Drill string valve and method

Method and drill string valve for closing a conduit through which a high pressure fluid flows. The drill string valve includes an elongated housing having an inside cavity, a seal element attached to a first end of the elongated housing, the seal element being disposed within the inside cavity such that a flow of liquid through the inside cavity from the first end to a second end of the elongated housing is allowed, a sliding valve disposed within the inside cavity and configured to slide to and from the seal element along the axis such that when the sliding valve contacts the seal element the flow of liquid is suppressed, a biasing cartridge disposed within the inside cavity, between the seal element and the second end of the elongated housing, and configured to apply a first force on the sliding valve such that the sliding valve is contacting the seal element, and a loading mechanism disposed within the inside cavity, between the biasing cartridge and the second end of the elongated housing, and configured to apply a second force on the biasing cartridge.

BACKGROUND

1. Technical Field

Embodiments of the subject matter disclosed herein generally relate to methods and valves and, more particularly, to mechanisms and techniques for interrupting a flow of liquid through a valve.

2. Discussion of the Background

During the past years, with the increase in price of fossil fuels, the interest in developing new oil production fields has dramatically increased. However, the availability of land-based production fields is limited. Thus, the industry has now extended drilling to offshore locations, which appear to hold a vast amount of oil reserves. One characteristic of the offshore locations is the high pressure to which the drilling equipment is subjected. For example, it is conventional to have parts of the drilling equipment designed to withstand pressures between 5,000 to 30,000 psi. In addition, the materials used for the various components of the drilling equipment are desired to be corrosion resistant and to resist high temperatures.

Existing technologies for extracting oil from offshore fields use a system10as shown inFIG. 1. More specifically, the system10includes a vessel (or rig)12having a reel14that supplies power/communication cables16to a controller18. The controller18is disposed undersea, close to or on the seabed20. In this respect, it is noted that the elements shown inFIG. 1are not drawn to scale and no dimensions should be inferred fromFIG. 1.

FIG. 1also shows that the drill string24is provided inside a riser40, that extends from vessel12to a BOP28. A wellhead22of the subsea well is connected to a casing44, which is configured to accommodate the drill string24that enters the subsea well. At the end of the drill string24there is a drill bit (not shown). Various mechanisms, also not shown, are employed to rotate the drill string24, and implicitly the drill bit, to extend the subsea well.

However, during normal drilling operation, unexpected events may occur that could damage the well and/or the equipment used for drilling. One such event is the uncontrolled flow of gas, oil or other well fluids from an underground formation into the well. Such event is sometimes referred to as a “kick” or a “blowout” and may occur when formation pressure inside the well exceeds the pressure applied to it by the column of drilling fluid (mud). This event is unforeseeable and, if no measures are taken to prevent it, the well and/or the associated equipment may be damaged. Although the above discussion was directed to subsea oil exploration, the same is true for ground oil exploration.

Thus, a blowout preventer (BOP) might be installed on top of the well to seal the well in case that one of the above events is threatening the integrity of the well. The BOP is conventionally implemented as a valve to prevent the release of pressure either in the annular space, i.e., between the casing and the drill pipe, or in the open hole (i.e., hole with no drill pipe) during drilling or completion operations. Recently, a plurality of BOPs are installed on top of the well for various reasons.FIG. 1shows two BOPs26or28that are controlled by the controller18.

However, ultra-deep water exploration presents a host of other drilling problems, such as substantial lost circulation zones, well control incidents, shallow-water flows, etc. Thus, many of these wells are lost due to significant mechanical drilling problems. These events increase the cost of drilling and reduce the chances that oil would be extracted from those wells, which is undesirable.

A new technology for deep water exploration, which is discussed with regard toFIG. 2, has been developed in response to these problems. While the traditional technology used single-gradient drilling, the new technology uses dual-gradient drilling for better controlling a bottom hole pressure, i.e., the pressure at the region around the drill bit30shown inFIG. 2. With the single gradient drilling, the bottom hole pressure is controlled by a mud (dedicated mixture of liquids used in the oil extraction industry) column extending from the bottom of the well32to the rig12, as shown inFIG. 2. However, with the dual gradient drilling, a better pressure control is achieved through a combination of (i) mud from the bottom32of the well to a mud lift pump34and (ii) mud from the mud lift pump34to the rig12.FIG. 2shows that the new technology employs a mud return line36and a seawater power line38to the mud lift pump34beside the riser40. The mud is provided through the drill string24to the drill bit30. A subsea rotating device42is provided close to the BOP26to maintain separation between the sea water in the riser above the subsea rotating device42and the mud returns below. Thus, the dual gradient drilling system shown inFIG. 2provides the mud pumped through the drill string24to the drill bit30and then pumped back up an annulus between the drill string24and the casing44by the mud lift pump34.

The system shown inFIG. 2, which needs to balance the different pressures between the mud and the seawater when the mud lift pump34is not active, may employ a drill string valve46, disposed below BOP26and close to drill bit30. The unbalanced pressure formed because of the U-tube effect of the mud could reach 5,000 psi, depending on mud weight and water depth. This is a large pressure that would normally destroy valves used in faucets, irrigation systems, blood dialysis and other technical fields that use valves. Due to these large pressures and the erosion problems posed by the saltwater and mud, one skilled in the art would not look or import components from valves used in these other technical fields because these valves are not designed to withstand large undersea pressures. Also, the sealing requirements for the drilling industry make those valves used in the low pressure fields inappropriate for the drilling industry.

The conventional drill string valve46is placed inside the casing44, close to the drill bit30. Thus, the drill string valve46is a downhole tool and this valve is illustrated inFIG. 3. The drill string valve46has a sliding valve50that is configured to seal a passage52from a passage54inside spring carrier48. The sliding valve50achieves the sealing in concert with cone seal56. Cone seal56may be made of a strong metal and fixed relative to the drill string valve46. The sliding valve50is movable along an axis Z and is biased by a spring58. The sliding valve50is closed in a default position. When the mud is pumped from the vessel12towards drill bit30(along axis Z inFIG. 2), the high pressure of the mud opens up the sliding valve50(by pressing down the sliding valve50) and compresses spring58. When the pumping from vessel12stops, the compressed spring58closes the sliding valve50, thus closing the drill string valve46.

A few disadvantages of the drill string valve46shown inFIG. 3are now discussed. A drill collar of the valve was designed in two sections. The two sections include a lower long collar62to house the long coil spring58and a short upper collar64to house the valve mechanism. This design requires machining drill collars to high-precision, making holding diameters and concentricities, especially in deep bores, a challenge. Because it is a two-piece collar, assembly and disassembly requires the use of heavy “tongs” or iron roughneck to make up and break the drill collar connection. This equipment is not available in the shop and must be made up and broken on the drill floor.

A spring package includes the long coil spring58, or tandem springs that make up a long spring, and these springs are provided in a spring chamber66. Buckling of the long springs58has been observed. The buckling increase a friction between the springs and the package as the coils contact with an outer diameter and an inner diameter of the spring chamber66. Also, the spring package is open to borehole fluids in this design. Even if the spring area is packed in grease, the grease eventually is replaced with mud during drilling. Thus, the springs are corroded by the borehole fluids, which further increase the friction between the springs and the walls of the spring chambers and also shorten the life of the springs.

Another disadvantage of the system shown inFIG. 3is related to the way in which the drill string valve46is assembled. The coil spring58and spring carrier48are installed in the long collar62, where the spring carrier48male thread is screwed into a mating thread63at the lower end of the collar. Once installed, the spring carrier48is extended out of the top of the lower collar62. The spring extension beyond the collar depends on the spring used, but could be up to 12 inches. This extreme condition would have the free length of the spring hanging out 3 inches beyond the spring carrier48with no support. The challenge is to handle the heavy upper collar64, swallowing an unsupported spring end and having to compress the spring while lining up for engagement with the lower collar thread65. The spring induced end load during these maneuvers could reach a few thousand pounds at thread engagement. This is a safety concern for the rig operator because of potential injury to the crew.

Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks.

SUMMARY

According to one exemplary embodiment, there is a drill string valve configured to be attached to a casing for connecting a drill to a rig. The drill string valve includes an elongated housing having an inside cavity, the housing extending along an axis and having a substantially constant outer diameter; a seal element attached to a first end of the elongated housing, the seal element having an outer diameter smaller than an inner diameter of the elongated housing, and the seal element being disposed within the inside cavity such that a flow of liquid through the inside cavity from the first end to a second end of the elongated housing is allowed; a sliding valve disposed within the inside cavity and configured to slide to and from the seal element along the axis such that when the sliding valve contacts the seal element the flow of liquid is suppressed; a biasing cartridge disposed within the inside cavity, between the seal element and the second end of the elongated housing, and configured to apply a first force on the sliding valve such that the sliding valve is contacting the seal element; and a loading mechanism disposed within the inside cavity, between the biasing cartridge and the second end of the elongated housing, and configured to apply a second force on the biasing cartridge.

According to another exemplary embodiment, there is a method for preparing a drill string valve to be connected to a casing for connecting a drill to a rig. The method includes a step of connecting a power source to a port of a biasing cartridge of the drill string valve, the drill string valve including (i) an elongated housing having an inside cavity, the housing extending along an axis and having a substantially constant outer diameter, (ii) a seal element attached to a first end of the elongated housing, the seal element having an outer diameter smaller than an inner diameter of the elongated housing, and the seal element being disposed within the inside cavity such that a flow of liquid through the inside cavity from the first end to a second end of the elongated housing is allowed, (iii) a sliding valve disposed within the inside cavity and configured to slide to and from the seal element along the axis such that when the sliding valve contacts the seal element the flow of liquid is suppressed, and (iv) the biasing cartridge disposed within the inside cavity, between the seal element and the second end of the elongated housing and configured to apply a first force on the sliding valve such that the sliding valve is contacting the seal element, and (v) a loading mechanism disposed within the inside cavity, between the biasing cartridge and the second end of the elongated housing, and configured to apply a second force on the biasing cartridge; a step of applying a pressure to the loading mechanism to generate the second force; a step of compressing a wave spring of the biasing cartridge; a step of locking a stop element to maintain the wave spring in a compressed state; and a step of releasing the applied pressure.

According to still another exemplary embodiment, there is a drill string valve configured to be attached to a casing for connecting a drill to a rig. The drill string valve includes an elongated housing having an inside cavity, the housing extending along an axis; a motor module disposed within the inside cavity; a seal element connected to the motor module and configured to move within the inside cavity along the axis; a seat disposed within the inside cavity and configured to receive the seal element to interrupt a fluid flow through the drill string valve when the seat touches the seal element; and a control element disposed within the inside cavity and configured to control a closing and opening of the seal element.

According to another exemplary embodiment, there is a method for controlling a drill string valve. The method includes a step of receiving from a flow meter unit a flow rate of a fluid through the drill string valve, a step of determining in a processor a position of a seal element that is configured to move to and from a seat to suppress a fluid flow through the drill string valve, and a step of searching a look-up table stored in memory connected to the processor for determining whether a motor has to be activated to close or open the seal element.

DETAILED DESCRIPTION

The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of a drill string valve. However, the embodiments to be discussed next are not limited to this type of valve, but may be applied to other systems that are configured to interrupt a fluid flow.

According to an exemplary embodiment, a novel drill string valve has a substantially constant outer diameter, includes a loading mechanism for loading a valve spring of a spring package, the valve spring includes a wave spring, the spring package is immersed in an oil filled chamber and the oil filled chamber pressure is compensated from an annulus pressure. The above noted features are discussed next in more details. It is noted that the following exemplary embodiments may include one or more of these features or other features and no exemplary embodiment should be construed to require all these features or a specific combination of the features noted above.

According to an exemplary embodiment,FIG. 4shows an overall view of a novel drill string valve70. As shown inFIG. 4, an outer diameter72of the drill string valve70has a substantially constant value along an entire length of the drill string valve70. The drill string valve70has a cone seal56attached to a first end74of the drill string valve70. The cone seal56cooperates with a sliding valve50for shutting down a liquid flow through the drill string valve70.

A second end76of the drill string valve70is configured to have a lower cap78. The lower cap78seals a cavity79of the drill string valve70from the mud existent in the casing44. Cavity79should be understood as extending from the first end74to the second end76. Cavity79includes plural chambers, as will be discussed later. A fluid80may flow through a conduit81, provided inside the cavity79of the drill string valve70. The conduit81extends inside the cavity79, from an upper flow nozzle82to a lower flow nozzle84. In operation, the drill string valve70of this embodiment may be positioned vertically or substantially vertically and it has the first end74displaced above the second end76, such that mud from the rig enters, in this order, first end74, upper flow nozzle82, conduit81, lower cap78, and lower flow nozzle84. It is noted that the drill string valve70is part of the drill string24, thus being provided inside casing44.

According to an exemplary embodiment, a body of the drill string valve70may include three portions, first portion86A, second portion86B, and third portion86C. The first two portions86A and86B may be connected together via a valve body92and the second portion86B may be connected to the third portion86C via a spring load cartridge110.

FIG. 4also shows a biasing cartridge90disposed inside the cavity79and configured to apply a first force on the sliding valve50such that the sliding valve50contacts the cone seal56. The cone seal56may be replaced with a seal having another shape. A threaded stop100is provided inside cavity79, between the biasing cartridge90and the second end76. The threaded stop100is configured, as will be discussed later, to apply a second force on the biasing cartridge90.

Sliding valve50is configured to slide to and from cone seal56along a Z direction, as shown inFIG. 5. Sliding valve50is activated by actuator94, which is configured to move side a biasing chamber96. Actuator94extends from the biasing chamber96, via the valve body92towards the cone seal56so that a flow diverter93may extend in parallel with sliding valve50. Flow diverter93may direct the flow of fluid80, when under a pressure larger than a pressure created by the biasing cartridge90, to move the sliding valve50downward to an open position. One or more wave springs98are also provided in the biasing chamber96for providing the first force on the actuator94. One end of the biasing chamber96is bordered by a valve body92and the other end of the biasing chamber96is bordered by a spring spacer99, as shown inFIG. 4. The drill string valve70may be included inside a collar162(seeFIG. 4).

In one exemplary embodiment, the wave spring98is not a coil spring but rather has one or more of the shapes shown inFIG. 6. Thus, according to an exemplary embodiment, the biasing cartridge90includes actuator94, biasing chamber96, and wave spring98. Optionally, the biasing cartridge90may include a fluid inside the biasing chamber96, for example, oil. For confining the fluid inside the biasing chamber96, appropriate seals are provided at the ends of the biasing chamber96for preventing fluid leaks.

When deployed under sea, the sliding valve50of the drill string valve70is biased by actuator94to actively engage cone seal56, thus sealing conduit81. The bias applied by actuator94to sliding valve50is a result of the compression of wave spring98. As will be discussed next, the wave spring98is initially deployed uncompressed inside the drill string valve70, in order to avoid possible hazardous conditions. An advantage of the wave spring98is its reduced length in comparison to a conventional coil spring for generating a same spring force.

The threaded stop100configured to load the biasing cartridge90is discussed next with regard toFIG. 7. Spring spacer99separates the biasing cartridge90from the threaded stop100.

According to an exemplary embodiment, the spring load cartridge110includes a hydraulic piston102and a threaded stop100. A port106into loading chamber108provides access to pump hydraulic fluid into the loading chamber108to actuate hydraulic piston102. Thus, hydraulic piston102moves from right to left inFIG. 7, in order to load the wave spring98. More specifically, the hydraulic piston102contacts spring spacer99and presses the spring spacer99against wave spring98, compressing (loading) the wave spring98. In this way, the wave spring98may be loaded to a desired predetermined pressure without posing any danger to the safety of the operating personnel as the wave spring98is entirely contained inside the biasing chamber96. A pressure sensor (not shown) may be included with the hydraulic pump so that a hydraulic fluid pressure in the loading chamber108may be correlated to a desired force generated by the wave spring98(i.e., a first force). Thus, the applied pressure may be stopped when the wave spring98has achieved the desired spring force. A force corresponding to the applied pressure is considered to be a second force.

Once the desired first force in the wave spring98is achieved, the hydraulic pressure applied to the loading chamber108is maintained constant and the threaded stop100is advanced toward the spring until the threaded stop100picks up the load of the wave spring98, i.e., the threaded stop100fixes the spring spacer99. At this point, the applied hydraulic pressure may be released from the loading chamber108. Port106may be connected to a pump that pumps, for example, oil for activating the hydraulic piston102. Other mechanism for hydraulic piston102may be used as would be appreciated by those skilled in the art.

The spring load cartridge110defines the border for loading chamber108and also provides a mating thread to the threaded stop100. Once the spring load bias has been set, the lower section86C is assembled, and the tool is ready to be installed in its collar.

According to an exemplary embodiment, the spring load cartridge110breaks the continuity of the external tubes86B and86C that constitute the outside wall of the drill string valve70. In other words, the outside wall of the drill string valve may be made up of plural tubes. For example, the embodiment shown inFIG. 4shows three different tubes86A,86B and86C making up the external wall of the drill string valve70. More or less tube components may be used depending on the units to be distributed inside the drill string valve70.

Still with regard toFIG. 7, a compensating piston120may be provided, according to an exemplary embodiment, inside a compensating chamber118, between the spring load cartridge110and the lower cap78. AlthoughFIG. 7shows both reference signs79and118pointing to the same chamber, as already discussed above, cavity79includes plural chambers, among which, the compensating chamber118. In other words, cavity79extends along the entire drill string valve70and includes, at least biasing chamber96, loading chamber108and compensating chamber118.

Compensating chamber118communicates via a port122with an annulus space around the drill string valve70for providing annulus pressure112inside a chamber124of the compensating chamber118, between the compensating piston120and the lower cap78. In this way, the borehole fluids are separated from the clean oil present in the biasing chamber96and part of the loading chamber108.

The next paragraphs summarize some of the features and/or advantages of the exemplary embodiments discussed above. While an exemplary embodiment may include one or more of these features/advantages, there are exemplary embodiments that include none of these features/advantages. The drill string valve body assembly has a constant outer diameter that enables horizontal or vertical insertion into the bore of the drill string valve collar.

The drill string valve collar is simple in design with a long counter bore terminating at a shoulder near the bottom and an internal thread near a top for a lock ring. The overall length may be short, for example, 13 ft (4 m). The body may be inserted in the collar and may land on a shoulder at the bottom of the valve. In one application there is no fixed orientation. The drill string valve may be retained and locked in place at the upper end with a threaded lock ring74(seeFIG. 5). The modular drill string valve body provides for quick turnaround after tripping out. A replacement drill string valve body can quickly be swapped out with the returning body, or if loaded into a standby collar, swapped out with the returning collar. This feature will eliminate the risk of injury during assembly, streamline assembly, and provide accuracy and repeatability of spring settings.

The spring is installed in the drill string valve body at its free length (no spring load). A mechanism (loading mechanism) to load the spring is installed below the spring package. The mechanism to load the spring is integral to the drill string valve body, not an auxiliary tool. The remainder of the drill string valve body is assembled after the spring force is set.

The type of spring used for the drill string valve has an effective free length that is shorter than the free length of a coil spring, for example, half the free length of a coil spring with the same spring rate. This feature reduces system friction. The spring package, interior dynamic seals, and bearings are immersed in a pressure balanced oil system. The pressure balance is achieved with a port through the collar wall that taps onto the well bore annulus. A mating port in the lower cap of the drill string valve body channels the annulus pressure to a compensating piston separating the borehole fluids from the clean oil system.

According to another exemplary embodiment, various analytical tools, for example, sensors, may be provided inside the drill string valve. Such tools may include pressure sensors, load cell sensors, temperature sensors and sensors for determining a position of the sliding valve50. This feature would optimize valve operation. As this type of valve opens very quickly, there is desired for the valve to open in a slower, controlled fashion to reduce the effect of pressure shocks on the well formation. Thus, the sensors discussed above may help monitor and control the drill string valve. According to an exemplary embodiment, a processor with memory capabilities may be deployed inside the drill string valve for collecting and processing the data from the above discussed sensors or others known in the art. Such capability may offer extended control of the drill string valve.

Analytical tools provide the ability to optimize a given spring for use over a wide range of operation. This will lessen the frequency of exchanging spring hardware during the course of drilling program. Simulation software provides the capability to input changing operating conditions and to determine the effects of them in a time sequence. This capability is desired for custom spring design.

This feature includes the addition of downhole diagnostic instrumentation, for example, a data acquisition system may be packaged in an electronics pressure vessel upstream of the drill string valve body. The time synchronized data acquisition may record pressures, acceleration, spring load, valve position, and temperature data. Pressure transducers ports may be positioned upstream and downstream of the valve seat for measuring local static and dynamic pressures.

A time synchronized data acquisition unit may be packaged with a linear measurement transducer to record valve position. Data ports may be built into the drill string valve body for data download, real-time data monitoring during lab testing, flow loop testing, and pre-check diagnostics prior to deployment. Hydraulic access ports may also be built into the drill string valve body for lab testing, flow loop testing and pre-deployment checks.

According to an exemplary embodiment, steps of a method for activating the drill string valve70are illustrated inFIG. 8. The method includes a step800of connecting a power source to a port of a biasing cartridge of the drill string valve. The drill string valve includes (i) an elongated housing having an inside cavity, the housing extending along an axis and having a substantially constant outer diameter, (ii) a seal element attached to a first end of the elongated housing, the seal element having an outer diameter smaller than an inner diameter of the elongated housing, and the seal element being disposed within the inside cavity such that a flow of liquid through the inside cavity from the first end to a second end of the elongated housing is allowed, (iii) a sliding valve disposed within the inside cavity and configured to slide to and from the seal element along the axis such that when the sliding valve contacts the seal element the flow of liquid is suppressed, (iv) the biasing cartridge disposed within the inside cavity, between the seal element and the second end of the elongated housing and configured to apply a first force on the sliding valve such that the sliding valve is contacting the seal element, and (v) a loading mechanism disposed within the inside cavity, between the biasing cartridge and the second end of the elongated housing, and configured to apply a second force on the biasing cartridge. The method also includes a step802of applying a pressure to the loading mechanism to generate the second force, a step804of compressing a wave spring of the biasing cartridge, a step806of locking a stop element to maintain the wave spring in a compressed state, and a step808of releasing the applied pressure.

According to another exemplary embodiment, a drill string valve160, different from the drill string valve70or other valves discussed above is now discussed with regard toFIG. 9. The drill string valve ofFIG. 9has one or more of the following advantages over a conventional valve. The conventional valve opens when the mud pumps are on and closes when the mud pumps are off. A throttling feature based on an amount of openness of the drill string valve provides smooth flow transitions. The conventional design uses a coil spring to close the valve. The spring force at closing was designed to support the weight of the mud column. The force was primarily based on the mud weight and depth of the water as well as other well planning parameters. Since the mud weight and water depth combinations constitute a 3-D matrix, a host of spring package designs are required.

The novel drill string valve shown inFIG. 9replaces, among others, the spring with a motor-driven valve actuation system having feed-back control. This new valve eliminates pressure bias on the poppet valve so that an actuation rod does not receive a large axial load. An electronic package that controls the opening and closing of the valve may include a microprocessor control with data acquisition. The instrumented drill string valve may include pressure transducers to monitor absolute pressure and differential pressures across the valve opening and an encoder for monitoring poppet position. A lithium battery may provide the necessary power for the electronic package. The drill string valve module may be mounted in a 8 ft (2.5 m) pony collar.

According to an exemplary embodiment, the drill string valve160includes a collar162inside of which various components are provided. For example, a motor module180is provided in contact with a poppet200. The poppet200seals a motor chamber182, in which the motor module is fixed, from a communication chamber210.FIG. 9shows that the motor module180includes a motor184that is attached to and configured to rotate a ball screw186. The ball screw186rotates in a ball screw nut188. The ball screw nut188connects to a guide sleeve189that is fixed to an actuation rod190for activating poppet200. Motor184, ball screw186and ball screw nut188may be distributed inside a metallic cavity192, to prevent any liquid passing through the drill string valve160from entering the motor module180. The motor module180may be controlled by a micro-processor230with a data acquisition board220. A power source for the electronics, sensors and motor may be a battery or a hydraulic source.

Actuation of the motor184determines the extension or retraction of the ball screw186and actuation rod190, which determine the movement of poppet200towards and away from poppet seat202. When the poppet200is in contact with the poppet seat202, no fluid (or an insignificant amount) passes through the drill string valve160. The metallic cavity192that accommodates the motor module180may be connected to a spider204, which is configured to accommodate poppet200. As would be recognized by one skilled in the art, appropriate seals are formed around various elements discussed above for preventing fluid entering the motor module.

A pressure inside the drill string valve160, may be monitored by pressure sensors222and224. A position of the poppet200may be monitored with an appropriate sensor228. Such a position sensor228and accompanying mechanism may be a LVDT, as described in Young et al., Position Instrumented Blowout Preventer, U.S. Pat. No. 5,320,325, Young et al., Position Instrumented Blowout Preventer, U.S. Pat. No. 5,407,172, and Judge et al., RAM BOP Position Sensor, U.S. Patent Application Publication No. 2008/0196888, the entire contents of which are incorporated herein by reference.

Based on the data provided by the pressure sensors222and224, and optionally by position sensor228, the microprocessor230may determine when to close or open poppet200. The microprocessor230may be provided in a custom made chamber in the body of the drill string valve160. According to an exemplary embodiment, the microprocessor230is configured to adjust the closing of the drill string valve160depending whether poppet200is completely closed, poppet200is starting to open or close, and/or poppet200is open. It is noted that a pressure in the annulus (i.e., outside the motor module180) is larger when the drill string valve is closed than when the drill string valve is opened. Thus, based on the pressure measurements and/or position of the poppet, the amount of opening of the poppet200may be controlled, thus achieving a feed-back controlled drill string valve.

With regard toFIG. 10, various pressures inside the drill string valve are illustrated. A pressure at location300in the pipe may be different from a pressure at location310around actuation rod190, which is equalized to an annulus pressure at location320. The annular cavity between spider204and poppet200is filled with a gas322at low pressure. The changes in pressure of gas322during deployment are insignificant compared to pressure at location300and pressure at location320. This balanced pressure on both sides of poppet200ensures that motor184needs to apply a small force for the actuation of rod190, comparative to the large pressures existent in the annulus, for displacing poppet200. The pressure at location310around actuation rod190is made equal to annulus pressure320by selecting diameters A1, A2, A3and A4. Thus, minimal motor torque requirements are needed for a proper functioning of the poppet and the drill string valve160works for all depths and mud weights.

Next, the operation of the drill string valve is discussed. The drill string valve is a pressure regulating check valve that uses a flow for compensation. The valve has two modes of operation, which are drilling mode with pumps on and non-drilling mode with pumps off. During the drilling mode the drill string valve becomes a flow compensated check valve. During the non-drilling mode, the drill string valve prevents the mud column above the valve from free falling when the mud pumps are turned off.

The drill string valve70employs a spring to control the valve opening. According to an exemplary embodiment, the design of the valve spring is dependent on the spring load, the spring rate, the flow rate, the mud weight, the back pressure of the bit nozzles, and the flow losses in the well from pipe friction, casing friction, and any downhole tools in the drill string. Because of the array of operating variables the throttling performance of a spring actuated valve is indeterminate.

The drill string valve160may use a microprocessor and sensor data from on board sensors to control valve position. The drilling mode is determined by measuring the broad band acceleration of the drill string valve. There is a distinctive change in the broad band when the mud pumps are turned off and on. The microprocessor may read acceleration, mud flow rate, valve position, and differential pressures. Before the tool is run, inputs for control and look-up tables for valve opening vs. time are downloaded via a communication device, for example, a computer. The look-up tables are constructed to meet the requirements of the well plan and may vary from application to application. When the microprocessor senses there is broad band response from the accelerometer, the microprocessor begins modulating the valve and controlling the valve opening based at least in part on information in the look-up table.

FIG. 11is a schematic of drill string valve160and shows the instrumentation used to control the valve. Flow meter226and valve position sensor228provide the data to the micro-processor230via data acquisition220. The micro-processor software algorithm is based on a user-defined relationship between flow rate and valve position (flow rate vs. position). The processor compares the actual valve position with the desired valve position based on real-time flow rate. The processor sends a command to the motor controller board227to have the motor184reposition the poppet200. According to an exemplary embodiment, a look-up table may be stored in a memory (not shown) connected to the micro-processor230and includes a flow rate threshold so that for any measured flow rate above the threshold, the micro-processor230is configured to close the seal element to suppress the fluid flow.

According to an exemplary embodiment, the seal element and the seat of the above discussed embodiments are configured, when closed, to withstand pressures between 5,000 and 30,000 psi and/or to work on the floor of the ocean while exposed to corrosion.

According to an exemplary embodiment shown inFIG. 12, there is a method for controlling a drill string valve. The method includes a step1200of receiving from a flow meter unit a flow rate of a fluid through the drill string valve, a step1202of determining in a processor a position of a seal element that is configured to move to and from a seat to suppress a fluid flow through the drill string valve, and a step1204of searching a look-up table stored in memory connected to the processor for determining whether a motor has to be activated to close or open the seal element.

The disclosed exemplary embodiments provide a system and a method for closing and opening a duct through which a fluid may flow. The exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.

This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other example are intended to be within the scope of the claims.