Patent Publication Number: US-2002007945-A1

Title: Composite coiled tubing with embedded fiber optic sensors

Description:
CROSS REFERENCE TO RELATED APPLICATION  
     [0001] This application claims priority from U.S. Provisional Application Ser. No. 60/196,277 filed on Apr. 6, 2000. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] 1. Field of the Invention  
       [0003] This invention relates generally to composite spoolable coiled tubing for use in oilwells and more particularly to composite coiled tubings including one or more fiber optic strings and fiber optic sensors.  
       [0004] 2. Background of the Art  
       [0005] Coiled or spoolable metal tubings are commonly used in various oilwell operations, which include drilling of wellbores, work over, completion and production operations. A coiled tubing is defined as a continuous tubing that is spooled on a reel and forms the conveying device for one or more downhole tools. An injector is used to run the tubing into and out of the wellbore. For drilling, a bottomhole assembly carrying a drill bit at its bottom (downhole) end is attached to the coiled tubing&#39;s bottom end. The coiled tubing is hollow or has a through passage which acts as a conduit for the drilling fluid to be supplied under pressure from the surface. For completion and workover operations, the coiled tubing is used to convey one or more devices into and/or out of the wellbore. Metal tubings are usually used as coiled tubings. Such tubings tend to wear out over repeated use due to fatigue and are relatively heavy. Composite coiled tubings, which are lighter than the metal tubing, have been proposed as alternatives. Composite tubings also tend to possess high strength and have high stiffness, which are desirable properties for coiled tubings.  
       [0006] Composite coiled tubings are often made with layers of different types of composite materials, such as graphite fibers, aramid fibers, fiberglass, etc. Such manufacturing processes also offer opportunities to include fiber optic data links and sensors in the composite tubings during the manufacturing process. Composite tubings also are relatively easy to machine, which allows making channels and/or cavities in the finished coiled tubing to have fiber optic strings. Fiber optics can be used both as data/signal transmission links and as sensor elements for downhole parameters, such as temperature, pressure and fluid flow rates. Large amounts of data may be transmitted over the optical fibers. The optical fibers can withstand very high temperatures and are less susceptible to the corrosive effects of wellbore fluids.  
       [0007] The present invention provides composite coiled tubings which include fiber optic data lines and fiber optic sensors disposed, spaced apart, along the composite coiled tubing, and also provides methods for making such composite coiled tubings.  
       SUMMARY OF THE INVENTION  
       [0008] The present invention provides spoolable or coiled tubings made from substantially nonmetallic materials for use in wellbore operations. The tubing is continuous and of sufficient length to reach a desired depth in the wellbore. The composite coiled tubing has a selected thickness and a through passage. The composite coiled tubing preferably includes a plurality of layers of composite materials, which may include, among other things, graphite, aramid fiber, and fiberglass. A fiber optic string is disposed in the composite coiled tubing, preferably during the manufacture of the composite tubing. A plurality of spaced apart sensor elements on the fiber optic string provide measurements of one or more downhole parameters of interest during the wellbore operations. Such sensors may include temperature, pressure, vibration and fluid flow sensors.  
       [0009] The fiber optic string may be disposed inside a tubing, which may be made from a suitable metal or a composite material. This tubing may then be affixed to the inside wall of the composite coiled tubing or embedded into a channel in the composite coiled tubing. This tubing may also be helically or otherwise wrapped around the composite coiled tubing. The fiber optic string may be embedded or placed along the composite coiled tubing. The tubing may be hermetically sealed to protect the optical fibers. Any channel made to accommodate the fiber optic string may be filled with a suitable epoxy. A liner may be disposed inside the composite coiled tubing to isolate the inner surface of the coiled tubing and the fiber optic string from the drilling or the wellbore fluid passing through the coiled tubing. The liner may be made from any suitable material including a suitable metal, polyurethane, nylon or fluoropolymer. The fiber optic string may be included in the composite coiled tubing during the manufacturing process of the composite tubing or it may be pumped into the metallic tubing after the manufacture of the composite tubing. Additional fiber optic strings may be disposed in the composite coiled tubing to serve as additional data communication links and/or to provide redundancy.  
       [0010] Examples of the more important features of the invention have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011] For detailed understanding of the present invention, reference should be made to the following detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, and wherein:  
     [0012]FIG. 1 is a schematic illustration of a composite coiled tubing with inner liner and a fiber optic string according to one embodiment of the present invention.  
     [0013]FIGS. 2 a - 2   c  show various embodiments of deploying fiber optic strings in a composite coiled tubing.  
     [0014]FIG. 3 is a schematic illustration of a composite coiled tubing with fiber optic strings disposed on channels along the outside of the composite coiled tubing according to one embodiment of the present invention.  
     [0015]FIG. 4 is a schematic illustration of a bottomhole assembly conveyed into a wellbore by a coiled tubing made according to one embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0016]FIG. 1 shows a schematic of an embodiment of a composite coiled tubing  150  made according to the present invention. The composite coiled tubing  150  preferably includes an inner liner  152  which is a hollow continuous tubular member. In the finished coiled tubing, as described below, the drilling fluid will flow through the liner  152  under pressure and the liner  152  will come in contact with the wellbore fluid that contains corrosive materials. Accordingly, the liner  152  is made from a material that can withstand the harsh environment in the wellbore and the various chemicals in the wellbore fluid. The liner  152  may be made from a suitable plastic material, such as polyurethane, nylon, or fluoropolymer. The liner  152  may also be made from a suitable metal, such as stainless steel.  
     [0017] In one embodiment, one or more optical fiber strings, such as string  155 , may be axially disposed along the outer surface of the liner  152 . A first layer  154  of a first composite material is then suitably placed around the liner  152 . The composite material utilized may include graphite, aramid fibers, fiberglass, or any other suitable material. Such materials are known and are commercially available from a variety of sources. A second layer  156  and a third layer  158  may be successively placed over the first layer  154 . A number of methods have been proposed for orientation and thickness of different types of composite materials. Suitable resins are used within and between the layers. For example, U.S. Pat. No. 5,419,916 describes one method of constructing a layered composite coiled tubing. U.S. patent application Ser. No. 09/080,413 assigned to the assignee of this application, describes another method of constructing a layered composite tubular. U.S. patent application Ser. No. 09/080,413 is incorporated herein by reference. For the purpose of this invention, any composite coiled tubing may be utilized, whether or not layered.  
     [0018] Still referring to FIG. 1, the fiber optic string or line  155  preferably includes optical fibers  157  extending the length of the string  155  and a plurality of sensor elements  159 , spaced apart along at least a selected section or segment of the composite coiled tubing  150 . The optical fiber  157  itself may be utilized as the sensor element. Such optical fiber sensors can be used to measure temperature, pressure, vibration and fluid flow.  
     [0019] In an alternative embodiment, as shown in FIG. 2A, the composite coiled tubing  170  may be made as desired with one or more channels  172  axially along the inside wall  173  of the coiled tubing. The channels  172  are made of sufficient size to accommodate the optical fibers  174   a,  which may include spaced apart or distributed sensors along its length. The channels  172  may be formed during the manufacturing process of the coiled tubing  170 . The channels  172  may be filled with a suitable epoxy. A liner  176  may be disposed in the coiled tubing  170  to isolate the optical fibers  174   a  from the borehole fluid.  
     [0020] In an alternative method as shown in FIG. 2B, the optical fiber string  186  may be disposed in a tubing  184 , which is placed inside the composite coiled tubing  182 . The tubing  184  may be integrated to the coiled tubing  182  during the manufacturing process. The optical fibers  186  can be pressure inserted, or pumped, into the tubing  184  after the assembly of the coiled tubing  182 . The tubing  184  may have a corrugated outer surface. The tubing  184  may be hermetically sealed to provide protection to the optical fiber from the downhole environment.  
     [0021] In yet another method, the optical fiber  191  disposed inside along the length of a tubing  192  may be helically wrapped around the composite coiled tubing  190 , as shown in FIG. 2C or it may be strapped axially (not shown) on the coiled tubing  190  outside. The optical fiber  191  may be loosely disposed in the tubing  192  so that stretching of the tubing  192  or the coiled tubing  190  will not cause the optical fiber to break or deteriorate its performance. The tubing  192  may have a corrugated outer surface. The tubing  192  may be hermetically sealed to provide protection to the optical fiber from the downhole environment.  
     [0022]FIG. 3 shows an embodiment of a composite coiled tubing  200  wherein fiber optical strings are disposed in channels made axially along the outside  202  of the coiled tubing. A channel  204  of sufficient dimensions is made axially on the outside wall  202  of the composite tubing  200 . One or more fiber optical strings  208  are disposed in the channel  204 . Cavities  210  may be formed in the composite tubing  200  to house various types of sensors. Channel  204  and the cavities  210  may be filled with a suitable epoxy to protect the fiber optic string and the sensors  212  from the outside environment. Additional channels, such as channel  216 , may be formed to house optical fibers, such as  218 , which may be used as redundant sensor strings or as data links.  
     [0023] Thus, the composite coiled tubing made according to the present invention includes a suitable composite tubing that is made for use in wellbores and to withstand the downhole environment. One or more fiber optic strings are included in the composite coiled tubing. The sensors may include temperature sensors, pressure sensors, vibration sensors, etc. Same or separate optical fibers may be used as data links to transmit data to the uphole end of the composite coiled tubing.  
     [0024]FIG. 4 depicts the use of the composite coiled tubing  300  made according to the present invention in drilling of a wellbore  304 . A bottomhole assembly (BHA)  315  carrying a drill bit  320  at its bottom end  315   a  is attached to the bottom end  300   a  of the composite coiled tubing  300  by a suitable coupling device  301 . The fiber optic string  310   a  may be connected to optical fibers  310  in the bottomhole assembly  315  by an optical coupler  314 . The BHA usually includes a variety of measurement-while-drilling (“MWD”) sensors, which typically include electromagnetic sensors for determining resistivity of the formation, acoustic sensors for determining borehole condition and formation acoustic velocity, and nuclear devices for determining the formation porosity. The BHA also includes sensors for determining the BHA direction and orientation. If an MWD sensor is a fiber optic sensor, then the fiber optic string  310  may be couple to such devices to provide light energy and to transmit signals from such sensors to the surface. Alternatively, the MWD sensors may include devices which convert the MWD sensor signals to optical signals, which are then passed on to the optical fiber  310  via a suitable coupler for transmission to the surface. In this case, the optical fibers  310  act as a data link.  
     [0025] The optical fiber string  310  includes spaced apart sensors S 1 -Sn  111  which may provide measurements for temperature, pressure, flow and vibration during drilling of the wellbore  304 . A light source  340  provides light energy to the string, and a detector/converter (D/C)  342  converts light signals to electrical signals and vice versa. A control unit  350 , which is preferably a computer, controls the operation of the light source  340  and D/C  342  and processes data received from the sensors  111  and the MWD sensors in the BHA  315 .  
     [0026] During drilling, the composite coiled tubing  300  is conveyed into the wellbore  304  from a reel  305  by a suitable injector (not shown). Drilling fluid  330   a  is supplied under pressure into the tubing  300  which discharges at the drill bit  320  bottom. The fluid  330   b,  carrying drill cuttings, returns to the surface via the annulus  306 . The sensors Si-Sn  111  provide measurements along the wellbore, while data from the MWD sensors in the BHA are transmitted uphole by the fiber optic string  310 .  
     [0027] It should be noted that FIG. 4 is an example of the manner the composite coiled tubing made according to the present invention may be utilized. The composite coiled tubing  300  may also be utilized as part of a completion string, workover string or a production string.  
     [0028] While the foregoing disclosure is directed to the preferred embodiments of the invention, various modifications will be apparent to those skilled in the art. It is intended that all variations within the scope and spirit of the appended claims be embraced by the foregoing disclosure.