US 2498159 A
Description (OCR text may contain errors)
Feb. 21, 1950 R. c. GAMMILL 2,498,159
WHIPSTOCK Filed May 12, 1944 Z-Sheets-Sheet 1 l I z I I l INVENTQR Bf g ATTORN EY Feb. 21, 1950 v c, GAMMILL 2,498,159
- WHIPSTOCK Filed May 12, 1944 2 Sheets-Sheet 2 20 C. Gum/721' INVENTOR la waadwg ATTORNEY Patented Feb. 21, 1950 WHIPSTOCK Roy 0. Gammill, Oklahoma City, Okla., assignor,
- by direct and mesne assignments, to Eastman Oil Well Survey Company, Dallas, Tex., and Denver, 0010., a corporation of Delaware Application May 12, 1944, Serial No. 535,220
This invention relates to new and useful improvements in whipstocks.
The invention relates particularly to an improvement on the whipstock shown in the patent to McVicar No. 1,970,761.
As is well known, whipstocks are in general use throughout the oil industry and are employed for the purpose of directing a drilling bit at an angle from the old well bore. The whipstock is useful in side-tracking operations, that is, offsetting the well bore from its old course and is also necessary in controlled directional drilling operations where it is desired to intentionally curve the well bore to reach a desired objective.
The usual practice has been to connect the drill bit, which is utilized with the whipstock, to the drill pipe or string by means of an ordinary drill collar which is relatively short. As exemplified by the McVicar patent, above mentioned, the drill collar or sub as it is commonly referred to extends is disposed below the collar.
Experience has shown that after the whipstock is set and the connecting pin sheared to permit downward movement of the bit along the inclined face of said whipstock, said bit is guided into the formation at an angle to the old well bore. As the bit enters the formation, the sub immediately above the bit rides in the arcuate inclined face of the whipstock and its rigidity aids in main- H taining the drill bit in its angular movement through the formation. So long as the sub is engaging the whipstock, the angular drilling direction is maintained because the sub is sufiiiciently rigid to prevent any change in such direction. However, as soon as the drilling has progressed far enough to cause the sub to clear the lower end of the whipstock, the, rigidity of the sub as an aid in maintaining the angular direction of drilling is lost. It is apparent that the drill pipe or string which is several hundreds, and in many cases, thousands of feet in length has an overall flexibility or resiliency which permits said pipe to bow or flex as the pressure is applied during the drilling operation. Thus,;as soon as the sub clears the-lower end of thewhipstock, the flexing of the drill pipe permits the drill bit to wander and no definite'guiding of said bit is maintained. Because the, sub is relatively short the'positive guiding of the drill bit is (Cl. 255-j-1.6)
lost before the new angular hole has been really started and in many instances, the new hole has not been drilled beyond the wall of the old bore. Obviously the tendency of the bit is to move back toward the old well boreand therefore, as soon as the guiding action of the sub is removed due to the sub moving below the whipstock, the bit moves back toward the old bore, thereby defeating the purpose. This is particularly truewhen drilling in hard formations which are diflicult to penetrate.
It is, therefore, desirable to increase the length of the sub or drill collar in order to obtain a guiding action until the bit has been well started in the new or offset bore so that by the time that the sub moves below the whipstock any danger of the bit to drift back into the old bore will have been eliminated. However, because the sub extends through the whipstock collar, as shown by the McVicar patent, said sub cannot be lengthened or extended upwardly without interfering with efficient operation. Because the drill bit engages the inclined face of the whipstock and is urged outwardly thereby, the sub must be short enough to clear the whipstock collar before any appreciable outward movement of the bit occurs; otherwise the sub will bind against the whipstock collar and upon rotation of the pipe and bit to perform the drilling, the friction created by the binding of the sub against the whipstook collar would cause a rotation of the \vhipstook to destroy itsoriented position. 1 It is one object of the present invention to provide an improved whipstock which is so con structed that an elongate sub or guide collar may be connected to the bit, whereby an effective guiding of the whipstocl; to effect proper drilling of the offset bore is assured.
Another object of the invention is to provide an improved whipstock which is formed with an elongate substantially straight portion between its inclined face and the whipstock collar, said straight portion accommodating an elongate guide sub or collar which connects the drill bit to the drill pipe.
A further object of the, invention is to provide a whipstock of the character described'wherein the elongate guide sub moves out of and below the whipstock collar when the drill bit engages the inclined face of said whipstock whereby bending of said sub within said collar is prevented;
" An important object is to provide a whipstock "having all of the'advanta'ges of the whipstock by reference to the accompanying drawing;
wherein an example of the invention is shown, and wherein:
Figure 1 is a longitudinal;verticahsectional view of a whipstock constructedinaccordance with the invention and showingeth'e sub in corinected position,
Figure 2 is a similar view-,with the sub div connected from said whipstock,
Figure 3 is an enlarged, horizontal sectional view, taken on the line 33 of Figure 2,
Figure 4: isan enlarged,horizontal-sectional view, taken onthe line" 4 -4 of -Figure 2,
Figure 5 is a view, similar t'oFigure 1, illustrating the drilling of an :offsetbore.
In thcdrawings, the numeral IO d-esignatesa whipstock which'is formed of an elongate body having a generally arcuateshape-in-cross-section. Theupper portion of the body has itswvall of a constant thickness whereby the face- I L of this portion of-the bodyissubstantially straight or parallel with the longitudinal axis of the-whipstock. This straight-portionof the body extends from the upper end of the body to the point indicated at A in-Figure 1. Below the point A, the body has a wedge'shape to form-an elongateinclinedguide surface IZwhiohsurf-aceiS concave clue to the'fact that saidbody'is of arcuate crosssection. The extreme lower endofthe body is preferably pointed or sharpened to: facilitate its setting within a: cement-plug orw-ithin: the formation, as the case-maybe;
A retrieving collari3 isprovided at the upper end of the whipstock bodyand is preferably formed integral with said body A drill bit l4 having an outside diameter greaterthanthe bore l5-'of the collar is" disposed-below said= collar and is=connected to-the lower end ofan elongate sub or guide'collar Hi. The elongate-sub'i san important-featureof the invention and=has its upper end connected tothe lower end of the drill pipe 11. As is clearly shown in. Figure 1, the outer diameter of the sub is slightly smaller than the bore ifi of' the Whipstock so'that said sub is freely movable therethrough. The drill pipe H is smaller in diameter than said sub.
The drill pipe, sub and bit are arranged to be conneotedwith' the whipstock body by afrangible means, such as a shear pin 58 whereby the drill pipe may be utilized to lower said whipstock within w-ellbore B. As'illustrated the shear pin extends through the wall of the whipstock body and isfastened in the body of the drill bit 14 although-of course; said pincould connect with the sub H5. When the parts are connected the extreme upper portion of the sub 16 is disposed within the collar l3 while the drill bit I4 is locateda sufficient distance above theinclined guide surface which begins atpoint A to permit a downward movement of the -bit to eilect-shearing of the pin 18 without wedging the bit against the-wall of the well bore B.- In orderto permit the use of a-substantially full-gage bit, the wall of: the whipstock body is provided with an opening Iii-for accommodating the blades 14a of the bit, however, if desired, this. opening. may be 4 omitted. It is apparent that the elongate sub l6 spaces the drill bit some distance below the whipstock collar when said bit is connected to said whipstock.
In the use of the device, the assembly is lowered into the well bore with the bit connected to the whipstock bythe shear pin, the lowering being accomplished by means ofthe drill pipe 11. After the whipstock has been set in position, the weight of the drill pipe is imposed on the pin l8 to shear said pin and permit the drill bit, sub and pipe to move downwardly with respect to the whipstock (Figure 2). Itis. noted that when in a connected positiomtheibit is spaced above the point A or abovez 'the upper end of the inclined guide surface 12-, whereby the bit may move downwardly; in aplane parallel to the longitudinal axis of the whipstock a distance sufiicient to shear the pin before striking the Wedge. It is noted that when the pin is sheared, a sudden drop inthe drill pipe and bitwilloccur and sufiicient space must be provided-below said-bitto prevent wedging saidbitbetween the inclined surface l2 and the wallof the well bore;
As the drill bit is moved downwardlyafterdisconnection from the whipstock'body; said bit .will engage the inclined guide surface vI 2- of the whipstock and will be directed outwardlyinto the formation at anangle withsrespect to thewellbore B; The length of the sub 16- issuchthat b the time the bit engages the upper portion of the. inclined guide'surfacatheupper end of saidsub has cleared the bore. l5 0f the collar, as is clearly shown in Figure 2.. Thus the smaller drill pipe. I I is extending through the collar. lit-when drilling begins and there is nodanger of a frictional engagement of the-rotating pipe and collar. which might be'suificientto impart a rotation to the 'whipstock and thereby move. itifromits set position. If the sub 16 were within the collar l3 when rotation was A started, a frictional engagement sufi'icient to turnthewhipstock wouldbe set up because ofthesub having a-diameter which isalmost equal to the diameter of the. bore .of said collar.
As the bit is urgeddownwardly. along the inclined surface of the whipstock during the drill.- ing operatiomsaidbit is directed outwardly at an angle to the main bore B, whereby an oifset or angular boreBB isformed As. soon asv the upper end of the bit body clears the lower endof the whipstock the elongate sub engagesthe inclined guide surface of thewhipstock, said sub lying within the concaved surface. Thesub-is :ofone piece andtherefore has an inherent. rigidit with the result thatso long as it is engaging the surface l2 of the. whipstock it directs the bitin its proper line of drilling and prevents the bit from tending to drift back into the main well. bore. Ascompared tothe drill pipe. which extends to the surface, the sub [6 is relatively short and does not have a tendency to flex or bend as does the long drill pipe. This rigidity is utilizedto guide or direct thebitinaproper direction during the starting ofthe angular bore BB. The sub. has a sufficient length that by the time the upper end of the sub clears the lower end of the whipstock and itsguiding. effectiveness is lost, the new bore BB is of sufficient depth andits lower end is willciently spaced from the old bore B that there is no tendency for. said bit to drift back toward said bore B.
With the elongatesub .20. which is the important feature of the invention, positive guiding or directing; of? the bit-is maintained untilv the new bore has been drilled to a depth suflicient to prevent drifting of the bit. The actual length of the sub may be varied within limits and so lone as said sub has suflicient length to assure that the new bore BB is well started the purposes of the invention will be accomplished. It might be noted that the device is particularly advantageous when drilling in hard formations although of course it may be used in any type of formation.
The foregoing description of the invention is explanatory thereof and various changes in the size, shape and materials, as well as in the details of the illustrated construction may be made, within the scope of the appended claim, without departing from the spirit of the invention.
What I claim and desire to secure by Letters Patent is:
A whipstock including, an elongate body having a collar at its upper end, the lower portion of the body being wedge-shaped to form an inclined longitudinal guide surface, the upper end of said guide surface being spaced a substantial distance from the collar and being connected to the collar by an elongate straight wall which comprises the upper portion of the body, a drill bit disposed below the collar, an elongate rigid sub connected to the drill bit, a drill pipe having the sub attached to its lower end, said drill pipe and sub being arranged to pass through the collar and means for detachably connecting the drill pipe, sub and bit assembly to the whipstock, said sub being of such length that when the drill pipe, sub and bit assembly is in attached position, the upper end of said sub is adjacent the collar and the bit is disposed contiguous to the straight wall sec tion of the whipstock and spaced above the inclined guide surface, detachment of the detachable means allowing the drill pipe, sub and bit to move downwardly with respect to the whipstock with the upper end of the sub moving downwardly below the collar prior to the time that the drill bit is urged a substantial distance outwardly by its engagement with the inclined guide face of the whipstock body, the elongate sub maintaining contact with the inclined surface of the body until the bit has drilled a deflected bore which is outside the confines of the original well bore, the outside diameter of said bit being greater than the bore of the whipstock collar and the straight wall section of the whipstock body having an opening for accommodating the bit blade When said bit is in its attached position, whereby the bit may be of substantiall the same diameter as the well bore in which the assembly is lowered.
ROY C. GAMMILL.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,970,761 McVicar Aug. 21, 1934 2,131,849 Tolson Oct. 4, 1938 2,293,706 Kothny Oct. 13, 1942 2,301,307 McMahan Nov. 10, 1942 2,327,658 Miller Aug. 24, 1943 2,331,293 Ballard Oct. 12, 1943' 2,334,747 Brantly Nov. 23, 1943