Patent Application
20050284629
Wells are generally drilled into the ground to recover natural deposits of oil and gas, as well as other desirable materials, that are trapped in geological formations in the Earth's crust. A well is drilled into the ground and directed to the targeted geological location from a drilling rig at the Earth's surface.
Once a formation of interest is reached, drillers often investigate the formation and its contents through the use of downhole formation evaluation tools. Some types of formation evaluation tools form part of a drill string and are used during the drilling process. These are called, for example, “logging-while-drilling” (“LWD”) tools or “measurement-while-drilling” (“MWD”) tools. Other formation evaluation tools are used sometime after the well has been drilled. Typically, these tools are lowered into a well using a wireline for electronic communication and power transmission. These tools are called “wireline” tools.
One type of wireline tool is called a “formation testing tool.” The term “formation testing tool” is used to describe a formation evaluation tool that is able to draw fluid from the formation into the downhole tool. In practice, a formation testing tool may involve many formation evaluation functions, such as the ability to take measurements (i.e., fluid pressure and temperature), process data and/or take and store samples of the formation fluid. Thus, in this disclosure, the term formation testing tool encompasses a downhole tool that draws fluid from a formation into the downhole tool for evaluation, whether or not the tool stores samples. Examples of formation testing tools are shown and described in U.S. Pat. Nos. 4,860,581 and 4,936,139, both assigned to the assignee of the present invention.
During formation testing operations, downhole fluid is typically drawn into the downhole tool and measured, analyzed, captured and/or released. In cases where fluid (usually formation fluid) is captured, sometimes referred to as “fluid sampling,” fluid is typically drawn into a sample chamber and transported to the surface for further analysis (often at a laboratory).
As fluid is drawn into the tool, various measurements of downhole fluids are typically performed to determine formation properties and conditions, such as the fluid pressure in the formation, the permeability of the formation and the bubble point of the formation fluid. The permeability refers to the flow potential of the formation. A high permeability corresponds to a low resistance to fluid flow. The bubble point refers to the fluid pressure at which dissolved gasses will bubble out of the formation fluid. These and other properties may be important in making downhole decisions.
Another downhole tool typically deployed into a wellbore via a wireline is called a “coring tool.” Unlike the formation testing tools, which are used primarily to collect sample fluids, a coring tool is used to obtain a sample of the formation rock.
A typical coring tool includes a hollow drill bit, called a “coring bit,” that is advanced into the formation wall so that a sample, called a “core sample,” may be removed from the formation. A core sample may then be transported to the surface, where it may be analyzed to assess, among other things, the reservoir storage capacity (called porosity) and permeability of the material that makes up the formation; the chemical and mineral composition of the fluids and mineral deposits contained in the pores of the formation; and/or the irreducible water content of the formation material. The information obtained from analysis of a core sample may also be used to make downhole decisions.
Downhole coring operations generally fall into two categories: axial and sidewall coring. “Axial coring,” or conventional coring, involves applying an axial force to advance a coring bit into the bottom of the well. Typically, this is done after the drill string has been removed, or “tripped,” from the wellbore, and a rotary coring bit with a hollow interior for receiving the core sample is lowered into the well on the end of the drill string. An example of an axial coring tool is depicted in U.S. Pat. No. 6,006,844, assigned to Baker Hughes.
By contrast, in “sidewall coring,” the coring bit is extended radially from the downhole tool and advanced through the side wall of a drilled borehole. In sidewall coring, the drill string typically cannot be used to rotate the coring bit, nor can it provide the weight required to drive the bit into the formation. Instead, the coring tool itself must generate both the torque that causes the rotary motion of the coring bit and the axial force, called weight-on-bit (“WOB”), necessary to drive the coring bit into the formation. Another challenge of sidewall coring relates to the dimensional limitations of the borehole. The available space is limited by the diameter of the borehole. There must be enough space to house the devices to operate the coring bit and enough space to withdraw and store a core sample. A typical sidewall core sample is about 1.5 inches (˜3.8 cm) in diameter and less than 3 inches long (˜7.6 cm), although the sizes may vary with the size of the borehole. Examples of sidewall coring tools are shown and described in U.S. Pat. Nos. 4,714,119 and 5,667,025, both assigned to the assignee of the present invention.
Like the formation testing tool, coring tools are typically deployed into the wellbore on a wireline after drilling is complete to analyze downhole conditions. The additional steps of deploying a wireline formation testing tool, and then also deploying a wireline coring tool further delay the wellbore operations. It is desirable that the wireline formation testing and wireline coring operations be combined in a single wireline tool. However, the power requirements of conventional coring tools have been incompatible with the power capabilities of existing wireline formation testers. A typical sidewall coring tool requires about 2.54 kW of power. By contrast, conventional formation testing tools are typically designed to generate only about 1 kW of power. The electronic and power connections in a formation testing tool are generally not designed to provide the power to support a wireline sidewall coring tool.
It is noted that U.S. Pat. No. 6,157,893, assigned to Baker Hughes, depicts a drilling tool with a coring tool and a probe. Unlike wireline applications, drilling tools have additional power capabilities generated from the flow of mud through the drill string. The additional power provided by the drilling tool is currently unavailable for wireline applications. Thus, there remains a need for a wireline assembly with both fluid sampling and coring capabilities.
It is further desirable that any downhole tool with combined coring and formation testing capabilities provide one or more of the following features, among others: enhanced testing and/or sampling operation, reduced tool size, the ability to perform coring and formation testing at a single location in the wellbore and/or via the same tool, and/or convenient and efficient combinability of separate coring and sampling tools into the same component and/or downhole tool.
In one or more embodiments, the invention relates to a wireline assembly that includes a coring tool for taking coring samples of the formation and a formation testing tool for taking fluid samples from the formation, wherein the formation testing tool is operatively connected to the coring tool.
In one or more embodiments, the invention related to a method for evaluating a formation that includes lowering a wireline assembly into a borehole, activating a formation testing tool connected in the wireline assembly to obtain a sample fluid from the formation, and activating a coring tool connected in the wireline assembly to obtain a core sample.
In one or more embodiments, the invention relates to a downhole tool that includes a tool body having an opening, a coring bit disposed proximate the opening in the tool body and selectively extendable therethrough, a flowline disposed proximate the coring bit and a sealing surface disposed proximate a distal end of the flowline.
In one or more embodiments, the invention relates to a method for taking downhole samples that includes obtaining a core sample using a coring bit disposed on a sample block in a downhole tool, rotating the sample block, establishing fluid communication between a flowline in the sample block and a formation, and withdrawing a formation fluid from the formation through the flowline.
In one or more embodiments, the invention relates to a method for taking downhole samples that includes establishing fluid communication between a flowline in a downhole tool and a formation by extending the a packer seal to be in contact with a formation, obtaining a core sample using a coring bit configured to extend inside a sealing area of the packer seal, ejecting the core from the coring bit and into a sample chamber, and withdrawing a formation fluid from the formation through the flowline.
In one or more embodiments, the invention relates to a field joint for connecting tool modules that includes an upper module having a bottom field joint connector at a lower end of the upper module and a lower module having a top field joint connector at an upper end of the lower module. The upper module may comprise a cylindrical housing for receiving the lower module, a first flowline, a female socket bulkhead having at least one female socket. The lower module may comprise a second flowline, a male pin bulkhead, and one or more male pins disposed in the male pin bulkhead so that at least a portion of the one or more male pins protrudes upwardly from the male pin bulkhead.
In one or more embodiments, the invention relates to a method of connecting two modules of a downhole assembly that includes inserting a lower module into a cylindrical housing of an upper module, inserting male pins in a male pin bulkhead in the lower module into female socket holes in a female socket bulkhead in the upper module, depressing the male pin bulkhead with the female socket bulkhead, and inserting a male flowline connector in the upper module into a female flowline connector of the lower module.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
Some embodiments of the present invention relate to a wireline assembly that includes a low-power coring tool that may be connected to a formation testing tool. Other embodiments of the invention relate to a field joint that may be used to connect a coring tool to a formation testing tool. Some embodiments of the invention relate to a downhole tool that includes a combined formation testing and a coring assembly.
The formation testing tool 102 includes a probe 111 that may be extended from the formation testing tool 102 to be in fluid communication with a formation F. Back up pistons 112 may be included in the tool 101 to assist in pushing the probe 111 into contact with the sidewall of the wellbore and to stabilize the tool 102 in the borehole. The formation testing tool 102 shown in
The coring tool 103 includes a coring assembly 125 with a coring bit 121, a storage area 124 for storing core samples, and the associated control mechanisms 123 (e.g., the mechanisms shown in
The apparatus of
Downhole tools often include several modules (i.e., sections of the tool that perform different functions). Additionally, more than one downhole tool or component may be combined on the same wireline to accomplish multiple downhole tasks in the same wireline run. The modules are typically connected by “field joints,” such as the field joint 104 of
In practice, a wireline tool will generally include several different components, some of which may be comprised of two or more modules (e.g., a sample module and a pumpout module of a formation testing tool). In this disclosure, “module” is used to describe any of the separate tools or individual tool modules that may be connected in a wireline assembly. “Module” describes any part of the wireline assembly, whether the module is part of a larger tool or a separate tool by itself. It is also noted that the term “wireline tool” is sometimes used in the art to describe the entire wireline assembly, including all of the individual tools that make up the assembly. In this disclosure, the term “wireline assembly” is used to prevent any confusion with the individual tools the make up the wireline assembly (e.g., a coring tool, a formation testing tool, and an NMR tool may all be included in a single wireline assembly).
In order to drive the coring bit 201 into the formation, it must be pressed into the formation while it is being rotated. Thus, the coring tool 210 applies a weight-on-bit (“WOB”) (i.e., the force that presses the coring bit 201 into the formation) and a torque to the coring bit 201. The coring tool 210 shown in
The WOB in prior art coring tool 210 is generated by an AC motor 212 and a control assembly 211 that includes a hydraulic pump 213, a feedback flow control (“FFC”) valve 214, and a kinematics piston 215. The AC motor 212 supplies power to the hydraulic pump 213. The flow of hydraulic fluid from the hydraulic pump 213 is regulated by the FFC valve 214, and the pressure of hydraulic fluid drives the kinematics piston 215 to apply a WOB to the coring bit 201.
The torque is supplied by another AC motor 216 and a gear pump 217. The second AC motor 216 drives the gear pump 217, which supplies a steady flow of hydraulic fluid to the hydraulic coring motor 202. The hydraulic coring motor 202, in turn, imparts a torque to the coring bit 201 that causes the coring bit 201 to rotate. Typically, the gear pump 217 pumps about 4.5 gpm (˜17 lpm) of hydraulic fluid at a pressure of about 500 psi (˜3.44 MPa). This generates a torque of about 135 in.-oz. (˜0.953 NM) while consuming between 2.5 kW and 4.0 kW, depending on the efficiency of the system. A typical operating speed of the coring bit 201 is about 3,000 rpm.
Referring now to
The first brushless DC motor 222 is operatively connected to a control assembly 221 including a hydraulic pump 223, a valve 224, and a kinematics piston 225. The DC motor 222 drives the hydraulic pump 223, and hydraulic fluid is pumped through a valve 224. The valve 224 is preferably a pulse-width modulated (“PWM”) solenoid valve. The valve may be operated in a manner to control the WOB. As will be described with reference to
A second brushless DC motor 226 drives a high pressure gear pump 227 that supplies hydraulic fluid to the hydraulic coring motor 202. In some embodiments, the high pressure gear pump 227 is used to deliver hydraulic fluid at a higher pressure and a lower flow rate than in prior art coring tools. This system provides what is referred to herein as “low-power.” For example, the coring tool 220 shown in
Such a configuration may enable a coring tool 220 to consume less than 2 kW of power. In certain embodiments, a coring tool 220 may consume less than 1 kW of power.
The first curve 301 shows the efficiency of coring motor 202 of
Typical formation testing tools are generally incapable of transmitting the power required by prior art coring tools. The low-power coring tool of
The valve 504 may be a pulse-width modulated (“PWM”) solenoid valve. The valve 504 is operatively connected to a PWM controller 508. The controller 508 operates the valve based on inputs from sensors 521, 531. Preferably, a PWM solenoid valve (i.e., valve 504) is switched between the open position and the closed position at a high frequency. For example, the valve 504 may be operated at a frequency between about 12 Hz and 25 Hz. The fraction of the time that the valve 504 is open will control the amount of hydraulic fluid that flows through the valve 504. The greater flow rate through the valve 504, the lower the pressure in the flowline 506 and the lower the WOB applied by the kinematics piston 507. The smaller the flow rate through the valve 504, the greater the pressure in the flowline 506 and the greater the WOB applied by the kinematics piston 507.
A PWM controller 508 may be operatively connected to one or more sensors 521, 531. Preferably, the PWM controller 508 is coupled to at least a pressure sensor 521 and a torque sensor 531. The pressure sensor 521 is coupled to the flowline 506 so that it is responsive to the hydraulic pressure in the flowline 506, and the torque sensor 531 is coupled to the coring motor 502 so that it is responsive to the torque output of the coring motor 502.
The valve 504 may be controlled so as to maintain an operating characteristic at a desired value. For example, the valve 504 may be controlled to maintain a substantially constant WOB. The valve 504 may also be controlled to maintain a substantially constant torque output of the coring motor 502.
When the valve 504 is controlled to maintain a constant WOB, the PWM controller 508 will control the valve 504 based on input from the pressure sensor 521. When the WOB becomes too high, the controller 508 OLE_LINK5 may operate the valve 504 to be in an open position a higher fraction of the time. Hydraulic fluid in the flow line 506 may then flow through the valve 504 at a higher flowrate, which will reduce the pressure to the kinematics piston 507, thereby reducing the WOB.
Conversely, when the WOB falls below the desired pressure, the controller 508 may operate the valve 504 to be in an closed position a higher fraction of the time. Hydraulic fluid in the flow line 506 flows through the valve 504 at a lower flowrate, which will increase the pressure to the kinematics piston 507, thereby increasing the WOB.
When controlling the system based on torque, the torque sensor 531 measures the torque that is applied to the coring motor. For a given rotary speed, the torque applied by the coring motor 502 will depend on the formation properties and the WOB. The controller 518 operates the valve 504 so that the torque output of the coring motor 502 remains near a constant level. The desired torque output may vary depending on the tool and the application In some embodiments, the desired torque output is between 100 in.-oz. (˜0.706 NM) and 400 in.-oz. (˜2.82 NM). In some embodiments, the desired torque output is about 135 in.-oz (˜0.953 NM). In other embodiments, the desired torque output is about 250 in.-oz. (˜1.77 NM).
When the torque output of the coring motor 502 is above the desired level, the controller 508 operates the valve 504 to be open a higher fraction of the time. A higher flow rate of hydraulic fluid flows through the valve 504. This decreases the pressure in the flow line 506, which decreases the hydraulic pressure in the kinematics piston 507. A decreased pressure in the kinematics piston 507 will result in a decreased WOB and a decreased torque required to maintain the rotary speed of the coring bit (not shown in
When the torque output of the coring motor 502 is below the desired level, the controller 508 operates the valve 504 to be in a closed position a higher fraction of the time. Hydraulic fluid flows through the valve 504 at a lower flow rate. This increases the pressure in the flow line 506, which increases the hydraulic pressure in the kinematics piston 507. An increased pressure in the kinematics piston 507 will result in an increased WOB and an increased torque required to maintain the rotary speed of the coring bit.
The upper module 701 includes a male flowline connector 711 with seals 727 to prevent fluid from passing around the male flowline connector 711. The male flowline connector 711 may, for example, be threaded onto the upper module 701 (e.g., at area shown generally at 712). A female flowline connector 751 in the lower module 702 is positioned to receive the male flowline connector 711 when the field joint 700 is made-up (made-up condition shown in
The upper module 701 also includes a female socket bulkhead 714. Socket holes 753 are located in the female socket bulkhead 714. The socket holes 753 are positioned in the upper module 701 to prevent extraneous fluids from being trapped or collected in the socket holes 753.
The lower module 702 includes a male pin bulkhead 754 with male pins 713 that extend upwardly from male pin bulkhead 754. The male pin bulkhead 754 and the male pins 713 are disposed in a protective sleeve 773. In some embodiments, the protective sleeve 773 is slightly higher than the top of the male pins 713. In some embodiments, the male pin bulkhead 754 is moveable with respect to the lower module 702 and the protective sleeve 773. For example,
Optionally, the upper surface of the male pin bulkhead 754 is covered by an interfacial seal 771 that is bonded to the top of bulkhead 754 and has raised bosses that seal around each male pin 713. The interfacial seal 771 is shown in more detail in
The protective sleeve 773 may be perforated or porous. This enables fluids trapped within the protective sleeve 773 to flow through the protective sleeve to a position where the fluids will not interfere with the electrical connection between the male pins 713 and the female socket holes 753 when the field joint 700 is made-up.
The male flowline connector 711 of the upper module 701 is received in the female flowline connector 751 of the lower module 702. Seals 728 on the male flowline connector 711 seal against the inner surface of the female flowline connector 751 to prevent fluid from flowing around the flow connector 711. In the made-up position, the male flow connector 711 establishes fluid communication between the flowline 717 in the upper module 701 and the flow line 757 in the lower module 702.
It is noted that this description refers to seals that are positioned in one member to seal against a second member. A person having ordinary skill in the art would realize that a seal could be disposed in the second member to seal against the first. No limitation is intended by any description of a seal being on or disposed in a particular member. Alternate configurations do not depart from scope of the invention.
In the made-up position, the female socket bulkhead 714 pushes downwardly on the male pin bulkhead 754. The spring 780 allows for the downward movement of male pin bulkhead 754. The male pins 713 are positioned in the female socket holes 753 to make electrical contact. The female socket bulkhead 714 is positioned at least partially inside the protective sleeve 773.
In the field joint shown in
The protective sleeve 773 may include a seal 775. In the non-made-up position (shown in
As discussed above, the protective sleeve 773 may be perforated or porous to allow fluid to flow through the protective sleeve 773. The protective sleeve 773 may be porous above the seal 775, but fluid cannot flow through the protective sleeve 773 below the seal 775. The seal 775 prevents fluid from flowing through the porous protective sleeve 773 and into a position between the male pin bulkhead 754 and the female pin bulkhead 714, and into the lower module 702.
The downhole tool 800 has a tool body 802 that surrounds the combined assembly 801. An opening 804 in the tool body 802 enables core samples and fluid samples to be obtained from the formation. The opening 804 is preferably selectively closable to prevent the flow of fluid into the downhole tool. The combined assembly 801 includes a sampling block 806. The sampling block 806 is positioned adjacent to the opening 804 so that the sampling block 806 has access to the opening 804.
The sampling block 806 may include a fluid probe 807 and a coring bit 808 on adjacent sides. The sampling block 806 may be rotated so that either of the fluid probe 807 and the coring bit 808 is in a position to access the opening 804.
The exact design of a fluid probe is not intended to limit the invention. The following description is provided only as an example. The fluid probe 807 includes a sealing surface 810, such as a packer, for pressing against the borehole wall (not shown). When the sealing surface 810 creates a seal against the borehole wall, the flowline 812 in the fluid probe 807 is placed in fluid communication with the formation. The sealing surface 810 may comprise a packer or other seal to establish fluid communication between the flowline and the formation.
As shown in
The tubing 813 is preferably a flexible tubing that maintains the connection between the second flowline 812 and the fluid sample line 814 when the sampling block 806 is rotated. The tubing 813 enables relative movement between the flowline 812 in the sample block 806 and the fluid sample line 814 in the tool 800, while still maintaining the fluid communication. For example,
In some embodiments, the tubing 813 is a telescoping hard tubing that allows for a dynamic range of positions. Other types of tubing or conduit may be used without departing from the scope of the invention.
To obtain a sample, the sample block 806 extends through the opening 804 so that the sealing surface 810 (e.g., a packer, as shown in
The coring bit 808 in the sample block 806 may be advanced into the formation to obtain a core sample of the formation material.
Referring again to
A core sample chamber 850 may include gate valves 852, 853. The gate valves 852, 853 may be used to isolate sections of the core sample chamber 850 into separate compartments so that a plurality of core samples may be stored without contamination between the samples. For example, lower gate valve 853 may be closed in preparation for storing a core sample. A core sample may then be moved into the core sample chamber 850, and the lower gate valve 853 will isolate the core sample from anything below the lower gate valve 853 (e.g., previously collected core samples). Once the core sample is in place, the upper gate valve 852 may be closed to isolate the core sample from anything above the upper gate valve 852 (e.g., later collected core samples). Using a plurality of gate valves (e.g., valves 852, 853), a core sample chamber may be divided into separate compartments that are isolated from other compartments.
It is noted that isolation mechanisms other than gate valves may be used with the invention. For example, an iris valve or an elastomeric valve may be used to isolate a compartment in a core sample chamber. The type of valve is not intended to limit the invention.
In some embodiments, a core sample chamber 850 may be connected to the fluid sample line 814 by a fill line 857. The fill line may include a fill valve 856 for selectively putting the core sample chamber 850 in fluid communication with the fluid sample line 814. In some embodiments, the core sample chamber 850 may be connected to the borehole environment through an ejection line 855. An ejection valve 854 may be selectively operated to put the core sample chamber 850 in fluid communication with the borehole. The term “borehole” is used to describe the volume that has been drilled. Ideally, mud packs against the borehole wall so that the inside of the borehole is sealed from the formation. Where the flowline (e.g., 812 in
A fill line 857 enables a fluid sample to be stored in the same compartment of a core sample chamber as the sample core that was taken from the same position in the borehole. Once a core sample in a stored position (i.e., between gate valves 852, 853, which are closed), the fill valve 856 and sample fluid may be pumped into the core sample chamber, in the same compartment as the core sample. The ejection line 855 enables fluid to be ejected into the borehole until the core sample is completely immersed in the native formation fluid from that location.
In
The coring bit 902 of
The probe 903 also includes a fluid seal or packer 906 and a flowline 908 for taking fluid samples. When the packer 906 is pressed against the formation wall, the flowline 908 is isolated from the borehole environment and in fluid communication with the formation. Formation fluids may be drawn into the coring tool 900 through the flowline 908.
The packer 906 creates a sealing area against the formation 912. Fluid communication with the formation is established inside the packer sealing area. An opening of the flowline 908 is preferably located inside the sealing area adjacent the packer 906. The flowline 908 is also preferably adapted to receive fluids from the formation via the sealing area. The coring bit 902 is extendable inside and through the sealing area of the packer 906.
In some embodiments, the coring tool of
Next, the method may include directing the core sample into a sample chamber, at step 1008; and directing the fluid sample into the sample chamber, as 1010. Steps 1008, 1010 are shown in this order because the core sample is preferably moved into the sample chamber before the fluid sample is then directed into the sample chamber. This enables the sample chamber to be filled completely with sample fluid after the core sample is already positioned in the sample chamber. However, those having ordinary skill in the art will realize that these steps may be performed in any order. It is also noted that steps 1008, 1010 are not required in all circumstances. For example, a core sample may remain in the coring bit for transportation to the surface.
Finally, the method may include retrieving the wireline assembly and analyzing the samples, at steps 1012, 1014. The analysis of the sample may provide information that is used in further drilling, completion, or production of the well.
Next, the method may include rotating a sample block in the downhole tool, step 1104. This will rotate the coring bit so that the sample core may be ejected from the coring bit, step 1106. The method may also include establishing fluid communication between a flowline and the formation, step 1108. Then, fluid may be withdrawn from the formation, step 1110. Finally, sample fluid is preferably directed into a sample chamber, step 1112.
The method may include ejecting the sample core from the coring bit into a sample chamber, step 1206. The method may also include withdrawing a fluid sample from the formation by drawing fluid through a flowline with its distal end inside the sealing area of the packer seal, step 1210.
Finally, the method may include directing the sample fluid into the sample chamber, step 1212.
Embodiments of the present invention may present one or more of the following advantages. Some embodiments of the invention enable both a coring tool and a formation testing tool to be included on the same wireline or LWD assembly. Advantageously, this enables core samples and fluid samples to be obtained from the same position in a borehole. Having both a core sample and a fluid sample from the same position enables the analysis of the formation and its contents to be more accurate. Additionally, one or more separate or integral coring and/or sampling components may be provided in a variety of configurations about the downhole tool.
Advantageously, certain embodiments of a coring tool operate with a high efficiency. Higher efficiency enables a coring tool to be operated using less power.
Advantageously, embodiments of the invention that include a low-power coring tool enable a core sample to be obtained using less power than the prior art. In certain embodiments, a low-power coring tool uses less than 1 kW of power. Advantageously, the circuitry that is required to deliver power to a low-power coring tool is much less demanding than that required with prior art coring tools. Thus, a low-power coring tool may be used in the same wireline assembly with other downhole tools that typically cannot deliver the high power required by prior art coring tools.
Some embodiments of a coring tool in accordance with the invention include PWM solenoid valves as part of a feed-back loop to control the hydraulic pressure applied to a kinematics piston or other device that applies WOB. Advantageously, a PWM solenoid valve may be precisely controlled so that the WOB is maintained at or near a desired value.
In at least one embodiment, a PWM solenoid valve is controlled based on a torque that is delivered to a coring bit. Advantageously, a coring tool with such a control device may precisely control the PWM solenoid valve so that the pressure applied to a kinematics piston results in a substantially constant torque delivered to the coring bit.
Some embodiments of the invention relate to a wireline assembly that includes a field joint with female socket holes located in the bottom of a tool or module. Advantageously, fluid cannot be trapped in the female socket holes, and the field joint will be relatively free of interference with the electrical contacts. Advantageously, some embodiments include a protective sleeve to prevent damage to male pins that may be disposed at the top of a module or tool. Additionally, embodiments of a protective sleeve that are perforated or porous enable fluid that might interfere with an electrical contact to flow through the protective sleeve and away from the electrical contacts.
Some embodiments of a wireline assembly in accordance with the invention include a sample chamber that enables a core sample to be stored in the same chamber or compartment as a fluid sample. Advantageously, a core sample may be stored while being surrounded by the formation fluid that is native to the position where the core sample was taken.
Advantageously, a sample chamber with one or more fill and ejection lines enables formation fluid to be pumped through the sample chamber while a core sample is in the sample chamber. Advantageously, at least a portion of the mud filtrate in the core sample (i.e., the mud filtrate that invaded the formation before the core sample was obtained) may be purged from the core sample and from the sample chamber.
While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised that do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.
