 illustrates a variation of the method and apparatus shown in Figures 1 and 3. Drillable casing, such as is indicated for use in strata, 3, 5 and 'I is obtainable with remarkable tensile strength. However, in some instances where the depth of the well hole between the rst section of drillable casing and the last is considerable,

the tension placed upon such sections of drillable casing is such that the safety factor in tension is lower than a desired value. In such cases the safety factor may be raised by suitably fastening an inner, hard wash pipe I8 inside of the primary oil string, preferably running from above the topmost section of drillable casing to below the bottom-most section of drillable casing. The tension of such division of the oil string is then partially carried by the wash pipe.

In Figure 4 the wash pipe is indicated by I8 and is shown connected with the primary oil string by appropriate means at I9 and 20. 'I'he sections of normal hard casing are indicated, as in Figures 1, 2 and 3, by 9, II and I3, and the sections of drillable casing by I0, I2 and I4 as in Figure 1.

In the embodiment here shown in Figure 4, the sections of drillable casing, I0, I2 and I4, are of the same diameter as the sections of normal hard casing, 9, II and I3. However, the use of smaller diameter drillable casing, as shwn in Figure 3, may also be used in conjunction with the use of the reinforcing wash pipe.

In addition to reinforcing the oil string in tension, the wash pipe I9 may also permit the circulation of uids through it.

After the primary oil string has been emplaced, as shown in Figure 4, from the lowest producing zone to above the highest, the string may be cemented in any desired manner. When the cement has hardened suiciently, the wash pipe may be separated from the attachments I9 and 20 and removed from the well. When this has been accomplished, the drillable sections of the string IIJ, I2 and I4 and the cement and mud surrounding them may all be removed as described under Figure 1, and the appearance of the treated portion of the well will lthen be as shown in Figure 2. As used herein, by the term wash pipe is meant a string or section of pipe or casing of smaller diameter than the primary oil string placed and fastened longitudinally within the primary oil string assembly.

Referring to Figure 5, as in Figures 1, 2, 3 and 4, strata 3, 5 and 1 are strata from which production is desired, and strata 2, 4 and 'Ii are strata which are desired to be shut off from the well. In Figure 5, sections of normal hard casing, S, I I and I3, are suitably fastened by connections 2|, 22, 23, 24 and 25, at predetermined intervals,

' on sections of smaller diameter wash pipe i8.

After the well hole has been drilled the wash pipe, with the sections of normal hard casing suitably fastened, as above described, are run into the well in such manner that the sections of normal casing 9, II and I3 are opposite the strata desired to be excluded, and the strata from which production is desired' 3, 5 and 1 are bare. Figure shows such assembly before the sections of normal casing 9, II and I3 have been cemented. At such stage, as in the similar stage shown in Figure 4, the iow of substances from productive zones is precluded 'by the hydrostatic pressure of uidsin the well, not shown in Figures 4 and 5.

The sections of normal casing 9, and I3 are then cemented in any desired manner, as by the forcing of cement down the wash pipe, out at the bottom and up the well above 9. When the cement has hardened the wash pipe may be cut free from its fastenings and removed from the well or it may be drilled up. The cement and mud opposite the strata 3, 5 and 1, from which it is desired to produce, are then drilled out. When this has been accomplished the appearance of the well is essentially the same as represented in Figure 2.

Figure 6 illustrates a variation of the apparatus and method disclosed in Figures 1, 2, 3, 4 and 5. When the well has been completed by using any or all, or combinations of, the processes and ap# paratus shown in Figures 1, 2, 3, 4, and 5, so that the appearance of the well at such stage is essentially that shown in Figure 2, there may be placed in the well a string of smaller diameter casing 35 containing appropriately spaced perforated portions 21, 29 and 3| and appropriately spaced blank sections 26, 28 and 30. This inner string of smaller diameter casing 35, which may be called the secondary oil string, is held in place by any appropriate means, as by an appropriate base, and by the packers 32,33 and 34, which packers 32, 33 and 34 also serve the function of preventing the passage of substances through the annulus between the sections of normal casing 9, II and I3 and the secondary oil string 35. The perforated portions 21, 29 and 3| of the secondary oil string 35 permit the ow of substances into the secondary string 35 and up the well.

Packers and other devices may be placed inside the blank sections 25, 28 and 30 of the secondary oil string to govern or'control the production from the various zones or portions of zones. Thus, a packer placed inside of the blank section 28 of the secondary oil string could, when desired, preclude production from strata-5 and 1, entirely or in part.

In the event it is desired to shut off any productive strata by reason, for instance, of encroaching water or undesirably largevolumes of gas, blank pipe with a diameter smaller than that of the secondary oil string 35 ma'y be placed opposite the strata to be shut o, and may be held there by packers suitably placed to prevent fluid from said strata from having access to the well, or said blank pipe with smaller diameter may be cemented into place, to prevent ilow from the productive stratum desired to be excluded. Such method of shutting oif productive strata may be adopted either in the embodiment shown4 in Figure 6 or in Figures l, Z, 3, 4 and 5.

The secondary oil string may be made of drillable material or of ordinary steel pipe. 'Ihe use of the drillable material here has the advantage that if the perforated portions 21, 23 and 3| become clogged with sand they may be drilled out and the portions of the Well adjacent to them be cleaned and scraped before operations are resumed, after having replaced the secondary liner. Or if productive strata 3, 5 and 1 cease to be productive, the secondary oil string may be drilled up and operations carried to lower productive horizons.

Where reference is made herein to normal casing there is meant the type of casing normally used in oil wells, such as Wrought iron, welded and seamless steel casing. While such casing is drillable to some extent, by drillable casing as usedherein is meant casing and oil string parts which are readily and easily drilled. Such alloy material is now available to the oil industry. It has high tensile strength and bursting pressures and its resistance to collapse, corrosion and abrasion compares favorably with common steel casing. Inasmuch as the specic gravity of such alloy drillable casing is approximately the same as shale, when it is drilled up the cuttings are carried away by the circulating ulds. Drillable casing is obtainable which can be drilled up as rapidly as twenty-five feet per hour. By drillable casing, therefore, is meant casing which, as distinguished from ordinary steel casing, is readily drillable and yet possessed of the characteristics necessary to perform its functions.

Drillable casing and oil well equipment of the nature described above is now obtainable in desired shapes and sizes composed of aluminum alloys. One such alloy suitable for manufacture of drillable oil well casing is composed of 0.7% silicon, 1.3% magnesium, 0.25% chromium, and the remainder of aluminum and aluminums normal impurities. Aluminum alloy of such composition is obtainable with the following characteristics:

Specic gravity 2.69 Weight, lbs. per cu. in 0.097 Thermal conductivity at 100 C., C. G.

S. units .37 Average coefficient of thermal expansion per degree Fahrenheit:

(5S-212 F 0.0000130 68-392" F 0.0000136 68-572 F 0.0000141 Elongation--percent in 2 inch round specimen 0.505 in. diam 20 Hardness, Brinell 500 kg. 10 mm. ball 80 Shearing strength, lbs./in 26,000 Endurance limit, lbs/sq. in 11,000

Yield Tensile Elongation Temps., F. strength, strength, in 2 inches,

. q. in lb./sq. in. percent While the methods and apparatus for casing and completing wells herein described are well adapted to carry out the objects of the invention, it is understood that various modifications and changes may be made without departing from the invention, and the invention includes all such modifications and changes which come within the scope of the appended claims.

I claim:

1. A method of operating a well comprising lowering into the well a string of casing made up of sections of normal casing and sections of drillable casing of smaller diameter than the normal casing, so that the sections of normal casing are substantially opposite portions of the well from which no production is desired and the sections of drillable casing of smaller diameter are substantially opposite portions of the well from which production is desired, cementing such string of casing in the well, drilling away the sections of drillable casing from portions of the well from which production is desired, and baring the surfaces of the portions of the well from which the drillable casing has been removed and from which production is desired.

2. A method of operating a well comprising lowering into the Well a string of casing made up of sections of normal casing and sections of drillable casing of smaller diameter than the normal casing, so that the sections of normal casing are substantially opposite portions of the well from which no production is desired and the sections of drillable casing of smaller diameter are substantially opposite portions of the well from which production is desired, cementing such string of casing in the well, drilling away the sections of drillable casing from portions of the well from which production is desired, baring the surfaces of the portions of the well from which the drillable casing has been removed and from which production is desired1 and lowering through the remaining sections of normal casing a perforated inner string seated opposite portions of the well from which production is desired.

3. A method of operating a well comprising lowering into the well a string of casing made up of sections of normal casing and sections of drillable casing so that the sections of normal casing are substantially opposite portions of the well from which no production is desired and the sections of drillable casing aresubstantially opposite portions of the well from which production is desired, securing a wash pipe insidesaid casing string, said wash pipe extending throughout the drillable sections and secured to said normal casing above and below said drillable sections, cementing said casing, in the well, removing said Wash pipe from the well and drilling sections of drillable casing from portions of the well from which production is desired and baring the surfaces of the'portions of the well from which the drillable casing has been removed and from which production is desired.

4. A method of operating`a well comprising lowering into the well a string of casing made up of sections of normal casing and sections of drillable casing so that the sections of normal casing are substantially opposite portions of the v well from which no production is desired and the sections of drillable casing are substantially opposite portions of the well from which production is desired, securing a wash pipe inside said casing string, said wash pipe extending throughout the drillable sections and secured to said normal casing above and below said drillable sections, ce menting said casing in the well, removing said wash pipe from the well and drilling sections of drillable casing from portions of the well from which production is desired, baring the surfaces of the portions of the well from which the drillable casing has been removed and from which production is desired, and lowering through the remaining sections of normal casing a perforated inner string seated opposite portions of the well from which production is desired.

5. A method of operating a well comprising lowering into the well spaced apart sections of casing secured to a string of pipe of smaller diameter within said-sections of casing, said sections of casing being so spaced apart on said pipe of smaller diameter that they come to rest substantially opposite portions of the well from which no production is desired, cementing such sections of casing in such positions, removing said pipe of smaller diameter, and baring the surfaces of the portions of the well from which production is desired.

6. A method of operating a well comprising lowering into the well spaced apart sections of casing secured to a string of pipe of smaller diameter within said sections of casing, said sections of casing being so spaced apart on said pipe of smaller diameter that they come to rest substantially opposite portions of the Well from which no production is desired, cementing. such sections of casing in such positions, removing said pipe of smaller diameter, baring the surfaces of the portions of the well from which production is desired, and lowering through the remaining sections of' normal casing a perforated inner string seated opposite portions of the well from which production is desired.

7. The method of operating a well which penetrates spaced productive strata which includes assembling in spaced relationship sections of normal casing, holding said sections by readily removable means of smaller diameter than said sections in such spaced relationship that they will be positioned in the well between the productive strata, positioning the assembly in the well and removing the readily removable means.

8. The method of operating a well which penetrates spaced productive strata which includes assembling in spaced relationship sections of normal casing, holding said sections by readily removable means of smaller diameter than said sections in such spaced relationship that they will be positioned in the well between the productive strata, positioning the assembly in the well, cementing the normal casing sections in place between the productive strata, and removing the readily removable means.

9. Casing adapted to be used in wells comprising spaced sections of normal casing and readily removable means holding the normal casing sections in assembled relation, said readily removable means being of smaller diameter than the normal casing sections.

10. Casing adapted to be used in wells comprising spaced sections of normal casing and readily removable casing sections connecting the normal casing sections. said readily removable casing sections being of smaller diameter than the normal casing sections.

l1. A casing for use in wells comprising spaced sections of normal casing, intervening sections formed of readily removable material, and readily removable means extending longitudinally through the sections and connected thereto for holding said sections in assembled relation and against parting.

12. A casing for use in wells comprising spaced sections of normal casing, intervening sections -formed of readily removable material, and av readily removable wash pipe v extending longitudinmy through the sections and connected thereto necting the sections of normal casing to said readily removable means to hold the sections in proper spaced relationship thereon.

14. A casing for use in wells comprising spaced sections of normal casing, a readily removable wash pipe extending therethrough, and means connecting the sections of normal casing to said readily removable wash pipe to hold the sections I in properly spaced relationship thereon.

l5. The method of operating a. well which penetrates a plurality of productive strata which includes assembling spaced sections of normal casing and one or more intervening sections of readily removable casing, holding the sections of normal casing against' separation by readily removable means extending-through the sections, lowering the assembly into a well to position the intervening sections opposite productive strata, and removing the readily removable sections and said readily removable means.

16. The method of operating a well which penetrates a plurality of productive strata which includes assembling spaced sections of normal casing and one or more intervening sections of readily removable casing, holding the sections of normal casing against separation by readily removable means extending through the sections,

lowering the assembly into a well to position the intervening sections opposite productive strata, cementing the normal casing sections in place, and removing the readily removable sections and said readily removable means.

17. The method of operating a well which vpenetrates av plurality of productive strata which -includes mounting a plurality of sections of normal casing in spaced relation on a readily removable wash pipe, lowering the wash pipe and sections into a well and positioning the normal casing sections between productive strata.

` 18. The method of operating a well which penetrates a plurality of productive strata which includes mounting a plurality of sections of normal casing in spaced relation on a readily removable Wash pipe', lowering the wash pipe and sections into a well and positioning the normal casing sections between productive strata, and removing the wash pipe.

19. The method of operating a Well which penetrates a plurality of productive strata which includes mounting a plurality of sections of normal casing in spaced relation on a readily removableV wash pipe, lowering the wash pipe and sections into a well and positioning the normal casing sections between'productive strata, cementing the sections of normal casing in place and removing the wash pipe. 20. The method of operating a well which includes assembling sections of normal casing with sections of readily removable casing, positioning the assembled casings in the Well so that the sections of readily removable casing will be opposite one or more productive strata, and removing the removable sections by means of explosives leaving the normal casing sections in the well.

21. The method of operating a well which includes assembling sections of normal casing withA sections of readily removable casing, positioningthe assembled sections in the well so that the sections of readily' removable casing will be opposite one or more productive strata, cementing the normal casing sections in place, and removing by means of explosives the readily removable casing sections leaving the normal casing sections in the well. j

RICHARD I. BROWN.

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