CA2755028A1 - Method and apparatus for sonic drilling - Google Patents

Abstract

A method and apparatus and for sonic drilling includes a casing shoe assembly and a sonic vibration assembly. The casing shoe assembly includes a heavy wall casing for providing an inertial mass for a coring bit and a coring bit for extracting an earth core. The sonic vibration assembly includes a sonic resonator for creating sonic vibrations to fluidize an earth formation and a core barrel for collecting the earth core from the coring bit. The casing shoe assembly has an internal engagement. The sonic vibration assembly has an external engagement for engaging the internal engagement of the casing shoe assembly.
The sonic vibration assembly is inserted into and engaged with the casing shoe assembly, such that the casing shoe assembly and the sonic vibration assembly vibrate together.

Description

TITLE
[0001] Method And Apparatus For Sonic Drilling FIELD

[0002] There is described an apparatus for sonic drilling and a method that has been developed for the use of the apparatus.

BACKGROUND

[0003] Sonic drilling is used to fluidize an earth formation and extract a core. It has been successful with relatively shallow wells. There is a recognized need for a better technology for deep drilling into subsurface formations to access, for example, new sources of gas, oil, groundwater, geothermal energy, metals and minerals resources. Drilling at depths is increasingly difficult and costly using present rotary, tubing drilling methods. Also, there is a recognized need to drill and coring at deeper depths to obtain subsurface material samples in the best conditions possible for laboratory analyses.

[0004] United States Patent 6,968,910 (Bar-Cohen et al) entitled "Ultrasonic/Sonic Mechanism of Deep Drilling" teaches the use of an ultrasonic or sonic drilling unit down hole at frequencies that will create a hammering of the earth bit. United States Patent 2,903,252 (Bodine Jr) entitled "Suspension System For Sonic Well Drill Or The Like"
teaches structure for vibration isolators to isolate portions of a drill string above the vibration isolator from vibrations occurring below the vibration isolator.

[0005] Drilling to greater penetration depths or into hard rock beyond the sedimentary layers can be extremely difficult and costly because of decreasing mechanical torque efficiencies with increasing depth. New state of the art drilling systems are needed to make access into the earth's subsurface easier, deeper, and less costly.

SUMMARY

[0006] According to one aspect there is provided an apparatus for sonic drilling which includes a casing shoe assembly and a sonic vibration assembly. The casing shoe assembly includes a heavy wall casing for providing an inertial mass for a coring bit and a coring bit for extracting an earth core. The sonic vibration assembly includes a sonic resonator for creating sonic vibrations to fluidize an earth formation and a core barrel for collecting the earth core from the coring bit. The casing shoe assembly has an internal engagement. The sonic vibration assembly has an external engagement for engaging the internal engagement of the casing shoe assembly. The sonic vibration assembly is inserted into and engaged with the casing shoe assembly, such that the casing shoe assembly and the sonic vibration assembly vibrate together.

[0007] According to another aspect there is provided a method of sonic drilling. A first step involves securing the casing shoe assembly to a remote end of a well casing string composed of multiple connected sections of pipe. A second step involves securing to a remote end of coiled tubing string the sonic vibration assembly. A third step involves inserting the sonic vibration assembly down through the casing shoe assembly and engaging the external engagement on the sonic vibration assembly with the internal engagement on the casing shoe assembly to couple the sonic vibration assembly and the casing shoe assembly so that, upon activation of the sonic resonator, the casing shoe assembly and the sonic vibration assembly vibrate together. A fourth step involves continuing to vibrate the sonic vibration assembly and the casing shoe assembly to cause the coring bit to fluidize and penetrate an earth formation to form an earth core, with the earth core passing up into the core barrel. A
fifth step involves disengaging the external engagement of the sonic vibration assembly from the internal engagement of the casing shoe assembly at periodic intervals and withdrawing the sonic vibration assembly to surface to remove the earth core from the core barrel.

[0008] Although beneficial results may be obtained through the use of the method and apparatus, as described above, continued exposure to sonic vibrations will over time damage equipment. Even more beneficial results may, therefore, be obtained when the well casing and the coil tubing string are isolated from sonic vibrations. It is, therefore, preferred that a casing vibration isolator be positioned between the well casing string and the casing shoe assembly to isolate the well casing string from sonic vibrations. It is also preferred that a tubing vibration isolator be positioned between the coiled tubing string and the sonic vibration assembly to isolate the coiled tubing string from sonic vibrations.

[0009] There are various configurations of vibration isolators which may be used, one of which is described in the Bodine Jr reference. The vibration isolator which will hereinafter described and illustrated has an outer tubular body and an inner tubular body.
The outer tubular body has an interior surface defining an interior bore. The inner tubular body has an exterior surface. A portion of the inner tubular body is received within the interior bore of the outer tubular body. A dampening assembly is positioned between the interior surface of the outer tubular body and the exterior surface of the inner tubular body to dampen relative axial movement of the outer tubular body and the inner tubular body.

[0010] There are various ways to dampen axial movement which could be used in the dampening assembly. One way to dampen movement is through the use of a spring.
Another way to dampen movement is hydraulically. The dampener assembly which will hereinafter be described and illustrated uses both. The hydraulic dampener portion includes a first hydraulic chamber and a second hydraulic chamber. At least one metering device is positioned between the first hydraulic chamber and the second hydraulic chamber. Hydraulic fluid has to flow between the first hydraulic chamber and the second hydraulic chamber in order for relative axial movement of the outer tubular body and inner tubular body to occur.
This creates a time delay that dampens movement in addition to and complementary with the action of the spring or springs.

[0011] There are, similarly, various external engagements and cooperating external engagement that can be used to latch the sonic vibration assembly to the casing shoe assembly. The engagement which will hereinafter described and illustrated is a latching system in which the internal engagement of the casing shoe assembly is a simple circumferential groove. The external engagement of the sonic vibration assembly are collet fingers movable between a radially expanded engaged position engaged with the circumferential groove and a radially contracted disengaged position. An interior face of the collet fingers has a wedge profile. The collet fingers are expanded radially by driving a sliding wedge to engaging the wedge profile, which moves the collet fingers from the disengaged to the engaged position. A solenoid coil is used to move the sliding wedge which forces the collet fingers radially outwardly to the engaged position.

[0012] It is important that the latching engagement disengage when power is discontinued to the solenoid coil. If the latch should fail to disengage, the sonic vibration assembly cannot be withdrawn as intended. It is, therefore, preferred that a spring bias the sliding wedge away from the wedge profile. This ensures that the collet fingers return to the disengaged position when the solenoid coil is deactivated.

[0013] According to a further aspect there is provided a vibration motor which causes vibration within the drilling system. This unconventional motor utilizes a magnet array that reciprocats transversally across the end of a cylinder to induce vibration in a coring system.
BRIEF DESCRIPTION OF THE DRAWINGS

[0014] These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:

[0015] FIG. 1 is a side elevation view of a sonic vibration assembly at a remote end of a string of coiled tubing.

[0016] FIG. 2 is a side elevation view, in section, of the sonic vibration assembly illustrated in FIG. 1 deployed within a casing shoe assembly.

[0017] FIG. 3 is a detailed side elevation view, in section, of a latch engagement between the sonic vibration assembly and the casing shoe assembly.

[0018] FIG. 4 is a detailed side elevation view, in section, of a vibration isolator used to isolate the coil tubing string and the well casing string from sonic vibrations.

[0019] FIG. 5 is a side elevation view, in section, of a vibration motor used to induce vibration.

DETAILED DESCRIPTION

[0020] An apparatus for sonic drilling and a method of use of that apparatus will now be described with reference to FIG. 1 through FIG. 5.
Structure and Relationship of Parts:

Rig Components [0021] Referring to FIG. 1, the rig components consist of a drilling sub-structure 1 which supports a folding derrick 2 and a cradle 11 and spool 3 of coiled tubing 4. The derrick 5 2 and the cradle 11 and spool 3 can be detached from the drilling sub-structure 1 so that the rig can be moved in pieces and re-assembled in a short period of time.
Ancillary equipment such as a mud pump 9, electrical generator 10 and hydraulic power unit 12 maybe attached to the drilling sub-structure 1 or be provided as separate packages which are connected to the rig once on site.

[0022] The coiled tubing 4 passes through a guide 5 which prevents buckling of the coiled tubing 4 as it passes through the top of the derrick 2. The coiled tubing 4 also passes through a straightener / injector 6 which straightens the coiled tubing 4 and uses a series of hydraulic grips to pull or push the coiled tubing 4 into or out of the borehole.

[0023] The cradle 11 incorporates a hydraulic drive unit to maintain appropriate tension on the coiled tubing and rotating connections on the hub for power and fluid circulation. A
control panel 8 controls all aspects of the rig operation.

Sonic Drilling Downhole Components [0024] A remote end of coiled tubing 4 is attached to the downhole sonic vibration assembly 7. Referring to FIG. 2, an electrically powered downhole sonic resonator is proposed as an alternative to sonic systems driven from surface. The device has an oscillating mass, excited (vibrated) axially by an electromagnetic system with alternating current. The core barrel, attached below the resonator would be vibrated at its resonant frequency. The vibrating mass may also be wound with electrical conductors to produce an opposing magnetic field to increase the magnetic forces and improve performance. An electrical cable 21 inside the coiled tubing transmits power to the tool.

[0025] A casing shoe assembly is provided which includes coring bit 13 attached to the bottom end of the heavy wall casing 15 by means such as a threaded connection.
It is preferred that a casing vibration isolator 20 be attached to the top of the heavy wall casing 15 to prevent transmission of the vibrations induced by the sonic resonator 16 to the well casing 22 attached to the top of the casing vibration isolator 20. The well casing 22 is composed of multiple sections of pipe connected to one another using a suitable threaded connection or other means. The assembly of the coring bit 13, heavy wall casing 15 is referred to as the casing shoe assembly, preferably, it also includes, casing vibration isolator 20.

[0026] Referring to FIG. 2, core barrel 14, which forms part of the sonic vibration assembly, fits inside the coring bit 13 and heavy wall casing 15 to contain the soil and rock materials that are penetrated as the borehole advances. The sonic resonator 16 is attached to the top of the core barrel 14 by a suitable threaded connection or other means. The electro-mechanical coupling mechanism 17 is located at the top of the sonic resonator 16 and serves to latch the sonic resonator 16 to the heavy wall casing 15 in the casing shoe assembly. The tubing vibration isolator 18 connects the coupling mechanism 17 to the coiled tubing 4 and prevents the vibrations of the sonic resonator 16 from being transmitted to the coiled tubing 4.
The tubing vibration isolator 18 may incorporate one or more ports 23 to allow fluid pumped through the coiled tubing 4 to be circulated inside the heavy wall casing 15 to ensure that debris does not interfere with the coupling mechanism 17. Alternatively, additional fluid passages may exist through the coupling mechanism 17 and sonic resonator 16 to allow circulation past the coring bit 13. An electrical connector 19 provides power from the power cable 21 inside the coiled tubing to the coupling mechanism 17 and the sonic resonator 16.
The assembly core barrel 14 of sonic resonator 16 are referred to as sonic vibration assembly.
However, when coupling mechanism 17, tubing vibration isolator 18 and electrical connector 19 are added, the entire assembly is collectively referred to as the bottom hole assembly.

Coupling Detail - Casing - resonator coupling [0027] Referring to FIG. 3, the electro-mechanical coupling mechanism 17 latches the sonic vibration assembly including sonic resonator 16 to heavy wall casing 15 of the casing shoe assembly. A circumferential groove 32 or other appropriate profile is provided in the interior surface of heavy wall casing 15. Collet fingers 30 are spread by a sliding wedge 31 and mate with profile 32 in the heavy wall casing 15. To activate the device, the wedge 31 is forced into the collet 30 by a solenoid coil 33, although other methods are possible. When deactivated, the wedge 31 is returned to the starting position by a spring 34.
With this method, the device automatically deactivates if the power to the solenoid coil 33 fails, allowing retrieval of the down hole tools.

Vibration Isolator Detail - Casing and tubing vibration isolator [0028] The upper 24 and lower 25 casing (or tubing) sections slide within each other.
The outer casing section contains a sealed 26 recessed section which contains damping fluid 27, a damping ring 28, and springs 29, if required. As the upper 24 and lower 25 casing move relative to each other, either spring 29 may be compressed between the damping ring 28 and lower casing 25. The damping ring 28 is attached to the upper casing 24 so that the damping fluid 27 is forced through an orifice in the damping ring 28 or between the damping ring 28 and lower casing 25 to provide a damping force. Spring 29 stiffness, damping fluid 27 viscosity, and damping ring 28 orifice size should be chosen to provide the required dynamic response.

Vibration Motor [0029] Referring to FIG. 5, a vibration motor 36 with an external armature 38 consisting of a cylinder 40 containing an inductive stator 42 and flange 44 is used to cause vibration.
Cylinder 40 is held in an outer casing 52 of vibration motor 36 by supports 54. Armature 38 has a flange 44 and magnet array 46 that reciprocate transversally across the end of cylinder 40 so as to induce vibration in a coring system. Stator assembly 42 is housed in cylinder 40, which is preferably made of non-ferrous metal but may also be made of any suitable material.
Cylinder 40 also houses electronmagnetic coils and cooling channels to dissipate variable frequency AC power. Armature 38 is a flange which is usually made of ferrous metal, however it will be understood that different suitable materials may be used to make an-nature 38. Rare earth magnets in magnetic array 46 are arrayed for optimum efficiency and flux density through a small air gap 48 maintained mechanically from stator assembly 42 by vibration absorbers 50. Vibration motor 36 may be attached to the remainder of the drilling assembly.

Operation:

Procedure for Casing-While-Drilling with Electrically Driven Sonic Drilling System [0030] Referring to FIG. 1, the rig and downhole components are transported by helicopter to the site where the well is to be drilled. One or more helicopter trips may be required depending on the helicopter size available. The drilling rig is divided into easily transportable components to facilitate smaller loads. These components incorporate a variety of quick coupling elements to ease re-assembly on location.

[0031] The casing shoe assembly, consisting of a core bit, one joint of heavy-wall casing, and the casing vibration isolator are assembled and supported in the rig derrick with the bottom of the assembly resting on the ground surface.

[0032] The end of the coiled tubing is passed through the tubing straightener and injector in preparation for connection to the bottomhole assembly. Alternatively, the coiled tubing, straightener, and injector may be transported while assembled.

[0033] The bottomhole assembly, consisting of the core barrel, sonic resonator, electro-mechanical coupling device, and tubing vibration isolator, is mechanically attached to the end of the coiled tubing and the electrical connection made between the power cable inside the coiled tubing and the sonic resonator using a suitable submersible electrical connector. The bottomhole assembly is then inserted into the casing shoe assembly as it stands in the derrick on the ground surface.

[0034] The bottomhole assembly is latched inside the heavy-wall casing in the casing shoe assembly by electrically energizing the electro-mechanical coupling device by way of the power cable running through the coiled tubing. Once the bottomhole assembly is latched in the casing shoe assembly, the sonic resonator is automatically energized and begins to vibrate axially. The vibration is transmitted through the coupling device into the heavy wall casing and core bit. The vibration motor may be utilized to induce further vibration on the heavy well casing and core bit.

[0035] Drilling commences by advancing the coiled tubing with the injector, applying any force on the coiled tubing to maintain an appropriate rate of advance of the casing shoe assembly into the ground. As the casing shoe assembly advances into the ground the core barrel fills with soil and rock material.

[0036] The casing shoe assembly is advanced into the ground until the core barrel is full or the casing vibration isolator is just above the ground surface. The sonic resonator is then de-energized, which stops the advance of the hole and unlatches the electro-mechanical coupling device, separating the bottomhole assembly from the casing shoe assembly.

[0037] The injector is used to pull the coiled tubing and bottomhole assembly from the hole, leaving the casing shoe assembly in the ground, to ensure the borehole remains open.

[0038] Once on surface, the core barrel is removed from the bottomhole assembly and the soil and rock material extracted for examination and storage and the core barrel reused.
Alternatively, the soil and rock material may be stored in the core barrel with a new core barrel used for each advancement of the hole.

[0039] The bottomhole assembly, with an empty core barrel, can then be run back into the borehole until it re-engages the casing shoe assembly. The hole can then be advanced by energizing the latching mechanism and sonic resonator and advancing the coiled tubing.

[0040] When the borehole has reached the depth where the casing vibration isolator is just above the ground surface, the bottomhole assembly is de-energized and pulled from the well. A joint of well casing is then connected to the top of the casing vibration isolator by means of a threaded connection or other mechanism. The bottomhole assembly is then inserted through the new casing and into the casing shoe assembly and the system energized to continue advancement of the hole.

[0041] The hole is thus advanced, collecting an uninterrupted sequence of samples of the geologic material. Each time the core barrel is filled, it is withdrawn to surface emptied or replaced by an empty core barrel. Each time the casing is advanced to the point where the top of the casing just above the ground surface, the bottomhole assembly is withdrawn from the hole, another joint of casing installed on the top of the casing string, and the bottomhole 5 assembly re-inserted to continue advancing the hole. The casing and core barrel lengths may be sized so these two events occur at the same time.

[0042] When the hole has reached the target depth, the bottomhole assembly is removed, leaving the well casing in the ground to keep the wellbore open. If, at any time, it is desirable 10 to remove the casing from the well it can be pulled either by simply pulling it out of the ground using a derrick and a winch system (not necessarily the drilling rig itself) or by running back in the casing with the bottomhole assembly, latching onto the casing shoe assembly and vibrating the casing as the injector pulls the coiled tubing out of the hole. If necessary, fluid can be circulated down the coiled tubing to clear any debris in the casing shoe assembly that may prevent the bottomhole assembly from latching on.

[0043] A set of diagnostic sensors can be superimposed on the drilling rig and the downhole components to monitor temperature, pressure, rate of penetration, and quality of the borehole in real time, providing information for control of the drilling process.
Advantages:

[0044] Weight/force may be applied to the coring bit. This is expected to improve penetration rates and assist with installation of casing while drilling. There is also expected to be better directional control or less tendency for the well to deviate from vertical compared to deploying a downhole tool on a wireline. In addition, circulation of fluid is also possible.
This may serve to cool the bit or other downhole equipment, circulate cuttings, and improve bit penetration.

[0045] In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

[0046] The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. Those skilled in the art will appreciate that various adaptations and modifications of the described embodiments can be configured without departing from the scope of the claims. The illustrated embodiments have been set forth only as examples and should not be taken as limiting the invention. It is to be understood that, within the scope of the following claims, the invention may be practiced other than as specifically illustrated and described.

Claims (9)

1. A method of sonic drilling, comprising:
securing to a remote end of a well casing string composed of multiple connected sections of pipe, a tubular casing shoe assembly comprising:
a heavy wall casing for providing an inertial mass for the coring bit;
and a coring bit for extracting an earth core, the casing shoe assembly having an internal engagement;
securing to a remote end of coiled tubing string a sonic vibration assembly comprising:
a sonic resonator for creating sonic vibrations in a frequency range that fluidizes an earth formation;
and a core barrel for collecting the earth core, the sonic vibration assembly having an external engagement for engaging the internal engagement of the casing shoe assembly;
inserting the sonic vibration assembly down through the casing shoe assembly and engaging the external engagement on the sonic vibration assembly with the internal engagement on the casing shoe assembly to couple the sonic vibration assembly and the casing shoe assembly so that, upon activation of the sonic resonator, the casing shoe assembly and the sonic vibration assembly vibrate together;
continuing to vibrate the sonic vibration assembly and the casing shoe assembly to cause the coring bit to fluidize and penetrate an earth formation to form an earth core, with the earth core passing up into the core barrel; and disengaging the external engagement of the sonic vibration assembly from the internal engagement of the casing shoe assembly at periodic intervals and withdrawing the sonic vibration assembly to surface to remove the earth core from the core barrel.

2. The method of Claim 1, wherein a casing vibration isolator is positioned between the well casing string and the casing shoe assembly to isolate the well casing string from sonic vibrations and a tubing vibration isolator is positioned between the coiled tubing string and the sonic vibration assembly to isolate the coiled tubing string from sonic vibrations.

3. An apparatus for sonic drilling, comprising:
a casing shoe assembly comprising:
a heavy wall casing for providing an inertial mass for a coring bit;
and a coring bit for extracting an earth core, the casing shoe assembly having an internal engagement;
a sonic vibration assembly comprising:
a sonic resonator for creating sonic vibrations at a frequency which will fluidize the earth formation;
and a core barrel for collecting the earth core from the coring bit, the sonic vibration assembly having an external engagement for engaging the internal engagement of the casing shoe assembly when the sonic vibration assembly is inserted into and engaged with the casing shoe assembly, such that the casing shoe assembly and the sonic vibration assembly vibrate together

4. The apparatus of Claim 3, wherein a casing vibration isolator is positioned between the well casing string and the casing shoe assembly to isolate the well casing string from sonic vibrations and a tubing vibration isolator is positioned between the coiled tubing string and the sonic vibration assembly to isolate the coiled tubing string from sonic vibrations.

5. The apparatus of Claim 4, wherein the casing vibration isolator and the tubing vibration isolator each comprising:
an outer tubular body having an interior surface defining an interior bore;
an inner tubular body having an exterior surface, a portion of the inner tubular body being received within the interior bore of the outer tubular body;
a dampening assembly positioned between the interior surface of the outer tubular body and the exterior surface of the inner tubular body to dampen relative axial movement of the outer tubular body and the inner tubular body.

6. The apparatus of Claim 5, wherein the dampening assembly includes a spring.

7. The apparatus of Claim 5, wherein the dampening assembly includes a first hydraulic chamber and a second hydraulic chamber and at least one metering device positioned between the first hydraulic chamber and the second hydraulic chamber, hydraulic fluid having to flow between the first hydraulic chamber and the second hydraulic chamber in order for relative axial movement of the outer tubular body and inner tubular body to occur.

8. The apparatus of Claim 4, wherein the internal engagement of the casing shoe assembly is a circumferential groove and the external engagement of the sonic vibration assembly are collet fingers movable between a radially expanded engaged position engaged with the circumferential groove and a radially contracted disengaged position, an interior face of the collet fingers having a wedge profile, a sliding wedge engaging the wedge profile to move the collet fingers from the disengaged to the engaged position, a solenoid coil being used to move the sliding wedge which forces the collet fingers radially outwardly to the engaged position.

9. The apparatus of Claim 8, wherein a spring biases the sliding wedge away from the wedge profile such that the collet fingers return to the disengaged position when the solenoid coil is deactivated.