US2514585A - Method for drilling wells - Google Patents

Description

July 11, 1950 M. 1... NATLAND METHOD FOR DRILLING WELLS Filed June 9, 1945 [NVEN To? MANL E) L. IVATLHND H MM & we

Haze/5, A7504 Patented July 11, 1950 UNITED STAT METHOD FOR DRILLINVG'WELLIS Manley L. Natland, Long Beach, Calif., assignor., by mesne assignments, of one-half to Lester Callahan Application June 9,1945, Serial No. 598,574

My invention relates to a novel method and apparatus for drilling wells andmore particularly. to a novel continuous coring methodand apparatussuited to obtaining core specimens or sections during continued drilling.

Core specimens of the earths strata are of.

inestimable value in planning and drillingoil' wells and in determining subterranean geolog1cal formations, contours of oil-containingwsandsor oil-retaining domes, geological age of ,subterranean strata, prospects for oil production;

N satis-- geological mapping of an area, etc. factory method of obtaining'sizable core speci-' mens during continued drilling has been come.

mercialized. Instead, present practice. involves the drill pipe to bring the core to the surface;

Much time, very considerable expense, and cer-..

tain dangers are involved in such aprocedure,

albeit that savings of thousands of dollar could be made in drilling each well if coring could be eliminated or if core specimens could be obtained during continued drilling.

: Attempts to solve the problem by analyzing the. nature of the cutting raised to the surface bythecirculating mud stream have not solved. the problem for many reasons. The cuttings'are of too small an average size, are too numerous to permit of individual inspection, even if a skilled geologist or paleontologist were constantly present, and give no indication of the slope or angle of the stratum being cut. v specimens of comparatively uniform size would be very desirable but, prior to the present invention,

have not been obtainable during continuation the drilling operation.

Much information of value is obtained from" the usual core specimen taken from a well. It may indicate, for example, the slope angle of the stratum, the character of the formation; the" amount of stratigraphic penetration,.etc When broken into small sections along natural cleavage planes, the resulting sections will often show Sizable core 4 Claims J01. 255 .4).

fossils, shells, or petrified fish scale whichare of inestimable value to a skilled paleontologist-in determination of geological age, position, and

history of the strata from which the sections come. Any temporary compaction or compressed mass of cuttings is. not a satisfactory substitute for suchcore sections or specimens.

The: present invention has among its objects the vprovisionof a novel method and apparatus for (1) drilling wells to obtain core specimens or sections during continued drilling, (2) for drilling in an annular zone of the well bore to leave s. central core portion while providing for the breakage from this core'portion of core sections. andthe'transport'ation-thereof to the surfacerofv theJground, (3) for discharging sizable core sections'linto. the stream of drilling mud or otherfiuidcirculated in the well for transportation to; the surface of the ground or other stationfor collection, (4) forsegregation of such coresections. from. the usual small cuttings carried upward by this stream of mud orother fluid, etc.

.As.used..herein,; the term core section has reference to. anactual'segment or portion of a subterranean geological formation as distinct from a. temporarily compressed mass of cuttings from a bit. It is an object of the invention to produce'said core sections and discharge same into the circulating. systemof the well to be in contact with the circulated fluid and to be carried upward-by the upward velocity of this fluid, typically the usual drilling mud employed in drilling of oilwells. Such drilling mud coats the core section with a protective coating facilitating its, reaching the .surfaceof the groundwithout undue abrasion or breakage.

It; is a further, object .to use the mud or other circulating fiuid'to aid in the discharge of core sections from the drilling structure and, if de sired,p.to;aid in the breaking of a core'portion along. naturalcleavage planes into core sections or;to; lubricate or protect the core sections dur-.

ing -movement along a passage. preparatory to discharge into the main stream for transportation upward in the well. v

- It is another object of the invention to provide a struc.ture for; cuttingv a core portion aflixed to the bottom. of the bore and for breaking this is shown as being used to drill a well or bore ID in the earth to penetrate strata suggested at H, l

a portion of the well being shown cased by a.

casing I2. The derrick floor is suggested atl3- and carrie the usual rotary drilling table If turned by a suitable powensource, .not 'shwm; to rotate a drill column ordrill ste'm l'fi formed of sections of drill pipe I! coupled by joints I8.

The upper end of the drill stemcarriesfthe usual;

swivel 23, the weight of the drill stem being carried by travelling block 21 through a'-bail'-22 The upper end of the drill stem is supplied with a fluid to be circulated inthewell to aid in the cutting and in thetransportation of cutting to the surface of the ground. This fluid is, typically, adense drilling mudv supplied to the swivel v under high pressure and at a very; considerable volume through hose 23 and pipe 24 by'circulating pump 25. I

v The drilling structure or unit-is ,securedtothe lower end of the drill stem I6 and isindicated generally by the numeral30. Essentially it includes a bit 3land a driving element 32 formed either by the lowermost portionofthe drill-stems or, more conventionally, as a drill collar. or a. sub: detachably connecting the bit? to the drillstemt-l The invention is, illustrated as associated with. a drivingelement comprising :a sub 33 securedto the drillstem by a. collar-:34, butit: shouldlbel clear that the inventionicanxbe adapted to other known arrangements of bitdriving: element. combinations. As shown, the sub 33 is of. novellformz. It1pro'- vides an externally threaded hub. 35 threading into a cavity 36 of the bit. 3| until shoulders? 31'; and 38, respectively, on the sub and bit, engage: At this time the hub 35 does not. completely fill-l the cavity but leaves an annular chamber 40 bounded'by a wall 4| of the cavity 36- and by a collar, depending from the hub 35 into. a taperended recess 43 ofthe bit 3|...

Thesbit-l3l may be of any construction.p'ro viding cutting elements disposed around; a oen' tral passage to cut into the bottomof' the wellin anannular zone in a manner to.'leave an up'- standing core-portion 5t!v still attached to the earthand around which thecutters move todeep en thewell, while. leaving the core portion. Merea ly for purpose. of illustration 1' have shown a bit t of .thefish tail or type havinga central pas's'ag c 5l .toreceive. the core portion as cutbycutters 52 having outer and inner. cutting portions 53 and, 554; the latter actually dete'rminingthe si'z'e ofnthe, core .portion 50. and preferably extending;

slightlyi'nto the peripheral confines of the cerv- 4 forms a part of this core passage means as does also a core passage 55 of the sub 33. This core passage communicates at one end with the central passage 51 and, at its other end, with the circulating mud stream. The core passage 55 can be considered as having a lower portion, termed a core-receiving opening 51, axially aligned with the central passage 5! of thebit "and extending through the collar 42, and an upper portion, termed a core-transmitting opening 60, which angles axially from the core-receiving opening 51 and which; terminates in an exit portion GI tralv passage 5.]: to produce a core portion-thatis:

slightly smaller in diameterthan the central pas-t sage-,;as.illustratecl inFig. 2..

In.the preferred arrangement, the drilling unit:

provides. a core passage means. which functions to;re.ceive=the. core. portion 50: td confine itwhile some point; of convenient. inspection: of the coresections, e g., tdthetop. of; the wellnli'nl the-11 lustrated embodiment the central passage 1 5 1i opening on'the circulating mud stream, e. g., disposed at the periphery of the sub 33 near the uppereiid'thereof. The core-transmitting opening is shown-as having a curved axis angling sidewise-fromthe axisof the core-receiving opening 51 and formed by any suitable cutting or cast- 7 ing'operation. For example, a straight opening can be bored through a block of material, the block being'subsequentlyf bent to givethe boreits curved. axis, and the block being. then turned between :lathe centers to the. contour shown.

The drilling structure 30 provides: fluid-con ducting passage means spaced laterally'from the core'passage 555i0'r conducting the mud stream to the'bity. Thus the sub 33 isshownas providing a plurality of fluid-conducting passages 63 communicatingat'their upper ends with the interior of'the drillstem; 1| Ii and'communicating, at their lowerends with the annular chamber 40. This chamber distributes themud to a. plurality. of openingswfi l of thebit from-which the mud disby't'he numeral 65- and :may be formed between thewalls oftherecesses 43 and the collar 42. The

main mud stream discharging 'from the openings 64:-p'rcks iup cuttings from; the bit 31' and moves upward :inthe annular space. between" the drill stem l6 and the side wall of the wellill; as indi cated by arrows 65. The mud stream. rises :past thesexit' portion M to receive the core-sectionsformed as hereinafter described, carrying these upwardflto: the top of the wells Any convenient means may be employed for 'separatingithe core; sections'fromnthe. drilling mud. Asr shown, the

drilling mudamoves: from. the casing 12 through a;..pipe.6'|.',discharging. onto a screen or grid" 68 through which: the mud and cuttings may dis chargetora sump-69;v If desired, astrearn ofwa teninay be sprayed onto the screen. E81-througha I during normal-drilling, the bit 3!. is rota-ted tocut into-the. bottomof the well in an annular zone, mud being circulated by the pump: 25 to flow downwardthrough the drillstem l6 and upward, asiiidicated by the arrows 66', as previously a described. Ascuttinglprogresses, the cutt'ersif leave theupstanding core portion 56 still secured to"thei'subterr'anean formation and. extending somewhatloosel'y'in the central passage 5! ofthej bit; The'cleavageplanes ofthiscore portion 50f usually correspond totheslopeof the surrounding strata." CorreSpondirrglW by -subjectingtlie core portion-5W tobending'stressesgit can be broken into the previously mentioned core sections.

ratheillustrative embodiment: the usualop eration-peim'litsupward movement of the core portion 50 relative to the downward movement of the drilling structure 30, the core portion extending somewhat lOOSely into the core-receiving opening 51. However, as soon as this core portion enters the axially-angling coretransmitting opening 60, it engages an arcuate wall thereof to subject the core portion 50 to peripherally-applied bending stresses. This breaks a core section 16 from the upper end of the core portion, usually along naturally-occurring cleavage planes following the slope of the strata. The resulting core section 16 tends to turn with the drilling structure.- To prevent abrasion between the now-severed core section 16 and the upper surface of the core portion 50 it is desirable to supply drillingmud to the central opening 5| of the bit or to the core passage 55. Some mud may enter therein by flow from the vicinity of the cutting elements 54, and this mud supply may be sufiicient to produce the desired lubrication or coating of the core portion 5! and its severed core section 16. It is also desirable, however, to supply an auxiliary stream of the drilling mud, and this is accomplished, in the embodiment shown in Fig. 2, by the auxiliary passage 65 which supplies sufiicient mud to the periphery of the core portion 50 to form a protective film therearound. It also tends to create an upward flow of the mud between the core portion and the walls of the core passage 55 whereby this .mud is available immediately to enter the space between the severed core section 16 and the still-stationary core portion 50.

I-IoweverQthis auxiliary flow of mud upward through the core passage 55 need not be relied upon to discharge the core section 16 therefrom into the main mud stream, although it may have this function if desired. Even in the absence thereof it will be apparent that continued drillin will successively break the core sections 16 from the core portion 50, and that the core sections will be forced successively from the exit portion 6| to be picked up by the rising mud stream and carried to the surface of the ground. During upward transportation of the core sections 16, they will be protected by the mud from any excessive abrasive contact with the mud-confining surfaces, to the end that the core sections 16 shall reach the surface of the ground in as nearly as possible their original shape when broken from the core portion 50.

In drilling the usual oil well I find it satisfactory for most purposes to provide for a core portion 50 of a diameter about one-half inch. A diameter of approximately three-quarters inch is usually preferred and provides core sections 16 of adequate size to determine the character of the strata through which the drill is passing.

The core section 16 will break off in cylinderlike or wafer-like form, and careful checking of the angle between the face and side wall thereof will give an indication as to the slope of the strata from which the core section originated. Observation of the surfaces of such core sections will usually show valuable geological data, such as shells, petrified fish scales, etc., or these can be exposed by further breakage of the core sections after they reach the surface of the ground.

In drilling through most formations it is desirable to provide some means for applying bending stresses to the upstanding core portion 50 to break off the core sections 16. This can most conveniently be accomplished by use of the axially angling passage shown. However, in drilling through other formations, particularly when usingcertain types of bits, thelateral vibrations of the bit in the bore hole may be sufiicient to break off core sections 16 from the core portion 50. In that event the core sections will stack up in the core passage and be expelled successively into the rising mud stream.

The invention comprehends the production of core sections 16 of relatively uniform size. This makes the core sections readily separable and distinguishable from the drilling mud or any chunk-like cuttings carried thereby. In addition, it provides for a regular discharge of a core section into the rising mud stream at intervals determined by the rate of drilling' of the bit 3|. Further, it provides for the elapse of a subst antially equal time between the discharge of a core section 16 from the exit portion 6| and the time when this core section reaches the top of the ground. The core sections can .thus be made-to reach the top of the ground in the same sequence;

as they were expelled from the exit portion 6|, thus leading to more accurate information as to" the subterranean strata being penetrated.

From the above it will be apparent that my invention includes, among other features, the continuous coring of a well during progressive drilling. The information available from the core sections segregated at the top of the well is usually sufficient, but, if desired, the drill stem [6 can be periodically removed to install a con, ventional coring bit to penetrate particularly critical zones. Various changes and modifications will be 'ap-r;

parent to those skilled in the art from the. ex-x emplary embodiment illustrated and can be made without departing from the spirit of the appended claims.

I claim as my invention:

1. A method of drilling a well in the earth by use of a single-walled rotating drill column to Which'is connected a bit having a central passage, which method includes the steps of: rotating said drill column and said bit to out into the earth in an annular zone to form a bore having a central core portion extending into said passage of said bit, said core portion having natural cleavage planes determined by the formation being drilled; forcing a stream of drilling mud downwardly inside said drill column during rotation thereof and discharging this drilling mud adjacent said bit to rise in an annular zone of said bore around said drill column; bending the upper end of said central core portion to break core sections therefrom along said natural cleavage planes, each core section being a short segment of said core portion and having a cross-sectional area substantially equal to the cross-sectional area of said core portion; moving these core sections to said annular zone and into the rising mud stream therein to be carried to the top of the Well in said annular zone by the mud stream therein, the size of said annular zone being sufiicient to pass said core sections without substantial rebreaking thereof during their journey to the top of the well; and separating said core sections from said drilling mud to obtain individual core sections accurately representative of the subterranean strata from which they originated.

2. A process as defined in claim 1 including the additional steps of dividing the downwardly moving mud stream into two portions, delivering one portion to the exterior of said bit to aid in its cutting, and delivering the other portion to the central passage of said bit at a positionbelow the-top 'ofsaid core portion and below the-*peintat which said 'core sections ar'ebroken from said core portion to coat the coreportion and the coreseetion's as they are broken therefrom.

3. A method-of continuously coring-a during drillinga well in the earth by use ofa singlewalled drill column, which method includes the steps off drilling into th'e-"ear-th-a-t a position below the bottom-ofsaid drill column and in an annular zone-to form a bore and to leave an upstanding core portion' -in the center of the here, said c'or'e portion having natural cleavage planes deter-mined by th'e formation beingdrilled, saidbore having an outer diameter -'substantially largerithan said drill column to provide a relativly wikie upright annular zone within-the bore around said driI-l'cominn; continuously fore ing a "stream or dense drilling mud downwardly through said drill column during continued drill-- ing and -disoha rging this drilling mud into-the lower end "of said annular zone to move "as an upwardly-flowing--annularstream therein to the sfli' fabe' of the 'earth; applying bending vforces to the upper portion of said core por tion to break periodically therefrom;along-said natural cleavage planes, cylinder' like cor'e sections; discharg sai'd core sections into said I annular stream of dense drillingmud ri'sing in said annular zone; maintaining the upward velocity of said annular stream -sufficient' to carry said c'ore secti'on's upwardly in said annular zone, the core sections rising therein while being-surrounded and .protectedv'against undue abrasion by the-dense mudof sa-id'annularstream, the horizontal widthof saidannular zone being sufiici'e'nt -to pass said core sections "without 1 pulverization thereof whereby sizable core speciments' are discharged periodically from the top ofsaid annular zone with the mud stream; and separating these sizable core specimens from the mud stream discharging from the top of said annular zone.

4. process as defined in claim 3', in which saidcore specimensare separated fromsaid mud stream by screening, and including the step of spraying water-on the core specimens duringthe screening thereof to remove mud therefrom;

MANLEYL. NATLAND.

REFERENGESKCITEDA The following re'ferences'are of record in file of this patent:

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