The present disclosure relates generally to a well construction drilling geo-steering apparatus, system and process.
In the oil and gas well drilling industry, it is important to obtain input from operations geologist while constructing the wellbore. The geologist may be skilled in steering or guiding the pathway of a new well under construction to achieve the optimum pathway through an oil or gas bearing subterranean formation. The geologist may provide such input from a remote location, which may be hundreds or thousands of miles from the well that is under construction. This may be accomplished using directional survey or other data sent by rig personnel from the rig at which the well is being drilled to the geologist at a location remote from the well. Then, the geologist may analyze the data and reply to the rig personnel with instructions relating to the future proposed pathway for the well.
Unfortunately, a significant amount of time is required for sending, analyzing, and then returning instructions to rig personnel. During this time interval, the well may be continuing along a drilling guide path that is less than desirable. The “lag” time between the request for input to the geologist and the receipt of instructions from the geologist at the well site is less than ideal, because during that interim time period, the well most likely is not being steered to the precise coordinates that achieve maximum benefits to future production from the well.
In summary, the present disclosure relates to a well construction drilling geo-steering apparatus, system, and process. The well construction drilling geo-steering arrangements provided herein, in some aspects, provide an efficient, fast means of deducing geological issues required for a remote steering process to take place. Such geo-steering arrangements allow a geologist to provide steering guidance to a plurality of rig sites on a near-realtime basis, while improving mechanisms by which those rig sites provide data to the systems used by the geologist, thereby reducing the time between when data is captured and when a rig site can receive directional drilling guidance from a remote geologist.
In a first aspect, embodiments of a geosteering system are disclosed. In a particular embodiment, the system includes a computing system at a facility remote from at least one rig site. The computing system includes at least one processor and computer storage medium comprising computer-executable instructions which, when executed by the at least one processor, cause performance of a method of remotely controlling steering of a drilling process at the at least one rig site. The method includes receiving a data stream from the at least one rig site, the data stream including subsurface drilling data and directional survey data. The method also includes receiving, from a user, guidance regarding directional steering of a drilling apparatus at the at least one remote rig site. The method also includes communicating the guidance to the at least one rig site via a realtime communications connection.
In a second aspect, embodiments of a computer-implemented method of remotely controlling steering of a drilling process of at least one rig site are disclosed. In a particular embodiment, the method includes receiving a data stream from a remote rig site, the data stream including subsurface drilling data and directional survey data, and receiving, from a user, guidance regarding directional steering of a drilling apparatus at the remote rig site. The method also includes communicating the guidance to the remote rig site via a realtime communications connection.
In a third aspect, embodiments of a computer storage medium comprising computer-executable instructions which, when executed, cause a computing system to perform a method of remotely controlling steering of a drilling process at each of a plurality of different rig sites. In a particular embodiment the method includes receiving a data stream from each of a plurality of different remote rig sites, the data stream including subsurface drilling data and directional survey data, and receiving, from a user, guidance regarding directional steering of a drilling apparatus at the remote rig site. The method also includes communicating the guidance to one or more of the plurality of different remote rig sites via a realtime communications connection.
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
The Figures illustrate various aspects of the invention, and are attached to this written description.
As briefly described above, the present disclosure is directed to embodiments of a well construction drilling geo-steering apparatus, system, and process. In general, the present disclosure relates to a geosteering application and method of its operation in which a data stream from one or more remote rig locations can be received, analyzed, and directional drilling guidance can be provided by a geologist at a central analysis station to the remote rig via a realtime communications component.
Accordingly, the present disclosure provides advances in the field of drilling geosteering by providing more efficient and effective methods, systems and apparatus for conducting real time surveys and receiving input from remotely located professional personnel during the construction of a well, thereby saving costs and avoiding the extent of wells diverging from a route preferred by the geologist assisting with well formation.
In some aspects, the geosteering process of the present disclosure may employ real time data and chat collaboration tools to streamline data integration and collaboration to allow a geologist at a remote location to steer multiple wells in a manner that is similar to doing such at the rig location. This may further provide improved cycle time for geosteering decision-making, integrating real time data systems with geosteering software, providing a platform for real time collaboration among other well advisors, and eliminating or automating administrative activities.
Still further, aspects of the present disclosure accelerate the increase in footage drilled in target subterranean zones by deploying a faster decision making process, using real time data. Further, there may be additional production value for oil and gas produced from the reservoir, due to the well being steered along a more desirable path in the formation. Costs may also be reduced. In some instances, there may be reduction in sidetracks, which are undesirable drilling procedures. The process may also result in increased data security over known systems for processing such data. More expert opinions may also be solicited and provided as input into well steering decisions at the well site.
Referring now to
In general, the systems described herein, and in particular the flowcharts of
In general, drilling rig sites 104 includes a drilling superintendent that has a responsibility to ensure a well plan is executed correctly and safely, and participates in an escalation process, as discussed in further detail below in connection with
A MWD (measurement while drilling) engineer provides survey data to the operations geology team, for example, based on verification of a survey data quality and accuracy. The MWD engineer may also communicate the geosteering instructions received from the operations geologists, transmits survey data to a data aggregator, and communicates geosteering results among the team at the rig. A mud logger logs information and transmits that information to a data aggregator. Other individuals may be present as well.
The memory 204 can include any of a variety of memory devices, such as using various types of computer-readable or computer storage media. A computer storage medium or computer-readable medium may be any medium that can contain or store the program for use by or in connection with the instruction execution system, apparatus, or device. By way of example, computer storage media may include dynamic random access memory (DRAM) or variants thereof, solid state memory, read-only memory (ROM), electrically-erasable programmable ROM, optical discs (e.g., CD-ROMs, DVDs, etc.), magnetic disks (e.g., hard disks, floppy disks, etc.), magnetic tapes, and other types of devices and/or articles of manufacture that store data. Computer storage media generally includes at least one or more tangible media or devices. Computer storage media can, in some embodiments, include embodiments including entirely non-transitory components. In the embodiment shown, the memory 204 stores a geosteering application 212, discussed in further detail below. The computing system 200 can also include a communication interface 208 configured to receive and transmit data, for example one or more data streams received from rigs 104a-c as seen in
In various embodiments, the geosteering application 212 includes a geological data retrieval component 214, a communications component 216, a geosteering component, and an escalation component 220. Of note, although the geosteering application 212 and components thereof will be discussed herein, those of ordinary skill in the art will appreciate that the disclosure is not limited to this example, and hardware, software, instructions (e.g., computer-executable instructions or computer usable instructions), program code (e.g., data and instructions), multiple applications, any combination thereof, etc. can be used. In the embodiment shown, the geological data retrieval component 214 is configured to receive a data stream of subsurface drilling data (e.g., for storage as drilling data 222) and directional survey data (e.g., data 224). The geological data retrieval component 214 can be stored in memory 204, for use by a geosteering component 218.
In some embodiments, the geological data retrieval component 214 receives a markup language data stream including metadata-labeled data retrieved from each drilling rig site, providing for easy integration and display of such data by the application 212.
The communications component 216 allows for a realtime communications connection to each of the rig sites. In example embodiments, the communications component 216 is a realtime chat communications program or program component, thereby allowing a person at the geological operations site 102 to communicate with a plurality of different drilling rig sites 104 at the same time (rather than requiring voice communication, which is typically only achievable on a one-at-a-time or a few at a time basis.
The geosteering component 218 is configured to present geological data retrieved via the geological data retrieval component 214, and from the data streams received by that system, to a geologist. The geosteering component 218 is capable of receiving feedback from a user relating to directional steering of a drilling apparatus at each rig site, thereby allowing the user to present geosteering instructions to the rig site from a location remote from the rig site, based on data provided to the geosteering application 212.
The escalation component 220 manages event escalation processes that may be triggered by a geologist using the geosteering application 212, and can include management of communication with one or more other individuals (including those individuals discussed above in connection with
It is noted that although computing system 200 is illustrated as executing a geosteering application 212 at a geological operations site (e.g., site 102 of
Referring now to
Referring now to
In the embodiment shown, the geosteering system 300 includes a mud logging process 302 and a directional survey process 304 that generate data at a rig site. Generally, the mud logging process 302 determines a production level of a particular drilling process, while the directional survey process 304 determines a current direction and location of a drill head and associated bore hole. The directional survey are performed at predefined regular depth intervals to pinpoint spatial position of the well bore. In some embodiments, once recorded, the directional survey data is stored in a WITS compatible directional software. Example details of the mud logging process 302 are provided below in connection with
Data from each of the mud logging process 302 and directional survey process 304 can, in the embodiment shown, be fed to a realtime data process 306. The realtime data process 306 can aggregate data from a plurality of different data sources and format that data for communication to a geological operations site 102. This can include, for example translating the data to a markup language format recognizable to systems at the geological operations site 102, such as a WITSML format. Other formats are useable as well. One example of operations of a realtime data process 306 are provided below in connection with
In the embodiment shown, data from the directional survey process 304 can be directly transmitted to the geological operations site 102 as well, to notify a geologist of new data from a rig (operation 308). At such time, a geosteering process 310 begins, in which the geologist can view the directional survey data. The geologist may opt to send a chat (at operation 312) to the rig, e.g., via the communications component 216, to indicate that a geosteering process is beginning.
In the embodiment shown, a geological data retrieval process 314 is then performed at the geological operations site 102. This geological data retrieval process 314 can be performed, for example, by the geological data retrieval component 214 of the geosteering application 212 of
A problem determination operation 310 assesses whether there exists a problem at one or more rig sites 104, for example based on the data received during the geological data retrieval process 314.
If a problem exists (e.g., a safety issue or unresolveable conflict) an escalation process 322 occurs. The escalation process 322 may be performed if there is an abnormal condition that is encountered. In such cases, both the rig and geosteerer have escalation procedures to follow based on a predetermined scenario list organized by severity level. This process allows for management by exception for individuals not involved in the process 24×7, so that the appropriate accountable resources are involved in discussions according to the severity of the situation. Details regarding an example escalation process are provided below in connection with
Upon completion of the escalation process, or in the event that no problem is detected during operation 320, a finalization operation 324 finalizes the route selected by the geologist. A communications operation 326 corresponds to the geologist using the communications component 216 to provide realtime communications (e.g., chat communications) to a rig site to communicate updated geosteering directions. As part of the communications operation 326, the geosteerer then communicates the results/instructions to the rig personnel through private chat message system. The rig personnel receive the message and execute the instructions. They also confirm to the geosteerer that the instructions have been received and executed. The private chat message system provides a transparent platform for collaboration with all the stakeholders in drilling the well that have been pre-authorized using the “entitlement process”. The chat message logs are attached to the drilling parameter log of each well and is recorded for auditing and long term accountability.
Furthermore, once the data is interpreted by the geosteerer or geologist, he/she communicates the spatial position of the wellbore in relation to the various formations to the rig via a secure chat message system. The chat system is bi-directional and allows the geosteerer and multiple individuals on the rig to discuss the current situation and make changes to interpretations as necessary. Once the agreed upon plan is implemented, the rig crew confirms execution through the chat system. A receipt and confirmation operation 328 performed at the rig site confirms that the geosteering directions were received, and an execution operation 330 performs the communicated instructions (e.g., as implemented by rig personnel).
It is noted that, due at least in part to receipt of a data stream from the rig site, and automated aggregation of data at that rig site and formatting for consumption by an application used by a geologist, the geologist can receive much more quickly data required to allow the geologist to provide geosteering instructions to the rig site. Additionally, the use of realtime communications with the rig site, and in particular chat-type instructions allows the geologist to communicate those geosteering instructions quickly as well as to communicate with a plurality of rig sites at the same time, thereby improving efficiency of the overall system 300.
Referring now to
In general, the escalation process 400 provides detailed information on how the geologist should handle issues and problems during the geosteering process. It provides clear responsibilities, accountabilities and instruction on when and who to escalate problems to the appropriate leaders/asset team members.
In the embodiment shown, the escalation process 400 includes problem identification (operation 402), which includes an operations geologist identifying a problem or issue, often times with the help of rig personnel. The geologist can then determine a severity level of the issue as well as an appropriate action (operation 404). The severity can be based, for example, on a low/medium/high severity classification.
Depending on the severity level of the event, the on-call operations geologist will take a different kind of action. In cases where the escalation process 400 identifies a problem as a low severity, the operations geologist will most often only be required to call the rig to remediate whatever problem has arisen.
Example Low severity events can include: a first attempted and failed communication with a rig, a slight deviation from existing direction (e.g., 1-3 degrees of deviation), a change of less than 10 feet in the event of a less than 100 foot horizontal drilling operation, low gas units, or a resolvable difference in opinion between the geologist and rig. Other events could be included as well.
A Medium severity level will require a little more from the Operations Geologist. The geologist or steerer will make contact with the rig personnel, similar to a low severity issue, and will follow up with the operations geology coordinator once the issue has been resolved. In most cases a medium severity issue will not require immediate contact with the Ops Coordinator, and an email summarizing the issue and plan of action will suffice.
Example medium severity events can include: failed second attempts at communication between a geologist and rig, H2S detection of greater than 10 ppm in the mud log, a moderate deviation in drilling angle from plan (e.g., 4-6 degrees), a dip of greater than about three degrees, a projection of being out of a target zone within about 100 feet, incomplete data, or inadequate directional drilling capabilities. Other events could be included as well.
If a High severity event were to take place, a call to the drill site manager (“DSM”) will occur first to halt drilling if the rig has not done so on their own first. Immediately following, a call will be made to the Ops Coordinator to debrief him/her of the situation. At that time, the Ops Coordinator will begin coordinating the necessary team members to resolve the situation. The on-call geosteerer may be asked to provide additional information or metrics to the Ops Coordinator as necessary to make an appropriate plan of action.
Example High severity events can include: an entirely unresponsive communication between a geologist and the rig, H2S detection at the rig floor, or significant safety events on the rig, a greater than 5 degree angle of deviation from plan, with the current drilling operation out of a target zone, an observed formation dip of greater than 5 degrees, faulting positions of the wellbore, or unresolvable differences of opinion. Other events could be included as well.
Table 1, below, illustrates example severity levels and operational actions that can be taken based on the severity level of a particular event or occurrence:
As illustrated, depending on the severity level of the event, a user, (e.g. the operations geologist) will take a different kind of action. In cases where the Escalation Process identifies a problem as a Low severity, the operations geologist will most often only be required to call the rig to remediate whatever problem has arisen.
For example, a medium severity level will require more from the operations geologist. The geologist/steerer will make contact with the rig personnel, similar to a low severity issue, and will follow up with the operations coordinator once the issue has been resolved. In most cases a medium severity issue will not require immediate contact with the operations coordinator, and an email summarizing the issue and plan of action will suffice.
By way of contrast, if a high severity event were to take place, a call will occur first to halt drilling if the rig has not done so on their own first. Immediately following, a call will be made to the operations coordinator to debrief him/her of the situation. At that time, the operations coordinator will begin coordinating the necessary team members to resolve the situation. The geosteerer (e.g., the geologist) may be asked to provide additional information or metrics to the operations coordinator necessary to make an appropriate plan of action.
Still referring to
In the embodiment shown, it is determined whether a new survey is needed, at operation 410, to validate existing conclusions or gather additional data regarding a particular issue. If so, a directional survey process 412 can be performed. Details of such a process are provided below in connection with
If relogging is not needed, a plan of action operation 418 determines a plan of action, for example based on feedback by both geologists and rig personnel. An approval operation 420 determines if approval is obtained (e.g., for high severity events); if no approval is obtained, a new plan of action is determined in the plan of action operation 418. If approval is obtained, a sidetracked operation 422 determines if the rig site needs to be sidetracked; if so, a sidetrack operation 424 occurs (e.g., as illustrated in
Referring now to
In the embodiment shown, a measurement while drilling operator will provide directional data flow (at operation 702), while a surface logging operator can transmit realtime surface data (at operation 704) and a mud logger can generate concurrent lithology and gas information (at operation 706) to a data aggregation process 708. Example data aggregation processes are provided below, in connection with
In example embodiments, surface logging data can include, for example, standard drilling parameters such as ROP, bit depth, and hole depth; other types of data from the mud logger and directional data flow are provided elsewhere herein.
In an example embodiment, the system captures both a gas sample (operation 802) as well as cuttings (at operation 804). The cuttings can be, for example, every 90 feet in the lateral and every 10 feet in the curve, or as otherwise defined per drilling procedure. The gas sample is analyzed at operation 806, and the cuttings are washed and dried at operation 808. The mud log is transmitted to a computer (at operation 810, and the cut sample is analyzed (at operation 812). The analysis and mud log data are provided to a realtime data collection process 306. Additionally, a report based on the cuttings can be provided to a mud logging distribution list (at operation 814) on a less frequent basis, e.g., every six hours.
Referring to
In a first embodiment as shown in
In a second possible embodiment, integration of surface level data from one or more sensors (at operation 1122), measurement while drilling data (at operation 1124) and mud logging data (at operation 126) for transmission directly to a realtime data server 602 (at operation 1138) for formation of a data stream. It is noted that aggregation process 1120 could occur at a server, or at a laptop device.
In accordance with the present disclosure, and as indicated in
The description and illustration of one or more embodiments provided in this disclosure are not intended to limit or restrict the scope of the invention as claimed in any way. The embodiments, examples, and details provided in this disclosure are considered sufficient to convey possession and enable others to make and use the best mode of claimed invention. The claimed invention should not be construed as being limited to any embodiment, example, or detail provided in this application. Regardless whether shown and described in combination or separately, the various features (both structural and methodological) are intended to be selectively included or omitted to produce an embodiment with a particular set of features. Having been provided with the description and illustration of the present application, one skilled in the art may envision variations, modifications, and alternate embodiments falling within the spirit of the broader aspects of the claimed invention and the general inventive concept embodied in this disclosure that do not depart from the broader scope.
For the avoidance of doubt, the present disclosure includes the subject-matter defined in the following numbered paragraphs:
A1. A geosteering system comprising: a computing system at a facility remote from at least one rig site, the computing system comprising: at least one processor; and computer storage medium comprising computer-executable instructions which, when executed by the at least one processor, cause performance of a method of remotely controlling steering of a drilling process at the at least one rig site, the method comprising: receiving a data stream from the at least one rig site, the data stream including subsurface drilling data and directional survey data; receiving, from a user, guidance regarding directional steering of a drilling apparatus at the at least one remote rig site; and communicating the guidance to the at least one rig site via a realtime communications connection.
A2. The geosteering system of claim A1, wherein the computer-executable instructions are further executed by the at least one processor to receive a plurality of data streams, each of the plurality of data streams received from a different one of a plurality of rig sites.
A3. The geosteering system of claim A1, wherein the computer-executable instructions are further executed by the at least one processor to receive problems identified by a user, and determine a severity of a problem and a plan of action to address the problem.
A4. The geosteering system of claim A3, wherein the computer-executable instructions are further executed by the at least one processor to trigger a geosteering directional survey process.
A5. The geosteering system of claim A1, further comprising, at the at least one rig site, a server configured to receive data from one or more sensors, positional and directional data associated with the drilling apparatus, and mud logging data, wherein the server is configured to output the aggregated data for transmission in the data stream.
A6. The geosteering system of claim A5, wherein the data stream comprises markup language data compliant with a wellsite information transfer specification.
A7. The geosteering system of claim A1, wherein the data comprises at least near-realtime data from the at least one rig site.
A8. The geosteering system of claim A1, further comprising a graphical interface for the user, thereby allowing the user to provide directions to personnel at the at least one rig site to steer the drilling apparatus in an area of interest.
A9. The geosteering system of claim A1, further comprising a plurality of rig sites.
A10. A computer-implemented method of remotely controlling steering of a drilling process of at least one rig site, the method comprising: receiving a data stream from a remote rig site, the data stream including subsurface drilling data and directional survey data; receiving, from a user, guidance regarding directional steering of a drilling apparatus at the remote rig site; and communicating the guidance to the remote rig site via a realtime communications connection.
A11. The method of claim A10, further comprising executing an escalation process based on an indication by the user based on the subsurface drilling data.
A12. The method of claim A11, wherein the escalation process includes a directional survey at the remote rig site.
A13. The method of claim A10, wherein the guidance is used at the remote rig site to adjust directional steering of the drilling apparatus at the remote rig site.
A14. The method of claim A10, further comprising periodically refreshing data from a well log.
A15. The method of claim A10, further comprising performing a mud logging process continuously at the remote rig site.
A16. The method of claim A10, wherein the data stream includes data that is aggregated at the remote rig site.
A17. The method of claim A10, wherein the guidance regarding directional steering of a drilling apparatus at the remote rig site is received at a geosteering component of a geosteering application.
A18. The method of claim A10, further comprising receiving a data stream from each of a plurality of different remote rig sites.
A19. A computer storage medium comprising computer-executable instructions which, when executed, cause a computing system to perform a method of remotely controlling steering of a drilling process at each of a plurality of different rig sites, the method comprising: receiving a data stream from each of a plurality of different remote rig sites, the data stream including subsurface drilling data and directional survey data; receiving, from a user, guidance regarding directional steering of a drilling apparatus at the remote rig site; and communicating the guidance to one or more of the plurality of different remote rig sites via a realtime communications connection.
A20. The computer storage medium of claim A19, wherein the method further includes executing an escalation process based on an indication by the user based on the subsurface drilling data, the escalation process including a directional survey at the remote rig site.
B1. A geosteering system comprising: a geological data retrieval system operable at a computing system at a facility remote from at least one rig site, the geological data retrieval system (or component) configured to receive a data stream including subsurface drilling data and directional survey data; a geosteering component receiving feedback from a user relating to directional steering of a drilling apparatus at the at least one rig site; and a communications component providing to the user a realtime communications connection to the at least one rig site.
B2. The geosteering system of claim B1, wherein the geological data retrieval system receives a plurality of data streams, each of the plurality of data streams received from a different one of a plurality of rig sites.
B3. The geosteering system of claim B 1, further comprising an escalation system (or component) receiving problems identified by a user of the geosteering component, the escalation system determining a severity of a problem and a plan of action to address the problem at a central operational facility.
B4. The geosteering system of claim B3, wherein the escalation system triggers a geosteering directional survey process.
B5. The geosteering system of claim B1, further comprising, at the at least one rig site, a data aggregation component including a server configured to receive data from one or more sensors, positional and directional data associated with the drilling apparatus, and mud logging data, wherein the server is configured to output the aggregated data for transmission to the geological data retrieval system in the data stream.
B6. The geosteering system of claim B5, wherein the data stream comprises markup language data compliant with a wellsite information transfer specification.
B7. The geosteering system of claim B1, wherein the data comprises at least near-realtime data from the at least one rig site.
B8. The geosteering system of claim B1, wherein the geosteering component presents a graphical interface to the user, thereby allowing the user to provide directions to personnel at the at least one rig site via the communications component to steer the drilling apparatus in an area of interest.
B9. The geosteering system of claim B1, further comprising a plurality of rig sites.
B10. A computer-implemented method of remotely controlling steering of a drilling process of at least one rig site, the method comprising: receiving a data stream from a remote rig site, the data stream including subsurface drilling data and directional survey data; receiving, from a user, guidance regarding directional steering of a drilling apparatus at the remote rig site; and communicating the guidance to the remote rig site via a realtime communications connection.
B11. The method of claim B10, further comprising executing an escalation process based on an indication by the user based on the subsurface drilling data.
B12. The method of claim B11, wherein the escalation process includes a directional survey at the remote rig site.
B13. The method of claim B10, further comprising applying the guidance at the remote rig site to adjust directional steering of the drilling apparatus.
B14. The method of claim B10, further comprising periodically refreshing data from a well log.
B15. The method of claim B10, further comprising performing a mud logging process continuously at the remote rig site.
B16. The method of claim B10, further comprising aggregating data at the remote rig site for inclusion in the data stream.
B17. The method of claim B10, wherein the guidance regarding directional steering of a drilling apparatus at the remote rig site is received at a geosteering component of a geosteering application.
B18. The method of claim B10, further comprising receiving a data stream from each of a plurality of different remote rig sites.
B19. A computer storage medium comprising computer-executable instructions which, when executed, cause the computing system to perform a method of remotely controlling steering of a drilling process at each of a plurality of different rig sites, the method comprising: receiving a data stream from each of a plurality of different remote rig sites at a geosteering application executing on a computing system, the data stream including subsurface drilling data and directional survey data; receiving, from a user of the geosteering application, guidance regarding directional steering of a drilling apparatus at the remote rig site; and communicating the guidance from the geosteering application to one or more of the plurality of different remote rig sites via a realtime communications connection.
B20. The computer storage medium of claim B19, wherein the method further includes executing an escalation process based on an indication by the user based on the subsurface drilling data, the escalation process including a directional survey at the remote rig site.
The present application claims priority from U.S. Provisional Patent Application No. 61/935,451, filed on Feb. 4, 2014, the disclosure of which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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61935451 | Feb 2014 | US |