Title:
Means for drilling boreholes of different curvatures and diameters
United States Patent 2336334


Abstract:
In my co-pending application, Serial No. 423,227, filed December 16, 1941, there was described a means of drilling bores deviating from the well bores. One form of apparatus used in the practice of this invention includes an elongated resilient member which has a normal curvature equal to the...



Inventors:
Zublin, John A.
Application Number:
US44396842A
Publication Date:
12/07/1943
Filing Date:
05/21/1942
Assignee:
Zublin, John A.
Primary Class:
International Classes:
E21B7/06; E21B7/08
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Description:

In my co-pending application, Serial No. 423,227, filed December 16, 1941, there was described a means of drilling bores deviating from the well bores. One form of apparatus used in the practice of this invention includes an elongated resilient member which has a normal curvature equal to the curvature desired in the bore to be made. In order to insert such an elongated resilient normally curved guide into the well bore for lowering to the point at which a lateral bore is to be made, it is necessary to forcibly straighten out the guide. The natural resiliency of the guide causes it to press itself and the bit against the walls of the well bore. This pressure is useful when the bit and guide have arrived at the point at which the lateral bore is to be made, but serves no useful purpose until such a point is reached. In fact, the pressure of the bit and guide on the walls of the bore may be great enough to cause damage to the bit and guide and to the well bore. It may be necessary to provide some means to prevent the' pressure of the walls of the bore on the bit and guide from causing damage to them while the bit and guide are lowered to the point at which drilling is to commence. In addition to this, unless special provision is made, the tendency of the bit to dig into the walls of the bore, together with the bent configuration of the guide may result in the jamming of the entire assembly in the well bore before the bit has reached the desired position.

From the above discussion it can be seen that inasmuch as the curved condition of the resilient drill guide serves no useful purpose while the assembly is being lowered in the well and in fact increases the difficulty of that operation, it would be most desirable to provide some means which will hold the guide straight, and thus prevent the bit and guide from being forced against the well hnre hv the tpnd-ncv of the guide to return -to a curved condition. Such a means must be canable of maninulation, while the entire guide and bit assembly are in the well, to release the guide so that it may exert its resilient tendency to curve on the well bore. to either cause the bit to enter a previously drilled lateral bore or to cause it to press against the side of the well bore, and thus drill laterally from that point.

In addition to this particular example, there are other situations in which it would be desirable to provide a drill guide with means for changing its curvature while it is either in the well bore or in a lateral bore. When a normally straight drill guide is used to produce a straight prolongation of a lateral bore, it is necessary to provide a means for causing the straight, resilient guide to initially enter the mouth of the lateral bore. If the straight drill guide were caused to assume sufficient curvature to press the bit lightly against the side of the well bore, the bit would, upon reaching the mouth of the lateral bore, enter the lateral bore. The guide could then be released from the means causing it to curve, and, after the bit is brought to the point in the lateral bore from which a straight bore is to be produced, drilling can commence in the usual way.

As a variation on this technique, a curved lateral bore can be drilled by using normally straight drill guide held in a curve by means controlled from the surface until the curved bore extends in the desired direction. The straight guide is then released from the means holding it curved, and drilling proceeds in a straight line. As the drill guide described in the above copending application is provided with an internal bore for the passage of fluid to the bit, it is feasible to provide a member in this internal bore, which will give the drill guide the desired configuration. After the drill guide has performed all the operations desired while it has that configuration, the internal member can be withdrawn from the interior of the drill guide, which will permit the drill to assume its natural confienration. exceot for the restrainine influence of the sides of the bore. This results in a saving in the number of round trips necessary. It is proposed in the practice of the present invention to lower an overshot through the interior of the drill pipe, which overshot will grip a head on the top of the internal member, after which the overshot and the internal member may be withdrawn from the well by means of the line to which the overshot is secured.

The selection of a proper type of internal member is dictated by the functions which are intended to be performed before and after the internal member is withdrawn. For example, if it is desired to utilize an internal member to hold 4 a normally curved resilient drill guide straight while the bit and guide are being lowered in the well, the internal member could be straight and stiff, thus holding the guide straight and permitting lowering of the bit to the mouth of the lateral bore, after which the internal member could be withdrawn to permit the bit to enter the mouth of the lateral bore. This internal' member need not be stiff, however, but on the contrary can have a certain degree of resiliency. If a resilient internal member is used, and it is desired to have the assemblage of the internal member and external drill guide take a straight configuration, the curvature of the internal member must normally be the reverse of that of the external member. The two resilient members acting on each other then hold themselves in a substantially straight line.

It may even be desirable to permit some slight curvature in the resilient drill guide while it is being lowered, said curvature being sufficient to permit the bit to ride gently against the side of the well bore. This would enable the driller to more readily find the mouth of the lateral bore.

In such an event, either a resilient curved or a resilient straight internal member can be used with a normally curved drill guide, the particular normal shape of the internal member depending upon the relative stiffness of the two members and the configuration which it is desired to have the assemblage take. When it is desired to have a normally straight drill guide enter a lateral bore, the internal member can be curved and resilient, thus forcing the drill guide to assume a curvature facilitating the entry of the bit into the lateral bore. After such entry has been made, drilling can commence, the curvature of the internal member holding the guide in a curved condition which results in the drilling of a curved bore. After the curved bore has extended in the direction desired, the internal member can be withdrawn. The straight, resilient drill guide released from all internal restraint, will then continue the lateral bore along a substantially straight line.

With the above brief discussion in mind it is a primary object of the present invention to provide a means for enabling the control of the curvature of an elongated resilient drill guide after it has been lowered into a well, independent of the walls of the well.

It is a further object of the present invention to provide a means for lowering a normally curved resilient guide member into a well without forcing it into contact with the walls of the bore.

It is a further object of the present invention to provide a means for holding a normally curved resilient drill guide straight.

It is a further object of the present invention to provide means for holding a normally curved resilient drill guide straight which can be released when the drill guide reaches the point at which drilling is to be begun.

It is a further object of the present invention to provide a means for preventing a normally curved resilient guide member from exerting excessive pressure on the walls of the well bore as it is lowered therein.

It is a further object of the present invention to provide a means for holding a normally curved resilient guide member in a straightened condition, which means can be rapidly caused to release the drill guide by means of a line lowered within the casing extending to the surface so that it may assume its normal curvature.

It is a further object of the present invention to provide an elastic member which can be associated with a normally curved guide member so that the assembly assumes a substantially straight condition.

It is a further object of the present invention to provide a means whereby a normally straight drill guide can be sufficiently curved to readily enter a lateral bore.

It is a further object of the present invention to provide a means to cause one and the same drill guide to drill a curved bore, and afterwards drill a straight prolongation.

It is a further object of the present invention to provide a means to cause one and the same drill guide to drill a straight bore, and afterwards a curved prolongation thereof.

Referring now to the drawings: Figure 1 is a view partly in section, showing one to form of the present invention when the drill guide is maintained in a straight condition; Figure 2 is a view similar to Figure 1, showing the means holding the drill guide in straight condition in the process of being removed to permit the drill guide to assume its curved configuration; Figure 3 is a view of the guide and the means for holding it straight in a modified form of the present invention; 2o Figure 4 is a view showing the device of the present invention being used for underreaming; Figure 5 is a view of the straight guide and a means for giving it a curved configuration; and, Figure 6 is a view showing an application of a2 the assemblage shown in Figure 5.

In the drawings the member 10 is a hollow metallic member which has been rendered easily flexible and resilient by cutting one or more helical slots I through the wall thereof. This member 10 is normally curved but due to its flexibility can be straightened to the configuration in Figure 1, in which it is shown as being approximately straight. Within the member 10 is a rubber hose or other tubing 12, which serves the primary purpose of conveying drill fluid to the bit and the lower end of the drill string. This tubing 12 may be secured to the outer menber 10 by means of metallic fittings 13, which engage internal threads on the member 10. Couplings 14 are used to connect the lengths of the drill guide 10 together. This connection is essentially the same as that described in my co-pending application No. 423,225, filed December 16, 1941, for a Flexible resilient drill pipe.

As was mentioned above, it is necessary to provide a means for holding this guide member 10 in an approximately straightened condition. This is done in the present instance by the provision of the internal member 15. This member 15 has a high degree of rigidity compared to the slotted member 10. This is easily accomplished in spite of the small diameter of member 15, inasmuch as the slots II reduce very greatly the rigidity of member 10. It can be seen that the member 15, being essentially rigid, will hold the member 10 substantially straight. When the member 10 is in this condition, the entire assembly can be readily lowered into a well without the member 10 or any of its connected parts being forced into contact with the side of the wall by the tendency of the member 10 to return to its normal condition.

After the guide member 10 has reached the proper position in the well for lateral drilling, which is to be done by the bit 16 rotating on the lower end of the member 10, it is necessary to release member 10 so that its tendency to curve can force the bit sideways into the formation.

This can be done by withdrawing the member 15 from the interior of the hose 12. For the purpose of effectuating this withdrawal a spear 17 is secured to the upper end of the member 15.

This spear can be grasped by an over-shot 18 of the usual form. This over-shot comprises a body 19 and carries a pair of dogs 20 pivoted to the body at 21. These dogs are held in position as shown in Figure 1 by means of springs 22, which urge them inwardly after the ends of the dogs have passed over the head 23 of the spear I7.

This over-shot can be most conveniently lowered in the well by means of a wire line. It may, if necessary, cooperate with jars to force the member 15 loose from the interior of the hose 12.

In Figure 2 the member 15 is shown in the position of withdrawal from the interior of the hose 12. As can be seen the flexible unit 10 takes a curvature, which is limited by the walls 26 of the well. In order to protect the hose member during this withdrawal, which permits the member 10 to bend, the lower end of the member 15 is provided with a smoothly rounded surface as at 26.

After the member 15 has been withdrawn from the flexible member 10 the flexible member 10 and the attached bit can be readily withdrawn from the well. Pulling on the upper end of the guide member results to a certain extent in the straightening of the guide member. Furthermore the bit is dull, and it is much less important to prevent further wear on the bit than it is to prevent wear on the bit when it is originally inserted in the well and before it has had an opportunity to cut the formation. The most important difference however, between going into and coming out of the well is that the bit would tend to catch on the walls of the well bore, and further lowering of the upper end of the guide would kink the guide member forcing the bit deeper and deeper into the walls of the well and eventually jamming the whole assembly in the well bore. This of course cannot happen as the guide is hoisted by its upper end from the well.

The member 15 has been described as rigid or substantially so. However, it is possible to allow a limited degree of flexibility in a straight internal member, so that the configuration of the internal and external members has a curvature sufficient to cause the bit to contact the wall of the bore on its downward movement. The bit will then naturally enter the mouth of the lateral bore, after which the member 15 can be withdrawn. This would be useful if the operator had difficultv in locating the mouth of the lateral bore. However. even this slight curvature might be disadvantageous in a tiht wAll. In such an event, the structure shown in Figure 3 can be utilized instead of that previously described. In this form of device the internal member is curved in a direction opposite to the natural curvature of the external member. Thus. as shown in the figure, the drill guide 10' is curved in one direction while the internal member 15' is curved in the opposite direction. It can be seen that if the member 15' is inserted in a drill guide 10' the reaction of these two members against each other will cause the assembly to assume a curvature which is less than that of either of the members.

The parts can be so proportioned that the entire assembly is held in a substantially straight condition by a reaction of member 10' against the member 15'. Of course, it will be realized that the member 15' must be held against rotation with respect to member 10' while the assembly is being lowered into a well. There are a number of ways of doing this but perhaps the simplest is the provision of a pin 27 extending into the interior bore of the member 10', which pin engages a slot 28 cut in the lowermost portion of the member 15'. It is not necessary that the member 15' be held against rotation while it is being withdrawn from within member 10', and the pin 27 is therefore positioned near the lowermost end of the member 10' to avoid the necessity of cutting a long slot in the member 15'. It will be understood that the bent member 15' can be withdrawn through the bore of the drill pipe, although perhaps not as readily as could a straight member.

The present invention is also adaptable to use in underreaming well bores. The underreaming can be done by simply lowering a curved member 10 to the point where the underreaming is to begin, after which the member 15 is withdrawn, permitting the natural tendency of member 10 to curve to exert a sideways force on the bit.

If the member 10 is rotated as the bit cuts, or is rotated with the bit, a bore larger than the diameter of the bit will result. Thus a bore can be produced which is larger than the diameter of the bore extending thereabove. This form of operation is shown in Figure 4. The guide 10 5is lowered until the bit is opposite the point P, the internal member 15 withdrawn and rotation started. The bit will cut the tapered bore 30. and, after a certain interval, will tend to cut a substantially straight bore 31. It must be understood, however, that in order to drill an oversize bore 31 the guide must be rotated while cutting is taking place. This can be done by utilizing the guide member 10 to rotate the bit in the same manner as a conventional bit is rotated by the drill pipe and drill collar. Alternatively the bit can be rotated by means of a turbine. The rotation of the member 10 is then merely for the purpose of causing the drilling of an oversize bore. When such practice is followed the rotative speed of member 10 can be comparatively low and the main cutting energy can come from the turbine which rotates the bit relative to the member 10. This method of underreaming does not renuire that the internal member be comnletely withdrawn. In fact, the size of the underreamed bore can be requlated by controlling the position of the internal member, withdrawing it to a P.reter extent for a larirer bore.

Openings. as in F'gure 5, must then be provided for the drilline fln, to pasq the internal member.

The above described modifications of the present invention are all directed to a curved resilient drill guide and means for modifying the tendency of the drill guide to assume a curved condition. In Figures 5 and 6 are shown a straight drill guide possessing sufflfient resiliency to permit it to be curved and a resilient member having a curvature, which when inserted in the drill guide, causes curvature of the guide. The drill guide 35 with its attached bit 36 is intended to be used alone for the production of a straight bore. Insertion of the member 37. which has a normal curved condition and which is itself resilient, causes the drill guide 35 to assume a curved 05 condition. This curvature of the drill guide can be used for several purposes. For instance, in Figure 6, assume that the drill guide contains the member 37, tending to curve the guide, when lowered to the position shown in dotted lines. It can be seen that the tendency of the guide and internal member to curve will force the bit against the walls of the well, so that further lowering of the bit and guide will cause the bit to enter the side bore 38. In fact, causing a rotation of the bit by means of a turbine or other rotation producing element will cause the bit to drill sideways in exactly the same fashion as was described in my co-pending application with a normally curved drill guide. It will be understood, of course, that if a bit and guide are lowered into a well in a curved condition, it may be necessary to provide a means to prevent the guide and bit from damaging the walls of the well.

If the bit is permitted to drill to the point 39 with the internal member in place, the path of the drilling will be a curve, which is substantially equal in radius to the radius of curvature assumed by the normally straight guide as influenced by the resilient, normally curved internal member. If it is desired to continue from point 39 in a direction substantially tangent to the curve, it is only necessary to withdraw the member 37 from the interior of the drill guide 35, which will permit the drill guide to straighten out as far as it can, the only restriction to its assuming a straight condition being the wall of the lateral bore 38. Continued drilling will then cause the prolongation of the curved portion of the bore in a straight line tangent to the end thereof.

As drilling is to be done with the curved, resilient member in place, it is necessary to provide a means for permitting drilling fluid to pass the member 37 to the bit. This has been done in the present instance by means of openings 40 at the top and bottom of the hollow member, which permit sufficient flow for drilling purposes.

I claim: 1. In a device for drilling curved bores, an elongated, resilient, normally curved drill guide, means holding said drill guide in a straightened condition, and means for releasing said holding means while said guide is in a well.

2. In a device for drilling curved bores, an elongated, resilient, normally curved drill guide having an internal bore, an elongated member within said bore holding said drill guide in a straightened condition, and means operable by lifting means lowered from the surface of the well releasing said member from said guide.

3. In a device for drilling curved bores, an elongated, resilient, normally curved drill guide having an internal bore, an elongated member within said bore holding said drill guide in a straightened condition, said member being removable from said guide when said guide is in a well.

4. In a device for drilling curved bores, an elongated, resilient, normally curved drill guide having an internal bore, an elongated, relatively stiff member within said bore holding said drill guide in a straightened condition, said member being removable from said guide when said guide is in a well.

5. In a device for drilling curved bores, an elongated, resilient, normally curved drill guide having an internal bore, an elongated member within said bore holding said drill guide in a straightened condition, and means on the upper end of said member engageable by lifting means lowered from the surface of the well, to thereby withdraw said member from within said guide.

6. In a device for drilling curved bores, an elongated, resilient, normally curved drill guide having an internal bore, an elongated normally curved member within said bore, means holding said member and said bore against relative rotation and in a position such that their normal curvatures are in opposite directions, whereby said members are held in a substantially straight condition and means on the upper end of said member engageable by lifting means lowered from the surface of the well to thereby withdraw said member from within said guide.

7. In a device for drilling a curved lateral bore from a well bore and a straight extension on said curved bore, an elongated resilient normally straight drill guide having an internal bore, an elongated, resilient normally curved member within said internal bore, and means on the upper end of said member for pulling said member from within said guide.

8. In a device for drilling a straight extension of a curved lateral bore from a well, an elongated, resilient normally straight drill guide having an internal bore, an elongated, resilient normally curved member within said internal bore, and means for withdrawing said internal member after said guide has entered said lateral bore.

9. In a device for lateral drilling from a well bore, an elongated resilient drill guide having an internal longitudinal bore, said drill guide having a normal unstressed configuration, an elongated member within said internal bore maintaining said drill guide biased from its normal unstressed longitudinal configuration, and means operable from the surface of the well for withdrawing said member from the interior of said internal bore to thereby release said resilient drill guide from the biasing influence of said internal member.

JOHN A. ZUBLIN.