US2607422A

US2607422A - Method and apparatus for suspending pipe in boreholes

Info

Publication number: US2607422A
Application number: US63406A
Authority: US
Inventors: Mercer H Parks; Marvin R Jones
Original assignee: Standard Oil Development Co
Current assignee: Standard Oil Development Co
Priority date: 1948-12-03
Filing date: 1948-12-03
Publication date: 1952-08-19
Anticipated expiration: 1969-08-19

Description

Aug. 19, 1952 M. H. PARKS ET AL METHOD AND APPARATUS FOR SUSPENDING PIPE IN BOREHOLES 2 SHEETS ISHEET 1 Filed Dec. 3, 1948 OMPETENT F0 RMATION SURFAOE CASING 5 WEL L TUBING DERRICK FLOOR PRODUCING SAND 'Aug. 19, 1952 M; H. PARKS ET AL 2,607,422

METHOD AND APPARATUS FoR-susPENDmc PIPE IN BOREE-IOLES Filed Dec s, 1948 2 SHEETSSHEET 2 4,4 lllllf'l 7 mvsrons.

' EERT FIG. 2.

Patented Aug. 19, 1952 METHOD ANDAPPARATUS'FOR SUSPEND- ING PIPE IN BOREHOLES Mercer H. Parks and Marvin R). Jones, Houston,

Tex,

assignors, by mesne assignments, to

Standard Oil Development Company, Elizabeth, 7 N. J., a corporation of Delaware Application December 3, 1948, Serial No. 63,406

reclai s.

This invention relates to new and usefulimprovements in methods and apparatus for suspending andsupporting tubular conductors, such as pipe, within a borehole.

The invention relates particularly to av method and means for suspending well casing or the like in well bores which initially penetrate ortravers'e an incompetent strata or formation having insuificient mechanical strength to support the weight of the pipe in the borehole;

In the drilling of wells for-oil,'"gas and other fluids, it is the general practice to employ casing or pipe to line the walls of the borehole for protection against caving formations, saltwater formation throughout its entire contact with said formation. e

A casing head is mounted on the upper end of the surface casing above the ground level and the first inner string of casing is run therethrough with its lower end extending a considerable distance below the outer casing, this lower end being cemented in place. Through the usual hanger arrangement within the outer casing head, the inner casing string is suspended, whereby the weight of the inner casing is transferred through the casing head to the outer casing and then through said outer casing to the sub-surface formation withinwhich said outer casing is anchored. The required number of inner casing strings, which vary according to the depth of the particular well, as well as the well tubing through which the well fluids are ultimately produced upon completion ofthe well, are progressively run in and suspended by the usual casing and tubing headarrangements. Each inner string has its weight transferred through the casing or tubing" head arrangement to the outer surface casing and through said casing to the subsurface'formation within which the outer casing is anchored The point of suspension or support for the various inner strings is at the surface usuallyjust below the derrick floor.

So long as the sub-surface'formationextending downwardly from the earths surface .and

2 e within which the outer casing is firmly anchored, is of sufficient strength to give the casing'adee quate lateral support, said casing is capable of bearing the weight of the various and relatively long inner strings of pipe or casing, and suspending or supporting the upper ends of the inner strings at a point adjacent to the derrick-floor at the upper end of the surface casing is satisfactory. In other words, if the formationlimmediately below the earths surface .is 'a competent one andcapable of imparting sufficient lateral support to the outer surface casing, the transfer of the weight of the inner strings of pipe through the usual casing and tubing head arrangements above the earths surface may be effectively carried out. :1-

However, in the drilling of wells at'sea or off:- shore, such as on the continental shelf in. the Gulf of Mexico, off coastal Louisiana and Texas, the initial sub-surface formation at the ocean floor which isencountered is ordinarily an in.-

competent one and although it may provide somev lateral support, it does not have sufficient strength to impart the necessary or required lateral support to the outer casing which would allow the'transfer of considerable weight through the casing. It has been found that the formation at the bottom of the sea or ocean floor consists of a structure which is of insufficient strength to reinforce the outer casing and to. support the Weight of the inner pipe strings and this incompetent formation may extendfroin 50 to several hundred feet below the ocean floor. Of course, the derrick floor is above the Water level so that the outer casing initially extends through the water which may have a depth of thirty to one hundred feet and this distance added to the depth of the incompetent formation at the ocean floor may locate the first competent sub-surface formation at a relatively great distance from the derrick floor. Thus, with the outer or surface casing firmly anchored in the first or initial competent formation, the upper end of said outer casing may be disposed from one .hundred to several hundred feet from the point of anchorage, with the. intermediate section of easing traversing the incompetent formation and the Water. Besides the incompetent. formation and water traversed by the section of easing, it also is exposed to the air forthe distance between the water level and the derrick floor whichmay be as muchv as 50 feet No support'through this distance is obtained.

The wavei action in waters of considerable depth impose a'lateral load on averti'cal column 3 such as the outer well casing and obviously, if said outer casing is not anchored for a relatively great distance from its upper end because of its extending through the water and also because of the lack of a competent formation immediately below the ocean floor, it is unstable and does not have the desired rigidity for carrying the heavy vertical loads imposed by the multiple inner casing strings, Therefore, in marine drilling suspension of the inner strings of pipe or casing by means of the usual casing head arrangements at the upper end of the outer casing adjacent the derrick floor is not practical. The transfer of the weight of the inner strings through the relatively unstable and unreinforced upper portion of the outer casing, which casing is constantly subjected to the wave action, is obviously most undesirable, since there is a constant risk of straining said outer casing beyond the breaking point. Also, suspension of the inner casing H strings from the unstable upper endof the outer casing results in an instability of theupper portions ofthe inner strings with the result that the danger of shearing or breaking of all of the casing strings is constantlypresent.

The same difiiculty with respect to supporting or suspending the inner strings of pipe or casing may also be encountered in some types of marshy or swampy terrain where the upper level or initial formation of the earth consists of sedimentaceous, unconsolidated deposits ,of insufficient strength to give the outer casing the required lateral support. s As a matter of fact, the problem exists in any area or terrain where the initial sub-surfaceformation is incompetent and has insufficient strength toreinforce the outer casing and to support the weight of the pipe strings, with the result that the outer casing cannot be anchored except at a point considerably below the earths surface which is, of course, at a point some distance from the upper end of said casing. H l c It is, therefore, one object of the presentinvention to provide an improved method and apparatus for efficiently suspending or supporting pipe, such as well casing, within a borehole which initially penetrates or traverses an incompetent formation and then extends into and through a competent formation.

An important object of the invention is to provide an improved method for suspending pipe within a well bore which initially penetrates an incompetent zone or formation and then extends through a competent formation, said method including, running an outer casing within the borehole so that said casing completely transverses the incompetent zone or formation and extends into the competent formation, anchoring the outer casing within the competent formation, running an inner pipe string within the outer casing whereby said inner string extends entirely therethrough, and supporting the inner pipe string within the outer casing at a point at which the casing has adequate strength to effectively support the weight of the inner string so that the weight of said inner pipe string is directly transferred through the outer casing to the competent formation within which said outer casing is anchored.

Another object of the invention is to provide an improved method, of the character described, whereby a plurality of inner pipe, strings may be effectively mounted or suspended, one within the other, and all within an outer casing, which casing is anchored within a competent subsur- 4 face formation located beneath an incompetent zone or formation in a well bore; all of said inner pipe strings being suspended or supported at a predetermined point within the outer casing so that the weight of said pipe strings is effectively transferred through the outer casing and thence to the competent formation within which the outer casing is anchored.

A further object of the invention is to provide an improved pipe suspending apparatus which permits an inner pipe string to be suspended or supported within an outer pipe string at any desired point within the outer string, whereby the particular location of the point of suspension or support of the inner string may be selected or predetermined to position said support adjacent a competent sub-surface formation capable of carrying the weight or load which is transferred through the support and outer pipe string to said formation.

A particular object of theinvention is to provide an improved pipe-suspending or supporting apparatus which is constructed to operate within the annular space between the inner and outer pipe strings and which is adapted to be actuated without the necessity of rotating or otherwise manipulating the inner pipe string, whereby said inner pipe string may have its lower end cemented in the sub-surface formation before the pipe-suspending apparatus is operated to transfer the weight of said inner string to an outer pipe string and to the competent sub-surface formation within which said outer string is anchored; said apparatus being constructed so that it may be set in the annular spacebetween adjacent pipe strings without sealing said annular space, whereby release of pressure or passage of fluids through the annular spaces to and from the surface may be accomplished after the apparatus is in its set position.

A still further object of the invention is to provide an improved pipe-suspending method and means which is particularly adapted for marine drilling, wherein the outer or surface casing is anchored within a competent formation within a borehole which formation is located a relatively great distance from the upper end of said outer casing, withthe result that the upper end portion of said casing is unstable and lacks desired rigidity; the improved method and means contemplating the suspension of the inner pipe strings within the outer casing at a point or elevation in the general vicinity of the point of anchorage of said outer string, whereby the point of support of said inner strings is well below the upper end of said strings and below the unstable upper portion of said outer casing to assure effective transfer of the weight of the inner pipe strings to the competent formation within which the outer casing is anchored, packing off between the various inner pipe strings and also between the inner string adjacent the outer casing and said casing being accomplished adjacent to or relatively 'closeto the upper ends of the pipe strings and easing, preferably at sub stantially the derrickfloor level;

Other and further objects and advantages will be understood by those skilled in this art from a consideration of the subsequent description or will be apparent or pointed out hereinafter.

In the accompanying drawings wherein I have illustrated a preferred embodiment'of the present invention and wherein like numerals designate corresponding parts throughout the various views:

Fig; 1 is a schematic, sectional view of a typical well-bore drilled at sea'or offshore and illustrat ing the various pipe strings supported by gripping Fig. 2 is a diagrammatic view illustrating the manner of transferring the weightof each inner pipe string outwardly to the outer casing;

' Fig-.3 is an enlarged, sectional view illustrating a modified form of apparatus for supporting the pipe strings; and, 1 Fig. 4 is a'sectional view-illustrating another means for supporting the inner pipe-string.

'As usecl herein, earths surface is" meant the surface of'the earth as envisioned by cartographers. Some placeson the earthssurface 'may be below sea level andwhere the earth ispene tratedby the drilling bit is considered to' be the earths surface in the present invention. In marine "drilling, the earths surface will be the IeVeI-of-"the sea and not the ocean fio'orw In marshy or swampy terrain, the'earths surface will be the surface exposed t'o the atmosphere, whether it be earth or water.-- Also, as referred is herein, incompetent zone or formation; is

meant to include any zone or area, such as water, I

or any formation which has insufficient strength to give the casing extending therethrough the required lateral support. I

The present invention will-be described as used in marine drilling, wherein a well'is drilled ofishore or at sea, such asalong the continental shelf in the Gulf of Mexico. In the drilling of such wells, it is customary to erect a platform or derrick fioor 19 at a sufiicient distance above the sea level to allow for safe working'conditions. The platform is usually supportedby pilings H which are driven into the ocean floor a sufiicient distance to support the weight of :the derrick and-its auxiliary equipment. The borehole. is then drilled in the usual manner down through the ocean floorand into the formations which itis desired to penetrate. As illustrated in Fig. 1, the borehole I2 first penetrates anincompetent structure or sub-surface formation A and then traverses a competent structure B. Ofv course, the zone or area between the water level and the. ocean floor is also to be considered an. incompetent zone. or formation, since obviously, the water is notcapable of impartinglateral support to thewellcasing. d 7

As is well known, it ;is customary practice to case, the borehole l2 witha series of easing .or pipe strings of varying diameters and a typical arrangement is illustrated in Fig.1. As shown, the outer or so-called surface casing I3 is run in and cemented as indicated at M after the well bore has been drilled to a-depth penetrating the initial competent structure B. The cement l4 firmly. anchors the outer or surface casing I3 to the competent formation B, whereby said casing is firmly anchored in position. The length of the outer casing l3will, of course, be variable with each well, but presuming the water which is an incompetent zone to have a depth of fifty feet. with the initiali'ncompetent structure is extending for sixty'feet, it'would probably be desirable. that the outer casing lt have anoverall length of 'three hundred feet, whereby an ample portion of said casing is disposed within the competent formation B. It will be evident that by anchoring the casing 13 within the competent formation B, said casing W111 be rigidly connected therewith; however, because the formation B is'at a considerable distance from the derrick floor I0 to which'the upper end of 6 the casing ls'extendsitwill be evident that .a considerable portion of the casingv l3 extends through the'incompetent formation A :andalso through-the" incompetent zone formed byv the water above 'the ocean floor. The formation A may impart some lateral'support to thelcasing but such support will be inadequateto reinforce j that portion of the casing extending there-' through sufiiciently topermit said portioni to carry a relatively heavy load Thus the upper portion of the outer casing l3 which is subjected 'tothe lateral'stresses induced by the wave actions is'more or less unstable andlacks rigidity as' a heavily loaded column. Because the competent formation B'is disposed a -considerable distance below the derrick fioor Ifl, the-point of anchorage of'the outer casing is at a considerable distance below the upper end of said casing. v 'As illustrated, the outer-casing i3 is shown as anchored in -the first competentformation B below the initial incompetentformation A, but itis apparent that if desired the'borehol e may be'drilled downwardly below-the formation B andthe casing anchored in suchlower formationfinsa 'matter' of fact, the derrick is ordinarily supported 'at its four corners by the piling II, and this results in projected bulbs of weight distribution which extend some distance below the earths surface. It is desirableandpreferable that the competent formation to whichthe outer casing I3 is anchored be below the bulbsof weight distribution of the derrick structure. 7 The exact distance, as has been stated, will be variable, but ordinarily formations competent to support the casing I 3-may be anywhere from one hundred to. six hundred feet below the waterlevel: 1

" After the outer or surface casing l 3 has been cemented or anchored in place, the borehole drilling-proceeds with the diameter of-the borehole beingreduced as indicated at 12a, and drilling in this manner may proceed for two'or three thousand feet, at which timeit is desirable to set the first inner string of easing [5. Thecasing 15 is of substantially the same diameter as the reduced portion [2a of the bore 12 and-is obviously of less diameter than'the outer casing I'3. The inner stringiis run within the reduced portion in and has its "lower end cemented asindicatedat It within the lower portion of the bore. The cementing operation is carried out while theinner string I5 is supporteclfby suitable means within thederrick, and afterth'e cement has set, it is desirable'to transfer the weight of the inner casing IE to theouter casing l3 and then to the competent formation As has been explained, it has been the practice in the past to provide'a casing head at the upper endof the'outer casing l3 and to suspe'nd "or support the inner'casing string l5 through the ,usual'casing head support arrangement. l:Iow.- 7

ever, because the upper portion of the outer casing I3 is unstable as a heavily loaded column due to the factthat a relatively largeYportion thereof extends through the incompetent zone formed by the water and the formation A, it is not" practical to locate the support at the extreme upper end of saidjcasing. If the point of suspension for the inner casing i5 is at the upper endof said casing, it' will be evident that the weight of the inner string l5 would be transferred solely through the unstable upper portion of the outer casing and then to the competent structure. The unsupportedjupper end of the outer casing 13 which does not have the required lateral reinforcement does not have adequate strength to transfer this weight downwardly therethrough to the competent structure: ther, since this upper portion extends throu h the water, it is constantly subjected to the lateral stresses exerted by the wave actions which 'place an additional strain thereon. a l

In carryingout the 1 present invention, the inner casing I is suspended or supportedwithin theouter casing I3 at a point below the unstable upper portion of said casing, .As shown in Fig 1, suitable slips I1 are disposed betweenthQlnner casing I5 and are arranged to engage the wall of the outer casing I 3." The slips are shown more or less schematically and may be of any type which may be set within the annular area between the casings and without rotation or other manipulation of the inner casing or pipe I5. The slips are disposed at any elevation at which the outer casing has suflicientlateral support to carry the load and said slips function to effectively transfer the weight of the inner string of casing I5 to the outer string I3 and then 'directly to the competent formation B which is capable of supporting this weight. The annular space between the inner casing I5 and outer casing I3 may be packed off by any suitable seal S which is preferably located at the upper ends of the casings near or adjacent the derrick floor I0. Obviously, the slips operate in the annulus between the casings and since the seal S is located at the upper end thereof the annular space is accessible from the surface. Also the slips do not seal or pack off the annulus so that flow of pressure fluid or release of pressure within said annulus'may be carried out after said slips are in a set position. I I

From the foregoing, it will be evident that the inner casing string I5 is effectively supported within the outer casing with the load or weight of said inner string being transferred through the outer casing to the formation B which is capable of supporting the weight. The slips I! are preferable since they may be selectively set at the desired elevation or location. The slips I! are illustrated as set at an elevation substantially opposite the competent formation B but it is noted that the particular elevation at which the slips I1 are located is variable and is dependent upon the conditions encountered in the well bore.

As has been explained, the incompetent structure A does not give the casing I3 the required lateral support which would permit the point of suspension of the inner string to be at theextreme upper end of the outer casing, as is the usual practice in ordinary land drilling; however, the formation A does impart some lateral support and therefore, the slips I1 may in some instances be set in the outer casing I3 at some point or elevation above the competent formation B." It will be apparent that the inherent strength of the casing, together with the relatively weak lateral support afforded by the incompetent formation A, will allow an effective transfer of the load of the inner string at some point above the competent formation B and thus, the slips I1 are set at any point in the outer casing at which said casing has sufficient stability and strength to efficiently transfer said load to the competent formation. By disposing the point of suspension of the inner casing at an elevation which effectively transfers the load through the outer casing to the competent formation, the upper unstable portion of the outer casingjI3, which is that portion extending through the incompetent formation A and also through the water, is not subjected to any load. The casing has ample inherent strength as a column to withstand'the lateral stresses due to the wave action provided that said casing need not carry any additional load. V a 7 Ther'well bore is completed by progressively reducing. its diameter as indicated at I21) and I20 and additional inner strings I5a and I 5b are su'c-' cessively run in and set within the well bore. The inner casing string I5 which is cemented at Mb in the reduced section I 212 of thebore is supported by slips IIa which are similar to the slips, IT. The slips Ila, which are mounted on the string I5a, engage the bore of theinner casing I5 and thus, the weight of the string I5a is transferred through the slips lla and "to the outer casing and then to the competentformation B. The string I5b has its lower end cemented at I 40 within the reduced sectionIZc of-the well bore, and is illustrated as extending into the producing sand C or formation C. The string I5!) is supported by slips I'Ib which are similar in construction to the slips fla and I-l. The slips Ila and I fl b are also illustrated aslow cated at an elevation or point opposite'the competent formation B, although as has been pointed out, these slips may be set at an elevation where the outer casing has su fficient strength to effectively transfer the load to the competent formation.

The annular space between the string I5a and the string I5, as well as the annular space between the string I51) and the string I5a, are packed off by suitable seals S which may be of the same construction as the seal employed for packing off between the outer casing I3 and the first inner string I5. These seals are preferably located at or adjacent the derrick floor I0.

' From the above, it will be seen that all of the inner strings are suspended so as to be effectively supported by the competent formation B. The weight of each inner string is transferred through its slip support and the adjacent outer string to the outer .casing I3 and then to the competent formationwithin which the outer casing is firmly anchored. The'upper portions of all of the casing strings extend upwardly through the incompetent formation A and also through the water above the ocean 11001. However, these upper portions which are subjected to the lateral forces exterted by the wave action do not carry any particular load and their inherent strength is capable of withstanding such stresses so long as they are not forced to carry additional load. The transfer of weight of the inner strings to the outer casing is at a point where the outer casing'has adequate strength to transfer the load through the firm anchorage or cement I4 to the competent formation B which is capable of supportingsuch load.

After the various casing strings which may vary in number in accordance with the particular well and its depth, have. been set, the well tubing T may be run through the innermost casing I5b and may, if desired, be supported by slips IIc which are of the same construction as the slips I'I, IM and I'lb. In this manner, the weight of the tubing string T will be. transferred through the various inner casings. to the outer casing 13 and then to the competent supportingjformation B. A suitable annular seal S located at or adjacent to the derrick floor I0 may pack off the annular space around the well tubing T and the casing I5b. Production ofthe well may thenbe ae mze 9 upwardly through the tubing string T in the usual manner. 7

The particular method of supporting the var ious pipe strings is clearly illustrated in Fig. 2 and as shown in this figure, the first inner casing I is provided ,with coupling collars 30 and 3| which are utilized to connect the supporting slip assembly in said casing string. The lower coupling 36 is designed so as to carry the lower portion of the casing I5 therebelowin tension, while the weight of the upper portion of the casing I5 above the .upper coupling 31 is carried by said collar in compression. The weight is transferred through the collar 3| and through the slip assembly IT to the outer casing. As'shown, the slips I l are set adjacent or opposite the cemented portion of the outer casing so that a directtransfer of the,load to the competent formation is effected However, as has been pointed out, the slips Il may be set at any level or elevation within the casing I3 where the outer casing has sufficient strength to transfer the weightof the inner strings to the competent formation. Thus, the exact location of the slips is variable within limits and is controlled by the load imposed by the inner strings, as well as by the amount of lateral support which the outer casing I3 is given by the incompetent formation.

The remaining inner strings are suspended in the same manner as the string I5, with the string I5a having couplings 30a and 3m which connect the slips Na in said string. Couplings 30b and SI?) are connected in the innermost casing string I51) and function in the same manner as the couplings 3i] and 36a and the couplings 3| and em. The slips Ila and Il'bare illustrated as set at respectively higher elevations which is possible since the load of each outer string is transferred to the next outer string and finally to the outer casin I3 and competent formation B. It is apparent that the casing I5 is anchored at the slips I! and thus the slips I la. transferring the weightof the next. inner string I5a may be set at any point within the stringI5 where said string I5 has sufficient strength to transfer the load. Similarly, the innermost string l5b' may have its slips set at any point above or below the anchor point of slips Ila where the string I5a has adequate strength to effectively transfer the load. It is obvious that with the arrangement shown, the weight of the inner strings is progressively transferred through the various strings to the other casing and through said outer casing to the competent formation.

The use of the slips I! to He is desirable since slips may be more readily set at desired or predetermined locations. However, it is possible to carry out the present invention with an arrangement such as shown in Fig. 3, wherein the outer or surface casing I3 which is anchored within the competent formation B is provided With a special coupling collar 20 having an internal flared seat ZI. Theinher casing I5 also has a special coupling collar 23a connected therein and the outer surface of this collar is adapted to engage the seat ZI to thereby support the inner casing within the outer casing I3 and to transfer the weight of said inner casing to the competent formation B. Suitable by-pass openings 22 may be formed in the coupling 20a; to permit by-pass of fluid as the inner casing is lowered. Similarly, the next inner casing I5a is provided with a special coupling 2921 which has its outer surface adapted to engage a seat 2m formed within the coupling 20a: of the, casing I5. Ob-

viously, the weight of the innermost casing I5a will be transferredthrough the couplings 20b and 20a to the outer casing I3 and thence to the competent formation B. Obviously, the supportin couplings will function in exactly the same manner asthe slips I'I. v I g Stillanother method of supporting the inner casing with .respect to the outer casing isillustrated in Fig. 4. In this case, only the outer casing I3and the first inner casing I5 is illustrated. After the inner casing is in position, a

suitable cement; plug 23 may be formed by introducing the cement slurry perforations 24 in the inner casing where it is allowed to set so as to form an annular connection between theinner casing I 5 and the outer casing I3. As an alternative procedure, the plug may be formed by pumping therequired quantity of cement down the annulus between I3 and I5 followed by the necessary amount of mud to place the cement at the desired support position which is located at a point where the outer casing has sufficient strength to transfer the load to the competent formation B. It will be apparent that this arrangement will transfer the weight of the inner string to the outer casing and then to the competent-formation B. In the form shown in Fig. 3, it is necessary because of the special couplings having the inclined seats therein to reduce the size of the casing strings at the point of connec tion of said coupling. This is a somewhat undesirable feature since different size pipe must be employed in the same string; however, so far as the support or suspension of the inner strings is concerned, the forms illustrated in Figs. 3 and 4. will function eiiicientlyto transfer the weight of said strings to the competent formation which is, as explained, at some distance below the upper end of the various pipe strings-and below the derrick floor.

Although the invention has been shown and described as employed in marine drilling, it is evident that it may be effectively used in any area where the initial zone or. formation penetrated by the borehole is of an incompetent nature. It will be apparent that the improved method contemplates the transfer of the weight of the inner pipe strings through each other and to the outer casing at a point where the load may be effectively transferred to the first compotent formation, rather than through a casing and tubing head assembly at the extreme upper end of the various pipe strings as has been the practice in the past. It will be evident that any number, of inner casing strings may be employed depending, upon the particular well and its depth. The foregoing description of the invention is explanatory thereof and various changes in the size, shape; and materials, as well as the details of the illustrated construction, may be made within the scope of the appended claims without departing from the spirit of the invention.

Having described the invention, we claim: I 1. The method of suspending an inner pipe string having its upper end at least above the earths surface within a well 'bore which initially traverses a zone of a strength incompetent to bear the weight of said inner pipe string and which then extends through a competent subsurface formation, said method including, lowering a well casing within the upper .portion of the bore to locate the lower end of said casing within the competent sub-surface formation with the upper portion of said casing traversing the incompetent zone, anchorin said casing to said competent formation, lowering an inner pipe String within the casing, suspending said inner pipe string intermediate its upper and lower end thereof from the casing at a point within the outer casing where said casing is of suflicient strength to effectively transfer the weight of said inner string to the competent formation within which the outer casing is anchored, and maintaining said suspended inner pipe string in said casing with its upper end extending at least above the earths surface and with its lower end extendin downwardly to a point :below the lower end of said casing.

2. The method of suspending an inner pipe string having its upper end at least above the earths surface within a well bore which initially traverses a zone of a strength incompetent to bear th weight of said inner pipe string and which then extends through a competent subsurface formation, said method including, lowering a well casing within the upper portio-nof the bore to locate the lower end of said casing within the competent sub-surface formation with the upper portion of said casing traversing the incompetent zone, anchoring said casing to said competent formation, lowerin the inner pipe string within the casing, suspending said inner pipe string intermediate its upper and a lower end thereof from the casing at a point within the outer casing where said casing is of sufficient strength to effectively transfer the weight of said inner string to the competent formation within which the outer casing is anchored, and sealing the annular space between the inner pipe string and the outer casing at the upper ends of said casing and string and at a point above th incompetent zone.

3. The method of suspendin an inner pipe string having its upper end at least above the earths surface within a well bore which initially traverses a zone of a strength incompetent to provide appreciable lateral support to a vertical column and which then extends through a competent sub-surface formation, said method including, lowering a well casing within the upper portion of the bore to locate the lower end of said casing within the competent sub-surface formation with the upper portion of said casing traversing the incompetent zone, anchoring said casing to said competent formation, lowering the inner pipe string within the casing, connecting the inner pipe string at a vpoint intermediate its upper and a lower end thereof to the casing at an elevation below the incompetent area traversed by the casing and at a point substantially adjacent the competent formation, whereby the weight of said inner pipe string is transferred to the casing and to the competent formation in which said casing is anchored, and maintaining said connected inner pipe string in said casing with its upper end extending at least above the earths surface and with its lower end extending downwardly to a point below the lower end of said casing.

4. The method of suspending an inner pipe string having its upper end at least above the earths surface within a well bore which initially traversesa zone of a strength incompetent to provide appreciable support to a vertical column and which then extends through a competent sub-surface formation, said method including lowering a well casing within the upper portion of the bore to locate the lower end of said casing within the competent sub-surface formation with the upper portion of said casing traversing 12 the incompetent zone, anchoring said casing to said competent formation, lowering the inner pipe string within the casing, supporting the inner pipe string intermediate its upper and a lower end thereof within the casing at a predetermined point within said casing which is at a point where the load may be effectively transferred through the casing to the competent formation in which said casing is anchored, maintaining said supported inner pip string in said casing with its upper end extending at least above the earths surface and with its lower end extending downwardly to a point below the lower end of said casing and sealing the annular space between the inner string and the casing.

5. The method as set forth in claim 3, with the additional step of sealing the annular space between the inner pipe string and th casing. 6. For use in a well bore which initially penetrates and traverses an incompetent zone which is incapable of forming a support for a well cas ing and which then penetrates a competent formation, a well casing extending within and through the bore to completely traverse the incompetent zone and having its lower end extending into the competent formation, means for anchoring said well casing to said competent formation, an inner pipe string extending with its upper end at least above the earths surface longitudinally within the bore of the casing, and means for transferring the weight of said inner string intermediate its upper and a lower end thereof to the casing at a point where said casing has adequate strength to effectively transfer said weight to the competent formation, said inner pipe string extending upwardly in said casing from the point where its weight is transferred to the casing so that the upper end of the inner pipe string is at least above th earths surface and downwardly from the weight transferring point to a point below the lower end of said casing.

'7. For use in a well bore which initially penetrates and traverses an incompetent zone which is incapable of forming a support for a well casing and which then penetrates a competent formation, a well casing extending within and through the bore to completely traverse the incompetent formation and having its lower end extending into the competent formation, an inner pipe string extending with its upper end at least above the earths surface longitudinally within the bore of the casing, means for transferring the weight of said inner string intermediate its upper end and a lower end thereof to the casing at a point below the incompetent formation and substantially opposite the competent formation, said inner pipe string extending upwardly in said casing from the point where its weight is transferred so that the upper end of the inner pipe string is at least above the earths surface and downwardly from the weight transferring point to a point below the lower end of said casing and means for sealing th annular space between the inner pipe string and the casing.

8.,The combination as set forth in claim 6, wherein the means for transferring the weight of the inner string to the outer string comprises gripping slips carried by the inner string and having gripping means engageable with the bore of the casing.

9. The combination as set forth in claim 6. wherein the means for transferring the weight of the inner string to the outer string comprises 13 a coacting seat and shoulder on said string and casing.

10. The combination as set forth in claim 6, wherein the means for transferring the weight of the inner string to the outer casing is an annular cement plug.

11. For use in a well here which initially penetrates and traverses an incompetent zone which is incapable of forming a support for a well casing and which then penetrates a competent formation, a well casing extending within and through the bore to traverse completely the incompetent formation and having its lower end extending into the competent formation, an inner pipe string extending with its upper end at least above the earths surface longitudinally within the bore of the casing, means for transferring the Weight of said inner pipe string intermediate its upper end and lower end thereof to the casing at a point below the incompetent formation and substantially opposite the competent formation, and means for sealing the annular space between the inner pipe string and the casing arranged adjacent the upper ends of the inner pipe string and the casing.

12. For use in a well bore which initially penetrates and traverses an incompetent zone which is incapable of forming a support for a well casing and which then penetrates a competent formation, a well casing extending within and through th bore to traverse completely the incompetent zone and having its lower end extending into the competent formation, means for anchoring said well :casing to said competent formation, a first inner ipipe string extending with its upper end at least above the earths surface longitudinally within the bore of the casing, means for transferring the weight of the first inner string intermediate the upper and lower ends thereof to the casing at a point where said casing has adequate strength to transfer said weight to the competent formation, a second inner pipe string extending through the first inner pipe string, and means for transferring the weight of the second inner string to the first inner string and through said first inner string to the well casing and competent formation.

13. The method of suspending an inner pipe string having its upper end at least above the earth's surface withinv a well bore which initially traverses a. zone of a strength incompetent to provide appreciable lateral support to a vertical column and which then extends through a competent sub-surface formation, said method including lowering a well casing within the upper portion of the bore to locate the lower end of said casing within the competent sub-surface formation with the upper portion of the said casing traversing the incompetent zone, anchoring said casing to said competent formation, lowering the inner pipe string within the casing, connecting the inner pipe string intermediate its upper and lower ends thereof to the casing at an elevation below the incompetent area traversed by the easing and at a point substantially adjacent the competent formation whereby the weight of said inner pipe string is transferred to th casing and to the competent formation in which said casing is anchored, sealing an annular space between the inner string and the casing at a point adjacent the upper ends of the inner pipe string and the casing, and maintaining said connected inner pipe string in said casing with its upper end extending at least above the earth's surface and with its lower end extending downwardly to a.

point below the lower end of said casing.

MERCER H. PARKS. MARVIN R. JONES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,079,690 Bowler et a1 Nov. 25, 1913 1,594,498 Day Aug. 3, 1926 1,836,419 Wigle Dec. 15, 1931 1,849,374 McEvoy et al. Mar. 15, 1932 1,857,101 Nixon May 3, 1932 1,866,038 Johnson July 5, 1932 2,173,034 Armentrout et al. Sept. 12, 1939 2,205,119 Hall et a1. June 18, 1940 2,215,913 Brown Sept. 24, 1940 2,379,079 Hayward June 26, 1945