Patents by Inventor Raghu Madhavan
Raghu Madhavan has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Publication number: 20060225926Abstract: An expandable tubular sleeve having utility for lining a downhole tubular member includes a tubular body having a portion that is predisposed to initiate expansion thereof under the application of internal fluid pressure. The predisposed portion of the body may be a plastically-deformed portion formed, e.g., by application of mechanical force to a wall of the body. The predisposed portion of the body may be defined by a portion of the body having reduced wall thickness. The reduced wall thickness may be achieved, e.g., by reinforcing the wall thickness everywhere except the predisposed portion. The predisposed portion of the body may be formed by modifying the material properties of the body, e.g., by localized heat treatment. The sleeve and related apparatuses and methods are useful for securing and protecting a cable having one or more insulated conductive wires for transmission of signals between locations downhole and at the surface.Type: ApplicationFiled: March 31, 2005Publication date: October 12, 2006Applicant: SCHLUMBERGER TECHNOLOGY CORPORATIONInventors: RAGHU MADHAVAN, BRUCE BOYLE, BRIAN CLARK
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Patent number: 7040415Abstract: A cabled communication link for a drill string includes spaced apart adapter subs within the drill string and a cable connecting the adapter subs for communication of a signal therebetween. The cabled communication link may be drill pipe joints are interconnected within the drill string between adapter subs to form a piped communication link, whereby the cabled communication link establishes a pathway to the piped communication link for transmitting a signal through the drill string. The cabled communication link may also be in a non-wired section of the drill string is disposed between adapter subs, whereby the cabled communication link establishes a pathway for transmitting a signal through the non-wired section of the drill string. Inductive couplings are preferably used for communication across the adapter subs and wired drill pipe joints. Another aspect of the cabled communication employs wireless transceivers at or near the surface of the wellbore.Type: GrantFiled: October 22, 2003Date of Patent: May 9, 2006Assignee: Schlumberger Technology CorporationInventors: Bruce W. Boyle, Nicolas Pacault, Jean-Michel Hache, Remi Hutin, Raghu Madhavan, Jacques Jundt
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Patent number: 6898339Abstract: A multiple mode pre-loadable fiber optic pressure and temperature sensor includes a generally cylindrical structure having at least one compression element, a fiber optic having a Bragg grating in contact with one side of the compression element, a diaphragm in contact with the other side of the compression element, and a fluid port in fluid communication with the diaphragm. According to preferred aspects of the, a groove is provided in at least one compression element for receiving the fiber optic. The sensor is pre-loaded by straining the diaphragm over the adjacent compression element when the cover is attached. The compression element in contact with the diaphragm preferably has a contoured surface contacting the diaphragm and the diaphragm is stretched to match that contour. By varying the contour of the compression element and the thickness of the diaphragm, the dynamic range of the sensor can be changed. The preferred diaphragm has a variable thickness and is made as an integral part of the structure.Type: GrantFiled: December 16, 2002Date of Patent: May 24, 2005Assignee: Schlumberger Technology CorporationInventors: Jagdish Shah, Robert Schroeder, Philip Dryden, Rogerio Ramos, Raghu Madhavan
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Publication number: 20050087368Abstract: A cabled communication link for a drill string includes spaced apart adapter subs within the drill string and a cable connecting the adapter subs for communication of a signal therebetween. The cabled communication link may be drill pipe joints are interconnected within the drill string between adapter subs to form a piped communication link, whereby the cabled communication link establishes a pathway to the piped communication link for transmitting a signal through the drill string. The cabled communication link may also be in a non-wired section of the drill string is disposed between adapter subs, whereby the cabled communication link establishes a pathway for transmitting a signal through the non-wired section of the drill string. Inductive couplings are preferably used for communication across the adapter subs and wired drill pipe joints. Another aspect of the cabled communication employs wireless transceivers at or near the surface of the wellbore.Type: ApplicationFiled: October 22, 2003Publication date: April 28, 2005Inventors: BRUCE BOYLE, NICOLAS PACAULT, JEAN-MICHEL HACHE, REMI HUTIN, RAGHU MADHAVAN, JACQUES JUNDT
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Patent number: 6866306Abstract: A first flux-loop inductive coupler element electrically couples with a second flux-loop inductive coupler element. The first flux-loop inductive coupler element comprises a first ring-like core having high magnetic permeability and a conical-section annular first face transverse to the plane of the first core. The first face has a first annular groove separating a first conical-section larger-diameter face and a first conical-section smaller-diameter face. A first coil is wound within the annular groove. The first and second cores form a low-reluctance closed magnetic path around the first coil and a second coil of the second flux-loop inductive coupler element. A first current-loop inductive coupler element electrically couples with a second current-loop inductive coupler element.Type: GrantFiled: June 14, 2001Date of Patent: March 15, 2005Assignee: Schlumberger Technology CorporationInventors: Bruce W. Boyle, Raghu Madhavan, Jacques Jundt
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Publication number: 20040114849Abstract: A multiple mode pre-loadable fiber optic pressure and temperature sensor includes a generally cylindrical structure having at least one compression element, a fiber optic having a Bragg grating in contact with one side of the compression element, a diaphragm in contact with the other side of the compression element, and a fluid port in fluid communication with the diaphragm. According to preferred aspects of the, a groove is provided in at least one compression element for receiving the fiber optic. The sensor is pre-loaded by straining the diaphragm over the adjacent compression element when the cover is attached. The compression element in contact with the diaphragm preferably has a contoured surface contacting the diaphragm and the diaphragm is stretched to match that contour. By varying the contour of the compression element and the thickness of the diaphragm, the dynamic range of the sensor can be changed. The preferred diaphragm has a variable thickness and is made as an integral part of the structure.Type: ApplicationFiled: December 16, 2002Publication date: June 17, 2004Applicant: SCHLUMBERGER TECHNOLOGY CORPORATIONInventors: Jagdish Shah, Robert Schroeder, Philip Dryden, Rogerio Ramos, Raghu Madhavan
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Patent number: 6641434Abstract: A robust, low-loss wired pipe joint is provided for service as a component of a wired pipe string for transmitting measurement data to a surface station from locations in a borehole in oil well drilling and oil well operations. Conductive layers reduce signal energy losses over the length of the drill string by reducing resistive losses and flux losses at each inductive coupler. The wired pipe joint is robust in that it remains operational in the presence of gaps in the conductive layer. A wired pipe joint includes an elongate tubular shank having an axial bore, a threaded box-end, and a threaded pin end.Type: GrantFiled: May 31, 2002Date of Patent: November 4, 2003Assignee: Schlumberger Technology CorporationInventors: Bruce W. Boyle, Raghu Madhavan, Jacques Jundt
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Publication number: 20020193004Abstract: A robust, low-loss wired pipe joint is provided for service as a component of a wired pipe string for transmitting measurement data to a surface station from locations in a borehole in oil well drilling and oil well operations. Conductive layers reduce signal energy losses over the length of the drill string by reducing resistive losses and flux losses at each inductive coupler. The wired pipe joint is robust in that it remains operational in the presence of gaps in the conductive layer. A wired pipe joint includes an elongate tubular shank having an axial bore, a threaded box-end, and a threaded pin end.Type: ApplicationFiled: May 31, 2002Publication date: December 19, 2002Inventors: Bruce W. Boyle, Raghu Madhavan, Jacques Jundt
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Publication number: 20020135179Abstract: A first flux-loop inductive coupler element electrically couples with a second flux-loop inductive coupler element. The first flux-loop inductive coupler element comprises a first ring-like core having high magnetic permeability and a conical-section annular first face transverse to the plane of the first core. The first face has a first annular groove separating a first conical-section larger-diameter face and a first conical-section smaller-diameter face. A first coil is wound within the annular groove. The first and second cores form a low-reluctance closed magnetic path around the first coil and a second coil of the second flux-loop inductive coupler element.Type: ApplicationFiled: June 14, 2001Publication date: September 26, 2002Inventors: Bruce W. Boyle, Raghu Madhavan, Jacques Jundt
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Patent number: 6315050Abstract: A packer for use inside a casing of a subterranean well includes a resilient element, a housing and a rupture disc. The resilient element is adapted to seal off an annulus of the well when compressed, and the housing is adapted to compress the resilient element in response to a pressure exerted by fluid of the annulus of a piston head of the housing. The housing includes a port for establishing fluid communication with the annulus. The rupture disc is adapted to prevent the fluid in the annulus from entering the port and contacting the piston head until the pressure exerted by the fluid exceeds a predefined threshold and ruptures the rupture disc.Type: GrantFiled: December 21, 2000Date of Patent: November 13, 2001Assignee: Schlumberger Technology Corp.Inventors: Vladimir Vaynshteyn, James D. Hendrickson, Jim B. Benton, Raghu Madhavan, Mitchell G. Willcox, Dinesh R. Patel
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Patent number: 6304686Abstract: Methods and apparatus for measuring differential pressure with fiber optic sensor systems are disclosed. The apparatus of the present invention include both monopolar and bipolar sensors, sensors incorporating side-hole fibers, sensors incorporating fibers without side holes, FBGs subjected to transverse strain, and FBGs subjected to longitudinal strain. All of the embodiments utilize FBGs. Two embodiments utilize a piston having oppositely extending rods, each of which is exposed to a different pressure. Seven embodiments utilize one or more silica diaphragms coupled to a silica body and exposed to two pressures. In each of these embodiments, pressure is converted into movement of the piston or diaphragm which is then used to strain the FBG(s). When each FBG is interrogated, the spectral information is indicative of the strain exerted by the piston or diaphragm on the FBG and thus the difference between the two pressures.Type: GrantFiled: February 9, 2000Date of Patent: October 16, 2001Assignee: Schlumberger Technology CorporationInventors: Tsutomu Yamate, Rogerio T Ramos, Raghu Madhavan, Robert J. Schroeder
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Publication number: 20010015277Abstract: A packer for use inside a casing of a subterranean well includes a resilient element, a housing and a rupture disc. The resilient element is adapted to seal off an annulus of the well when compressed, and the housing is adapted to compress the resilient element in response to a pressure exerted by fluid of the annulus of a piston head of the housing. The housing includes a port for establishing fluid communication with the annulus. The rupture disc is adapted to prevent the fluid in the annulus from entering the port and contacting the piston head until the pressure exerted by the fluid exceeds a predefined threshold and ruptures the rupture disc.Type: ApplicationFiled: December 21, 2000Publication date: August 23, 2001Inventors: Vladimir Vaynshteyn, James D. Hendrickson, Jim B. Benton, Raghu Madhavan, Mitchell G. Willcox, Dinesh R. Patel
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Patent number: 6246048Abstract: An optical fiber is provided with a Bragg grating formed along a portion of its core and a mechanical structure arranged adjacent to the Bragg grating for amplifying longitudinal strain on the fiber in the vicinity of the grating. The mechanical structure is designed to convert ambient pressure into longitudinal strain on the fiber in the vicinity of the grating and to allow the fiber to pass through the structure so that several pressure measuring apparatus may be arranged along a single optical fiber. An intermediate structure is provided between the fiber and the mechanical structure for minimizing buckling of the fiber. The methods of the invention include converting pressure into longitudinal strain on an optical fiber, amplifying the effect of pressure on the longitudinal strain, measuring pressure by determining the spectral location related to peaks (or minimums) of light reflected from an optical grating subjected to longitudinal strain.Type: GrantFiled: May 18, 1999Date of Patent: June 12, 2001Assignee: Schlumberger Technology CorporationInventors: Rogerio T. Ramos, Raghu Madhavan, Tsutomu Yamate, Stephen C. Balkunas, Robert J. Schroeder
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Publication number: 20010002621Abstract: A packer for use inside a casing of a subterranean well includes a resilient element, a housing and a rupture disc. The resilient element is adapted to seal off an annulus of the well when compressed, and the housing is adapted to compress the resilient element in response to a pressure exerted by fluid of the annulus of a piston head of the housing. The housing includes a port for establishing fluid communication with the annulus. The rupture disc is adapted to prevent the fluid in the annulus from entering the port and contacting the piston head until the pressure exerted by the fluid exceeds a predefined threshold and ruptures the rupture disc.Type: ApplicationFiled: February 9, 2001Publication date: June 7, 2001Inventors: Vladimir Vaynshteyn, James D. Hendrickson, Jim B. Benton, Raghu Madhavan, Mitchell G. Willcox, Dinesh R. Patel
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Patent number: 6218661Abstract: The apparatus of the present invention include an optical fiber with a Bragg grating formed along a portion of its core and a mechanical structure arranged adjacent to the Bragg grating for amplifying transverse strain on the fiber in the vicinity of the grating. In particular, the mechanical structure is designed to convert ambient pressure into transverse strain on the fiber in the vicinity of the grating. The methods of the invention include converting pressure into transverse strain on an optical fiber, amplifying the effect of pressure on the transverse strain, measuring pressure by determining the spacing between spectral locations related to peaks (or minimums) of light reflected from an optical grating subjected to transverse strain, and measuring the temperature of the grating by determining the locations of the spectral locations related to the peaks (or minimums) of light reflected from the grating.Type: GrantFiled: October 26, 1998Date of Patent: April 17, 2001Assignee: Schlumberger Technology CorporationInventors: Robert J. Schroeder, Tsutomu Yamate, Rogerio T. Ramos, Raghu Madhavan, Eric Udd
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Patent number: 6186227Abstract: A packer for use inside a casing of a subterranean well includes a resilient element, a housing and a rupture disc. The resilient element is adapted to seal off an annulus of the well when compressed, and the housing is adapted to compress the resilient element in response to a pressure exerted by fluid of the annulus of a piston head of the housing. The housing includes a port for establishing fluid communication with the annulus. The rupture disc is adapted to prevent the fluid in the annulus from entering the port and contacting the piston head until the pressure exerted by the fluid exceeds a predefined threshold and ruptures the rupture disc.Type: GrantFiled: April 21, 1999Date of Patent: February 13, 2001Assignee: Schlumberger Technology CorporationInventors: Vladimir Vaynshteyn, James D. Hendrickson, Jim B. Benton, Raghu Madhavan, Mitchell G. Willcox, Dinesh R. Patel
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Patent number: 5685574Abstract: A latch is adapted to be connected to a tubing string and will snap into a packer disposed in a wellbore. A predetermined first number of pounds is required to snap the latch into the packer and a predetermined second number of pounds, greater than the first number, is required to pull the latch out of the packer in the wellbore. In order to maintain constant the first and second number of pounds, the latch has the following special characteristics. The latch has a plurality of flanges separated, respectively, by a plurality of gaps, that snap into the packer, each flange having external threads disposed around its periphery, each thread including an engaging surface and a disengaging surface, an angle between the surface of each disengaging thread relative to a vertical being in a range from 20 to 28 degrees. An elastomeric barrier occupies the gap between adjacent ones of the flanges.Type: GrantFiled: February 28, 1995Date of Patent: November 11, 1997Assignee: Dowell, a division of Schlumberger Technology CorporationInventors: Harjit S. Kohli, L. Michael McKee, Raghu Madhavan, Andrew J. Tucker