Patent Application
20060081398
The present invention relates generally to an apparatus and method for hard rock sidewall coring of a borehole, and more particularly to a rotary sidewall coring tool that employs a direct drive mechanism, which operates at an enhanced efficiency, a coring bit control circuit, which provides for precise control of bit advancement, and a carousel core storing device that enables the storage of a large number of core samples.
Conventional tools for hard rock sidewall coring of a borehole employ complex drive mechanisms, which are not very efficient. Many of these systems also provide inadequate torque delivery at the coring bit making them incapable of delivering reliable core operation. In one such system, the drive mechanism comprises an electric motor coupled to a hydraulic pump, which in turn is coupled to a hydraulic motor, which drives the bit. There is a significant power loss in the hydraulic pump and hydraulic motor of such systems. This is because the down hole temperatures are very high, which lowers the viscosity of the hydraulic fluid in the hydraulic pump and motor, which in turn causes a significant amount of the hydraulic fluid to seep past the pistons in the hydraulic pump and motor, which results in a loss of power output by the pistons. Up to sixty percent (60%) of the efficiency of the hydraulic pump and motor can be lost through the drop in viscosity of the hydraulic fluid. Additional efficiency of such systems are lost because they employ a second hydraulic pump to drive the auxiliary devices, which is a drain on the power output of the electric motor. Thus, such systems can lose up to seventy percent (70%) of their efficiency. Hydraulic motors, therefore, have losses due to low volumetric efficiency (fluid loss) and mechanical efficiency (losses due to gears and bearings) which make their overall efficient less than ideal.
In another conventional system, the drive mechanism comprises an electric motor coupled to a hydraulic pump, which is in turn coupled to a hydraulic motor in turn coupled to a 90° transmission. This system has the same drawbacks of the previously described system, namely that there are significant loses due to the decrease in viscosity of the hydraulic fluid in the hydraulic motor. The drive mechanism in this system outputs a low speed and high torque to the bit. Because of its slow speed, this system takes longer than the other systems to remove each core sample. Thus, it requires more rig operation time, thereby making it more expensive to employ.
Furthermore, conventional tools for hard rock sidewall coring of a borehole employ limited feedback of operating conditions. While such devices have the ability to control the advancement of the core bit during coring, they do not have the ability to monitor in real time the torque of the bit. Since torque is a primary factor in determining the rate of penetration of the bit, conventional coring devices lack an important piece of information to prevent stalling of the bit during the coring operation. Rather, such devices infer the torque or RPM from the pressure response or motor current changes during the coring operation. However, because inferential readings are inherently inaccurate, conventional coring devices are susceptible to stalling.
Another disadvantage of conventional tools for hard rock sidewall coring of a borehole is that they have limited space in which to store the core samples. Accordingly, only a limited number of samples can be stored in such devices during a single run of the tool. In certain wells, therefore, the tool must be run down hole more than once to collect all of the desired core samples. A tool with larger core sample storage capacity is desirable.
The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the exemplary embodiments, which follows.
In one embodiment, the present invention is directed to a rotary sidewall coring tool. The coring tool comprises a drive motor, e.g., an electric motor or hydraulic motor, a flexible drive shaft coupled to the drive motor and a coring bit assembly coupled to the flexible drive shaft, such that the coring bit is directly driven by the drive motor. The coring tool further comprises a clutch, which couples the drive motor to the flexible drive shaft and a gear assembly, which couples the clutch to the flexible drive shaft. As used herein, the terms “couple,” “couples,” “coupled” or the like, are intended to mean either indirect or direct connection. Thus, if a first device “couples” to a second device, that connection may be through a direct connection or through an indirect connection via other devices or connectors. The coring tool according to present invention further comprises a hydraulic pump coupled to the drive motor, which drives auxiliary devices. The coring tool also comprises a bit control circuit and sensor, which controls advancement of the coring bit and measures the rpm of the flexible drive shaft, respectively.
The coring bit is mounted on a platform, which is part of the coring bit assembly. The coring bit assembly includes a gear assembly described below. The coring bit assembly can move from a vertical storage position to a horizontal operable position by a hydraulic piston and lever arms. The hydraulic piston is powered by a hydraulic pump, which is in turn driven by the drive motor.
The hydraulic piston also manipulates the coring tool to deposit coring samples into a rotating carousel, which is also powered by the hydraulic pump and ultimately the electric motor. The coring tool further comprises a core separator disposed adjacent to the rotating carousel, which comprises a plurality of labeled discs that identify each core sample collected and a spring loaded plunger that dispenses a labeled disc with each core sample loaded into the rotating carousel. The coring tool also comprises a pair of back-up pistons disposed within the tool, one of which is disposed above the coring bit assembly and the other of which is disposed below the coring bit assembly, which upon activation thrust the tool against one side of the well bore just prior to the coring operation. The coring tool further comprises a potentiometer for measuring the length of the core sample.
In another embodiment, the present invention is directed to a method of coring a borehole in a hard rock subterranean formation. The method comprises the steps of activating the drive motor to rotate an output shaft; coupling the output shaft of the drive motor to the flexible drive shaft; and rotating the coring bit with the flexible drive shaft. Other steps of the method include rotating the coring bit from the vertical storage position to the horizontal operable position; advancing the coring bit laterally into the hard rock subterranean formation; reducing the rotational speed being transmitted to the flexible drive shaft by the output shaft of the drive motor. Other steps in accordance with the present invention include driving auxiliary devices with a hydraulic pump driven by the drive motor and providing feedback signals to the bit control circuit, which are indicative of the rpm and torque of the coring bit and lateral advancement of the coring bit. Still further steps include discharging a core sample from the coring bit, measuring the length of the core sample, depositing the core sample into the rotating carousel; dispensing a labeled disc into the rotating carousel; and thrusting the coring bit against one side of a well bore just prior to commencing the coring operation.
The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the embodiment that follows.
The following figures form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the description of the embodiments present herein:
The details of the present invention will now be described with reference to the accompanying drawings. Turning to
The coring tool 10 includes a coring bit 22, which is shown in
Additional details of the coring tool 10 in accordance with the present invention will now be described in connection with
A gear assembly 72 is coupled to main shaft 68, as shown in
The output shaft 74 of the gear assembly 72 is coupled to a flexible drive shaft 76, best shown in
Referring to
The details of the coring bit assembly 50 in accordance with the present invention will now be described. Coring bit assembly 50 comprises coring bit 22, which is capable of being rotated from a vertical storage position to a horizontal operable position, as shown generally in
Linkage assembly 88 operates to tilt the platform 86 from a vertical storage position to the horizontal operable position. Linkage assembly 88 comprises a generally triangle-shaped lever arm 92. Lever arm 92 has a slot 94 formed along its base portion. Another lever arm 96 is coupled to lever arm 92. Lever arm 96 is connected to a positioning piston 97 operated by a hydraulic pump 106 (shown in
Linkage assembly 90 comprises a pair of lever arms 98, 99 disposed on opposite ends of the coring bit 22. Lever arms 98, 99 are connected by connecting rod 100, which in turn has a mounting eye hook 102 for connecting to a bit advance piston 101, also driven by the hydraulic pump 106. Linkage assembly 90 further comprises guide pin 104, which attaches to coring bit assembly 50 and slides in slot 94. As lever arms 98, 99 are moved axially by the bit advance piston 101, they pivot at one end about pivot point 103 and slide at the other end along slot 94 carrying guide pin 104, which in turn forces the coring bit assembly 50 to move horizontally thereby enabling it to advance into the subterranean formation. In the vertical storage position, coring bit assembly 50 is housed in generally cylindrical recess 105. The positioning piston 97 and bit advance piston 101 are used to drive linkage assembly 88 and linkage assembly 90, respectively, are hydraulically connected to the section 40, which in turn is fed with pressurized hydraulic fluid via hydraulic pump 106, shown in
Referring to
The bit control circuit 600 further comprises a SVdump control valve 606, which in one exemplary embodiment is a three-way, two-position electronically controlled solenoid valve also controlled by the tool's electronic control system. In the first position, the SVdump control valve 606 connects fluid line 608 and rod side 610 of bit advance piston 101 via fluid line 612. In the second (unpowered) position, the SVdump control valve 606 connects fluid line 608 to the hydraulic reservoir tank that supplies the hydraulic pump 106. The SVdump control valve 606 thus operates to relieve the pressure of the fluid being supplied to the bit advance piston 101 when the pressure exceeds a desired value.
The bit control circuit 600 further includes a SVretract control valve 614. In one exemplary embodiment, the SVretract control valve 614 is a three-way, two-position solenoid valve. In the first (powered) position, the SVretract control valve 614 connects the input fluid line 602 to the piston side 611 of the bit advance piston 101 via input and output fluid line 616 and fluid control line 618. In the second (unpowered) position, the SVretract control valve 614 blocks the pump pressure and connects fluid control line 618 to the tank. The SVretract control valve 614 operates to retract the coring bit 22 by supplying the piston side 611 of the bit advance piston 101 with pressurized fluid, which in turn advances the piston and correspondingly pivots the lever arms 98, 99 about pivot point 103 in a clockwise direction thereby causing the coring bit assembly 50 to retract away from the subterranean formation. The bit control circuit 600 also includes an accumulator 619 which is connected to fluid control line 618. The accumulator 619 accumulates the fluid during activation of the SVretract control valve 614 to dampen pressure spikes, which would otherwise occur if the SVretract control valve 614 connected the piston side 611 of the bit advance piston 101 directly to the hydraulic pump 106. Accumulator 619 also helps to retract the bit away from the wall if the SVdump control valve 606 is energized to reduce torque instantly.
The bit control circuit 600 further includes a pressure transducer 620, which is disposed in fluid line 608. The pressure transducer 620 sends a feedback signal to the electronic control system, which in turn monitors the pressure being supplied to the bit advance piston 101. SVADVANCE Control Valve 604, SVDUMP Control Valve 606, and SVRETRACT Control Valve 614 are all electrically connected to the electronic control system and in turn are controlled by that system. In other words, the each of these valves move between the first and second position in response to electronic control signals received from the electronic control system.
The bit control circuit 600 further includes a check valve 622, which is disposed between the pressure transducer 620 and the SVadvance control valve 604. The check valve 622 prevents the fluid in fluid line 608 from flowing back to the tank when the SVadvance control valve 604 is in the second (unpowered) position. The bit control circuit 600 also includes an accumulator 624 which is connected to fluid line 612. The accumulator 624 accumulates the fluid during activation of the SVadvance control valve 604 to dampen pressure spikes, which would otherwise occur if the SVadvance control valve 604 connected the rod side 610 of the bit advance piston 101 directly to the hydraulic pump 106. In one exemplary embodiment, the fluid pressure being output by the hydraulic pump 106 is approximately 2,500 psi, and the fluid pressure being supplied to the bit advance piston 101 during advancement of the coring bit assembly 50, is between 1000 psi and 1500 psi. As those of ordinary skill in the art will appreciate, other pressures and pressure ranges may be acceptable depending upon the parameters of the system.
The bit control circuit 600 operates as follows. SVADVANCE Control Valve 604 and SVRETRACT Control Valve 614 are initially in the closed (unpowered) position and SVdump control valve 606 is in the open position (unpowered). In this position, the SVADVANCE Control Valve 604 and SVRETRACT Control Valve 614 block pump flow (normally closed) and SVdump control valve 606 allows the flow to go to the tank (normally open). When it is desired to advance the coring bit 22, SVADVANCE Control Valve 604 and SVDUMP Control Valve 606 are powered, i.e., moved to the first position by the electronic control system via electronic control signals. This connects the rod side 610 of the bit advance piston 101 to the hydraulic pump 106, supplying it with pressurized fluid. Once the fluid pressure reaches the desired range, which in one exemplary embodiment is approximately 1000 to 1500 psi, the SVadvance control valve 604 is removed of power. The SVdump control valve 606, however, remains closed (powered). Because the check valve 622 prevents the pressurized fluid from flowing back into the SVadvance control valve 604, the fluid lines 608 and 612 remain pressurized. Once the pressure drops below the desired minimum pressure, the SVadvance control valve 604 is activated again, i.e., powered, until the pressure is once again back into the desired range. In the event that the fluid pressure exceeds the maximum desired pressure, the SVdump control valve 606 is opened to connect fluid line 612 to the tank and thereby reduce the pressure in the line with the aid of accumulator 619.
When it is desired to stop the coring operation and retract the coring bit 22, e.g., once a core sample has been obtained, the electronic control system sends control signals to SVADVANCE Control Valve 604 and SVDUMP Control Valve 606 to connect to the tank. At the same time, the electronic control system sends a control signal to the SVretract control valve 614 to connect the piston side 611 of the piston to the hydraulic pump 106. This in turn forces the bit advance piston 101 completely open, thereby retracting the coring bit 22.
Next, positioning piston 97 is operated to rotate coring bit assembly 50 from the horizontal operable position to the vertical storage position. Once coring bit assembly 50 is in the vertical storage position, core sample 131 is ready to be measured and then deposited into the core sample storage device, rotatable carousel 54. To measure, the core sample 131, a push rod 121, which is shown in
After the measurement has been taken, the core sample 131 is ready to be deposited into the core sample storage device. This is done by opening the trap door 127 and activating the push rod 121. The trap door 127 opens when the back-up pistons 128 and 130 are closed. When the back-up pistons 128 and 130 are closed, the same pressure is routed to the back side of the trap door piston to open the door 127. The push rod 121 is then extended once again and this time the core sample 131 will be pushed into a storage tube 114.
The details of the core sample storage device in connection with the present invention will now be described in connection with
The rotatable carousel 54 is rotated by operation of a ratcheting mechanism shown generally in
Core sample separating device 118 in accordance with the present invention will now be described. Turning to
Turning to
Coring tool 10 further comprises a pair of back-up pistons 128 and 130, which are shown in the retracted position in
Operation of the coring tool 10 in accordance with the present invention will now be described. The coring tool 10 in accordance with the present invention is positioned within well bore 14 adjacent sidewall 16 in the area of the subterranean formation of interest. Back-up pistons 128 and 130 are activated thereby positioning the coring tool 10 against sidewall 16. The positioning piston 97 and bit advance piston 101 also controlled by section 40 which receives control signals from surface control unit 20 will operate linkage assemblies 88 and 90 so as to move the coring bit 22 from the vertical storage position to a horizontal operable position and thereafter laterally advance the coring bit 22 into engagement with sidewall 16. Torque sensor 80 and pressure transducer 620 provide feedback signals to the electronic control system. These control signals supply the electronic control system with the rpm of the bit, a phase shift between the two reluctance sensors from which torque can be derived, and the fluid pressure being supplied to the coring bit, which in turn is indicative of the lateral position of the coring bit 22 relative to the subterranean formation. In the event that the coring bit 22 gets stuck or cannot operate at the desired rpm and/or torque, the electronic control system can reduce the torque on the coring bit 22 or retract the bit completely, if needed.
Once the core sample 131 has been cut from sidewall 16 of the subterranean formation, the coring bit 22 is rotated from the horizontal operable position to the vertical storage position. The tool 10 then measures the core sample 131 and deposits it in the removable storage tube 114. The disk dispensing mechanism 124 then dispenses a labeled disk into the removable storage tube 114 opposite the one into which the core sample 131 is deposited. The back-up pistons 128 and 130 are then retracted and the coring tool 10 is ready to be moved to the next area in the subterranean formation from which a core sample will be obtained. This process is repeated until all of the core samples are collected or the rotatable carousel 54 is full, after which the coring tool 10 is pulled out of the well bore 14. Once all of the removable storage tubes 114 have been emptied and placed back into the rotatable carousel 54, the coring tool 10 is ready for use again either in well bore 14 or another well bore in another subterranean formation.
Therefore, the present invention is well-adapted to carry out the objects and attain the ends and advantages mentioned as well as those which are inherent therein. While the invention has been depicted, described, and is defined by reference to exemplary embodiments of the invention, such a reference does not imply a limitation on the invention, and no such limitation is to be inferred. The invention is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent arts and having the benefit of this disclosure. The depicted and described embodiments of the invention are exemplary only, and are not exhaustive of the scope of the invention. Consequently, the invention is intended to be limited only by the spirit and scope of the appended claims, giving full cognizance to equivalents in all respects.
