Patent Publication Number: US-2016230531-A1

Title: Abandoned well monitoring system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None. 
     FIELD OF INVENTION 
     The present invention relates generally to operations performed and equipment utilized in conjunction with a subterranean well and, in an embodiment described herein, more particularly provides methods and apparatus for monitoring abandoned wellbores. 
     BACKGROUND OF INVENTION 
     Wells are abandoned for various reasons, typically at the end of their productive or commercially viable life span. A reservoir or productive zone eventually becomes depleted, such that it is no longer economical to produce hydrocarbons from the reservoir or zone. If the well is an injection well, then the need for such injection may no longer exist. Methods and apparatus for plugging and abandoning wells is known in the art and not described herein. 
     Even though a well is abandoned, however, it may be desirable to continue monitoring the well, the wellbore, or the downhole conditions in the wellbore, such as temperature and pressure. Where one or more wells in an oilfield is abandoned, but other wells in the field continue to be used for production, injections, or other operations, for example, it may be desirable to monitor the abandoned well or wells. The information gathering may be useful in determining how to treat the formation, other wellbores, or the efficacy of such procedures. Further, use of an abandoned well may prevent the need for and expense of drilling an observation well. Finally, environmental concerns regarding plugged and abandoned wells may be alleviated if the wells are monitored for stable or sustainable parameters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures in which corresponding numerals in the different figures refer to corresponding parts and in which: 
         FIG. 1  is a schematic of an abandoned well monitoring system positioned in a wellbore according to an embodiment of the disclosure; 
         FIGS. 2A-B  are schematic elevational and end views of the mandrel assembly according to an aspect of the disclosure; and 
         FIG. 3  is a schematic of an abandoned well monitoring system utilizing multiple mandrel assemblies and instrument tools positioned in a multi-zone wellbore according to an embodiment of the disclosure. 
     
    
    
     It should be understood by those skilled in the art that the use of directional terms such as above, below, upper, lower, upward, downward and the like are used in relation to the illustrative embodiments as they are depicted in the figures. Where this is not the case and a term is being used to indicate a required orientation, the specification will make such clear. Upstream, uphole, downstream and downhole are used to indicate location or direction in relation to the surface, where upstream indicates relative position or movement towards the surface along the wellbore and downstream indicates relative position or movement further away from the surface along the wellbore, unless otherwise indicated. 
     Even though the methods herein are discussed in relation to a vertical well, it should be understood by those skilled in the art that the system disclosed herein is equally well-suited for use in wells having other configurations including deviated wells, inclined wells, horizontal wells, multilateral wells and the like. Accordingly, use of directional terms such as “above”, “below”, “upper”, “lower” and the like are used for convenience. Also, even though the discussion refers to a surface well operation, it should be understood by those skilled in the art that the apparatus and methods can also be employed in an offshore operation. 
     DETAILED DESCRIPTION 
     The present inventions are described by reference to drawings showing one or more examples of how the inventions can be made and used. In these drawings, reference characters are used throughout the several views to indicate like or corresponding parts. In the description which follows, like or corresponding parts are marked throughout the specification and drawings with the same reference numerals, respectively. The drawings are not necessarily to scale and the proportions of certain parts have been exaggerated to better illustrate details and features of the invention. In the following description, the terms “upper”, “upward”, “lower”, “below”, “downhole”, “longitudinally”, and the like, as used herein, shall mean in relation to the bottom, or furthest extent of, the surrounding wellbore even though the wellbore or portions of it may be deviated or horizontal. Correspondingly, the “transverse” or “radial” orientation shall mean the orientation perpendicular to the longitudinal orientation. In the discussion which follows, generally cylindrical well, pipe and tube components are assumed unless expressed otherwise. 
     The disclosed methods and apparatus are designed to provide long-term monitoring in wells where the operator may have a considerable amount of sunk capital, but rather than simply abandoning the well, it is used to provide downhole data. For example, downhole or formation pressure, temperature, salinity, etc., is measured using appropriate sensors and communicated to the surface for use by the operator of nearby wells. 
       FIG. 1  is a schematic of an abandoned well monitoring system  10  positioned in a wellbore according to an embodiment of the disclosure. Wellbore  12  extends through at least one subterranean zone or formation  14 . A casing  16  is cemented into position along at least a portion of the length of the well. A liner  19  is shown hanging from the casing  16  and extending along the wellbore below the casing. The system is shown with a wellhead, tubing hanger, or other device  27  schematically represented. It is understood that the well can have various configurations, tubulars, surface and subsurface equipment, etc. Alternately, the liner can hang from a liner hanger or other tubular. The liner is often cemented into position as well. A tubing string  18  has been run-in to the well and extends to the surface. The tubing string defines an open bore therein. The tubing string  18  can be coiled tubing, a series of tubulars made-up into a string, etc., as is known in the art. A tubing annulus  20  is defined between the casing and tubing. 
     The well has been or is considered abandoned and can have zero or positive formation pressure at depth. Where the well has been plugged and abandoned it is common to place a cement plug  24  in the tubing annulus. Often a pressure barrier  25 , such as a packer, plug tool, etc., is positioned downhole, below the cement plug, during plugging operations and left in the well. The system can be deployed in wells having various types of plugs, packers, etc. In some instances, the system can enhance or even replace a cement plug or packer since the mandrel assembly provides a pressure seal. 
     An abandoned well monitoring system  10  is seen deployed in the well. The system  10  includes a mandrel assembly  26  positioned uphole from, and connected to, an instrument tool  30  below. The system  10  is run-in via wireline, slick-line, coiled tubing, work string, or other method, in the tubing string  18 . Alternately, the mandrel assembly can be pumped or flowed downhole. A cable  42  extends from the surface, through the mandrel assembly  26  and to the instrument tool  30 . The cable  42  is preferably a control line and communicates the sensor, gauge, instrument readings, and various outputs from the instrument tool, etc., to the surface. The cable can also be a wireline, etc., as is known in the art. The instrument tool  30  can hang in the tubing string or below the tubing string, as shown. Depending on the wellbore and equipment in place, the tool can hang in a space defined by a perforated or non-perforated tubing, liner, casing, or open hole. 
     The disclosure focuses on a specific embodiment to facilitate discussion. It is understood, however, that the apparatus and methods are applicable to a wide variety of situations. For example, the monitoring system can be deployed in vertical, horizontal, or deviated wellbores; in cased, lined, or open-hole bores; in wellbores having multiple zones of interest; in played-out or dry wells; in wells having no, one, or multiple plugs or pressure isolation barriers; in zero pressure or positive pressure wells; onshore or offshore; with or without full rig and hoist; with various wellhead, Christmas tree, BOP, risers, and other termination and control equipment; etc. 
       FIGS. 2A-B  are schematic elevational and end views of the mandrel assembly according to an aspect of the disclosure. 
     The mandrel assembly has a mandrel body  32 , sealing element(s)  28 , a longitudinal through-bore  34  defined therethrough, and connectors  36  for assembling the device on a tool string, tubular, etc. The mandrel assembly is seen having a threaded connector  36  and connected to hardware  38  and upper and lower tubular conduits  40 . The hardware can include tube fittings, tubes, connectors, and the like. Swagelok (trade name) commercially supplies such hardware. 
     Since space is at a premium in most tubing strings, the mandrel body is preferably of relatively small OD, and more preferably about one inch OD. The sealing element  28  is preferably low-profile in its pre-expanded state, and more preferably has a run-in OD of about 1⅛ inch. The mandrel body  32  defines a through-bore  34  which is preferably of about ⅜ inch ID. A communication cable  42  runs through the bore  34 . Preferably the cable is about ¼ inch in diameter. The mandrel assembly includes connectors  36 , which, in a preferred embodiment, include a ⅜ inch NPT female threaded connector. The hardware can include ⅜ inch NPT male threaded connections, bored-through. Cable options can include ¼ inch, of stainless steel, such as A825/316 Stainless. Where the system is deployed in a casing or open hole wellbore, the mandrel dimensions are preferably larger. 
     The mandrel assembly  26  has a gripping and sealing element  28 , or elements, mounted on the mandrel  32  for sealingly engaging the interior surface of the tubing string. Such elements are well-known in the art and not described in detail herein. One or more elements can be employed. Preferably, due to the tight space restrictions in a typical tubing string, the sealing element(s) are low-profile on run-in and do not require bulky actuation devices such as slips, wedges, hydraulic or electric actuators, etc. In the preferred embodiment shown, the sealing element  28  is made of swellable materials. Swelling of the element causes radial expansion into sealing engagement with the interior of the tubing string. The sealing element  28  can be sized and made of selected materials according to the specifics of the wellbore. For example, when deployed in a casing, the element can have a greater OD. Similarly, when deployed in an open hole, the element materials may be selected to better seal against the open bore wall. Other arrangements will be apparent to those of skill in the art. 
     Swellable materials are known in the art and will not be described in detail herein. An example of a swellable material is a 50 duro nitrile with a low CAN content, or a soft EPDM. These substances swell in the presence of hydrocarbons, so the activating fluid can be in situ wellbore fluids. Alternately, the activating fluid can be pumped-down or introduced artificially to the wellbore. Further possible swellable materials include, but are not limited to, hydrogenated nitrile, polychloroprene, butyl, polyurethane and silicon, for instance, which swell in benzene. Similarly, brake fluid will swell elements made of fluorocarbon, hifluor, and flourosilicon, for example. Diesel will cause swelling of ethylene propylene, polyurethane, butyl, butadiene, isoprene and silicon, for example. Other swellable materials and activating fluids will present themselves to those skilled in the art, including those which activate in response to heat, pH, etc. Finally, in some embodiments of the disclosed apparatus, the sealing element can be made of swellable material with a delay mechanism which retards swelling for a period. The material itself can react slowly upon exposure to the activating fluid, or the element can have a temporary protective coating, etc. The time delay can be used to position the device in the wellbore. 
     Hung below the mandrel assembly  26 , preferably by tubing  40 , is one or more measuring or instrument tools  30 . The instrument or measuring tool can include various sensors, gauges, optical cable, computing devices, recording devices, transmitters, and the like, all of which are known in the art. For example, tools and instruments can be used such as SmartLog (trade name) gauge, available commercially from DescoEMIT, ROC (trade name) downhole gauge, commercially available from Halliburton Energy Services, Inc., quartz gauges, strain gauges, piezoelectric gauges, fiber optic sensors, etc., as are known in the art. The instruments can be used in conjunction with fiber optic distributed measurements to provide distributed temperature sensing or distributed acoustic sensing. The parameters to be measured can include temperature, pressure, pH, salinity, and other parameters. Further, more than one instrument tool can be run-in, spaced apart from one another. For example, a single downhole permanent or temporary gauge, a multi-drop downhole permanent or temporary gauge (up to six or more), or a downhole permanent or temporary gauge with fiber optic DTS can be used. These are merely examples of gauge types which can be used. Downhole measurement or instrument tools are available which provide reliable, real-time data about downhole conditions. Such tools can be used for single or multi-zone monitoring applications. In multi-zone applications, dual, triple, or quad splitter block assemblies can be used for multi-drop capabilities. 
     Several methods of deployment are envisioned. For example, a low cost onshore monitoring method and system can be as simple as lowering an instrument tool, such as a Smartlog (trade name) gauge, on the mandrel inside the tubing on a well that is considered abandoned. The cable can be terminated at the surface through the top of the Christmas tree or other surface equipment. A pressure barrier is provided by the swellable mandrel and a secondary pressure barrier can be provided at the surface, for example, at the wellhead. This method allows use of an abandoned well, potentially avoiding the commercial outlay for drilling an observation well. The mandrel and instrument tool can preferably be run from a spooling unit rather than deploying a work-over hoist to recomplete the well, for example. 
     In another embodiment, a platform-based, offshore monitoring method and system are provided. Such a system is more suited for higher-end applications where several zones have been drilled but deemed uneconomical to produce. Multiple mandrels can be run-in hole, with the swellable sealing elements providing isolation between zones. Alternately, packers, plugs and the like can provide isolation. Distributed temperature, and single-point pressure and temperature gauges can be employed. The system provides valuable data on field pressure depletion, monitoring of enhanced recovery operations, such as water flood, validation of reserves, and long-term field pressure monitoring. Deployment can be by spooling unit, or using a hoist to make-up a string. It may be necessary in some applications to use a side-door splitter or BOP stack for pressure control. 
     In this regard,  FIG. 3  is a schematic of an abandoned well monitoring system utilizing multiple mandrel assemblies and instrument tools positioned in a multi-zone wellbore according to an embodiment of the disclosure. An abandoned wellbore  50 , with multiple zones  51  of interest isolated by packers  53  or other isolation devices for sealing the annulus between the string  57  and casing  55 . A monitoring system  52  is deployed having a plurality of mandrel assemblies  54  and instrument tools  56 . The swellable elements can provide isolation between zones. Alternately, isolation can be provided by packers and other devices known in the art. Within the zones of interest, one or more instrument tools is positioned to measure environmental parameters. The gathered data is transmitted uphole, preferably by wire  28 . Alternately, the data can be transmitted wirelessly or by any other known means. Multiple instrument tools can be daisy-chained together to utilize a shared computer and/or transmission device. 
     In another embodiment, a subsea well monitoring method and system are provided. Rather than abandon a subsea well that has been drilled, the well can be populated with instrument tools and mandrels, providing value in the form of field data. In projects where the wells are batch-drilled for completion at a later time, the system can be deployed in conjunction with a downhole computer and transmission system. For example, a tree transmission system, such as commercially available from Sonardyne Group of Companies, can be used to provide data back to surface before the subsea infrastructure and Floating Production Storage and Offloading unit are in place. For the methods and systems described herein, the transmission of data from downhole can be via wire or wireless, or by any known or future means. 
     In another embodiment, a horizontal well monitoring method and system are provided. In wells with significant wellbore deviation, where the deviation has passed the feasible limits for using wireline deployment, one method of deployment is pumping or flowing the mandrel assembly into the wellbore. A time-delay for activation of the swellable seal can be used to prevent the mandrel from deploying prematurely. Alternately, suction cups can be employed to pump the system into the well. 
     The methods and systems disclosed herein allow savings in utilizing a depleted well for long-term observation and monitoring rather than drilling a dedicated observation well. Further, savings are available where the system can be deployed on a wireline intervention set-up instead of a work-over hoist and rig. Savings are also realized since the system can be run inside an existing completion instead of pulling the existing completion and running new tubing. Savings in deploying gauges allows longer term monitoring in a field instead of running production logging tool interventions. Running data transmission systems allows longer term monitoring of single-phase and multi-zone wells to validate operations such as water flood, polymer flood, etc. The low cost barrier provided by the swellable element reduces cost in comparison to a cement pumping operation. 
     Support for the claimed methods and steps of methods is provided here. It is explicitly understood that each of the steps can be performed in any order, repeated, omitted, performed before or after additional steps, named and unnamed, etc., unless stated otherwise. A preferred method of monitoring an abandoned wellbore extending through a subterranean formation, comprises the steps of: a) running into an abandoned wellbore an environmental parameter measuring device below a pressure isolation assembly; b) providing annular pressure isolation across the annulus defined exterior to the pressure isolation assembly; c) measuring at least one downhole environmental parameter in the wellbore downhole from the isolation assembly using the measuring device; and d) transmitting data related to a measured parameter to the surface. In a preferred method step a) can further comprise running the measuring device and isolation assembly in hole on a wire line, slick line, coiled tubing, or tubing string. In a preferred method, step a) further comprises running the measuring device and isolation assembly into a tubing string positioned in the wellbore. In a preferred method, step b) further comprises radially expanding at least one sealing element. In a preferred method, the sealing element is radially expanded into sealing engagement with the tubing string. In a preferred method, the sealing element is swellable upon contact with an activating fluid. In a preferred method, step c) further comprises measuring a downhole temperature, pressure, pH, or salinity. In a preferred method, step c) further comprises using at least one of a quartz gauge, piezoelectric gauge, or distributed optical cable. In a preferred method, step d) further comprises transmitting data via wire or wirelessly to the surface. In a preferred method, the wellbore extends through multiple zones, and further comprising the steps of: positioning a plurality of environmental parameter measuring devices in the wellbore, at least one measuring device in each of the plurality of zones. A preferred method, further comprises the step of: positioning a plurality of pressure isolation assemblies adjacent the plurality of zones. A preferred method further comprises steps of radially expanding the plurality of isolation devices and isolating a plurality of zones. 
     While this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments as well as other embodiments of the invention will be apparent to persons skilled in the art upon reference to the description. It is, therefore, intended that the appended claims encompass any such modifications or embodiments.