Patent Publication Number: US-2012043079-A1

Title: Sand control well completion method and apparatus

Description:
This application claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/375,977, entitled, “METHOD OF CONDUCTING A SAND CONTROL WELL COMPLETION OPERATION,” which was filed on Aug. 23, 2010, and is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The disclosure generally relates to a sand control well completion method and apparatus. 
     Fluid producing and injection wells are often located in subterranean formations that contain unconsolidated particulates that can migrate out of the formation with the oil, gas, water, or other fluid produced from the well. The production of such particulates such as sand is undesirable because they may abrade the production and surface equipment such as tubing, pumps, and valves. In addition, the particulates may partially or fully clog the well and reduce the fluid production which might ultimately create the need for expensive remedial work. 
     Before a gravel pack operation is conducted, an overall job plan typically is prepared in which information about the well is used. This information typically is obtained from measurements taken while the well was drilled as well as information from nearby wells, if available. The information may include the depth of the well; hole depths and diameters; downhole formation pressures to be encountered; the amount of fluids that will likely need to be pumped; the volume and type of gravel that will be needed; etc. 
     SUMMARY 
     In an embodiment of the invention, a technique includes running a sand control completion system into a well, where the system includes at least one sensor, a gravel packing service tool and a sand control section. The sand control completion system is used to perform a gravel packing operation in the well in which a slurry is communicated downhole through the service tool to deposit gravel near the completion section. The technique includes prior to the gravel packing operation, performing a given operation in the well and regulating the given operation based, at least in part, on data acquired by the sensor(s) and communicated to an Earth surface of the well while the given operation is being performed. 
     In another embodiment of the invention, a technique includes running a sand control completion system into a well, where the system includes at least one sensor, a gravel packing service tool and a sand control section; and performing a gravel packing operation in the well, where the performing includes communicating slurry downhole through the service tool to deposit gravel near the completion section. The technique includes regulating at least one of movement of the service tool and a screenout pressure based, at least in part, on data acquired by the sensor(s) and communicated to an Earth surface of the well while the gravel packing operation is being performed. 
     In another embodiment of the invention, a technique includes running a sand control completion system into a well, where the system includes at least one sensor, a gravel packing service tool and a sand control section. The sand control completion system is used to perform a gravel packing operation in the well in which a slurry is communicated downhole through the service tool to deposit gravel near the completion section. The technique includes, after the gravel packing operation, performing a given operation in the well and regulating the given operation based, at least in part, on data acquired by the sensor(s) and communicated to an Earth surface of the well while the given operation is being performed. 
     In another embodiment of the invention, a system includes a controller that is disposed at the Earth surface and a sand control completion system, which includes a tubular string, sand control section, a gravel pack service tool and at least one sensor. The sand control section is adapted to be secured to the string to be run into the well and installed in the well, and the gravel pack service tool is adapted to be run downhole as a unit with the sand control section and be released after the sand control section is installed in the well to allow the gravel pack service tool to move with respect to the sand control section. The sensor(s) are also adapted to be run downhole as part of the unit. The controller communicates with the sensor(s) during a gravel packing operation in which a slurry is communicated downhole through the string and through the service tool to deposit gravel near the sand control section. The controller is adapted to display information to an operator indicative of at least one of a screenout pressure and an unintended movement of the service tool during the gravel packing operation based at least in part on the communication. 
     In another embodiment of the invention, a system includes a controller that is disposed at the Earth surface and a sand control completion system, which includes a tubular string, sand control section, a gravel pack service tool and at least one sensor. The sand control section is adapted to be secured to the string to be run into the well and installed in the well, and the gravel pack service tool is adapted to be run downhole as a unit with the sand control section and be released after the sand control section is installed in the well to allow the gravel pack service tool to move with respect to the sand control section. The sensor(s) are also adapted to be run downhole as part of the unit. The controller communicates with the sensor(s) at least before a given operation that precedes a gravel packing operation in which a slurry is communicated downhole through the string and through the service tool to deposit gravel near the sand control section. The controller is adapted to display information to an operator indicative of the given operation during the given operation to allow the operator to selectively perform corrective action in response thereto. 
     In yet another embodiment of the invention, a system includes a controller that is disposed at the Earth surface and a sand control completion system, which includes a tubular string, sand control section, a gravel pack service tool and at least one sensor. The sand control section is adapted to be secured to the string to be run into the well and installed in the well, and the gravel pack service tool is adapted to be run downhole as a unit with the sand control section and be released after the sand control section is installed in the well to allow the gravel pack service tool to move with respect to the sand control section. The sensor(s) are also adapted to be run downhole as part of the unit. The controller communicates with the sensor(s) at least before a given operation that proceeds a gravel packing operation in which a slurry is communicated downhole through the string and through the service tool to deposit gravel near the sand control section. The controller is adapted to display information to an operator indicative of the given operation during the given operation to allow the operator to selectively perform corrective action in response thereto. 
     Advantages and other features of the invention will become apparent from the following drawings, description and claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a well illustrating a sand control completion system according to some embodiments of the invention. 
         FIG. 2  is a schematic diagram of the sand control completion system illustrating a run-in-hole/washdown state of the system according to some embodiments of the invention. 
         FIG. 3  is a schematic diagram of the sand control completion system illustrating a packer set/test state of the system according to some embodiments of the invention. 
         FIG. 4  is a schematic diagram of the sand control completion system illustrating a squeeze/injecting state of the system according to some embodiments of the invention. 
         FIG. 5  is a schematic diagram of the control completion system illustrating a circulating state of the system according to some embodiments of the invention. 
         FIG. 6  a schematic diagram of the control completion system illustrating a reverse state of the system according to some embodiments of the invention. 
         FIG. 7  is a flow diagram depicting a technique to control a downhole operation prior to a gravel packing operation using at least one sensor disposed on the sand control completion system according to some embodiments of the invention. 
         FIG. 8  is a flow diagram depicting a technique to control a gravel packing operation using at least one sensor disposed on the sand control completion system according to some embodiments of the invention. 
         FIG. 9  is a flow diagram depicting a technique to control a downhole operation subsequent to the gravel packing operation using at least one sensor disposed on the sand control completion system according to some embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following detailed description, terms such as ‘upper,” “lower”, “downhole,” and the like are relative terms to indicate the position and direction of movement of various components shown in the drawings. Usually these terms are relative to a line drawn perpendicularly downward through the center of the borehole as would be the case in a straight, relatively vertical wellbore. However, when the wellbore is highly deviated or horizontal, such terms may refer to left or right, right to left, or diagonal relationships as appropriate. Also, in the following detailed description, various sensors and the measurements to be taken by such sensors might be described with reference to one or more figures but not in others. Such omissions are solely for the purpose of providing clarity with the understanding that any combination of sensors and measurements taken may be used without departing from the spirit and scope of the invention. 
     Traditionally, after a gravel packing plan is finalized and operations associated with the gravel packing plan begin, the conventional gravel packing system provides relatively little feedback at the Earth surface from which determinations may be made regarding whether the operations are proceeding as planned. Contrary to conventional arrangements, systems and techniques are disclosed herein, which allow downhole parameters associated with gravel packing-related operations to be monitored at the Earth surface in real time or near real time so that appropriate actions may be undertaken to regulate or control these operations as the operations are occurring. 
     In the context of this application, the “real time or near real time” communication of a downhole parameter measurement to the Earth surface means that the data indicative of the measurement is communicated from a downhole location in the well where the measurement is acquired to equipment at the Earth surface within a few seconds or minutes. As described herein, in accordance with some embodiments of the invention, the real time or near real time communication of the data uphole occurs at a sufficiently fast enough rate to permit a downhole operation that influences or is influenced by the measurement to be regulated or controlled using equipment at the Earth surface based on the data. 
       FIG. 1  generally depicts a well, in accordance with some embodiments of the invention. In general, as shown in  FIG. 1 , a wellbore  14  traverses one or more formations and is illustrated in  FIG. 1  for this example, as being partially cased by a casing string  16 , which lines, or supports, at least part of the wellbore  14 . In this manner, for the example that is depicted in  FIG. 1 , the casing string  16  extends downhole from the Earth surface into the wellbore  14 , leaving a bottom portion of the wellbore  14  uncased. It is noted, however, that the wellbore  14  may be entirely cased, in accordance with other embodiments of the invention. Moreover, although the wellbore  14  is illustrated in  FIG. 1  and the following figures as being a vertical wellbore, the wellbore  14  may be a lateral or a deviated wellbore, in accordance with other embodiments of the invention. It is noted that  FIG. 1  depicts a simplified schematic diagram of the well, in that various aspects of the well, such as the casing shoe at the lower end of the casing string  16 , cement surrounding the casing string  16 , etc., are not depicted in  FIG. 1 . 
       FIG. 1  depicts a tubular work string  12  (a drill string, for example) that extends downhole inside a central passageway of the casing string  16 ; and at its lower end, the work string  12  contains a tubing  18  that connects to a sand control completion system  10 . More specifically, at its lower end, the tubing  18  is connected to a service tool assembly  20  of the sand control completion system  10 , and for the example depicted in  FIG. 1 , the service tool  20  extends into a lower completion section  30  of the sand control completion system  10 . 
     In general, the lower completion section  30  includes a sand control section  46  (a sand screen, a perforated pipe, a slotted pipe, etc.), which for the example that is depicted in  FIG. 1  extends into the uncased section of the wellbore  14  and includes a shoe  47  at its bottom end. In addition to the sand control section  42 , the lower completion section  30  includes a gravel pack packer  32 , which, when radially expanded, or set, anchors itself to and forms an annular seal with the casing string  16 . 
     In general, the service tool  20  and the lower completion section  30  are run downhole as unit into the well on the end of the work string  12 . Although the service tool  20  is initially secured to the lower completion section  30 , the service tool  20  is constructed to be released from the lower completion section  30  and controlled from the Earth surface of the well for purposes of performing various gravel packing-related operations. One of these gravel packing-related operations is the gravel packing operation itself in which a gravel-laden slurry is communicated downhole, and a carrier fluid exits the slurry to leave a filtering substrate of gravel (not depicted in  FIG. 1 ) deposited around the sand control section  46 . 
     More specifically, the carrier fluid returns to the Earth surface via a path that extends through a passageway, or inner bore  23 , of a wash pipe  22  of the service tool  20  and a casing annulus  24 , which is the annular region between the tubing  18  and the inside of the casing string  16 . A cross-over assembly  25  of the service tool  20  may be configured in a number of different states (described below), among which is a state that allows fluid from the washpipe inner bore  23  to cross over to the casing annulus  24 . 
     In general, the cross-over assembly  25  controls fluid communication between an inner bore  44  of the tubing  18 ; a circulating port  40  of the lower completion section  30 , which is in fluid communication with an annulus  34  below the gravel pack packer  32 ; a circulating port  41  of the service tool  20 , which is in fluid communication with the casing annulus  24  above the gravel pack packer  32 ; and the inner bore  23  of the wash pipe  22 . The flow path(s) through the cross-over assembly  25  are a function of the particular state of the assembly  25 , as further described below. 
     For the state of the cross-over assembly  25  that is depicted in  FIG. 1  (which may be used for gravel packing), the cross-over assembly  25  establishes fluid communication between an inner bore  44  of the tubing  18  and the annulus  34 , and the cross-over assembly  25  establishes fluid communication between the inner bore  23  of the wash pipe  22  and the casing annulus  24 . In this manner, seals  42  and  43  (located on the outside of the service tool  20 , for example) form annular seals above and below the circulating port  40 , which forces fluid from the inner bore  44  of the tubing  18  through the cross-over assembly  25  and into the annulus  34 . The circulating port  40  may be isolated with seals (not shown) when the production tubing (not shown) is run in order to prevent production through the circulating port  40 . A port closure sleeve (not shown) may also be used to close the circulating port  40  on pull out of the hole (POOH) of the service tool  20  in order to isolate the well and prevent fluid loss. Other embodiments may also use multiple valves in the service tool  20  to enable crossover flow. These valves can be actuated using a number of different mechanisms, including hydraulically with the application of well pressure; mechanically with an intervention tool, or by manipulation of work string  12 ; and electrically with wire, wireless assemblies, or fiber optics. 
     When the lower completion section  30  and the service tool  20  are run together via the work string  12  into the well, the lower completion section  30  is positioned at the desired location, and then the gravel pack packer  32  is set, which firmly secures the lower completion section  30  to the casing string  16  and forms an annular seal. As non-limiting examples, the gravel pack packer  32  may be a weight set packer or a hydraulically set packer. As another example, in accordance with some embodiments of the invention, the gravel pack packer  32  may be set by physically manipulating the work string  12 . 
     After the gravel pack packer  32  has been set, the service tool  20  may be released from the lower completion section  30  to perform various gravel packing-related operations, such as the gravel packing operation itself, as well as operations that occur before and after the gravel packing operation. 
     For purposes of establishing a real time or near real time communication path between sensors (described below) of the sand control completion system  10  and Earth surface-disposed monitoring equipment  100  (herein called the “surface equipment  100 ”), the work string  12  includes a control station  50 . Depending on the particular implementation, the control station  50  may be part of the service tool  20  or may be disposed on another part of the work string  12 . The control station  50  may include a processor (one or more microprocessors and/or microcontrollers, for example), memory and a power and telemetry module to allow communication between downhole sensors and the surface monitoring equipment  100 . The control station  50  may be used to process multiple readings from the sensors and communicate the processed information to the Earth surface, and the control station  50  may be used to receive commands communicated from the Earth surface for purposes of controlling certain downhole sensors. In addition, the control station  50  may communicate signals to components in the well that automatically change treatment of the well including 1) partially or fully opening/closing valves to control flow rates and pressures in the well  14 ; or 2) stopping movement or rate of movement of the service tool  20 . The control station  50  may also include various additional sensors (pressure, temperature, acoustic, etc) that may be used to acquire measurements that are communicated in real time or near real time to the Earth surface, in accordance with some embodiments of the invention. The sensors of the sand control completion system  10  are linked to the control station  50  by either a wired or wireless telemetry system, depending on such factors as the distance between the sensor and the control station  50 , space limitations, and the like. 
     In general, the well contains at least part of a communication path  52  between the downhole control station  50  and the surface monitoring equipment  100 . As a non-limiting example, the communication path  52  may include at least one fiber optic cable that is connected to the control station  50  and extends to the Earth surface via the work string  12 , for example. As another non-limiting example, the communication path  52  may be formed from one or more electrically conductive wires that are disposed in the string  12  (for example, the string  12  may be a wired drill pipe). However, the communication path  52  may be formed at least in part from a wireless communication path, in accordance with other embodiments of the invention. In this manner, as non-limiting examples, this wireless communication path may use such wireless communication techniques as acoustic communication, electromagnetic (EM) communication, pressure pulse communication, etc. Thus, many variations are contemplated and are within the scope of the appended claims. 
     The surface monitoring equipment  100  may take on numerous different forms, depending on the particular embodiment of the invention. In general, the surface monitoring equipment  100  may be, in accordance with some embodiments of the invention, a processor-based machine, which contains a processor  102  (one or more microcontrollers and/or microprocessors, as non-limiting examples) that executes machine executable instructions that are stored in a non-transitory memory  104  (a semiconductor memory, an optical memory, a magnetic storage-based memory, etc., as non-limiting examples) for purposes of processing sensor or sensor-derived measurements that are communicated to the Earth surface by the control station  10  in real time or near real time. 
     In this manner, in accordance with some embodiments of the invention, using this execution of software, the surface monitoring equipment  100  is constructed to provide (on a monitor, or display  106 , for example) indications of direct measurements and indirect measurements of various downhole parameters to a surface operator. Based on these measurements, the surface operator may then take the appropriate measures, or remedial actions, to control or regulate downhole operations to achieve the desired results. 
     As non-limiting examples, the sensors of the sand control completion system  10  may be constructed to directly or indirectly measure, alone or in combination, one or more of the following: pressure, temperature, force, torque, density, rheology, pH, flow rate, acoustic energy, seismic energy, acceleration, gravel pack logging images and/or other downhole properties. These measurements or information based on these measurements are communicated to the Earth surface in real time or near real time via the control station  50  and its associated telemetry system (e.g., a telemetry system including the communication path  52 ) in order to allow an operator at the Earth surface to monitor an ongoing downhole operation; control or regulate the operation in real time or near real time; determine whether a given downhole operation is proceeding according to plan; make decision regarding corrective actions, if any, which should be taken; and monitor these corrective actions, as just a few non-limiting examples. 
     As non-limiting examples, the corrective actions that may be taken at the Earth surface of the well based on the information that is communicated uphole from the sand control completion system  10  may include actions to regulate a fluid pumping rate, regulate the introduction of fluid stages, regulate the volumetric amounts of certain fluids that are introduced into the well, time the introduction of fluid stages, regulate gravel delivery (start, end and/or concentration, as examples), regulate a force that is applied at the Earth surface to the work string  12 , regulate manipulation (turning, up/down movement, etc.) of the work string  12 , regulate an amount of weight placed on the work string  12 , regulate travel of the work string  12 , and so forth. 
     Examples of specific sensors of the sand control completion system  10 , measurements that may be acquired by the sensors of the sand control completion system  10  and the general uses of these measurements for purposes of controlling downhole operations are next described below. 
     Pressure Measurements 
     In accordance with some embodiments of the invention, the sand control completion system  10  may contain sensors to measure pressures at various downhole locations. For example, in accordance with some embodiments of the invention, the sand control completion system  10  includes one or more of the following pressure sensors: a pressure sensor  60  that is located inside the tubing  18  and measures the pressure within the work string inner bore  44 ; a pressure sensor  62  that is located outside the tubing  18  and measures the pressure within the casing annulus  24 ; a pressure sensor  64  that is located on the outside of the wash pipe  22  and measures pressure in the annulus between the sand control assembly  46  and the wash pipe  22 ; a pressure sensor  66  that is located on the inside of the wash pipe  22  and measures the pressure inside the wash pipe  22 ; and a pressure sensor  68  that is located above the sand control section  46  to on the lower completion section  30  to measure pressure in the annulus  34 . The sand control completion system  10  may also include pressure sensors  70  that are disposed in a distributed fashion on the lower completion section  30  along the outside of sand control section  46  to acquire pressure measurements along the sand control interval. Moreover, the sand control system  10  may contain a pressure sensor  72  that is disposed on the lower completion section  30 , near the shoe  47  and below the lower completion section  46  to measure pressure below the sand control section  30 . The sensors may be distributed discretely or continuously along the service tool string  20  and/or the lower completion section  30  at the locations discussed above. 
     Thus, the arrangement that is depicted in  FIG. 1  differs from conventional arrangements in that the sensors  70  may be installed along the length of the sand control section  46  and accessed in real time or near real time in connection with a gravel packing-related operation. The sensors  70  installed along the length of the sand control assembly  46  are connected via a cable  72  to a female component  74   a  of an inductive coupling  74  that is mounted below the gravel pack extension on the outer completion section  30 , as shown in  FIG. 1 . A proximate male component  74   b  is mounted on the service tool  22 , and this component  74   b  is coupled (by a cable, for example) to the control station  50 . In other embodiments of the invention, wireless connections may be used instead of, or in combination with, cable connections to communicate between the sensors along on the screens, the control station mounted above the service tool and the surface. 
     The above-disclosed pressure sensors of the sand control system  10  may allow various pressures to be transmitted to the Earth surface and observed in real time or near real time such that appropriate real time/near real time actions may be taken from the Earth surface. As non-limiting examples, the pressure measurements may include rate of change measurements with respect to time and volume as well as measurements that hydrostatic pressures and differential pressures to be derived. Moreover, the pressure differentials may be used for purposes of calculating a friction pressure. 
     As a more specific example, during static conditions when fluid is not being pumped from the Earth surface, downhole pressure measurements indicate whether the downhole fluid pressure is within a suitable range to control the well. If the pressure reading is too low indicating an underbalanced condition, then heavier fluid may be pumped from the surface. If the pressure reading is too high indicating an overbalanced condition where formation fracturing might occur, then a lighter fluid may be pumped from the surface. 
     Other exemplary operations that may benefit from the pressure sensors of the sand control completion system  10  include an operation in which fluid is pumped from Earth surface in order to set the gravel pack packer  32  within the casing string  16 . In this manner, pressure readings from the sensor  60  may indicate whether the pressure is too low to set the gravel pack packer  32  and if so, the pressure can be increased. Once the gravel pack packer  32  has been set, a packer element test may be conducted in which a pressure measurement is taken below the packer  32  with the sensor  64 . If pressure is observed below the gravel pack packer  32 , then a leak is indicated; and setting of the gravel pack packer  32  is attempted again, or the gravel pack packer  32  is replaced. If pressure is not indicated, then the gravel pack packer  32  was seated and sealed properly. Other exemplary pressure measurements, discussed later in more detail, may be taken when the well is in a dynamic condition, i.e., when fluid is being pump from the surface and there is fluid flow through the system. 
     Additional pressure measurements maybe taken downhole via the pressure sensors of the sand control completion system  10  and communicated uphole to monitor operations in real or near real time in order to take remedial action, if needed. For example, various downhole components that are subject to differential pressure may be provided with pressure sensors across the differential and monitored so that the pressure rating of such devices are not exceeded during pumping operations. 
     For example, the sensor  62  above the packer  32  and the sensor  68  below the gravel pack packer  32  may be monitored in real time so as not to exceed the pressure rating of the packer  32 . If the pressure on the gravel pack packer  32  as detected based on measurements from sensors  68  and  60  reaches a predetermined level, then steps in real or near real time may be taken to reduce the pressure on the packer  32 . These steps may include reducing the rate and pressure of fluid being pumped at the Earth surface. Other examples of other components where differential pressure measurements may be taken include inside and outside the service tool  20  and across the fluid loss control seals  42  and  43 . The sand control system  10  may include a formation isolation valve, and pressure sensors may sense pressures above and below the valve, in accordance with some embodiments of the invention. 
     In addition, the sensor  68  may be positioned below the circulating port  40  so that pressure measurements can be made during the gravel packing operation. If pressure during the gravel packing operation exceeds a predetermined level, then the rate and pressure of fluid pumped from the Earth surface may be reduced to prevent pressure from exceeding the collapse rating. In addition, pressure measurements may be taken during swabbing. While the service tool  20  is adjacent the gravel pack packer  32 , the pressure below the packer  32  decreases when the service tool  20  is moved upwards in relation to the packer  32 . The sensor  64  or the sensor  68  may be used to monitor the pressure of the fluid within the annulus  34  to ensure that the observed pressure does not fall below the fluid pressure within the reservoir for the wellbore  14 . If the observed pressure drops below a certain level, then movement of the service tool  20  may be stopped to allow the downhole pressure to equalize, or the rate of the movement of the service tool  20  may be reduced in order to decrease the swabbing effect of such movement. 
     Once the service tool  20  is positioned in the wellbore  14  and the gravel pack slurry is pumped downhole, the sensor  64  may be monitored to ensure that the fluid pressure within the annulus  34  does not exceed the reservoir fracture pressure during a gravel operation. If the sensor  64  records such an elevated pressure reading, then the rate of the slurry flow may be reduced or chokes at the Earth surface of the well may be fully or partially opened. For fracturing treatments, the sensor  64  may also be monitored to ensure that fluid pressure within the annulus  34  does not fall below the reservoir fracture pressure. If the pressure sensor  64  records a measurement falling below a predetermined pressure level, then the pressure may be increased within the annulus  34  by increasing flow rate or chokes at the surface or in the well may be fully or partially closed. 
     The pressure sensors may be used to monitor other parameters, in accordance with many potential embodiments of the invention. In real time or near real time, for example, pressure may be monitored across downhole components. Therefore, if the measured pressure is higher than a rating (a burst or collapse rating, as examples) for the component, then the surface pump rate may be decreased or a surface choke may be opened to maintain the component within the appropriate operating envelope. The differential pressure across the gravel pack packer  32  may also be monitored. In this manner, the sensor  68  may be used as well as sensor on top of the wash pipe  22  to ensure that the collapse pressure of the blank pipe ensure is not exceeded. 
     As another example, the pressure sensors may be used to observed friction pressures throughout the system. For example, packing mechanisms, fluid changes, screen plugging, etc. may be monitored and compared with expected trends. If different, corrective action may then be taken to adjust the flow rate and/or choke pressure from the Earth surface. If necessary, the current operation may be stopped and reversed out. The pressure sensors may also be used to calibrate design models to match friction pressures in real time or near real time and facilitate better predictions for future events. 
     The pressure sensors of the sand control completion system may also be used to detect the arrival of different stages in a multiple stage fluid treatment process. In this manner, the pressure sensors  64  and/or  70  may sense fluid pressure at various points downhole to identify the arrival of the different stages. These measurements may also be used to estimate roping such that the volumetric calculations performed at the Earth surface may be adjusted to take this into account. 
     The pressure sensors of the sand control completion system  10  may also be used to regulate a screenout pressure, as further described below. 
     Fluid Property Measurements 
     In accordance with some embodiments of the invention, the sensors that are disposed on the sand control completion system  10  may acquire measurements of various fluid properties, such as density, rheology, pH, etc., as a non-limiting list of examples. These sensors may be disposed at various locations of the sand control completion system  10 , such as, as non-limiting examples, above the service tool  20 , on the service tool  20  and on the lower completion section  30  at various points along the sand control interval. In accordance with some embodiments of the invention, these sensors may acquire distributed measurements along the entire sand control interval. 
     For example, in accordance with some embodiments of the invention, at least some of the sensors  70  along the sand control section  46  may be fluid property-sensing sensors  70  (replacing or in addition to the other sensors, which are disclosed herein). The fluid property-sensing may be used to identify the presence of acid during a cleanup treatment with an acidic treatment fluid, for example. For effective cleanup, the acidic treatment fluid should cover the entire interval selected for the cleanup treatment. However, the acidic treatment fluid may divert preferentially through open perforations or highly conductive open hole sections and thus, not achieve an effective cleanup. As a more specific example, the sensors  70  may be constructed to measure pH and identify, in real time, where the acid is going and enable the treatment to be better targeted. 
     In this manner, the acidic treatment fluid may be pumped through the annular bore  44  of tubing  18 , through the circulating port  40  and into the annulus  34 . The acidic treatment fluid flows into the perforations or fractures in the casing string  16  and into the surrounding reservoir. If the wellbore  14  is uncased and is thus, an open hole wellbore, then the acidic treatment fluid flows directly into high permeability zones in the reservoir walls that surround the wellbore  14 . If there is a high permeability zone, for example, adjacent an upper portion of the sand control section  46 , then the acidic treatment fluid may not treat the interval of the reservoir adjacent the lower portion of the sand control section  46 . In such a situation, the pH sensors positioned along the upper portion of the sand control section  46  measure a higher acidic readings, as compared to the pH sensors that are positioned along a lower portion of the sand control section  46 . 
     In response to such pH readings, the appropriate may be taken at the Earth surface of the well such as the use of mechanical or chemical diversion to temporarily block the conductive sections. After the temporary block, acidic treatment fluid may be pumped to force the acidic treatment fluid along the remainder of the interval, for example the interval adjacent the lower section of the sand control assembly  46 , and ensure an effective cleanup. The chemical or mechanical diversion may include pumping viscoelastic diverting acid (VDA), which forms a gel on contact with formation fluids or mechanical ball sealers, which temporarily plug and divert the acid, among other options. When pumped, the VDA or mechanical ball sealers flow thru the conductive sections and form a blocking gel or mechanical ball sealer blockage to limit flow through the conductive sections. 
     The pH sensors of the sand control completion system  10  may then be used to observe, from the Earth surface, various problems that occur downhole in real time or near real time so that corresponding corrective action may be undertaken to address these problems. For example, the sand control completion system  10  may include a pH sensor on the service tool  22  above the gravel pack packer  32  for purposes of detecting the arrival of the acid in a work string pickle. In this manner, if the pH reading acquired by this pH sensor indicates a detected acidity, then pumping may be ceased, and the acid may be reversed back the Earth surface. 
     As another example, fluid properties in the wellbore region during a filter cake removal or acid treatment may also be monitored. If the fluid is not being delivered to the required zones or areas, a diverter (a mechanical or chemical diverter) may be pumped to ensure that full coverage is achieved. For this purpose, the sensors may be disposed along the sand control assembly  46  and possibly along the wash pipe  22 . As another example, the fluid properties in the wellbore  14  may be measured to ensure complete displacement of fluids. If the measurements indicate the presence of a previous fluid stage, then pumping may be increased at a faster rate in order to more effectively displace the fluid. 
     It is also possible to rotate the work string  12  from the Earth surface in some situations to improve displacement. For these measurements, sensors along the sand control assembly  46  or wash pipe  22  may be used to detect the fluid properties and ensure that full displacement has occurred. As yet another example, design models may be calibrated to match bottom hole conditions in real time using bottom hole fluid properties derived from the sensors for purposes of facilitating better predictions for future events. 
     Temperature Measurements 
     The sand control completion system  10  may contain, in accordance with some embodiments of the invention, sensors to acquire distributed temperature measurements and/or measurements at discrete downhole locations. The temperature readings from the sensors may be monitored in real time or near real time at the Earth surface before, during and after the gravel pack-related operations to verify whether the operations are proceeding according to plan and if not, whether remedial steps should be taken. Such temperature measurements may be direct measurements, may be taken over time, and may, in general, be functions of the amount of fluid pumped downhole. 
     In this manner, a wide range of temperature measurements may be acquired by temperature sensors of the sand control completion system  10 , such as direct measurements and rates of change of temperature with respect to time and volume. Moreover, distributed temperature measurements, similar to distributed temperature sensing (DTS) measurements may be made, in accordance with some embodiments of the invention. 
     As a more specific non-limiting example, during circulation, temperature measurements taken along the wellbore  14  may show a decrease in temperature at certain points, which would indicate that fluid is being lost at nearby locations. In response to such reduced temperature readings, remedial action may be taken such as introducing loss control pills into well; mechanically or chemically diverting fluid; or stopping, re-designing, or continuing with the operation. In accordance with some embodiments of the invention, the sensor  68  and/or at least some of the sensors  70  (replacing or in addition to the other sensors, which are disclosed herein) may be temperature sensors. These temperature sensors may, for example measure temperatures during fracturing treatments, which indicate fluid flow information; and if predetermined temperatures are reached, zones may be isolated and separate treatments may be performed in other zones. 
     The temperature along the wellbore  14  may also be measured after a given treatment. In this manner, a technique called “the warmback technique” may be used to identify specific zones that are taking fluid during a treatment so that the zones may be isolated. Moreover, design models may be calibrated to match temperatures in real time and facilitate better predictions for future events. 
     Force/Displacement Measurements 
     In some embodiments of the invention, sensors of the sand control completion system  10  may be used to measure the displacement of the sand control completion system  10  and/or the forces that are acting on the system  10 , such as tension, stress, strain, torque, etc. These types of sensors are commonly referred to as strain gauges. Such physical measurements may be made using a strain sensor  60  (replacing or in addition to the other sensors, which are disclosed herein) that is located on the service tool  20  above the gravel pack packer  32  and a strain sensor  64  (replacing or in addition to the other sensors, which are disclosed herein) that is located on the wash pipe  22 . Additional sensors that are constructed to acquire tension measurements may be disposed on the service tool  20  between the sensor  60  and the sensor  64 . 
     Force measurements that are acquired taken by the strain sensors during the gravel pack operation may be monitored to determine whether the operation is proceeding according to the plan and if not, whether remedial actions need to be taken. For example, the sensor  72  (replacing or in addition to the other sensors, which are disclosed herein) at the bottom of the lower completion section  46  may be a strain sensor. For this example, if the sensor  72  indicates a sudden increase in compression force while the service tool  20  is being run into wellbore  14  with the lower completion section  30 , the sudden increase indicates that a restriction has been encountered. If so, and if wellbore  14  is an openhole wellbore, fluid may be pumped from the Earth surface to eliminate the restriction with the service tool  20  being raised and lowered as appropriate. If the service tool  20  becomes stuck in the wellbore  14 , the above-disclosed strain sensors may be monitored at the Earth surface while applying pulling and rotational forces from the Earth surface to ensure that the forces that are exerted on service tool  20 , the lower completion section  30  and in general, the components of the sand control completion system  10 , do not exceed equipment failure limitations. 
     The measurement of the forces acting on the work string  12  and the sand control completion system  10  may be used to control other operations, in accordance with other embodiments of the invention. For example, if the work string  12  becomes stuck, the work string  12  may be manipulated while ensuring in real time or near real time that equipment limitations are not exceeded by adjusting the surface hook load. As another example, the sensors of the sand control completion system  10  may be used to measure the tension and/or compression on downhole tools, such as the gravel pack packer  32  and the service tool  20 . In this manner, the surface hook loads may be adjusted to attain the correct tension/compression values on downhole tools for their required operation. As another example, small forces may be measured from collet indications that may be observed on the Earth surface to confirm the position of the service tool  20 . If the service tool  20  is in the wrong position, then the work string  12  may be manipulated to re-position the tool. The forces on the service tool  20  may be observed during pumping. In this regard, if the service tool  20  begins to move upwardly out of position due to the pressure below, then additional weight may be set down on the service tool  20  from the surface to keep it in place. Moreover, design models may be calibrated to match the strain in real time or near real time and facilitate better predictions for future events. 
     In accordance with some embodiments of the invention, the sand control completion equipment  10  may include sensors on the service tool  20  that are constructed to acquire measurements that are indicative of the movement of the service tool  20 . Depending on the particular embodiment of the invention, the sensors may directly measure the position of the service tool  20  and/or the sensors may indirectly measure the position of the service tool  20 . As a more specific example, in accordance with some embodiments of the invention, these sensors may be accelerometers, and the sensor  60  (replacing or in addition to the other sensors, which are disclosed herein) may be an accelerometer that acquires a measurement of the acceleration of the service tool  20 . The second integral of the acceleration with respect to time may be used for purposes of determining displacement of the service tool  20 . Depending on the particular embodiment of the invention, the sensed acceleration and/or the calculated displacement may be communicated to the Earth surface from downhole in real time or near real time so that the communicated measurements may be monitored at the Earth surface to determine whether a gravel pack-related operation is proceeding as planned (i.e., for purposes of determining whether corrective action needs to be taken). 
     For example, after the gravel pack packer  32  has been set within the casing string  16 , a test may be performed to determine whether the setting is sufficient to hold the packer  32  and the connected service tool  20  firmly in place. In conducting such a test, the hook load on the work string  12  may be increased and decreased during a push/pull test. If the sensor  60  indicates movement of the service tool  20  and the connected gravel pack packer  32 , this movement in turn indicates in real time or near real time at the Earth surface that the gravel pack packer  32  has not been set properly and additional pumping pressure is needed to set the packer  32 . Therefore, pumping pressure may be increased to set the gravel pack packer  32  before proceeding forward with a treatment. 
     In addition, the sensor  60  may be used to measure acceleration and/or displacement to more accurately place the service tool  20  into position with respect to the lower completion section  30 , which may be relatively difficult to otherwise determine from the Earth surface because of the pipe stretch. After the gravel pack packer  32  is set, the service tool  22  may be physically disconnected from the packer  32 . The service tool  22  may then be moved up and down in relation to the gravel pack packer  32  to place the seals  42  in the appropriate positions for various flow paths and with respect to the circulating port  40 . For example, the seals  42  may be positioned above and below the circulating port  40  for purposes of providing a flow path from the tubing inner bore  44  through the circulating port  40  to the annulus  34 . The slurry may then be pumped into the annulus  34  during the gravel treatment. The position of the service tool  22  with respect to the circulating port  40  may be determined based on displacement measurements from the sensor  60 . 
     Also during the gravel pack pumping operation, the measurements from the sensor  60  may be used to indicate whether, for example, the service tool  20  is moving out of position due to pressure below the service tool  20 . If so, the position of the service tool  20  may be adjusted in real time or near real time by applying additional hook load from the Earth surface. 
     Torque Measurements 
     The sand control completion system  10  may include sensors to measure torque such that the measured torque may be observed in real time or near real time at the Earth surface, in accordance with embodiments of the invention. For example, the sand control completion system  10  may contain a torque sensor on the service tool  20 , which acquires a torque measurement for the scenario in which the lower completion section  30  has become stuck and a rotational force is being applied to the work string  12  in an attempt to rotate the lower completion section  30 . The measured torque may be monitored at the Earth surface in real time or near real time for purposes of controlling the torque that is applied at the Earth surface to avoid exceeding downhole equipment limitations. 
     As non-limiting examples, the torque sensors may be disposed above the service tool  20  and may be disposed on the shoe  47  at the bottom of the string  12 . The torque may also be measured at the service tool  20  for purposes of identifying when the service tool  20  begins rotating such that the required number of turns of the work string  12  may be observed at the Earth surface in real time or near real time. For example, such turning of the work string  12  may be used for purposes of setting the gravel pack packer  32 , testing a particular position, etc. As another non-limiting example, the rotation may also be used and monitored for purposes of releasing the gravel pack packer  32 . 
     Imaging Measurements 
     The sand control completion system  10  may contain an imaging sensor  80  (shown in  FIG. 1  as being located in this non-limiting example near the bottom of the wash pipe  22  for purposes of acquiring a pack log, which may be viewed in real time or near real time from the Earth surface. As non-limiting examples, the sensor  80  may be a neutron or gamma ray-based imaging sensor for purposes of acquiring a surrounding image of the gravel pack as the service tool  20  is moved up and down. The sensor  80  may be a sonic, or acoustic, sensor, in accordance with other implementations. 
     Using the sensor  80 , the gravel pack may be logged in real time or near real time and observed from the Earth surface at the end of the gravel packing operation to ensure the presence of a sufficient coverage of the gravel around the sand control section  46 . If sufficient coverage has been obtained, then the service tool  20  is pulled out of hole. If however, the sensor  80  indicated inadequate coverage, then corrective action may be taken such as a top-off job, a job that involves pumping resin consolidation treatment downhole, screen isolation or similar remedial action to prevent sand production from unpacked areas. 
     Acoustic/Seismic Measurements 
     The sand control completion system  10  may, in general, include one or more acoustic or seismic sensors that are disposed along the service tool  20  or along the sand control section  46  for purposes of obtaining other real time or near real time downhole acoustic and/or seismic measurements in connection with gravel packing-related operations. For example, such sensors may be used to measure the downhole vibration at the service tool  20  for purposes of identifying arrival of proppant at the service tool  20  to indicate any roping in the work string  12 . Volumetric calculations may then be adjusted while the gravel slurry is being pumped. The downhole vibration along the sand control section  46  may also be observed at the Earth surface in real time or near real time to identify packing trends (e.g., alpha/beta, slurry pack, etc.) to indicate the height of the alpha wave or bridge forming. Based on the real time or near real time observations from the Earth surface, the flow rate and/or choke pressure may be regulated to ensure the correct alpha wave height and prevent bridging. 
     Flow Rate Measurements 
     The sand control completion system  10  may contain one or more flow rate sensors, in accordance with some embodiments of the invention. In this manner, the flow rate sensors may be disposed along the sand control section  47  discretely or disposed to acquire a distributed measurement, depending on the particular implementation. Using flow rate sensors, the flow rate along the wellbore region may be measured and monitored in real time or near real time from the Earth surface. Using these measurements, the location of any losses in the system may be identified and targeted with loss control pills or similar treatments. Therefore, such corrective action minimizes losses and maximizes the potential success of the treatment. 
     The above-described sensors are examples of a few sensors that may be disposed on the sand control completion system  10  for purposes of allowing downhole parameters to be remotely observed at the Earth surface in real time or near real time, in accordance some of the many potential embodiments of the invention. As yet another example, in accordance with some embodiments of the invention, the sensors to monitor downhole parameters may be formed from downhole tools, such as a packer, a service tool, a fluid loss control device, etc. This feedback may be used to identify and record tool position, verify tool activation, etc. In this manner any tool, typically referred to as an “intelligent” tool, may be used to provide this feedback. 
     The cross-over assembly  25  may be configured in various states, depending on the particular operation being performed.  FIG. 2  generally depicts a state of the cross-over assembly  25  when configured for a run-in-hole or washdown state in which a flow  200  may be communicated from the inner bore or passageway of the tubing  18  down through the wash pipe  22  and out through the bottom end of the shoe  47 , as depicted in  FIG. 2 . Thus, in this state, the circulating ports  40  and  41  are closed. 
       FIG. 3  depicts a state of the cross-over assembly  25  for the packer set/test position. In this state, the cross-over assembly  25  establishes fluid communication between the inner bore, or passageway, of the tubing  18  and the inner bore  23  of the wash pipe  22 , with communication through the circulating ports  40  and  41  being closed. 
       FIG. 4  depicts the cross-over assembly  25  in a state for squeeze/injecting. In this regard, as shown in  FIG. 4 , in this state, the cross-over assembly  25  blocks fluid communication between the inner bore  23  of the wash pipe  22  and the inner bore or passageway of the tubing  18  and allows communication through the circulating port  40 . Thus, as depicted by the flows  204 , fluid may be communicated through the inner bore of the tubing  18 , through the circulating port  40  and into the annulus  34 . 
       FIG. 5  depicts a state of the cross-over assembly  25  that may be used to establish a flow  210  that is used in the pumping of the gravel slurry and recovery of the gravel slurry fluid during a gravel packing operation. In this regard, in this state, the cross-over assembly  25  permits a flow  210  as depicted in  FIG. 5  through the following path: from the inner bore or passageway of the tubing  18 , through the circulating port  40 , into the annulus  34  (where the gravel is deposited), through the lower end of the wash pipe  22  (where the fluid from the gravel slurry returns), through the cross-over assembly  25 , through the circulating port  41  and into the casing annulus  24 , where the fluid returns to the Earth surface. 
       FIG. 6  depicts the cross-over assembly  25  for a reverse state in which fluid may be communicated between the inner bore or passageway of the tubing  18  and the annulus  24  as depicted by bi-directional arrow  220 . Thus, for this state, the cross-over assembly  25  blocks fluid communication between the inner bore of the tubing  18  and the service tool  20  below the gravel pack packer  32 , and opens the circulating port  41  to establish fluid communication between the inner bore of the tubing  18  and the annulus  24 . 
     As described in the examples discussed above, the sensors on the sand control completion system  10  may be used for purposes of monitoring and controlling various aspects of gravel packing-related operations. These operations include operations that occur prior to the beginning of the gravel packing operation in which the gravel laden slurry is communicated downhole, the gravel packing operation itself and operations after the gravel has been deposited around the sand control section  46 . Specific exemplary, non-limiting uses of the sensors of the sand control completion system  10  to control gravel packing-related operations are described below. 
     Operations Preceding Gravel Packing 
     As a first example of an operation that precedes gravel packing and may use the sensors, the mud/brine weight may be monitored during the running of the lower completion section  30  to ensure that the mud/brine weight maintains a certain degree of overbalance. Fluid density may change with temperature and although this relationship is understood, it may be difficult to accurately determine the temperature profile. Therefore, downhole pressure measurements acquired using sensors that are disposed on the sand control completion system  10  may be used to directly measure the overbalance and calculate the fluid density using depth in real time. Based on the monitored pressure and calculated fluid density, weighted fluid may then be displaced from the Earth surface to correct any fluctuations in the pressure and ensure that the pressure is at the desired level. 
     As another example of an operation that may be monitored during the running of the sand control completion system  10  downhole, the work string  12  may become stuck during the running and need to be worked free, i.e., pushed and pulled from the surface repeatedly to free the string  12 . However, exceeding the tensile and/or compressive ratings of downhole equipment is a concern. For example, exceeding the ratings may result in damage (the splitting of sand screens, for example), which may be detrimental to the sand control treatment. Although conventionally, torque and drag modeling has been used to estimate downhole forces from measured surface hook load, this modeling may be relatively subjective and difficult to verify accurately. Therefore, large safety factors have traditionally been built in, which unnecessarily limits the forces that may be applied to free the work string. 
     Therefore, by using the sensors on the sand control completion system  10  to acquire force measurements along the system  10 , the following measurements and control may be performed. First, force measurements along the sand control completion system  10  may be acquired to identify whether the work string  12  has become stuck, as well as the specific location of the sticking point. Torque measurements may also be acquired and monitored from the surface in real time or near real time for purposes of identifying the sticking point if the lower completion is being rotated. A sensor that is disposed above the service tool  20  and another at the end of the work string  12  may be used to provide information to the operator at the Earth surface in real time or near real time for purposes of identifying the location at which the work string  12  is stuck. The same sensors may be used, for example, to directly measure the local downhole forces on the downhole equipment while tensile and/or compressive forces are applied on the work string  12  in order to ensure that these forces are within the limits of the downhole equipment. 
     The sensors on the sand control completion system  10  may also be used to monitor washdown and circulation operations involving the sand control completion system  10  prior to the beginning of the gravel packing operation. During this operation, the service tool  20  is manipulated up and down the borehole. However, the end of the work string  12  may become stuck in an openhole section due to collapse or swelling, for example; and as a corrective action, fluid may need to be circulated through the wash pipe  22  for purposes of removing the material that causes the blockage and freeing the work string  12 . Traditionally, washdown operations have been performed at the highest flow rate possible for purposes of effectively removing the material. However, if a non-pressure sensitive (NPS) tool is used, the packer setting mechanism is isolated, and the limiting rate is the minimum rate that causes swabbing of the packer elements. If a standard tool (i.e., not an NPS tool) is used, then the limiting rate is the rate that causes the packer setting pressure inside the service tool  20  to be exceeded due to dynamic fluid friction. 
     Traditionally, the annular flow rate is measured at the Earth surface with a flow meter and controlled accordingly; and pressure inside the service tool may be estimated using friction models. Safety factors are included to ensure that the packer is not accidentally set in the wrong position, which means the maximum possible rate is not utilized. However, by using one or more downhole pressure sensors on the sand control completion system  10 , real time or near real time pressure reading may be acquired to allow these pressures to be monitored at the Earth surface of the well. In other words, the pressures may be monitored so that operations may be controlled to maintain the packer setting pressure below a certain threshold by adjusting the flow rate of fluid into the well from the Earth surface. This allows the highest flow rate possible and improves the chances of freeing the work string  12 . 
     One or more sensors of the sand control completion system  10  may be used to monitor the pressure that is being transmitted downhole. In this regard, the pressure that is applied internally inside the work string  12  to set the gravel pack packer  32  may not be completely transferred downhole due to compressibility and the yield effects of some fluids. It is noted that a minimum pressure is applied to fully set the gravel pack packer  32 . If this pressure is not transmitted to the packer  32 , the packer  32  is not set and several attempts may be made, thereby potentially consuming a significant amount of valuable rig time. 
     By using the pressure sensors of the sand control completion system  10 , the local pressure that is present downhole at the gravel pack packer  32  may be monitored at the Earth surface in real time or near real time so that the surface pressure may be increased until sufficient setting pressure is achieved at the gravel pack packer  32  on the very first attempt. In accordance with some embodiments of the invention, the sand control completion system  10  may include sensors inside the gravel pack packer  32  (sensors to indicate position of the thimbles or sealing rings, as non-limiting examples) for purposes of confirming whether the packer  32  has been set. 
     Pressure sensors on or near the gravel pack packer  32  may also be used for purposes of pressure testing the packer  32 . In this regard, the downhole pressure that is created at the packer for purposes of testing packer elements is not traditionally completely known due to compressibility and yield effects of the fluid. Moreover, pressure below the gravel pack packer when set traditionally has not been exactly known as the region below the packer is isolated by packer&#39;s annular seal. Therefore, conventional pressure tests may not be entirely accurate. 
     However, by using sensors that deployed on the sand control completion system  10 , the precise local, downhole pressures and more specifically, the precise differential pressures across the packer&#39;s sealing ring may be monitored in real time or near real time from the Earth surface. Therefore, an operator at the Earth surface may take the appropriate measures (adjusting a flow rate of a surface-disposed pump, for example) so that the downhole pressure(s) are adjusted to meet the requirements of the test. 
     The pressure test also traditionally is conducted for purposes of detecting leakage. In this regard, leakage may occur around the packer&#39;s annular seal, through the casing string  16  or even through Earth surface lines (a faulty valve, for example). However, these leakages may be relatively difficult to identify, which may incur a significant amount of valuable rig time. Traditionally, the surface lines may be isolated and tested independently to ensure that the leak is not there, which again consumes valuable rig time; and leaking through the casing string  16  and various downhole elements may be relatively difficult to discriminate from the surface pressure alone. 
     However, pressure sensors of the sand control completion system  10 , which are disposed below the gravel pack packer  32  may be used to monitor the pressure below the packer  32  in real time or near real time from the Earth surface for purposes of identifying an increasing pressure (which indicates that the seal element of the packer  32  is leaking) in response to an increase in the applied pressure from the Earth surface. In this manner, if the leak is occurring through, for example, the casing string  16  or the surface lines, and the monitored pressure below the packer  32  is not increasing, then a leaking packer  32  may be quickly eliminated as the potential problem. 
     A push/pull test may be conducted on the work string  12  prior to the beginning of the gravel packing operation to determine whether the gravel pack packer  32  is set. In a deep, or highly deviated or horizontal well, it has traditionally been challenging to determine how much force is being transmitted downhole due to such effects as pipe buckling and friction against the casing string. Therefore, traditionally, there may not be enough weight being slacked off or picked up on the Earth surface to obtain a proper test on the packer for purposes of determining whether the packer is set. Therefore, a false positive may result if the weight is actually being slacked off on the casing string, for example. Conventionally, torque and drag modeling has been used to estimate downhole forces from a measured surface hook load. However, this modeling may be relatively subjective and difficult to verify accurately. 
     In accordance with embodiments of the invention described herein, however, the sensors of the sand control completion system  10  may be used to measure force in real time or near real time so that this force may be monitored at the Earth surface for purposes of providing an accurate measurement of the transmitted force so that the surface hook load may be regulated to ensure that the push/pull test is performed at the required downhole rating. The sensors of the sand control completion system  10  may also be used to acquire accelerometer measurements such that these measurements may be monitored in real time or near real time at the Earth surface to observe relatively small movements downhole, which may be especially helpful in deep, highly deviated wells. 
     In the cased hole environment, a sump packer (not shown in  FIG. 1 ) supports the lower completion and a push test on the gravel pack packer may be rather inaccurate. Additionally, if an anchor latch is used with the sump packer, then the pull test may also be relatively inaccurate. Therefore, under certain circumstances, it may not have been traditionally possible to perform either a push or pull test to verify that the slips are set, they are assumed to be set if the packer pressure test is successful. Traditionally, the weight on the packer is offset, and corresponding movement of the string is observed from the surface to verify whether or not the slips are set. In this manner, if no movement is observed, then the slips are properly set. However, using sensors on the sand control completion system  10 , tension/compression measuring sensors of the system  10 , which are disposed on either side of the gravel pack packer  32  may be observed in real time or near real time at the Earth surface for purposes of determining whether the slips are set. 
     The sensors on the sand control completion system  10  may also be used to observe/confirm the release of the service tool  20 . In this regard, as a non-limiting example, pressure may be applied internally to the work string  12  for purposes of releasing the service tool  20 . However, this pressure applied internally to the work string  12  from the surface of the well may not completely be transferred downhole due to compressibility and yield effects of the fluid. It is noted that a minimum pressure is needed to release the service tool  20 . 
     If the appropriate pressure is not transmitted to the service tool  20 , then the service tool  20  does not release, and several attempts may be made before using, for example, a backup mechanical release, which, in turn, may consume a significant amount of valuable rig time. Therefore, traditionally, the minimum required pressure is applied at the Earth surface, and then a pull up force is exerted on the work string  12 . If the service tool  20  does not release, then this process is repeated with a higher pressure up to a certain maximum pressure threshold. Eventually, if the service tool is not released, then the string may be rotated to release the service tool mechanically. 
     Unlike these conventional arrangements, however, pressure sensors on the sand control completion system  10  may be used to monitor the downhole local pressure that is present at the service tool  20 . Therefore, an operator monitoring this pressure in real time or near real time at the Earth surface may increase the pressure until the required release is achieved to release the service tool  20  in the first attempt. It is noted that, in accordance with some embodiments of the invention, sensors disposed in the service tool  20  may be used to provide a real time or near real time indication to the operator at the Earth surface whether or not the service tool  20  has been released. As non-limiting examples, the sensors may measure the position of the service tool  20  relative to the lower completion section  30 , measure a relative position of a collet that latches the service tool  20  in place, etc. 
     It is noted that the pressure below the gravel pack packer  32  may have bled off to the formation, thereby creating a net downward force on the service tool  20 , and this force need to be overcome for purposes of moving the service tool  20  uphole. In this regard, if not enough weight is being picked up on the work string  12  to overcome this force, the incorrect impression that the service tool  20  has not released may be observed. Thus, unnecessary attempts may be made to release the service tool  20  or engage the mechanical back up release of the service tool  20 , which consume valuable rig time. 
     Traditionally, the worst case pressure differential across the service tool  20  is assumed, and the force to be applied to the work string at the Earth surface is calculated accordingly, using, for example, torque and drag modeling software. These measurements may be relatively difficult to verify and may not be entirely accurate. However, by using sensors on the sand control completion system  10 , the exact pressure differential that is experienced by the tool  20  may be monitored at the Earth surface in real time or near real time. The sensors may also allow the surface operator to monitor the force that is applied to the service tool  20  to ensure that the correct force is applied to the tool  20  downhole. 
     As described above, sensors may also be deployed on the service tool  20  for purposes of indicating whether the service tool  20  has been successfully released, and sensors of sand control completion system  10  may also be used to measure torque to verify whether the service tool is being rotated in the event that the mechanical backup release mechanism of the service tool  20  is engaged. 
     Conventionally, during the movement of a service tool, especially more complex service tools, it has been traditionally been challenging to locate certain downhole positions quickly or accurately. In this manner, the accidental shearing of collets may make it very challenging to find a given position. Moreover, on deep, highly deviated wells, it may be relatively difficult to observe indications provided by location identifying collets on the Earth surface, especially if the collets have become worn. Furthermore, the heave on floating rigs may result in unintended downhole movements that accidentally shear collets or move the service tool out of position. The position of the service tool may be relatively important in certain parts of the operation, such as reversing out after screenout. 
     In accordance with embodiments of the invention, the sand control completion system  10  may include one or more sensors to the position of the service tool  20  so that the Earth surface operator may monitor the actual position of the tool  20  in real time or near real time without inferring the position from other measurements. In this manner, one or more sensors on the sand control completion system  10  may measure acceleration so that a second order integration of the measured acceleration may be used to determine the position of the service tool  20 . It is noted that the initial position of the service tool  32  may be inferred from the position of the service tool  20  when the tool  20  is latched to the lower completion section  30 . The sensors may also acquire downhole force measurements, which allow the Earth surface operator to observe collect indications that may not be observable from the Earth surface. 
     The movement of the service tool uphole may create a swabbing effect in the wellbore above the gravel pack packer  32 , due to the fact that this region is isolated (i.e., a closed volume). This may typically be a significant concern in open hole completions. The swabbing creates a pressure reduction in the wellbore which, on becoming lower than the reservoir pressure, may create a suction to draw in fluid from the reservoir and damage the filtering cake, which is placed along the openhole during drilling. Therefore, the swabbing may create losses in the wellbore area, which may have a detrimental effect on the sand control treatment. Traditionally, anti-swab service tools are used for openhole completions, which minimize this effect, although openhole treatments may also be performed with standard tools, that do not contain the anti-swabbing features. Even with an anti-swab service tool, however, the service tool conventionally is moved relatively slowly in order to allow the pressure to equalize throughout the process. 
     By using sensors on the sand control completion system  10  to monitor the downhole pressure, the pressure below the service tool  20  may be monitored in real time or near real time to allow this pressure to be managed during the movement of the service tool  20  by varying the service tool&#39;s speed and even stopping, if needed. Moreover, acceleration measurements acquired using the accelerometers on the sand control completion system  10  may be used to monitor the actual tool movement of the service tool  20  in real time or near real time so that this movement may be controlled from the Earth surface and kept within acceptable limits. 
     Sensors of the sand control completion system  10  may also be used to detect the presence of pickle stages (gel caps, acid, etc), which, if not for the measures described herein, may be accidentally displaced through the service tool  20  and into the annulus  34 , which is not desirable. The pickle, in general, cleans the work string  12  and picks up debris (rust, etc.) in the process, which would otherwise settle on top of the packer seal elements if pushed into the annulus and may introduce problems in retrieving the packer  32  as well as contribute to the sticking of the service tool  20 . In this regard, the acid may attack the packer&#39;s seal element and cause damage, thereby resulting in a leak that would be detrimental to the gravel pack and future operations. 
     Traditionally, the workstring pickle has been performed with the service tool in the reverse position, pumping the pickle down the workstring to within 100 to 200 feet from the top of the gravel pack packer before reversing the pickle back to the Earth surface through the annulus. Displacements are therefore calculated theoretically assuming that the piston/block fluid interfaces and flow. However, these calculations may not be entirely accurate. In this manner, roping, u-tubing and non-uniform displacements may result in fluid stages arriving at the packer earlier than expected. 
     Therefore, in accordance with embodiments of the invention disclosed herein, one or more fluid property sensors of the sand completion system  10  (sensors disposed on the tubing  18 , for example) acquire downhole rheology/viscosity/density measurements so that these measurements may be communicated to the Earth surface of the well in real time or near real time to allow the surface operator to determine when fluid stages arrive downhole due to detected fluid property changes. These measurements may also be used to account for roping and non-uniform displacement effects, which cause the fluid to arrive earlier than expected theoretically, ensuring that pumping is stopped at the surface before the pickle is displaced into the annulus  34 . It is noted that in accordance with other embodiments of the invention, the stages may be detected using pressure and temperature readings that are provided by temperature and pressure sensors of the sand control completion system  10 , although more indirectly. Moreover, in accordance with some embodiments of the invention, one or more of the sensors of the sand control completion system  10  may measure pH, which allow the surface operator to determine the location of the acid. 
     The sensors of the sand control completion system  10  may also be used by the surface operation to determine whether a certain fluid or fluids are completely displaced from a given section. Fluid displacements typically are conducted to ensure that chemically incompatible fluids do not contact one another. However, a fluid may not be completely displaced from the section due to non-uniform displacements, losses or rates too low to achieve turbulence. If the fluid is not completely displaced, the fluid may have a negative effect on a latter part of the operation. 
     Traditionally, the fluids are displaced using a flow that is introduced at the surface at the highest possible rate to achieve turbulence, subject to the rate being limited to ensure that an estimated downhole pressure does not exceed a threshold. Moreover, safety margins typically are introduced, which further limit the rate. However, by using fluid property measurements (rheology, viscosity, density, etc.) that are provided by the fluid property sensor(s) of the sand control completion system  10 , these measurements may be monitored in real time or near real time from the Earth surface to directly measure the displacement and mixing of different fluids. 
     Pressure may also be acquired by one or more sensors of the sand control completion system  10  for purposes of ensuring that equipment limitations and fracturing pressures are not exceeded, thereby allowing the maximum flow rates be pumped for effective displacement. In this manner, the rates may be adjusted from the Earth surface for purposes of achieving complete displacement. The sand control treatment model may be calibrated using data conducted from step rate tests. Traditionally, certain variables of the model have been calibrated using Earth surface-acquired pressure magnitudes and trends. However, these measurements have not considered bottomhole pressures, due to the data being previously available. Using pressure measurements acquired by the sensor(s) of the sand control completion system  10 , bottomhole conditions may be accurately monitored at the Earth surface in real time or near real time so that the sand control treatment model may be calibrated using surface-acquired as well as these downhole-acquired measurements. Therefore, a more accurate model may be obtained. 
     One or more sensors of the sand control completion system  10  may also be used to provide the Earth surface operator with indications whether various problems have occurred with the step rate test. For examples, these problems include restriction in the system, debris in the service tool, wellbore collapse, screen plugging, and so forth. Depending on where the restriction is located, the restriction may have different effects on the operation. For example, a restricted flow through the cross-over assembly  25  may create a relatively high risk of screening out at the cross-over port. Wellbore collapse or shale swelling may increase the risk of bridging, while screen plugging prevents the formation of a tight pack in the corresponding section. Conventionally, step rate tests are performed at multiple rates in reverse and circulating positions of the service tool for purposes of gauging the surface pressure. In this manner, the measured surface pressure has conventionally been compared to surface pressures measured in similar wells for purposes of obtaining a relative idea of the magnitude. 
     Although a relatively high surface pressure may indicate a restriction, this indication alone does not identify the location of the restriction. However, using downhole pressure measurements acquired by one or more sensors of the sand control completion system  10 , downhole pressure measurements may be used to identify exactly where a restriction is located downhole due to the increased friction at that point. For example, a wellbore collapse shows additional pressure drop in that section of the openhole only. Similarly, debris in the service tool  20  is indicated by the detection of friction there but not in the open hole. 
     Depending on the scenario, a corresponding action may be taken from the Earth surface based on the real time or near real time pressure measurements. For example, debris in the service tool  20  may result in the operator pulling the string  20  out of hole and running a backup service tool instead. Wellbore collapse provides an indication of where bridging occurs in a shunt tube job so that the job may be designed correspondingly. For open hole water packing jobs (i.e., no shunt tubes), the operator may rectify the situation before proceeding. 
     One or more sensors of the sand control completion system  10  may also be used to identify locations where fluid losses are occurring in the well. In this regard, fluid losses occur when the fluid return rate is less than a fluid pump rate at the Earth surface. These losses may cause bridging during the gravel pack treatment, which may terminate the job completely or force fluid through the shunt tubes (if used). Losses at the heel of the well may have a far different effect than losses at the toe of the well. However, conventional systems do not permit discrimination as to the precise location of the fluid losses. 
     One or more sensors of the sand control completion system  10  may, however, be used to allow multiple downhole rate measurements to be acquired along the screens or sandface; and these measurements may be monitored by the surface operator in real time or near real time to identify where losses are occurring. As described above, these rate measurements may be acquired directly or may be acquired indirectly using pressure or temperature measurements. In general, losses at the heel of the well may be far more detrimental to the sand control job than losses at the toe, so the measured rate measurements permit an informed decision to be made. The location of any potential bridging may also be therefore determined and considered when pumping the treatment. 
     Thus, referring to  FIG. 7 , a technique  300  includes running (block  304 ) a sand control completion system into a well and using (block  308 ) the system to prepare the well for an upcoming gravel packing operation in which the system is used to communicate a slurry downhole and form a gravel pack around a lower completion. At the Earth surface of the well, parameters that are sensed by sensors disposed on the system are monitored in real time or near real time, pursuant to block  312 ; and in response one or more of the monitored parameters, the running of the system into the well and/or the use of the system to prepare the well for gravel packing is regulated, pursuant to block  316 . 
     Gravel Packing Operation 
     The sensors of the sand control completion system  10  may be used for purposes of monitoring the actual gravel packing operation in which a gravel-laden slurry is communicated downhole through the work string  12 , the carrier fluid returns uphole via the annulus  24  and the gravel is deposited about the sand control section  46  (see flow  210  of  FIG. 5 , for example). In this manner, one or more sensors of the sand completion system  10  may be used to monitor a variety of downhole parameters during the gravel packing operation in order to allow the operator at the Earth surface of the well to take any appropriate action to regulate the gravel packing operation. 
     As a non-limiting example, one or more pressure sensors of the sand control completion system  10  may be used to monitor a screenout pressure. In this scenario, the screenout pressure below the gravel pack packer  32  may be monitored in real time or near real time at the Earth surface and may be used to anticipate the screenout. It is noted that the screenout may be a premature screenout due to bridging and resulting in shunt activation. Based on the monitored screenout pressure, the slurry flow rate and proppant concentration may be regulated from the Earth surface in order to ensure that the screenout is achieved within the limitations of the equipment and system downhole. This control scheme removes the need for large safety factors when designing the well and choosing the appropriate equipment, potentially reducing cost, complexity, etc. 
     As another example, the operator may monitor parameters in real time or near real time provided by one or more sensors of the sand control completion system  10  for purposes of monitoring for a condition called “roping.” In general, roping results in the slurry stages arriving bottomhole earlier than expected volumetrically. Although traditionally, models may be used to predict roping, these models may be relatively inaccurate, due to the inability to conventionally monitor the actual downhole conditions. However, by using one or more sensors on the sand control completion system  10 , fluid properties may be monitored at the Earth surface in real time or near real time to detect changes in fluids so that the arrival of certain fluid stages downhole may be accurately measured. Moreover, pressure measurements provided by certain sensors of the sand control completion system  10  may also be used for this purpose. This allows the surface operator to know exactly when certain trends or changes are expected and react accordingly, such, for example, by changing the rate at which fluid is pumped downhole. 
     During the gravel packing operation, the service tool  20  may be forced up out of position during high pressure pumping due to a net upward force that is exerted on the tool  20 . If the circulating port  41  (see  FIG. 5 , for example) moves into the gravel pack packer  32 , there is sudden unexpected pressure increase that may damage downhole equipment. In an open hole water packing treatment, such a scenario may terminate the job due to screenout at the cross-over assembly  25 . 
     Traditionally, calculations may be made (based on simulations and pressure predictions, for example) for the worst case scenario for the net upward force exerted on the service tool  20  during the treatment. A weight is set down on the service tool  20  using torque and drag modeling to calculate this from the surface hook load. However, these procedures typically involve assumptions and are difficult to verify accurately. By using one or more sensors of the sand control completion system  10 , the service tool&#39;s position may be monitored indirectly or directly in real time or near real time at the Earth surface for purposes of allowing the surface operator to detect when the service tool  20  is moving and even calculate the distance that the service tool  20  has moved in real time. One or more sensors of the sand control completion system  10  may also be used to measure a net force that is exerted on the service tool  20 , which obviates the need to calculate this force based on assumptions. 
     If due to these measurements, the surface operator observes a movement in the service tool  20 , more weight may be set down from the surface to push the service tool  20  back into the appropriate position. 
     One or more sensors of the sand control completion system  10  may be used to monitor for the occurrence of bridging (packing occurring in an unexpected place) during the gravel packing operation. In an open hole water packing job, bridging may end the job prematurely and prevent the area beneath the bridge from being packed. In a job involving shunt tubes, bridging may force fluid through the shunt tubes, which means that the surface rates/pressures are subsequently controlled to ensure that the limitations of the shunt tubes are not exceeded. 
     More specifically, in accordance with some embodiments of the invention, pressure sensors that are disposed along the sand control assembly  46 , such as the sensors  70  (see  FIG. 1 , for example), measure pressures (which are communicated to the Earth surface in real time or near real time) to identify which section is being packed through changes in friction, which are indicated by the pressure measurements. Monitoring of the bridging may be useful in multi-zone and openhole isolation jobs where there may be multiple sections that are simultaneously packing. If bridging is observed, the surface operator may take the appropriate measures to limit, prevent or delay the bridging, such as increasing or decreasing the rate at which the slurry is pumped downhole, for example. 
     One or more sensors (such as pressure sensors, for example) on the sand control completion system  10  may be used for purposes of allowing the surface operator to monitor whether a hole forms in the sand control section  46  (see  FIG. 1 , for example) during the gravel packing operation. For example, a hole may form in a sand control screen. A hole in the sand control section  46  allows gravel to displace into the wash pipe  22  (see  FIG. 1 ) and into the casing annulus  24  above the packer  32 , which risks significant equipment damage as well as the possibility of the service tool  20  becoming stuck. Traditionally, it is relatively difficult to observe that hole has formed in the sand control section, as it is usually discovered when there is no screenout but a significant amount of gravel is reversed after the treatment. At this point, the risk has been taken unknowingly and damage may or may not have occurred. 
     In accordance with some embodiments of the invention, the surface operator may determine whether a hole has formed in the sand control section  46  based on pressure measurements that are acquired by the sand control completion system&#39;s sensors. The packing mechanism may be completely different to the mechanism that is expected, as it takes place inside the screens and thus, may be detected early on using such pressure sensors. Acceleration measurements acquired by accelerometers placed on the sand control completion system  10  may also be used to detect the presence of gravel inside the screens. 
     After the surface operator identifies the formation of a hole in the sand control section  46  in real time or near real time using the sensors, the operator may then stop the job and reverse the slurry out before the slurry enters the casing annulus  24 . Other remedial measures includes pulling the sand control completion assembly  46  out of hole or other remedial treatments. 
     One or more sensors on the sand control completion system  10  may be used, in general, to observe at the Earth surface whether the gravel packing operation has proceeded as planned. Traditionally, a successful gravel packing operation may not be confirmed until the service tool is pulled out of hole and data from any memory gauges of the tool are downloaded and analyzed. However, because the sand control completion system  10  allows data to be monitored at the Earth surface in real time or near real time, the operator has the peace of mind knowing that everything is going well throughout the treatment. Moreover, the next phase or operation for the well may be planned even before the service tool  20  has been retrieved from the well. 
     Thus, referring to  FIG. 8 , a technique  350  in accordance with embodiments of the invention disclosed herein includes running (block  354 ) a sand control completion system into a well and using (block  358 ) the system to perform a gravel packing operation in which the system is used to communicate a slurry to form a gravel pack around a lower completion. At the Earth surface of the well, sensors that are disposed on the system are monitored in real time or near real time, pursuant to block  362 . The technique  350  includes, in response to one or more of the monitored parameters, regulating (block  366 ) the gravel packing operation to control a screenout pressure and/or control positioning of a service tool of the system. 
     Operations Proceeding Gravel Packing 
     One or more sensors of the sand control management system  10  may also be used to monitor operations that occur after the gravel pack has been formed. For example, in accordance with some embodiments of the invention, one or more sensors of the sand control completion system  10  may be used to monitor in real time or near real time the pressure of the casing annulus  24  while the service tool  20  is being moved to prevent u-tubing into the annulus  24 . In this regard, gravel in the casing annulus  24  may cause the service tool  20  to become stuck in the packer bore during movement. If the service tool cannot be freed, relatively extreme action may be needed, such as chemical cut or even a side track. Traditionally, the theoretical hydrostatic difference in pressure between the tubing and annulus is calculated, and then an additional safety margin (500 pounds per square inch (psi), for example) may be added. However, these calculations assume ideal displacements and do not account for roping effects and non-uniform displacements. By using one or more sensors of the sand control completion system  10  to measure pressure, the exact hydrostatic pressure on screenout may be monitored in real time or near real time from the Earth surface. Therefore, the correct pressure may be applied without the need to add excessive safety factors. 
     One or more sensors of the sand control completion system  10  may also be used to detect and free the work string  12  if the work string  12  becomes stuck when going to reverse out position. In this manner, without the use of the sensor(s), it may not be possible to determine precisely the location at which the work string  12  is stuck. In this manner, the work string  12  may be stuck at the wash pipe  22 , at the service tool  20 , etc. Therefore, it is unclear as to how much upward force may be exerted on the work string  12  without exceeding the stuck component&#39;s tensile rating. Therefore, traditionally, it is assumed that the component of the work string  12 , which has the minimum tensile rating is stuck; and the work string  12  is worked within those limits. If the work string  12  is not freed, then the exerted force is increased to the next lowest minimum tensile rating, etc. 
     Torque and drag modeling traditionally has been used to calculate the downhole force from the surface-applied force. However, this modeling may not be accurate or verifiable. Therefore, by using one or more sensors disposed on sand control completion system  10 , several determinations may be made in real time or near real time: first, the component that is stuck may be identified by, for example, pulling upwardly on the work string  12  and then measuring the force at various points downhole to see where it is being transmitted; and secondly, the work string  12  may then be worked within the limits of the stuck component&#39;s maximum tensile rating by adjusting the surface force to get the required force downhole, as measured directly downhole and provided to the surface operator. 
     One or more sensors of the sand control completion system  10  may further be used to monitor and regulate the removal of the filter cake and/or an acid treatment. In this manner, although fluid may be communicated downhole through the end of the wash pipe  22  for the removal of filter cake, the filter cake and gravel pack fluid may not be effectively cleaned up, which results in reduced retained permeability and increased skin, which have negative effects on subsequent production. 
     Traditionally, the workstring is moved up and down along the sandface while pumping the treatment to ensure that the treatment is spotted along the entire interval. However, it is not possible to know exactly where the fluid is being communicated, especially if there are losses somewhere along the wellbore. Although traditional equipment may contain memory gauges that may provide an indication as to this condition, the string is already retrieved from the well when the data is retrieved from the gauges. However, using the sensors of the sand control completion system  10 , fluid changes may be detected by corresponding pressure, temperature or fluid property measurements acquired by the sensors such that an operator at the Earth surface may monitor in real time or near real time where a given fluid is being communicated downhole in the well. Therefore, the operator may adjust the rate of fluid being pumped into the well and/or position the wash pipe  22  more accurately to treat the required interval. The remedial action may also include, in certain cases, pumping diverting agents or similar corrective fluid downhole to direct the fluid. 
     The sensors of the sand control completion system  10  may also be used to monitor the work string  12  when the string  12  is pulled out of hole, or retrieved from the well. In this manner, as described above, the various sensors of the sand control completion system  10  may monitor the forces present on the string  12  during removal, etc. 
     Thus, referring to  FIG. 9 , a technique  400  in accordance with embodiments of the invention includes using (block  404 ) a downhole sand control system to perform a downhole gravel packing operation to form gravel pack around a lower completion. At the Earth surface of the well, parameters that are sensed by sensors disposed on the system are monitored in real time or near real time, pursuant to block  408 . After formation of the gravel pack, the technique  400  includes performing (block  412 ) one or more subsequent operations using the system before pulling the service tool of the system from the well, pursuant to block  412 . In response to the one or more monitored parameters, the technique  400  includes regulating (block  416 ) one or more of the subsequent operations. 
     While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.