CURVED STRUCTURAL PIPE SHOE

Abstract

A system for orienting a drill bit prior to drilling into a formation, comprising a first pipe having an inside pipe diameter, the first pipe being positioned in a hole in the formation, and a curved shoe positioned in said first pipe at a desired orientation, said curved shoe including a funnel portion having an outlet that is off-center within the first pipe and a guide portion having a guide inlet in communication with the funnel outlet and an guide outlet that is off-center within the first pipe, the guide outlet occupying a different azimuthal position within the first pipe than is occupied by the guide inlet.

Description

RELATED CASES

Not applicable.

FIELD OF THE INVENTION

The invention relates to a device and method for achieving directional drilling at a relatively shallow depth.

BACKGROUND OF THE INVENTION

In the context of hydrocarbon production, it is often desired to drill a well that deviates from a vertical axis. The various reasons for this are well known in the art and may include subsurface configuration, equipment costs, and environmental considerations. In offshore operations, which are particularly constrained by higher equipment costs, deviated or directional wells are common. Typically, such wells are drilled using a steerable system. From an initial, non-deviated orientation, the well can be steered using geomagnetic information. In order to avoid magnetic interference from equipment in the well, it is common to initiate deviation several feet below the last piece of equipment. Once sufficient build (typically 3 degrees of deviation from vertical) has been achieved, inclinometers can be used to steer the drilling tool. In many wells, this amount of build is only achieved after several additional feet of drilling.

Because of the need to avoid magnetic interference and the difficulty in building curvature, it is relatively difficult to achieve a high degree of deviation at shallow depth. Nonetheless, it is becoming increasingly desirable to produce from shallow formations. Hence, it is desirable to provide a device and method that can be used to drill a well with a high degree of deviation at shallow depth and particularly with a high degree of deviation near the surface or seabed.

SUMMARY OF THE INVENTION

Preferred embodiments of the invention provide a device and method that can be used to drill a well with a high degree of deviation at shallow depth. The present invention can be used onshore or offshore, and in either shallow or deep wells. The present invention provides a means for achieving a high degree of deviation in a relatively short distance.

As used in this specification and claims the following terms shall have the following meanings:

“Above” and “below” refer to positions that are relatively closer to and farther from, respectively, the top of the borehole.

“Vertical” refers to the primary axis of the borehole above the device.

In certain embodiments, the invention comprises a system for orienting a drill bit prior to drilling into a formation. The system may include a first pipe having an inside pipe diameter, the first pipe being positioned in a hole in the formation, and a curved shoe positioned in the first pipe at a desired orientation. The curved shoe may include a funnel portion having an outlet that is off-center within the first pipe and a guide portion having a guide inlet in communication with the funnel outlet and an guide outlet that is off-center within the first pipe. The guide outlet may occupy a different azimuthal position within the first pipe than is occupied by the guide inlet.

In further embodiments, the diameter of the guide inlet may be less than half the inside pipe diameter, the guide portion may be configured such that the axis of its outlet defines an angle of between 2 and 10 degrees with the axis of the first pipe, and the azimuthal position of the guide outlet within the first pipe may be diametrically opposite the azimuthal position of the guide inlet within the first pipe. The system may include a float valve within the guide portion.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed understanding of the invention, reference is made to the accompanying wherein:

FIG. 1 is a schematic vertical cross-section of a device in accordance with one embodiment of the invention;

FIG. 2 is a horizontal cross-section taken along lines 2-2 of FIG. 1; and

FIG. 3 is a horizontal cross-section taken along lines 3-3 of FIG. 1.

It will be understood that some components or features of the invention may be exaggerated in order to better illustrate the concepts disclosed herein. Thus, the Figures are not drawn to scale.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the Figures, preferred embodiments of the invention include a curved shoe 10 that is mounted in a length of structural pipe 20. As shown, structural pipe 20 depends from another length of pipe 22 and is coupled thereto at 24. Structural pipe 20 is typically the lowermost in a string of pipe extending into a subsurface formation.

Curved shoe 10 includes a funnel portion 12 and a guide portion 14. Funnel portion 12 is preferably an oblique circular frustoconical shape having an upper edge 15 and a lower edge 16. The configuration of upper edge 15 preferably corresponds to the inside diameter of structural pipe 20, while lower edge 16 defines a circular funnel outlet 17 lying off-center within structural pipe 20 and preferably tangential to the inner surface thereof. In preferred embodiments, upper edge 15 of funnel portion 12 has a diameter D₁ that is substantially equal to the inside diameter of structural pipe 20 and the lower edge 16 has a diameter D₂ that is substantially smaller than the inside diameter of structural pipe 20. D₂ is preferably less than three-quarters of D₁, more preferably less than half of D₁, and still more preferably less than one-quarter of D₁. At the same time, diameter D₂ is preferably incrementally larger than the outside diameter of the equipment that will be passed through shoe 10.

Funnel portion 12 may be constructed from a plurality of curved panels, such as are shown at 12a-d, or may be constructed in any other suitable manner. In some embodiments (not shown), rather than including a continuous frustoconical surface, funnel portion 12 may comprise any suitable device that is configured to define an outlet at the bottom of funnel portion 12, such as a cage, guides, or the like.

Guide portion 14 of curved shoe 10 preferably comprises a curved circular guide having a constant or nearly-constant diameter. The outlet 17 of funnel portion 12 is preferably also the inlet of guide portion 14. The lower edge 18 of guide portion 14 preferably defines an outlet 19 lying off-center within structural pipe 20 and preferably tangential to the inner surface thereof. As shown in FIG. 3, guide portion 14 may be provided with support struts 30 or other means for maintaining and supporting guide portion 14 within pipe 20. As with funnel portion 12, guide portion 14 may include a continuous cylindrical surface or may be defined by any other suitable device.

The position of outlet 19 within structural pipe 20 is preferably diametrically opposite inlet 17, as can be seen by comparing FIGS. 2 and 3. In other, less preferred, embodiments, outlet 19 may not be diametrically opposite inlet 17 and may occupy some other azimuthal position within pipe 20. Regardless, it is preferred that outlet 19 does not occupy the same azimuthal position within pipe 20 as inlet 17. With respect to a desired pipe position and orientation, funnel portion 12 can be said to provide negative build, while guide portion 14 can be said to provide build.

The amount of build can be determined by comparing the orientation of the axis of outlet 19, as indicated by dashed line 42 in FIG. 1, with the axis of structural pipe 20, as indicated by dashed line 40. It will be understood that the shape and curvature of curved portion 14 determine the direction of line 42 and therefore also the degree of build provided by curved shoe 10. The degree of build may be more or less than that illustrated in the Figures and is limited only by mechanical limitations of the system. In preferred embodiments, the system is configured to provide between 2 and 10 degrees of build and more preferably between 3 and 7 degrees of build.

In some embodiments, a float valve 50 may be included within guide portion 14. Such valves are known in the art and serve to prevent backflow of cement into the device.

The respective lengths of funnel portion 12 and guide portion 14 may be selected as desired. In some embodiments, the vertical length of guide portion 14 may be greater than the vertical length of funnel portion 12.

By way of example only, in one embodiment, D₁ may be in the range of 20-60 inches and D₂ may be in the range of 5-30 inches. Also by way of example, the vertical length of guide portion 14 may be in the range of 5-100 feet and the vertical length of funnel portion 12 may be in the range of 10-500 feet. More preferably, the vertical length of guide portion 14 may be in the range of 20 to 50 feet and the vertical length of funnel portion 12 may be in the range of 20 to 500 feet, and more preferably 20 to 200 feet. Also by way of example, line 42 may define an angle in the range of 1-6 degrees with line 40.

Thus, in one exemplary embodiment, D₁ may be 34 inches, while D₂ may be 20 inches. Also by way of example, the vertical length of guide portion 14 may be 7 feet, while the vertical length of funnel portion 12 may be 36.5 feet. Also by way of example, line 42 may define an angle of 3.7 degrees with line 40, so that curved shoe 10 provides 3.7 degrees of build. It will be understood that these dimensions are intended to be illustrative only and do not limit the scope of the invention.

It will be understood that these dimensions are intended to be illustrative only and do not limit the scope of the invention.

In preferred embodiments, the volume between pipe 20 and the funnel and guide portions 12, 14 may be filled with cement.

When it is desired use a curved shoe in accordance with the present invention, the shoe, including funnel portion 12 and guide portion 14, is installed in a length of structural pipe and provided with the desired mechanical support. Once the curved shoe is in place, the length of pipe 20 may be inserted into a pre-dilled hole and grouted in place. Because curved shoe 10 is a directional device, it is possible and preferable to orient the pipe containing the shoe so that the guide outlet 19 has a desired azimuthal orientation prior to grouting the pipe in place. In an alternative embodiment, the pipe could be grouted in place prior to orientation and installation of the curved shoe therein.

In preferred embodiments, pipe 20 is installed below the mud line, and in some embodiments at depths of hundreds or thousands of feet.

With the structural pipe 20 and curved shoe 10 in place, drilling equipment, such as a streerable bit or the like (not shown), can be lowered through shoe 10. As the bit enters and descends through funnel portion 12, it is guided to one side of pipe 20. After the bit enters and descends through guide portion 14, it is guided along a curved path and exits from outlet 18. If a float shoe is present, the bit drills through it. Once the bit exits outlet 18, drilling can commence.

As it exits shoe 10, the bit will have the same orientation as the lower end of guide portion 14 and will thus begin drilling with a relatively high degree of initial deviation from vertical. This may allow even the initial stages of drilling to be guided by inclinometer, avoiding the issues related to magnetic guidance. Thus, the present invention permits shallower kickoff than has heretofore been possible, permits a greater build rate at shallow depths, and enables development projects that require shallow, extreme directional profiles. The present invention also enables orienting off the high side of the well.

The present invention may also be advantageous in attaining a desired bit angle in soft formations, where it might otherwise be difficult to build angle at a desired rate.

It will be understood that the present invention has been described herein in terms of preferred embodiments and that variations and modifications could be made to those embodiments without departing from the scope of the invention. For example, the dimensions, relative dimensions, curvature, and manner of construction of the components of the present device can all be varied. Thus, the scope of the invention is set out in the claims that follow. It will be understood that, unless explicitly stated otherwise, the sequential recitation of steps is not intended to require that the steps be performed sequentially.

Claims

1. A method for orienting a drill bit prior to drilling into a formation, comprising:

a) positioning in the formation a first pipe having an inside pipe diameter and a a curved shoe positioned in the first pipe at a desired azimuthal orientation, said curved shoe including: a funnel portion having an outlet that is off-center at a first azimuthal position within the first pipe; and a guide portion having a guide inlet in communication with the funnel outlet and an guide outlet that is off-center at a second azimuthal position within the first pipe, the second azimuthal position being different than the first azimuthal position;

b) inserting a drill bit and drill string through the curved shoe such that the bit extends from the curved shoe at an angle with respect to said first pipe.

2. The method according to claim 1 wherein step a) includes cementing the first pipe into the formation.

2. The method according to claim 2 wherein step a) includes cementing the curved shoe into the first pipe.

3. The method according to claim 1 wherein the angle in step b) is at least 3 degrees.

4. The method according to claim 1 wherein the azimuthal position of the guide outlet within the first pipe is diametrically opposite the azimuthal position of the guide inlet within the first pipe.

5. The method according to claim 1 wherein the guide portion includes a float valve therein.

6. A system for orienting a drill bit prior to drilling into a formation, comprising:

a first pipe having an inside pipe diameter, said first pipe being positioned in a hole in the formation; and

a curved shoe positioned in said first pipe at a desired orientation, said curved shoe including: a funnel portion having an outlet that is off-center at a first azimuthal orientation within the first pipe; and a guide portion having a guide inlet in communication with the funnel outlet and an guide outlet that is off-center at a second azimuthal orientation within the first pipe, the guide outlet occupying a different azimuthal position within the first pipe than is occupied by the guide inlet.

7. The system according to claim 6 wherein the diameter of the guide inlet is less than half the inside pipe diameter.

8. The system according to claim 6 wherein the guide portion is configured such that the axis of its outlet defines an angle of between 2 and 10 degrees with the axis of the first pipe.

9. The system according to claim 6 wherein the guide portion is configured such that the axis of its outlet defines an angle of between 3 and 7 degrees with the axis of the first pipe.

10. The system according to claim 6 wherein the azimuthal position of the guide outlet within the first pipe is diametrically opposite the azimuthal position of the guide inlet within the first pipe.

11. The system according to claim 6, further including a float valve within the guide portion.