Abstract:
One embodiment of a system for determining a wellbore parameter includes a pulse generator positioned in fluid communication with a wellbore such that a fluid can flow from the wellbore through the pulse generator, wherein the pulse generator selectively releases the fluid to flow through the pulse generator causing pressure pulses in the wellbore; a receiver in operational connection with the wellbore, the receiver detecting the pressure pulses; and a controller in functional connection with the receiver, the controller determining a wellbore parameter from receipt of a signal from the receiver in response to the detected pressure pulses.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 10/992,060 filed Nov. 18, 2004. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to well production and more specifically to determining wellbore parameters. 
       BACKGROUND 
       [0003]    In the life of most wells the reservoir pressure decreases over time resulting in the failure of the well to produce fluids utilizing the formation pressure solely. As the formation pressure decreases, the well tends to fill up with liquids, such as oil and water, which inhibits the flow of gas into the wellbore and may prevent the production of liquids. It is common to remove this accumulation of liquid by artificial lift systems such as plunger lift, gas lift, pump lifting and surfactant lift wherein the liquid column is blown out of the well utilizing the reaction between surfactants and the liquid. 
         [0004]    Common to these artificial lift systems is the necessity to control the production rate of the well to achieve economical production and increase profitability. It is common for the production cycle of a particular lift system to be estimated based on known well characteristics and then adjusted over time through trial and error. Prior art systems have been utilized to automate the control system such that incremental changes are automatically implemented in the production cycle until the lift system fails, and then the production cycle is readjusted to a point before failure. A need still exists for a method and system for obtaining wellbore parameters in real-time to optimize an artificial lift system in real-time. 
       SUMMARY 
       [0005]    One embodiment of a system for determining a wellbore parameter includes a pulse generator positioned in fluid communication with a wellbore such that a fluid can flow from the wellbore through the pulse generator, wherein the pulse generator selectively releases the fluid to flow through the pulse generator causing pressure pulses in the wellbore; a receiver in operational connection with the wellbore, the receiver detecting the pressure pulses; and a controller in functional connection with the receiver, the controller determining a wellbore parameter from receipt of a signal from the receiver in response to the detected pressure pulses. 
         [0006]    An embodiment of a method for determining a wellbore parameter includes the step of releasing a burst of fluid from the wellbore causing a pressure pulse in the wellbore; detecting the pressure pulse; and determining a wellbore parameter utilizing the detected pressure pulse. 
         [0007]    The foregoing has outlined some of the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The foregoing and other features and aspects of the present invention will be best understood with reference to the following detailed description of a specific embodiment of the invention, when read in conjunction with the accompanying drawings, wherein: 
           [0009]      FIG. 1  is a schematic drawing of a well production optimizing system of the present invention; 
           [0010]      FIG. 2  is a schematic drawing of a well production optimizing system utilizing plunger lift; 
           [0011]      FIG. 3  is a partial cross-sectional view of a flow-interruption pulse generator of the present invention; and 
           [0012]      FIG. 4  is a view of another embodiment of a flow-interruption pulse generator of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. 
         [0014]    As used herein, the terms “up” and “down”; “upper” and “lower”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements of the embodiments of the invention. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point. 
         [0015]      FIG. 1  is a schematic drawing of a well production optimizing system of the present invention, generally denoted by the numeral  10 . The figure is illustrative of well under artificial lift production, which may include systems such as, but not limited to, gas lift, surfactant lift, beam pumping, and plunger lift. The well includes a wellbore  12  extending from the surface  14  of the earth to a producing formation  16 . Wellbore  12  may be lined with a casing  18  including perforations  20  proximate producing formation  16 . The surface end of casing  18  is closed at surface  14  by a wellhead generally denoted by the numeral  24 . A casing pressure transducer  26  is mounted at wellhead  24  for monitoring the pressure within casing  18 . 
         [0016]    A tubing string  22  extends down casing  18 . Tubing  22  is supported by wellhead  24  and in fluid connection with a production “T”  28 . Production “T”  28  includes a lubricator  30  and a flow line  31  having a section  32 , also referred to as the production line, upstream of a flow-control valve  34 , and a section  36  downstream of flow-control valve  34 . Downstream section  36 , also referred to generally as the salesline, may lead to a separator, tank or directly to a salesline. Production “T”  28  typically further includes a tubing pressure transducer  38  for monitoring the pressure in tubing  22 . 
         [0017]    Wellbore  12  is filled with fluid from formation  16 . The fluid includes liquid  46  and gas  48 . The liquid surface at the liquid gas interface is identified as  50 . With intermittent lift systems it is necessary to monitor and control the volume of liquid  46  accumulating in the well to maximize production. 
         [0018]    Well production optimizing system  10  includes flow-control valve  34 , a flow-interruption pulse generator  40 , a receiver  42  and a controller  44 . Flow-control valve  34  is positioned within flow line  31  and may be closed to shut-in wellbore  12 , or opened to permit flow into salesline  36 . 
         [0019]    Flow-interruption pulse generator  40  is connected in flow line  31  so as to be in fluid connection with fluid in tubing  22 . Although pulse generator  40  is shown connected within flow line  31  it should be understood that pulse generator  40  may be positioned in various locations such that it is in fluid connection with tubing  22  and the fluid in wellbore  12 . 
         [0020]    Pulse generator  40  is adapted to interrupt or affect the fluid within the tubing  22  in a manner to cause a pressure pulse to be transmitted down tubing  22  and to be reflected back upon contact with a surface. Pulse generator  40  is described in more detail below. 
         [0021]    Receiver  42  is positioned in functional connection with tubing  22  so as to receive the pressure pulses created by pulse generator  40  and the reflected pressure pulses. Receiver  42  recognizes pressure pulses received and converts them to electrical signals that are transmitted to controller  44 . The signal is digitized, and the digitized data is stored in controller  44 . 
         [0022]    Controller  44  is in operational connection with pulse generator  40 , receiver  42  and flow-valve  34 . Controller  44  may also be in operational connection with casing pressure transducer  26 , tubing pressure transducer  38  and other valves (not shown). Controller  44  includes a central processing unit (CPU), such as a conventional microprocessor, and a number of other units interconnected via a system bus. The controller includes a random access memory (RAM) and a read only memory (ROM), and may include flash memory. Controller  44  may also include an VO adapter for connecting peripheral devices such as disk units and tape drives to the bus, a user interface adapter for connecting a keyboard, a mouse and/or other user interface devices such as a touch screen device to the bus, a communication adapter for connecting the data processing system to a data processing network, and a display adapter for connecting the bus to a display device which may include sound. The CPU may include other circuitry not shown herein, which will include circuitry found within a microprocessor, e.g., an execution unit, a bus interface unit, an arithmetic logic unit (ALU), etc. The CPU may also reside on a single integrated circuit (IC). 
         [0023]    Controller  44  may be located at the well or at a remote locations such as a field or central office. Controller  44  is functionally connected to flow-control valve  34 , receiver  42 , and pulse generator  40  via hard lines and/or telemetry. Data from receiver  42  may be received, stored and evaluated by controller  44  utilizing software stored on controller  44  or accessible via a network. Controller  44  sends signals for operation of pulse generator  40  and receives information regarding receipt of the pulse from pulse generator  40  via receiver  42  for storage and use. The data received by controller  44  is utilized by controller  44  to manipulate the production cycle, during the production cycle in real-time, to optimize production. Controller  44  may also be utilized to display real-time as well as historical production cycles in various formats as desired. 
         [0024]    An example of the operation of optimizing system  10  is described with reference to  FIG. 1  to determine the liquid level in tubing  22 . Controller  44  sends a signal to pulse generator  40  to create a pressure pulse within tubing  22 . Pulse generator  40  and its operation is disclosed in detail below. The pressure pulse travels down tubing  22  and is reflected back up tubing  22  upon encountering objects or surfaces such as liquid surface  50 , plungers, collars, sub-surface formation and the like. Receiving unit  42 , which is in fluid or sonic connection with pulse generator  40  and tubing  22  receives the pulse from pressure generator  40  and the reflected pressure pulses. The pulse received is converted to an electrical signal and transmitted to controller  44  for storage and use. This data received by controller  44  may be filtered and analyzed by the controller to determine well status information such as, but not limited to, the position of liquid surface  50 , liquid volume in the well, and the change in liquid level  50  over time. Controller  44  may then utilize this information to operate flow-control valve  34  between the open and closed position as necessary. 
         [0025]      FIG. 2  is a schematic drawing of a well production optimizing system  10  utilizing a plunger-lift system. The well includes a wellbore  12  extending from the surface  14  of the earth to a producing formation  16 . Wellbore  12  may be lined with a casing  18  including perforations  20  proximate producing formation  16 . The surface end of casing  18  is closed at surface  14  by a wellhead generally denoted by the numeral  24 . A casing pressure transducer  26  is mounted at wellhead  24  for monitoring the pressure within casing  18 . 
         [0026]    A tubing string  22  extends down casing  18 . Tubing  22  is supported by wellhead  24  and in fluid connection with a production “T”  28 . Production “T”  28  includes a lubricator  30  and a flow line  31  having a section  32 , also referred to as the production line, upstream of a flow-control valve  34 , and a section  36  downstream of flow-control valve  34 . Downstream section  36 , also referred to as the salesline, may lead to a separator, tank or directly to a salesline. Production “T”  28  typically further includes a tubing pressure transducer  38  for monitoring the pressure in tubing  22 . 
         [0027]    A plunger  52  is located within tubing  22 . A spring  54  is positioned at the lower end of tubing  22  to stop the downward travel of plunger  52 . Fluid enters casing  18  through perforations  20  and into tubing  22  through standing valve  56 . Lubricator  30  holds plunger  52  when it is driven upward by gas pressure. A liquid slug  58  is supported by plunger  52  and lifted to surface  14  by plunger  52 . 
         [0028]    Well production optimizing system  10  includes flow-control valve  34 , a flow-interruption pulse generator  40 , a receiver  42  and a controller  44 . Flow-control valve  34  is positioned within flow line  31  and may be closed to shut-in wellbore  12 , or opened to permit flow into salesline  36 . 
         [0029]    Plunger-lift systems are a low-cost, efficient method of increasing and optimizing production in wells that have marginal flow characteristics. The plunger provides a mechanical interface between the produced liquids and gas. The free-traveling plunger is lifted from the bottom of the well to the surface when the lifting gas energy below the plunger is greater than the liquid load and gas pressure above the plunger. 
         [0030]    In a typical plunger-lift system operation, the well is shut-in by closing flow-control valve  34  for a pre-selected time period during which sufficient formation pressure is developed within casing  18  to move plunger  52 , along with fluid collected in the well, to surface  34  when flow-control valve  34  is opened. This shut-in period is often referred to as “off time.” 
         [0031]    After passage of the selected “off-time” the production cycle is started by opening flow-control valve  34 . As plunger  52  rises in response to the downhole casing pressure, fluid slug  58  is lifted and produced into salesline  36 . In the prior art plunger-lift systems when plunger  52  reaches the lubricator its arrival is noted by arrival sensor  60  and a signal is sent to controller  44  to close flow-control valve  34  and end the cycle. It also may be desired to allow control-valve  34  to remain open for a pre-selected time to flow gas  48 . The continued flow period after arrival of plunger  52  at lubricator  30  is referred to as “after-flow.” Upon completion of a pre-selected after-flow period controller  44  sends a signal to flow-control valve  34  to close. Thereafter, plunger  52  falls through tubing  22  to spring  54 . The production cycle then begins again with an off-time, ascent stage, after-flow, and descent stage. 
         [0032]    Optimizing system  10  of the present invention permits the production cycle of the plunger-lift system to be monitored and controlled in real-time, during each production cycle, to optimize production from the well. Controller  44  may be initially set for pre-selected off-time and after-flow. To control and optimize the well production, controller  44  intermittently operates pulse generator  40  creating a pressure pulse that travels down tubing  22  and is reflected off of liquid surface  50  and plunger  52 . The pressure pulse and reflections are received by receiver  42  and sent to controller  44  and stored as data. Controller  44  may receive further data such as casing pressure  26 , tubing pressure  38  and flow rates into salesline  36 . Additional, data such as well fluid compositions and characteristics may be maintained by controller  44 . This cumulative data is monitored and analyzed by controller  44  to determine the status of the well. This status data may include data, such as, but not limited to liquid surface  50  level, fluid volume in the well, the rate of change of the level of liquid surface  50 , the position of plunger  52  in tubing  22 , the speed of travel of plunger  52 , and the in-flow performance rate (IPR). The status data may then be utilized by controller  44  to alter the operation of the production system. This status data may also be utilized by controller  44  or an operator to determine the wear and age characteristics of plunger  22  for replacement or repair. 
         [0033]    For example, during the off-time the well status data may indicate that the downhole pressure is sufficient to lift the accumulated liquid  46  to surface  14  before the pre-selected off-time has elapsed. Or that the liquid volume is accumulating to a degree to inhibit the operation of plunger  52 . Controller  44  may then open flow-control valve  34  to initiate production. 
         [0034]    In another example, as plunger  52  ascends in tubing  22 , the well status data calculated and received by controller  44  may indicate that the rate of ascension is too fast and may result in damage to plunger  52  and/or lubricator  30 . Controller  44  may then signal flow-control valve  34  to close or restrict flow through valve  34  thereby slowing or stopping the ascension of plunger  52 . 
         [0035]    In a further example, controller  44  may recognize that plunger  52  is ascending too slow, stalled or falling during the ascension stage. Controller  44  may then close flow-control valve  34  to terminate the trip, or further open flow-control valve  34  or open a tank valve to allow plunger  52  to rise to lubricator  30 . 
         [0036]    In a still further example, during after-flow the controller  44  well status data may indicate that liquid  46  is accumulating in tubing  22 , therefore controller  44  can signal flow-control valve  44  to close and allow plunger  52  to descend to spring  54 . Then a new production cycle may be initiated. 
         [0037]    As can be determined by the examples of operation of optimizing system  10 , an artificial lift system can be controlled in real-time in a manner not heretofore recognized. Although operation of optimizing system  10  of the present invention is disclosed with reference to a plunger-lift system in  FIG. 2 , optimizing system  10  is adapted for operation in any type of artificial or intermittent lift system including gas lift and surfactant lift. 
         [0038]      FIG. 3  is a partial cross-sectional view of a flow-interruption pulse generator  40  of the present invention. Pulse generator  40  includes a valve body  62  forming a fluid channel  64 , a cross-bore  66  intersecting channel  64  and a piston  68 . Electromagnetic solenoids  70  and  72  are connected to the first and second ends  66   a  and  66   b  of bore  66  respectively. Solenoids  70  and  72  are functionally connected to controller  44  ( FIGS. 1 and 2 ) for selectively venting bore  66  and motivating movement of piston  68 . Operation of solenoids  70  and  72  moves piston head  74  from the second end  66   b  of bore  66  into channel  64  and then back into bore  66 . 
         [0039]    Operation of pulse generator  40  to create a pressure pulse is described with reference to  FIGS. 1 through 3 . Pulse generator  40  is connected within flowline  31  through channel  64 . Controller sends a signal to solenoid  70  to vent motivating piston  68  and moving piston head  74  into channel  64 . Controller  44  then sends a signal to solenoid  72  to vent motivating piston  68  and moving piston head  74  from channel  64  and toward second bore end  66   b . This fast acting movement of piston head  74  into flow channel  64  creates a pressure pulse that travels through the fluid in flowline  31  and tubing  22 . 
         [0040]      FIG. 4  is a view of another embodiment of a flow-interruption pulse generator  40  of the present invention. Pulse generator  40  includes a fast acting, motor driven valve  76  in fluid connection with flowline  31 . Motor driven valve  76  is in operational connection with controller  44 . To create a pressure pulse in flowline  31  and tubing  22 , controller  44  substantially instantaneously opens and closes valve  76  releasing gas from flowline  31 . Pulse generator  40  may include a vent chamber  78  connected to fast-acting valve  76 . Vent chamber  78  may further include a bleed valve  80  to facilitate bleeding gas captured in vent chamber  78  to be discharged to the atmosphere. 
         [0041]    From the foregoing detailed description of specific embodiments of the invention, it should be apparent that a method and apparatus for monitoring and optimizing an artificial lift system that is novel and unobvious has been disclosed. Although specific embodiments of the invention have been disclosed herein in some detail, this has been done solely for the purposes of describing various features and aspects of the invention, and is not intended to be limiting with respect to the scope of the invention. It is contemplated that various substitutions, alterations, and/or modifications, including but not limited to those implementation variations which may have been suggested herein, may be made to the disclosed embodiments without departing from the spirit and scope of the invention as defined by the appended claims which follow.