US2382933A - Method of drilling holes - Google Patents

Description

Aug. 14, 1 945. J. A. ZUBLlN v METHOD OF DRILLING HOLES Filed Dec. 16, 1941 IIIIII INVENTOR dbH/v A. Z052 IN,

Patented Aug. 14, 1945 METHOD OF DRILLING HOLES John A. Zublln, Los Angeles, cam.

Application December 16, 1941, Serial No. 423,227

3 Claims.

This invention relates to methods of drilling angular holes which primarily originate and terminate within the oil sand and which deviate strongly from the axis of an existing well bore for the purpose of tapping oil sands too distant from the well for drainage by the well itself.

Present methods of drilling holes which deviate from the axis of an existing well are confined mainly to two methods; firstly, to exert with whi stocks, knuckle joints or similar deviatingdevices a sidewards pressure on the bit attached to the customary string of drill pipe used for drilling oil wells to such an extent as to deviate this bit and pipe from the original axis of the hole; secondly, to attache a very flexible section at the bottom of regular drill pipe, this flexible section being of the nature of metallic flexible hose or jointed short individual sections enabling the drilling of lateral holes at right angles to the well bore with a very sharp turn from the vertical axis of the well.

Of the two methods, only the first is in practical use for the purpose of reaching underground sources of oil which are not vertically under the derrick of the well. This inclined drilling, however, proceeds, because of the stiffness of the regular drill pipe, only at very small angles with bit which is slightly smaller in diameter than the bit will provide a guide for the bit itself. Now then, since a. curved guide of this character will force a bit to drill a curved hole, and a straight 'uide of this character will force a bit to drill a straight hole, it is only necessary when the deviation from a straight hole into a curved hole is planned, to introduce a curved guide forcibly into the straight bore, said guide being flexible enough to allow it to be pushed into the straight hole. If it be desired to drill a straight bore from a curved bore, a flexible straight guide is inserted into the curved bore. If now the bit is placed at the point where the side hole is to be started and deviated from the original hole, all that remains -o be done is to rotate the bit with adequate means without however rotation of the guide. The resiliency of the long tubular guide forcibly bent in the original hole exerts a considerable side pressure on the drilling bit rotatably connected with it to such an extent that a proper type drilling bit will upon its rotation dig immediately into the side of the wall at the point of contact. If the tubular guide is now lowered, the bit will continue to drill sidewardly but also downwardly, the

guide following the bit as drilling progresses.

minimum radii of curvature of more than 500 feet, making it impossible to confine these deviating holes to the thickness of the average oil sand. Deviation therefore must start above the oil sand, calling for casing and cementing and all other expensive requirements necessary in the drilling of standard vertical holes. The second method has the opposite disadvantage of being too flexible, making it impossible to obtain a bore in a defined horizontal and vertical direction beyond a certain distance from the well, since the extreme flexibility does not give the bit sufficient rigidity to drill the oil sand and to maintain a predetermined direction.

The present invention combines to some extent the advantages of both methods, eliminating at the same time their weaknesses, making it therefore practical to drill side holes from an existing well whether vertical or not, the side hole starting from the original hole Within the oil sand at any place, and extending in any direction with a curve of a radius from 10 to 100 feet.

Drilling of this curved hole can be stopped at will and continued with a straight hole. Alternating of curved hole and straight hole at will is entirely feasible in any direction and at any angle, thus enabling by this method the drilling of substantially horizontal holes from a vertical bore penetrating an oil sand, carrying this horizontal hole within the oil sand to any desired point, where oil saturated strata are located, to allow oil to flow through this horizontal bore into the well.

It is a known fact that a tubular carrier for a The resiliency of the forcibly bent guide will continue to exert a side pressure on the bit until the guide has reached its tensionless state of original curvature. In other words the bit will be forced to continue this curved hole under the side pressure of the guide exerted on it.

Now then, if an amount of curved hole has been made substantially equal in radius to the radius of the curved guide in tensionless condition, the

relation between curved hole and curved guide will be reversed to the point that whereas in the beginning the guide forced the bit to drill a curved hole, said curved hole now causes the relaxed guide to continue along this curve as long as desired. In other words, a guide of aradius of 25 feet and a length of 20 feet will continue to guide the bit in the drilling of a hole of the same radius even \after the length of this drilled hole has exceeded the 20 foot length of the curved guide.

Additional guides of this type above the curved guide connected with the :bit need not necessarily be curved themselves. They may be straight, being forcibly bent into a curve in the first part of the curved hole, in the same manner as the curved guide was bent into a straight line in the straight hole of the original well bore. This combination will permit lowering into a vertical well, cased or uncased, a string of guides composed of one bent section and one or more straight sections, greatly reducing the side pressure on the bit and the friction of these guides, since only the first guide close to the bit is of the curved type. and following sections being of the straight type. It is further clear that if the bit is withdrawn from the hole and the curved guide immediately behind the bit is replaced with a straight guide, this straight guide will exert on the bit opposite side pressure, forcing the bit now to discontinue the drilling of a curved hole, drilling from there on a straight hole. This method of deviation of bores is therefore reversible from straight hole t curved hole at will, at any point and in any direction.

Although the above brief description is directed to a device which utilizes a resilient guide which is forcibly bent by the walls of the hole, it is also contemplated that a normally straight guide could be utilized of such construction that after it has been inserted in a straight hole it can be curved by means other than the resiliency of the member itself. For instance, a normally straight resilient guide can be so constructed that starting the pumps at the surface causes it to curve. The operation of such a guide would be no different from that of the above-described structure as the hydraulic pressure would impart a new normal curvature to the guide which would then have the resiliency necessary to supply the energy t force the bit sidewise in the bore. It is also possible to provide a normally curved guide which straightens out under the influence of hydraulic pressure for drilling a straight bore from a curved bore.

Modern methods and means of orienting bore holes and the tools for drilling same are sufllciently accurate to guide the drilling of a devi-' ated substantially horizontal hole in the desired direction. In the same way as it is possible to drill a side hole out of an existing vertical hole, it is also possible to drill a second side hole out of the first side hole in the desired direction, making it possible t supply a well with a number of side holes which leave the vertical bore of the well at diflerent points, these side holes having additional side holes, and thus forming a ramification of holes around the well which will effectively drain all the oil which possibly can be recovered from the area allotted to this well.

The economic advantage of drilling side holes out of an oil well within the oil bearing formation is very great. With the present practice of drilling one well for approximately 25 acres of potential oil sand, it is inevitable that large amounts of oil held in the oil sand at certain distances from the well bore cannot reach the well due to lack of gas pressure or due to great resistance to flow through a tightly packed .oil sand, or. due to both. To increase the ultimate recovery of oil from a given oil field is one of the major problems of national economy since the most qualified experts on this subject agree that present recovery from an oil sand varies between 20 and 35 per cent of the available oil. New oil sands which are discovered today are mostly at depths exceeding 7,000 feet. To drill a well to this depth, to set the necessary strings of casing and to protect the oil sand from water encroachment, a large expense must be undertaken. The present practice of locating 'wells on the approximate basis of one to 25 acres of land spaces the wells about 1,000 feet apart. It is therefore obvious that if substantially horizontal small size open holes can be drilled right within the oil sand. covering with their ramifications all of the 2.5 acres allotted to one well and carrying most of this oil to that one well from which these side holes originate, this will be a far cheaper and more efficient undertaking than drilling additional wells from the surface to recover that oil which has not been produced by those wells originally allotted to the oil field. The drilling of substantially horizontal ope holes entirely within the oil sand is further faciliated because most of the impervious cap rocks which enclose an oil sand are of greater hardness and have more resistance to the drill than the oil sand sandwiched in between them. If therefore the bit of a'hole drilled horizontally within this oil sand should strike the impervious cap rocks on the upper or on the lower side of the oil sand, the bit would strike them at a willciently small angle so as to be deviated back into the oil sand without having a chance to perforate this impervious cap.

The efficiency of the repressuring of partly depleted oil sands or the furnishing of high-pressure gas from one sand to another is similarly aifected by the resistance of the sand as is the production of liquid oil. It is therefore understood that the invention herein described will lend itself equally well to the distribution of gas throughout the sand flowing through the deviating holes from an intake well as it does in facilitating the flow of oil from the sand through deviated holes into another producing well. In fact, the combination of both, mainly the eflect of side holes drilled in the oil sands from one well for a distribution of gas combined with the effect of side holes drilled in the oil sand from another well for the recovery of oil is the subject of another patent application entitled Method of increasing oil production, filed on the same date as this application.

Although this invention is primarily designed to drill deviating holes out of an existing open hole it is however possible to use the same method of drilling out windows through the casing within a well, the successful performance being only a 0 matter of suflicient lateral pressure of the resilient curved guide.

The invention is also applicable to the obtaining of side wall samples from a well bore. It becomes a simple matter to attach a conventiorial core head to the resilient guide and to utilize the entire device as if proceeding to drill a side hole, but stopping the operation of the device after the head has advanced sufficiently to take a core.

Another use of the curved guide and bit assembly is to perform the function of a whipstock; i. e., the starting of a bore at a small angle to an existing bore, After such bore has been produced, it becomes necessary to merely withdraw the guide and bit from the well and proceed in the usual manner.

With the deficiencies of present day apparatus and methods in mind, it becomes a primary object of the present invention to provide improved apparatus and methods for the production of deviating bores.

It is a further object or the present invention to provide methods and apparatus which will be capable of producing a sharply curved bore.

It is a further object of the present invention to provide apparatus which will enable the production of curved bores which requires less orientation than present day apparatus.

It is a further object of the present invention to provide a method and apparatus for the production of curved bores which do not depend upon the setting of successive deviating devices for curvature of the bores.

It is a further object of the present invention to provide apparatus for the production of deviways.

which can operate through a, curved bore.

It is a durther object of the present invention to provide a method and means which will permit the drilling of lateral bores in an oil well and which can be used to produce branching or ramiflcation of these lateral holes.

It is a further object oi! the present invention to provide a method ior drilling bores which extend laterally from the well bore within the producing sand without passing through the other strata, and therefore need no casing.

, It is a further object to provide a means to take side wall formation samples.

Other objects and advantages will become apparent as the description proceeds.

Rerierring now to the drawing:

Figure 1 is a view showing a device embodying the present invention in place in a well bore and starting a lateral hole;

Figure 2 is a view similar to Figure 1 showing the drilling of a lateral bore at a later stage of operation;

Figure 3 is a, view similar to Figures 1 and 2 showing a drilling bit in a curved hole, the apparatus being arranged to continue the bore in a straight line;

' Figure 4 is a view partly in section of a suitable means for rotating the drill without rotating the guide to which it is attached;

Figure 5 is a, view of a device employed in taking side wall samples; and

Figure 6 is a partial section of a. drill guide which although normally straight is forced into a curve by hydraulic pressure.

Referring first to Figure 1, an existing well bore [0 is indicated in section, and it is desired to start a lateral hole at point Ii. The resilient curved guide 12 is utilized immediately above the bit Hi. This curved guide member l2 in its normal condition is more sharply curved than shown in Figure 1 and is :forcibly bent to the shape shown in Figure 1 by the pressure of the walls of the hole Ill. The natural tendency of the resilient member l2 to return to its original bent position forces the bit against the wall of the hole ill at point II. The pressure with which the bit bears against the wall depends upon the resiliency of member I: and its departure from its tensionless position. If the bit be rotated without however rotating the guide l2 the pressure exerted by the bit against the side wall at II will cause the bit to drill sideways. the entire drill pipe [from the surface of the ground after the bit has cut some hole will cause the bit to drill in a downward direction but the side pressure causes the bit to also travel side- Eventually this drilling action will result in a circumferentially complete bore leading out of the main bore Ill. The curved guide will continue to exert a side pressure on the bit as long as it is held against returning to the curvature which it has when there is no straightening force acting upon it. By this time however suflicient of the guide will have entered the side bore being produced, and as the curvature of this bore closely corresponds to the curvature of the guide I2 the guide l2 will slide around this bore and drive the bit in a continuing curved path. This will continue as long as the guide I! is fed into the curved bore :being produced.

As it may be desired to produce a curved bore which eventually takes a horizontal direction, and as it is often impracticable to utilize a curved guide I! which in its relaxed position has a dualter-circle configuration the arrangement shown in Figure 2 is utilized. In this figure the member i2 is as described in connection with Figure 1 but the member I4 is different. This member I4 is flexible but instead 01' returning to a. curved configuration when there are no forces acting upon it, it is normally straight. It thus oilers no hindrance to being lowered into the well with the member I2. When this member it reaches the curved bore ll being produced by the bit ll and the member II, the member I will bend around the curve and will have no effect upon the bit, thebit being guided solely by guide II. This combination of members I2 and II, the member l2 being attached to the bit and the member ll following member I2 into the curved Lowering bore, will cut a hole which continues to curve no matter how far drilling is carried.

When the assembly described in connectio with Figure 2 has drilled a, hole which points in a direction which it is desired to have this bore take, it may be desired to cause the hole I! to thenceiorth be straight. This can be accomplished by the substitution of member I for guide I2 immediately above the bit. Thus the guide l2 and the bit I! are removed from the drilling string, and the bit attached directly to member I. A condition similar to that shown in Figure 3 will then exist. Uponfirst introducing the bit I3 and the flexible straight member it into the hole the member I will be bent to the shape shown in Figure 3 by the action of the walls of the curved hole on the bit and upon the member It. The force which is necessary to curve the member it into the shape shown causes the bit to have a thrust onthe formation so that it does not .drill a hole which is directly tangent to'the bore i5 but is set at a slight angle thereto as shown in Figure 3. This slight departure from true tangency is of no practical importance and may be minimized by selection of a 'bit which has little tendency to cut sideways even when there is side aforce on it. After the bit has gone sufficiently far into the straight part of the hole it will continue to drill straight, member ll acting as a guide to hold it in its proper course.

It can be appreciated from the above description that itis essential for the present type of drilling that the guide I! be prevented from rotating. For this reason the drill pipe It may be held stationary at the surface and other means utilized for causing the bit to rotate. The bit may be rotated in a numberof diiferent ways but one of the simplest methods is the provision of a turbine between the guide I! and the bit. For the sake of illustration I have shown in Figure 4 one type of turbine. This turbine consists of two parts, a stator and a rotor, the stator being secured to the guide I2 and the rotor being attached to the bit. As shown, the rotor is secured to the stator by means of a center pin 20 and one or more rows of balls 21 running in races on the stator and rotor. The balls serve the dual purpose of securing the stator and rotor together and providing a means for minimizing friction between these two parts. The propulsive force for turning the turbine comes from the drilling fluid. The drilling fluid is guided through a series of openings 22 annularly surrounding the pin 20. These openings 22 are defined by guides or vanes 23. These vanes are helically disposed around the center pin so that they impart to the drilling fluid a rotational velocity as it passes them. The rotor 25 of the turbine is likewise provided with vanes 26 which are also helically disposed about the axis of the turbine. These vanes however are directed in the opposite direction from those on the stator, similarly to the vanes in any axial flow turbine. Thus the drilling fiuid passing through the vanes in the stator is given a rotational velocity which causes a reaction on the blades of the rotor and exerts a. torque thereon which will drive the bit about in the hole without turning the guide |2. In Figure 4 there has been shown a type of bit similar to that described in my Patent No. 1,859,948 which has been found particularly suitable for turbine drives because of a gear reduction effect as described in the above-mentioned patent. However any suitable type of bit may be used.

It is to be understood that other means of rotating the bit which permit the guide member to remain stationary may be used, as, for example, a fiexible interior shaft driven from the surface. The members l2- nd I4 have merely been described as flexible and no attempt has been made to describe their particular construction. The construction of these members may be similar to that in my application for Flexible drill guide" filed concurrently herewith.

It is to be understood that in order to gain the beneficial effects of lateral drilling such as is contemplated in connection with the present invention, the operator must have sufficient knowledge of the position of the drill at all times. There are many methods of assuring that the bit is pointed in the right direction when it first starts deviating from the main well bore. Checks from time to time as the curved bore is produced will assure the operator that the drilling is proceeding as planned. The angle which the bit makes with the vertical as well as the azimuth of the bore being produced are readily measured with numerous testing instruments.

As was mentioned before it is sometimes desirable to drill a branch or ramification from one of the lateral bores produced by this instrument. This can be done by introducing the guide |2 into the horizontal bore and rotating it 90 degrees so that the curvature instead of being vertical now tends to be horizontal. The bit will then exert a side force on the bore and drill a hole which curves in a horizontal plane rather than in the vertical plane which has been described above.

In Figure 5 is shown a device for side wall samples. This consists essentially of a core cutter mounted on the end of one of the resilient guides above described. In this form of device, the core head 40, which comprises essentially a rotary bit so {formed as to leave a core as it cuts into the formation, is rotated by means of the string of pipe extending to the surface, it being understood that the guide remains stationary because of frictional contact with the walls of the bore. The resilient guide 4| is furnished with bearings 42, 43, on its interior, and a flexible tubular member 44 is mounted within said resilient guide for rotation on said bearings. The cutter head 40 is mounted on member 44. Rotation cat the pipe leading to the surface rotates the head. Core catchers 46 are provided within the core head and barrel. Operation is exactly as when taking a core with a conventional core head, the resilient guide 4| serving to cause the core to be taken at an angle to the side wall of the bore within which the resilient guide is supported.

In Figure 6 is shown a guide for drilling a curved hole which operates in a little different manner from the devices above described. In this figure an exterior guide 50 is shown of resilient construction somewhat similar to the guides shown in the previous figures. However it will be noted that this guide 50 is provided with slots 5| cut in at one side.' A flexible tube 52 of rubber or similar material fits tightly in the interior of the guide 50 and is secured at each end thereto. The guide is provided with suitable threads for connection with the rest of the drilling string. When pump pressure is applied to the interior of the tube 52, the tube changes in length. Continued change in length of the tube 52 can then take place only by change in length of the slotted side 54 of guide 5|. The unslotted side 53 cannot change in length appreciably and thus the result of the change in length of side 53 is a change of the curvature of the guide 50 and the tube 52. As soon as the pumps are stopped, the guide will return to its normal curvature due to its resiliency.

I claim:

1. The method of drilling a curved bore deviating from an existing straight bore comprising pressing a drilling bit sidewardly into the wall of the existing bore with energy furnished by reaction of an elongated normally curved resilient guide forcibly flexed to a lesser curvature by the walls of the existing bore.

2. The method of drilling a curved bore deviatmg from an existing bore and a straight contlnuation of the curved bore which comprises pressing a drilling bit sidewardly into the wall of the existing bore with energy furnished by reaction of an elongated normally curved resilient guide forcibly fiexed to a lesser curvature by the walls of the existing bore and rotating the drilling bit to drill a curvedbore deviating from the existing bore, then pressing a drilling bit into the wall of the above mentioned curved bore with energy furnished by reaction of an elongated normally straight resilient guide forcibly flexed to a curve by the walls of the curved bore and rotating the bit to drill a straight continuation of the curved bore.

3. A method for drilling a curved well bore deviating from an existing straight well bore comprising setting up forces in a fiexible drill guide of a character adequate to cause the same, when unrestrained, to assume a curved configuration approximately that of the desired deviating bore, restraining the drill guide against assuming such unrestrained curved configuration by contact with the side walls of the existing straight bore, holding the guide while thus restrained against rotation and simultaneously rotating and advancing the drillbit at the lower end of said guide and pressing the drill bit into one side of the existing straight well bore by energy expended against the opposite side thereof while said drill guide tends to assume its unrestrained curved configuration.

JOHN A. ZUBLIN.

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