US2646254A - Method for controlling deviation in drilling - Google Patents

Description

July 21, 1953 D. s. JOHNSTON METHOD FOR CONTROLLING DEVIATION 1 DRILLING 5 Sheets-Sheet 1 Filed Sept. 2, 1950 INVENTOR.

DEN/EL S; JOHNSTON (f .11 Ilia n..

July 21, 1953 D. s. JOHNS'IV'ON METHOD FOR CONTROLLING DEVIATION IN DRILLING 5 Sheets-Sheet 2 Filed Sept. 2, 1950 INVENTOR. DAN/E1. ,5 U0

5 TON BY wag 2 ATTORNEY,

July 1%3 D. s. JOHNSTON 2,646,254

METHOD FOR CONTROLLING DEVIATIQN IN- DRILLING Filed Sept. 2, 1950 5 Sheets-Sheet s & F INVENTOR.

@DflN/EL S. ziomvsro/v ATTORNEy,

July 21, 1353 v D. s. JOHNSTON 2,546,254

METHOD FOR CONTROLLING DEVIATION IN DRILLING Filed Sept. 2, 1950 5 Sheets-Sheet 4 E g. Z 7a.

' IN VEN TOR.

Dmvgz. 5. (JOHNSTON .H T TORNEY:

July 21, 1953 D. s. JOHNSTON 2,646,254

METHOD FOR CONTROLLING DEVIATION IN DRILLING Filed Sept. 2, 1950 -5 Sheets-Sheet 5 INVENTOR. DEN/EL JOHNSTON ATTORNEY.

Patented July 21, I953 METHOD FoR ooNTRoLfiNo ISEVIATION I IN DRILLING Daniel S. Johnston, Rolling Hills, Galih, assignor to Signal- Oil and Gas Company I-ios Amgelesl Calif a corporation of Delaware Application September 2, 1950, Serial No. isaoon 6 Claims.

1 This invention relates to a method of controlling the direction of migration of a drilling bit such as is used in the rotary drilling of bore holes, as, for example, in the production of oil.

well bore holes and water well and similar bore holes.

The present method of drilling such-bore holes consists of employing long strings of drill. pipe which are connected by connectors, called tool joints, and applying at the end thereof a drilling bit, and immediately above the drill bit and between the drill pipe sections and the bit, secti'ons-of pipe which are much heavier and stiffer than the drill pipe, and which are known as drill collars.

There are two general methods of drilling oil wells. One is to drill vertical bore holes in which the purpose is to drill a perfectly straight and vertical drill bore, and the other is the method of drilling directional bore holes in which the bore holes describe, generally, a curve through the earth. 7

It is common practicein drilling such bore holes to rotate the drill clockwise because all drill strings and all screw threads'employed in the: drill string aremade up by clockwise rota-.

tion and it is necessary to rotate them clockwise inorder to prevent the drill string from unscrewingat the screw joints, and are termed right-hand threads for that reason. 7

In drilling vertical bores in the earth, as, for example, for the purpose of producing fluids from the earth, such as oil, gas, or water, the drill string is very long and because of its large slenderness ratio, it is very limber.. Since some weight must be placed on the bit in order that it'cut the bore in the earth, it has been found in practice that the bore hole tends to wander in a. manner not predictable by'the prior art knowledge.

Thus, the axis of the bore takes an acute angle to the vertical and the axis of the bore appears to be directed in an. accidental manner,

that is, the direction in which the axis of the bore at the bottom thereof will point in relation to north cannot be predicted by prior art knowledge.

- It is common practice 'in'drilling such vertical wells, when the angle has drifted to an undesirmeans of the tension imposed upon the drilling line. In order to control the weight on the drill- I ing bit, a fraction, usually less than all, of the weight of the drill string suspended upon the drilling line so that a portion of the drill string is. in tension while the lower portion is in com.-

pression, thus imposing a thrust on the drilling bit due to the weight of that portion of the drill string which is incompression. The point in the drill string at which-ithe change-over from tension. to: compression is: knownas the transition': point or neutral point. p

fDeviated bore holes are distinguished from vertical boreholes by the fact that they are drilled to an objective sand to be bottomed at some distance from a. pointdirectly beneath thewe'llsite. -r

In drilling a deviated bore hole, it is the present practice to direct the bore hole to pass in a large arcuate path to a desired point in a target formation. Thus. the course of the well results in the axis having an increasing vertical deviation orv drift as. the bore is advanced. 'This procedure-is termed' building or increasing drift angle". .The rate of. increase of .drift and the rn'axi'nmmv desirable angle of drift is determined by a; number of considerations. Among the most important and controlling is the slenderness: ratio of themechanical' system of casing,

" drill pipe, and also the phenomenon of key seating. x

As a practical matter, the maximum rate of increase or driftusually employed in commercial This is accom- V practice is about 3-4 per hundred feet of bore hole and the usual maximum; deviation found desirable is about fill-70. These limits are dependent upon and are determined by the physical characteristics'of the bore: hole and the size and character of casing anddrill tubing employed in drilling wells. Ordinarily, for conventional tubing and easing the practical limit is as indicated.

The frictional resistance to the introduction of.

casing holes'of much'greater degree of curvature, or greater total deviation, is excessively large and largely impractical. e

It frequently conventional practice to start a deviated hole as a vertical bore through the unconsolidated formations lying at the surface. Depending on'the location and the course desired'f'or the bore, such vertical bores may be up to 1 000" or more; After the desired vertical depth is attained, drift angle is built up. Thus, 7

depending upon the depth of the vertical bore and the rate of building of drift angle, the bottom-of the hole when the maximum drift angle- 3 is built may be at some distance from the target. It is then conventional to continue the bore in a straight course at a constant drift angle.

It is frequently desirable to end the bore hole as a vertical bore. This is desirable in order to space the bore holes for efiicient drainage of the formations. When penetrating a formation at an angle to the'vertical, the bore hole intervals at the top of the formation will, in practically all cases, be different from the bottom of the formation. If they are spaced for eflicientdrainage at the top or bottom, the spacing at the other end of the formation will be inefficient since the bore holes in going through the formation will in practically all such cases make an angle with each other.

Where there is a plurality of oil horizons separated by non-productive zones, it is usually desirable to penetrate the zones at a predetermined position of the structure for maximum efficiency of production. Since in the usual case the various oil producing horizons have similar dips and strikes, it may be that if the course of the bore is inclined to the vertical, the bore hole will penetrate at different positions of the structure. Since, as is frequently necessary, it may be desirable to finish the hole to produce from selected formations, the position of the bore hole may be unfavorable at the selected zone. A vertical bore obviates these difficulties.

The reverse bend created by the decreasing of drift angle in any of the above cases increases the hazard of key seating, since the conditions for key seating are aggravated. in such circumstances.

It is thus necessary in drilling a deviated bore hole to build and decrease angles during the course of the bore hole.

In drilling such bore holes it is conventional practice to introduce a guide near the drill bit and to place drill collars between the drill bit and guide and also above the guide. This guide may be and usually is a reamer, the gage .or cuttingdiameter of which is about that of the drill. Its main function is to act as a fulcrum to cause the drill to be deflected downwardly or upwardly to increase or decrease the drift angle of the bore.

As a practical matter, it is desirable ideally to drill the bore hole so that its axis traverses as nearly as possible a plane which intersects the well locationand the target point in the target sand. This makes not only for minimum length of hole, but also reduces difiiculties in drilling.

It is, however, as a practical matter, impossible to maintain the azimuthal direction of the bore hole in the desired plane. The bore hole wanders to the leftv of the desired plane (1. e. develops left deviation) or to the right of the desired plane (develops right deviation) in an unpredictable manner; left and right being here and elsewhere defined in relation to a fictitious observer at the bottom of the bore looking downward in the direction of the axis of the bore,

In both the drilling of vertical bores and in drilling of deviated bores, Whether the hoi wiu deviate to the rightor left will depend upon one or all or a combination of the following factors which makeup the drilling environment: The type of drilling bit, that is, its design, whether it is a roller bit or a drag bit; if a roller bit, on the number of rollers and their sharpness; whether or not a reamer is used, and if a reamer is used, on the number of reamers and sharpness thereof, and on its design; onthe length,

size, and stiffness of the drill bit and drill collar placed between the reamer and bit and above the reamer; the size and type of drill pipe string, the size of the bore hole, the relative amount of cased and uncased hole, inclination and degree of curvature of the bore, type and condition and circulation rate of the mud, the weight placed on the drilling bit, the R. P. M. of the drill bit, the lithology, bedding, dip, and strike of the formation.

Variation in any one of the above factors causes a change in the deviation in a. manner which is unpredictable in the prior art. In order to change the direction of such deviation or establish an initial deviation, the prior art has employed directional whipstocks.

A directional Whipstock is a wedge which has the diameter of the bore hole and weighs from 1 to 2 tons. It is set in the bore hole by means of pipe and turned in the direction so that the faceof the whipstock is in the desired direction. Special drills, such as knuckle jointed drills, may be employed. When the hole ha been deviated, the whipstock is removed and reintroduced when the direction must again be corrected. The difficulty of setting and running whipstock,;particularly in deep holes, creates a serious hazard in oil wells. The danger is great that the whipstcck will wedge in the key seats or other portions of the bore holes. If this should occur, there is no way to dislodge and recover the whipstock, and the hole must be abandoned or the whipstock side-tracked. The cost of runninga whipstock, even when the operation proceeds without difficulty, is great and if the whipstock must be run with any degree of frequency, the cost may be prohibitively large.

I have devised amethod and drilling apparatus by which I can effect the direction and degree of deviation without employing whipstocks.

I have observed, in the case of the drilling of a vertical bore where no reamer is used above the drill andbetween drill collars, and in the case of the deviated bore holes where such reamers are employed, that the rate of deviation, that is, the number of degrees the drill wanders azimuthally per foot of drilled depth, is reduced or, in fact, may be changed to the opposite hand, for example, from left to right, when the drill starts reducing drift angle, that is, tends to straighten out or approach vertical, as the hole is drilled.

. My studies of the dynamics of the mechanical system which is employed in the rotary drilling of bore holes have resulted in a drilling procedure which permits of superimposing on the tendencies which the drilling environment, 1. e., all of the mechanical forces which are imposed on the bit, another Variable which is at the control of the operator and thus permit of the introduction of an influence which is at the disposal of the operator to affect the migration of the drill bit in the azimuthal plane.

It is characteristic of all wells with which my invention is concerned that they are directed downward into the earth, that is, that the axis of the bore hole is inclined from the horizontal to a degree which may be from 90 for vertical wells up to about 30 to 20 or more for deviated wells. In all such cases not all of the drill string is in compression. The upper part of the drill string is in tension and the lower part of the drill string is in compression. This is because the drilling line on which the drill pipe is suspended takes up art, but not all, of the weight load. of

' is called the'neutral point-of thestring.

. the-drill string. Thusthere is a pom-mule drill string Where the string changesover' from an axial tension to anaxial compressive stress 7 with the upper portion of the drill string intension and the lower portionofthe drill string in compression. Attheregionof change-over the strain and stress are minimum, and this region r The control ofthe change of drift angle build to cause the drill to move upward to build drift angle or downward to reduce drift angle in the prior art techniques of drilling both vertical and deviated bore holes is by controlling the position of the neutral point and'the' magnitudeof. the compressive forces in the lower end of the drill by changing the length and weight of the drill collars and by varying the degree of tension-"1n the drilling lines. a

' As a result of long experience with theabove' 'tion of the drill and also by controlling the direction of the component of the force acting on the bitperpendioular to its axisand thus I can control the'magnitude and direction of-the resultant force vector on the bit. Thus, holding" all of the other factors of the drilling environment constant, I accomplish this by (a) changing the ployed in overcoming the frictional-resistance.

For this reason the conventional threaded coupling's are'made up with considerable tensionfand are all of a hand-to be tightened during rotation.

In order to permit of this'reversal of rotation without danger of'unscrewing the various threaded joints, I employ a threaded coupling which will not unscrew on reversal of rotation of the drill I which has attained a non-vertical direction;

- Figs."2, 2a. and 2b are somewhat schematic showings of the bore endof the directionally deviated bore hole, showingthe drill collar in compression;

' Fig. 3 is a vertical section somewhat similar to Fig. 2,.showing the upper portion of the drill collar in tension;

Fig. 4 is a section taken on line '-4 of Fig. 2, showing thev forces on the drill pip at this line of section with the drill string rotating clockwise;

Fig. 4a is a section taken on line 44 of Fig. 2, V

showin'g'the forces on the drill stringat this section with the drill string rotating counterclockwise; 1

Fig. 5 isza section taken on line 5-5 of Fig. 3,

.. showing the forces onthe drill collar: with the character of the'lever-action on the .bit, and

(b) by changing the direction of rotation of the drill string. In the drilling procedure of my invention, when the drilling operation has resulted in an increase of drift ofthe bore hole and a deviation of the azimuthal direction of the'bore'hole, if said'deviation is to theleft and I desire to oppose this lefthand deviation to reduce its-rate or to introduce a right-hand deviation, I may proceedin thefollowing manner: I

If the rotation has been clockwise, I reverse the rotation to rotate the drillcounterclockwiseand simultaneously so control the weight on the. drillingline to cause the drift to increase or decrease, and by so doing I will, depending on the other environmental factors, reduce or cancel the left hand or right-hand deviation tendency, respectively, and impose aright-hand or left-hand deviation tendency, respectively. By so doing I will,

depending on the-other drillingconditions, re-

duce, cancel out the respective right-hand deviation orintroduce a left-hand deviating tendency.

. are right-handed, that is, they tighten when the cutting part into the screw joint is rotated clockwise. With such screwed joints reversal of rotation of the drill pipe is impractical and dangerous. since there is a danger that the joints will become unscrewed. This results from the fact that the frictional resistanceof theearth against the bit and the side walls of the bore hole against the side of the tubing isverylarge in drilling. In fact, substantially the entire drilling load,

running up to 100 horsepower and'more, is emdrill string rotating clockwise;

Fig. 5c is a section taken on line 5.-5'of .Fig. 2, showing the forces on the drill collar with .th drill string rotating counterclockwise; 1 Fig. 6 is a section taken on line 6-B of Fig. :6; showing the forces on the drill bit with the drill string rotating clockwise; t

Fig. 6a is a'section taken on line B-6 of Fig. 2, showing the forces on the bit with the drill string rotating counterclockwise;

. Fig. 7 is a section taken on line l! of Fig;

showing the forces on the drill pipe at this line of section with'vthe drill string rotating clockwise;

Fig. 7a isa section taken on lineL -l ofFigr 3, showing the forces on the drill pipeatsthis sec-. tionwith thefidrill string rotating counterclockwise; 1 Fig. 8 is'a section taken on line 8--8 of Fig.3.

showing the forces on the drill collar'when the drill string is rotating clockwise;

Fig. 8a is a section taken on line 88 of Fig. 3, showingthe forces on the drill collar when the drill string is rotating counterclockwise;

Fig. 9 is a section taken on line 9-9 of Fig. vll, showing the forces on the drill bit when the drill string is rotating clockwise; w j If Fig. 9a is a section taken on line 9-9 of Fig. 3,

Showing the forces on thedrill bit when the drill string is rotating counterclockwise; W Fig. 10 is a section similar to Fig. 2, but showing the use of a drill collar and a guide or reamer positioned above the drill bit;

Fig. 11 is a similar construction used in the'sit uation shown. in Fig. 3, showing a drill collar and bore hole-.-.dr i1le'd by. using my. drilling technique in which the course of the hole is projected onto a horizontal plane.

InFig. 1, I is the conventional drilling rig derrick in which there is a crown block 2 and a drilling block 3 over which are threaded the drilling lines 4 which are wrapped around the hoistdrum 5. Suspended upon the block is a hook ion which is suspended the swivel 8 to which is connected the mud lines 9 which through the media of the pump Ill take mudfrom the pit [2. Connected to the swivel is a tool joint 13 to which is also connected the square drilling shaft or kelly M which passes through the rotary table which has a circular gear, as is well known, and the kelly passes through the tubing head I! into the vertical conductor pipe 22 which is setin'the earth and upon which is positioned the conventional control valve 2|. The kelly 14 is connected by means of a tool joint l3 to a string of drill pipe 23 which is also made up in sections, usually 20 in length, and connected together to form a long string of pipe by means of the tool joints l3. At the bottom of the string there may be positioned the drilling collar 24 connected by tool joint [3 to the drill pipe 23 and to the bit 25'. In the conventional operation this construction, as is shown here so far, is conventional.

The variation which I employ in my invention is,.instead of driving the gear by means of any power source which drives always clockwise, the use of a power set-up which permits me to drive the rotary either clockwise or counterclockwise. I illustrate this in Fig. 1 by means of the main power source and a reversing mechanism 19 such'as a reversing gear box or other reversing means, thus driving the rotary as shown by the gear 13 either clockwise or counterclockwise. Any other similar manner for reversing rotation may be employed. It is desired to rotate the rotary table either clockwise or counterclockwise and those skilled in the art will understand how to design equipment for this purpose;

In operating the rig, the pipe is rotated by the rotation of the rotary which rotates the kelly swiveling on the swivel 8. The mud is circulated through 9 down the drill pipe and upward between the drill pipe and the bore hole wall and the. casing 23, and out the pipe 26 back into the sump l2. The tension is maintained on line 4 to regulate weight on the bit, as is herein described, and the drill pipe is advanced while it is rotated, retaining the desired tension on line 4.

It will be observed that with ordinary drilling strings all threads are right-handed, and for that reason the clockwise rotation of the drill pipe is necessary in order to preventthe unscrewing of the drill pipe at its threaded connection. In order to be able to drill either clockwise or counterclockwise, I employ at all screw joints at which connections are made a form of connection which will not unscrew irrespective of whether the drill pipe is rotated clockwise or counterclockwise. I form the conventional box and pin 2'! of a tool joint such as a standard tool joint which, as is well known, is thread connected, as shown at 24 and 24, to the pipe 23, and which may be also welded in position as shown at 24 or may be integrally formed with the pipe 23 or welded thereto as is conventional in oil field operations. The box and pin are screwed together with the conventional right-hand screw thread at 26 and the threads 24 and 24 may also be right-handed, but in this case there is a welded connection between the box and the pin and. the pipe.

The exterior circumference of the box is formed with a left-hand thread 32 and over the pin is slipped a sleeve 30 which has an internal shoulder 3| and which carries a left-hand thread to engage thread 32 and is screwed down tight, and when so screwed .the internal shoulder 3| is screwed down against the shoulder 28 of the pin. This form of tool joint will not unscrew on either right-hand or-left-hand rotation of the drill pipe. Other forms of such construction as shown in various co-pending applications may be employed. No claim is made for the particular construction of the tool joint in this case which may be used in the combination of the invention described in this application.

Instead of using a collar 24 made up of various lengths, I may separate the collar into two sections 35 and 36 and introduce between the collar sections, as shown in Fig. 10, a guide 33 of diameterequal to the diameter of the hole, which may be in the form of a reamer, the cutters 34 of which may be either dull or sharp, and which has a gage equal to the gage of the drill bit 25'.

Assume that the drill string is rotated clockwise and that the weight on the drilling lines 4 hasbeen adjusted to place the drill collar 24 in compression, i. e., to that the weight of the drill string from the kelly to the top of the drill collar is suspended on the drilling lines. This is accomplished by holding the required tension on the drilling lines 4 by applying the proper braking force on the hoist drum 5 on which the lines are wound. Theconventional instruments used for such purposes will supply the necessary information for such control. This procedure will be fully understood by those skilled in the art.

Fig. 2 illustrates what happens to the drill string in the procedures employing my novel technique of drilling in a well the axis of which is deviated from the vertical.

Assumethat the neutral point is chosen as illustrated at 31, Fig. 2. It will be observed that the drill collar below the neutral point is in compression and that the drill collar at the neutral axis point will, because of its weight, rest on the low side 38 of the bore hole. Since the drill pipe in the vertical section 39, Fig. 1, of the hole is centrally positioned and is in tension between the hook and the neutral point, the drill string is, in the portion under tension, pulled to the upper side. 40 of the bore hole.

Fig. 4, taken on section line 4-4, indicates the position of the drill pipe 23 on the upper portion of the hole. The tension in the drill pipe will causethe drill pipe to press with a force which is schematically indicated by a vector A which is directed perpendicular to the axis of the drill pipe and the bore hole at that point. If I rotate the drill pipe clockwise, as indicated by the arrow, the drill pipe will tend to travel down the lefthand side of the bore hole (usin the convention established above) and thus a force directed as indicated by arrow B will also be imposed on the pipe and the pipe will thus beunder force acting in the resultant direction C. It will be observed that the drill collar is, as stated, positioned at the bottom of the bore, as illustrated schematically in Figs. 2 and 5, and the weight of the drill collar 24 presses it against the low side of the hole 38 with a force illustrated by the vector D. The right-hand rotation clockwise of the drill pipe causes a like rotation of the drill collar 24 to cause it to tend to move up the right-hand side of the bore hole and thus a force directed in the direction of the vector E is imposed on the drill V pipe. Theresultant of these forces isa force on the direction of thevector F.

The center of mass is shown at ll in Fig. 2 and [the gravitational weight is indicated by the vecwill be observed that the magnitude of the vector H" depends on the weight of the system acting at'center of gravity and on the value of the angle b which depends on the drift angle of the bore holev and value of the angle a. between the axis of the bore hole 42 and the axis 430i the drill collar. Since the drill'bit is of greater gage than the outer diameter of the drill collar, the system may be treated as a beam loaded at the center of gravity Al and resting at 42' and at 44. Thus a force directed as the vector is exerted (see Figs. 2 and 6). Since the axis of the drill collar makes an angle a with the axis of the bore (see Fig. 2) the compression force has a component in the direction of the vector G (see Figs. 2 and 6). The magnitude of the component depends on the magnitude of the component H and the angle a which depends on the difference between the diameter of the drill collar and the gage of the bore which in turn depends on the gage of the bit. If the magnitude of the force vector G is more than H, the net force will be directed in the direction of the vector I. V

The force vector E, acting at the point of contact between the'drill collar andthe bore hole, acting through thelever arm of the drill collar 24, will cause a force directed in the direction of the vector J. The magnitude of J for any value of the force vector E will depend on the length of the lever arm, i. e., the length of the drill collar 24. The net force vector K will be upward andto the left. of these forces is to direct the drill to build a drift angle to move further from vertical and to move to the left, and if continued will cause the drill to execute a counterclockwise spiral to the left; If the force vector H is greater'than G, as will be the case in high angle bore holes, i. e., those which are directionally drilled to execute a curved path, for example, for illustrative purposes, where the angle is above about 7, the drill will move downward to lose angle and drill to the leftin a counterclockwise spiral.

It will be observed that the magnitude of, the rate of deviation will-depend on the relative proportions'of the force vectors I andjJ andtha't relative position of the neutral point and the drift angle of the bore hole. Fora borehole at any drift angle, the greater the weight and the less the value of the angle a, the less the Value of I and the greater the rate of deviation to the left. Thus, by proportioning the weight of the drillcollars, I can influence the degreeof left deviation obtained by the clockwise rotation, I. may not, however, reverse the direction of; the' force vector J to the right while maintainirle the drill collars against the low side of the hole by r the expedient of proportioning the relative value of G and H as the drill advances into the earth. This left-hand tendency will cause the drill to execute a left-hand or counterclockwise spiraling This means that the influence 7 10 tirely undesirable, since it may result in the bore crossing a boundary line to the left such as 41 (see Fig. 14), and also since most drilling requirements are that the hole be within acylinder of specified radius of the well head, the bore may wander outside this cylinder.

I may tighten this spiral so as to cause the drill to turn more sharply to the left by increasing the relative magnitude of the force vector G with respect to J as described above, for example, to execute the spiral arc 48.

I may also increase the magnitude of the force componentG and thus decrease the rate of lefthand deviation tendency and increase drift angle buildup, employing the same value of the weight at the center of mass by employing a reamer or other fulcruming guide'as indicated in Fig. 10. The force G is multiplied by the lever ratio resulting from the fulcruming action at the reamer 33 and the value of the component H is reduced, since, this being the efiect of weight and part of the weight is supported at the reamer, the weight component of the structure between the reamer and the bit being less than the entire mass'of the structure below the neutral point,- the component I is always upward when the neutral point contacts the low side of the hole as describedabove. But in this case, also, the tendency of the right-hand or clockwise rotation is a force vector J to the left to cause the drill to Wander, but in a tighter spiral arc, e. g., 48, Fig. 14, than the are 46.

It is to be observed, however, that whereas the greater the ratio of the force vectors G to J,

I may, however, reverse the direction of the force vector J so that it is directed to the right I rather than to the left by the simple expedient of reversing the direction ofrotation of the drill pipe by the means described above. This causes the drill pipe to tend to move down the righthand side of the bore hole so that the vector B is reversed in direction. Thus, by this reversal the force vectors B and C are directed to the right (see Fig. 4a), and the force vectors E." and are directed to the left (see Fig. 5a) and the force vectors J 15; and K" are directed to the rightlsee Fig. 60:) for the reasons described above, The spiraling are is thus reversed so that it now tends to move in a clockwise direction to follow the coursealong arc dd, as illustrated in 'ig. 14, while; increasing or decreasing drift as described in connection with Figs. 4a to caabove.

I may as described above tighten this are to follow. for example, are 59. by reducing the right-hand deviation tendency and I accomplish this by relatively increasing the ratio of the force I to the force J as described above by the expedients described above. In this manner the rate of deviation and the number of degrees of I left turn or right turn per foot of depth penetrated may be controlled. I

It is frequently desirable, as described above,

, to cause the drill which has built up drift an ie are (See Fig. 14) and if continued willevem tually extend in the curve 46. This may be. ene

to now drill downward with reducing drift, angle, 1. e., to cause the prolonged axis of the bore to become more vertical; This is accomplished by increasing the tension of the drilling lines and adiustment of. thelengthof the drill collar or using both expedients. The net result of this procedure is to cause the neutral point 55 to move downward more closely to the bit (see Fig. 3) than in the case of Fig. 2. The result of this procedure is to cause the drill collars which are of smaller diameter than the hole to pivot to the upper side ll! of the bore hole to contact the upper side at 55 (see Fig. 3).

The weight of the drill collar is indicated as the vector R, and this results in an axial compression force vector X and a side thrust vector 5 as a result of the angle b for reasons which will be clear from the above discussion with respect to Fig. 2. This force S, acting on the lever arm of the drill collar fulcrumed at 55, exerts a force in the direction '1. Because of the angle a, i. e., the inclination of the axis 42 of the bore hole at the drill collar to the axis 56 of the drill collar 24 in Fig. 3, there is a force vector U which is directed in the same direction as T, tendin to cause the drill to lose drift angle and to approach the vertical as drilling progresses.

Referring now to the forces on the various portions of the drill string in this situation, it will be observed that at the section 7-1, see Fig. '7, the tension in the drill string has drawn the drill pipe to the upper side 4! of the hole as indicated in Fig. 3 in a manner similar to that shown in section l4 of Fig. 4. This results in a force pressing the pipe against the upper side of the hole in a direction normal to the axis of the hole, 1. e., a vector directed as indicated at L in Fig. 7. The clockwise rotation of the pipe as indicated by the arrow in Fig. '7 causes the pipe to travel down the left-hand side of the hole and under a force directed as vector M in Fig. '7 in a manner similar to that described in Fig. l, resulting in vector N directed similar to that of vector C. At section 88 the drill collar is against the upper side of the hole contacting at 55, as indicated in Figs. 3 and 8, with a force which holds the drill collar against its weight pressed against the upper side of the hole. This force is indicated by the vector 0. The clockwise rotation of the drill collar causes a force vector in the direction P, with a resultant force vectored as shown at Q. The drill collar now tends to ride down the left-hand side of the hole.

Referring to the forces at section 99, it will be observed that since the vector T and the vector U, as previously described in connection with Fig. 3, are directed in a direction normal to the axis of the drill collar, they are additive and the resultant force vector will be the sum of the vectors T and U. The force P directed to the left, acting through the lever arm of the drill collar 2%, exerts a force which is directed in the direction of the vector V, that is, to the right, see Fig. 9.

It will be observed both in Figs. 2 and 3 that the combination of the drill collar and the bit forms a bell crank lever, one arm of which is made up of the length of the drill collar 24 and the perpendicular arm of which is made up of the pitch diameter of the drill bit 25. Thus if one end of the bell crank, that is, the upper end of the drill collar, has exerted upon it a force directed to the left, the force on the opposite edge of the bit, at the end of the short arm of the bell crank lever, will be directed to the right or vice versa. If the long arm of the bell crank lever, i. e., the length of the drill collar, is to the right, as in Fig. 5, the force at the opposite edge of the bit will be to the left, as in Fig. 6. Referring now to Fig. 9, the resultant force on the bit, as the result of the force vectors T, U, and V will be a force in the direction of the vector W, which will be downward and to the right.

Therefore, drilling with drill collars, drill bits with controlling weights, to position the neutral point within the drill collar and close to the bit, will result in the bit seeking to attain a more vertical position to lose drift angle and to turn in a clockwise, right-hand spiral such as is illustrated at 49in Fig. 14.

As described in connection with Figs. 2 and 4 to 6a, inclusive, I can decrease the rate of deviation, that is, the number of degrees at which the drill will move to the right clockwise per linear foot of bore thus drilled, by increasing the sum of the vectors T and U in relationship to the vector V. By so doing the rate of deviation is decreased, resulting in a tighter spiral curve 53, as shown in Fig. 14. It will thus be possible to hold the drill bit within a desired circumference from the well site within a smaller cylinder centered at the well site than in the previous case.

This may be accomplished by the use of the reamer as is illustrated in Fig. 11. There it will be seen that the lever ratio has been established, as in the previous case, Fig. 10, around the fulcrum of the reamer so that for any given weight centered at the center of gravity for any given force 0, the force V will be increased. It will be observed that in the case shown in Fig. 3 no reamer is employed, whereas in the case shown in Fig. 10 the reamer is employed to accentuate the rate of build-up. By employing the reamer, however, as shown in Fig. 11, the weight of the drill collar, acting above the reamer, acts-to produce a multiplied force fulcrumed at the reamer which adds to the force T rather than subtract ing from it. I may thus increase the rate of drift angle build-up of hole drilled to widen the arc 49 to decrease the rate of deviation per foot of hole drilled. This may be desirable where a tighter arc is undesirable as, for example, where it would cross a property line or approach another well.

In all such cases, however, where one is drilling to decrease drift angle, the force vector acting on the drill bit is to the right. The variation of the relative values of the force vectors will not reverse this right-hand deviation tendency, although it affects its magnitude.

To reverse this tendency and to impose upon the drill string, because of the forces previously described, a left-hand deviation tendency, I may, as in the previous case, reverse rotation to rotate the drill string counterclockwise instead of clockwise. In such case, as illustrated in Figs. 7a to 9a, the force L in Fig. 7a is similar to the force L in Fig. '7; the force vector Y isnow to the right since the drill string tends to move down the righthand side of the hole, and the force vector Z is directed to the right. The drill collar is also against the upper side of the hole, as indicated in Fig. 8a, and the force vector 0- is similar to the force vector 0 in Fig. 3. The force vector P is directed to the right, whereasthe force vector P is directed to the left because now the drill collar tends to move down the right-hand side or" the hole. The force vector Q is thus therefore also directed to the right. The force vector P being to the right, the force vector V, Fig. 9a, is to the left instead of to the right, and the force vectors T and U, acting with the force vector V, are not to the left at W, instead of to the right at W. Thus, we are executing a left-hand turn or a o nterclockwise spiral such as 46 instead of a 13 clockwise spiral.'- When the rotation of the drill string is; of the. type that is clockwise, as 45,1 may effect the rate of deviation per foot in the. same manner as described in connection with Figs. 7, 7a, 8, 8a, 9, and 9a by controlling the relative. magnitude of the force vectorsT and U by the expedients previously described to change the direction of the force: vectors V and V by means 01" the control of the length of the lever arm, its weight, and the use of a fulcruming guide such as a reamer, as previously described.

In the previous methods as described above, the reversal of rotation has been employed for c the purpose of directing the course of a well vertical inclination as well as the azimuthal direction of the axis of the bore hole may be determined. This is'a' well known and well estab lished technique in oil well drilling.

"If the survey indicates that the well has deviated in any direction to the vertical in an amount, for example, from' about to 1%, T

I may without altering the weight on the bit reverse the direction of deviation. If the direction of deviation is to the right, using the conventions previously described, I can without changing the tension in the'drill stringer in anyway changing the other environmental factors of the drilling operation impose an oppQs ing tendency, I may thus cut down the righthand deviation tendency or cancel it out or impose a left-hand deviation tendency by the'single expedient of reversing rotation of the drill pipe. If the deviation tendency as determ'inedlby the well survey indicates the deviation is 'tothe left, I may in like manner, without changing any of the environmental factorsof the drilling operation, introduce a right-hand tendency whichwill.

oppose, cancel out, or overcome this left-hand deviation tendency and impose a right-hand deviation tendency to introduce a right-hand spiralingefiect upon the drillpipe in themanunderstand how to determine the number of times the. drill pipe. has twisted axially under any condition of operation.- As a practical mat-V ter, it will berfound that it will be desirable to set the reversal upon some time frequency scale,

depending upon the rate at which the drill prothe vertical. The reversal imposes reversals in the direction of spiraling-tendency to give an av- I erage straight line direction'ofv the bit.

The more frequent reversals of rotation of the drill bit has theaadvantage that its produces a longer Iife'of the bit and reduces the frequencyat which bits must be changed. This is one of drilling technique, those skilled inthe art will know how to apply my. new drilling-technique.

My invention includes the practice of rotary bore hole drilling into the earth below the horizontal in which the drillstringis rotated counterclockwise, or, if desired, alternatelyclockwise andcounterclockwise.

My invention also includes a drill string all I th'e'sc'rew joints of which will not unscrew, irrespective of whetherthe string is rotated clockner previously described. In such operation,

therefore, I surveythe well periodically and when the deviation is established to a predetermined degree, I reverse rotation and continue the direction of rotation until the azimuthal de-' viat-ion to the left is in an amount substantially, for example, of the order of that of the orig-' inal deviation to the right.

An alternative procedure which avoids the necessity of periodic reversal of rotation with intermediate well surveys for the purpose of determining the direction of drift, is to establish a frequency cycle in drilling a vertical bore hole which includes a periodic reversal of rotation first clockwise then counterclockwise after the rotary has made a number of-turns greater than the number of turns necessary to wind up the pipe. put in axial twist due to the fact thatthe drill pipe is pressing against the bottom, and the top of the drill string is free to swivel on swivel. The result .of this operation is that the drill pipe takes a number of turns before the drill starts rotating. These turns may be anywhere from one to twelve or more. Those skilled in the art wise 'or counterclockwise.

My invention includes a drilling technique whereby a bore hole is advanced into the earth in a direction downward, that is, below the horirental, by means of a drill string which is rotated in a bore hole, whose lower section adjacent the drill has an inclination to the vertical and in which the drill pipe is under an axial force, said.

force in the'upper portion of the drill string being inaxial tension and the lower portion of the drill string adjacentthe drill pipe being in tion'of rotation of the drill string either clockwise or counterclockwise to control the direction of deviation of the drill bit and the degree of such deviation per foot of hole drilled by the bit.

' invention also includes the simultaneousfulcruming of the drill string adjacent the bit to control the vertical angle of drift and to increase or diminish the said angle of driftby con- It is; well known that the drill'pipe is trol-of the relative tension-on the drilling-lines.

ploying the above convention, that is, in a di rection perpendicular to the; vertical plane through the axis of the bore hole at said bit, by controlling the direction of rotation of the drill string as described above while controlling the tension in the drill string in the manner stated hereinabove. I

The specific construction of the tool joint de-' scribed above and shown in'Figs. 12 "and 13 is the joint invention of applicant and James Moon and is the subject matter of application Serial No. 642,079, filed January 18, 1946, and no claim to sole invention thereof is made herein.

While I have described a particular embodiment of my invention for the purpose of illustration, it should be understood that various modifications and adaptations thereof may be made within the spirit of the invention as set forth in the appended claims.

The present application is a continuation in part of my copending application for Letters Patent Serial No. 642,080 filed on January 18, 1946, now abandoned; and the present application is also a continuation in part of my copending application Serial No. 136,533, entitled Directional Drilling, filed January'S, 1950.

Iclaim:

1. A method of rotary drilling of a deviated bore hole downward int the earth which comprises rotating, in one direction, a drill string carrying a rotary drill at the end thereof, placing the end of said'drill string above said drill in compression and placing the portion .of said drill string above said compressed end in axial tension thereby fulcruming said drill string at a point above said drill and thereby generating a force component in a direction perpendicular to a vertical plane passing through the axis of saidbore at said drill, and reversing the direction of rotation of said drill string and reversing the direction of said force component by said reversal of rotation and thereby altering the direction of travel of said drill.

2. A method of rotary drilling of deviated bore holes downward into the earth which comprises rotating, in one direction, a drill string carrying a rotary drill at the end thereof, placing the end of said drill string above said drill in compression and placing the portion of said drill string above said compressed end in axial tension, thereby fulcruming said drill string at a point above said drill and thereby generating a force component in a vertical direction in a vertical plane passing through the axis of the bore hole adjacent said drill, and thereby also generating a force component in the direction perpendicular to said plane to cause the drill to travel in a direction having upward and azimuthal components, and reversing the direction of rotation of said drill string thereby reversing the direction of said force component perpendicular to said plane and causing the drill to travel in an altered azimuthal direction.

3. A method of rotary drilling of deviated bore holes downward into the earth which-comprises rotating, in one direction, a drill string carrying a rotary drill at the end thereof, placing the end of said drill string above said drill in compressionv and placing the portion of said drill string above said compressed end in axial tension, thereby fulcruming said drill string at a point above said drill and thereby generating a force component in a downward direction in a vertical plane passing through the axis of the bore hole adjacent said drill, and thereby also generating a force component in the direction perpendicular to said plane causing the drill to travel in a direction having downward and azimuthal components, and reversing the direction of rotation of said drill string thereby reversing the direction of said force component perpendicular to said plane and causing the drill to travel in an altered azimuthal direction. a

. 4. A method of rotary drilling of deviated bore holes downward into the earth which comprises rotating in one direction a drill string including a drill pipe, a drill collar and a drill positioned at the end of said drill collar, placing the lower end of said drill collar above said drill in compression and placing the drill collar above said compressed end in axial tension, thereby fulcruming said drill collar in said bore hole and thereby generating a force component in a vertical direction in a vertical plane passing through the axis of said bore at said drill, and thereby also generating a force component perpendicular to said plane and reversing the direction of rotation of said drill string and reversing the direction of said force component by said reversal of rotation and thereby altering the direction of travel of said drill.

5. A method of rotary drilling of deviated bore holes downward into the earth which comprises rotating in one direction a drill string including a drill pipe, a drill collar and adrill positioned at the end of said drill collar, placing the lower end of said drill collar above said drill in compression and placing the drill'collar above said compressed end in axial tension, thereby fulcruming said drill collar in said bore hole and thereby generating a force component in an upward direction in a vertical plane passing through the axis of the bore hole at said drill and thereby also generating a force component perpendicular to said plane to cause the drill to travel in a direction having upward and azimuthal components, and reversing the direction of rotation of said drill string thereby reversing the direction or" said force component'perpendicular to said plane and causing the drill to travel in an altered azimuthal direction.

6. A method of rotary drilling of deviated bore holes downward into the earth which comprises rotating in one direction a drill string including a drill pipe, a drill collar and a drill positioned at the endof said drill collar, placing the lower end of saiddrill collar above said drill in compression and placing the drill collar above said compressed end in axial tension, thereby fulcruming said drill collar in said bore hole and thereby generating a force component in a downward direction in a vertical plane passing through the axis of the bore hole at said drill and thereby also generating a force component perpendicular to said plane, to cause the drill to travel in a direction having downward and azimuthal components, and reversing the direction of rotation of said drill string thereby reversing the direction of said force component perpendicular to said plane and causing the drill to travel in an altered azimuthal direction.

DANIEL S. JOHNSTON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,859,490 Atkinson May 24, 1932 1,891,329 Le Compte et al. Dec. 20, 1932 2,147,537 Lowrey Feb. 14, 1939 2,173,035 Armentrout et al. Sept. 12, 1939 2,215,928 Hornbrook Sept. 24, 1940 2,280,851 Ranney Apr. 28, 1942 FOREIGN PATENTS Number Country Date 448,693 Germany Aug. 20, 1927

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