Abstract:
A person-carried hydrogen sulfide instrument is adapted for use with a conventional SCADA system or other type of fault monitoring system normally intended for monitoring well-related conditions at a well site. In response to detecting an abnormally high concentration of hydrogen sulfide gas, the instrument triggers the fault monitoring system to record an H2S fault and convey that information to a remote computer. In some embodiments, the instrument includes a signal relay unit that listens to a conventional H2S monitor. The signal relay unit has a learning mode that teaches the unit to recognize an audible alarm from the H2S monitor. In response to hearing the H2S alarm, the signal relay unit emits a trigger signal to the fault monitoring system.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The subject invention pertains to the hazards of hydrogen sulfide and more specifically to a personal system for responding to an excessive amount of hydrogen sulfide. 
   2. Description of Related Art 
   Hydrogen sulfide, H2S, is a toxic gas that often accompanies the production of gas, oil and water. H2S can usually be contained, but if it escapes, an H2S monitor can be used for alerting personnel in the area. In response to sensing about 10 to 20 ppm of H25, typical H2S monitors will sound an alarm that warns of the danger. Once the alarm sounds, personnel often have sufficient time to vacate the area. In some cases, however, someone or everyone in the area may be overcome by the gas and fall to the ground. Since H2S is heavier than air, an unconscious person lying on the ground may continue breathing the toxic gas. If outside help is not quickly summoned to the area, eventually those continuing to breath the gas may die. 
   U.S. Pat. No. 6,252,510 discloses an H2S system that calls for outside help upon sensing an excessive amount of H2S at a distant location. The system appears to be designed for an established chemical plant where the H2S monitor is at a fixed, known location. Such a system may be fine for monitoring hydrogen sulfide gas at a particular location, but it may be inadequate for protecting an individual moving from one location to another. 
   In the case of an outdoor well site that includes a stationary H2S monitor, an undetected problem may occur if a hydrogen sulfide leak is downwind of the H2S monitor, and an oilfield worker is downwind of the leak. The worker may be exposed to the hydrogen sulfide gas, but the monitor may fail to detect the leak. 
   Today, H2S monitors, various fault monitoring systems, and wireless communications are used for monitoring conditions at a well site. SCADA (Supervisory Control And Data Acquisition) is perhaps the most common system for monitoring the pumping conditions at a well site and for communicating pumping-related faults to another location. Various transducers that sense a pumping condition (e.g., fluid pressure, fluid level, power failure, etc.) are hardwired to the hardware portion of the SCADA system. Hardwiring a person-carried H2S monitor to a SCADA system, unfortunately, would drastically limit the portability of the H25 monitor. Thus, person-carried H2S monitors are generally stand-alone devices that simply sound an alarm upon sensing a certain concentration of hydrogen sulfide gas. Such an alarm, however, may not necessarily alert outside help. 
   Consequently, a need exists for a completely portable, person-carried H2S monitor that can summon help from a remote location. It may be beneficial to have such a system where an existing conventional H2S monitor can be incorporated into a conventional SCADA system, thereby avoiding the cost of an entirely new monitor and communication system. 
   SUMMARY OF THE INVENTION 
   It is an object of some embodiments to provide a person-carried H2S monitor that communicates with a stationary fault monitoring system, which in turn communicates with a distant host computer. 
   It is an object of some embodiments to provide a personal alarm system where an existing conventional H2S monitor can be incorporated into a conventional SCADA system, thereby avoiding the cost of an entirely new monitor and communication system. 
   It is an object of some embodiments to use a microphone to help communicate an H2S fault to a fault monitoring system such as a SCADA system. 
   It is an object of some embodiments to provide a signal relay unit with a leaning mode so that the unit can adapt itself to different types of H2S monitors. 
   It is an object of some embodiments to provide a signal relay unit with a leaning mode for learning and storing multiple audible alarm patterns so that the unit can respond to a variety of H2S monitors. 
   It is an object of some embodiments to store the occurrence of an H2S fault event until a host computer pings the fault monitoring system. 
   It is an object of some embodiments to send an inquiry signal or ping a fault monitoring system to establish the location of where an H2S fault may have occurred. 
   It is an object of some embodiments to use a SCADA or other type of fault monitoring system to monitor pumping-related faults at fixed locations within a well site and to monitor H2S-related faults at indeterminate locations within the well site. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  is a schematic diagram showing a personal alarm system for responding to hydrogen sulfide gas at a well site. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  is a schematic diagram illustrating a personal alarm system  10  for detecting hydrogen sulfide gas  12  at a well site  14 , which is at a remote location relative to a host computer  16 . The term, “remote” refers to a distance of at least ten miles. 
   Alarm system  10  comprises a person-carried alarm instrument  18  and a fault monitoring system  20 , wherein fault monitoring system  20  is placed (e.g., mounted, parked, installed, set up, etc.) at a generally fixed location at well site  14 . System  20  can be any electrical system for receiving, storing and transmitting electrical signals. In some embodiments, fault monitoring system  20  is a conventional SCADA (Supervisory Control And Data Acquisition) system for monitoring and recording the conditions of a well-related operation  22  at well site  14  and making the stored monitored information, particularly well-related faults, available to host computer  16 . A pressure sensor  24 , for example, may send an operational fault signal  26  when the pumping pressure (or other operational characteristic, such as flow rate, temperature, liquid level, strain, load, etc.) at well site  14  is abnormal. Well-related operation  22  is schematically illustrated to represent operations that include, but are not necessarily limited to, producing gas, water or petroleum; repairing a well; servicing a well; inspecting a well; etc. In some cases, a service vehicle  23  can be used to help facilitate performing well-related operation  22  and can be used to transport system  20  to well site  14 . 
   In cases where conventional SCADA software is used, host computer  16  accesses the stored monitored information by pinging system  20 , whereby an alarm status signal  28  corresponding to fault signal  26  is conveyed to host computer  16  via a wireless communication link  30 . Computer  16  can ping fault monitoring system  20  by sending an inquiry signal  32  to system  20  via wireless communication link  30 . Inquiry signal  32  and the pinging process enables computer  16  to access well-related data of a particular well site that is at a location known to computer  16 . 
   In other cases, however, fault monitoring system  20  provides alarm signal  28  over wireless communication link  30  without having to first be pinged. In such cases, system  20  may also provide a well location signal  35  that indicates the location of well site  14 . Well location signal  35  can be in the form of an address, APIN or well number, or a gps reading (coordinates of a conventional global positioning system). Host computer  16  is thus informed of the H2S fault and its location. 
   Another wireless communication link  34  places fault monitoring system  20  in communication with person-carried alarm instrument  18 . The term, “person-carried” refers to an item having one or more features that makes the item readily carried by a person. Such person-carried features include, but are not limited to, a belt clip, pocket clip, strap, compact size, lightweight, etc. Alarm instrument  18  is shown being carried by an oilfield worker  36 , so instrument  18  actually travels or moves relative to fault monitoring system  20 . 
   Upon sensing that a concentration of hydrogen sulfide gas  12  has reached a predetermined limit (e.g., 10 ppm), person-carried alarm instrument  18  provides a trigger signal  38 . Wireless communication link  34  conveys trigger signal  38  to fault monitoring system  20 , and fault monitoring system  20 , in turn, provides an alarm status signal  40 . The other wireless communication link  30  then conveys alarm status signal  40 , and in some cases well location signal  35  and well-related operation data such as alarm status signal  28 , to one or more designated host computers  16 . In some embodiments, alarm status signals  28  and  40  are both communicated to computer  16  upon computer  16  pinging fault monitoring system  20 . Alarm status  40  corresponds to trigger signal  38 , so host computer  16  is notified that a hydrogen sulfide gas problem has occurred at well site  14 . Thus, host computer  16  can be used for dispatching assistance to well site  14 . 
   Wireless communication link  34  can be of various forms including, but not limited to, radio waves, infrared, spread spectrum, etc. Communication link  34  can have a range of a few hundred feet, which is appreciably less than that of communication link  30 . Communication link  30  has a range of several miles, which can be achieved using technology such as satellite communications, radio waves, cell phone technology, etc. In some embodiments, communication with one or more host computers  16  involves the use of the Internet. 
   Alarm instrument  18  can be a single unit or may comprise two separate units. With two separate units, alarm instrument  18  may comprise a conventional H2S monitor  42  and a signal relay unit  44  Signal relay unit  44  provides a way for a conventional H2S monitor to communicate with a conventional SCADA system, such as fault monitoring system  20 . The functional relationships of fault monitoring system  20 , H2 3  monitor  42 , and signal relay unit  44  can be further understood with a description of their operation. 
   When H2S monitor  42  senses that the concentration of hydrogen sulfide gas  12  exceeds a predetermined allowable limit, monitor  42 , being a conventional H2S monitor, sounds an audible alarm signal  46 . Signal relay unit  44  includes a microphone  48  that detects alarm signal  46 , and signal relay unit  44  responds by generating trigger signal  38 . A receiver  50  associated with fault monitoring system  20  receives trigger signal  38  and responds by recording the event on fault monitoring system  20 . The H2S fault is recorded or stored to ensure that the awareness of the event is not lost before computer  16  pings fault monitoring system  20  or before alarm status signal  40  is communicated to computer  16 . For instance, if computer  16  only pings fault monitoring system  20  once every ten minutes, computer  16  should receive alarm status signal  40  even if alarm signal  46  were cleared prior to system  20  being pinged. The step of recording the event can be carried out by tripping a conventional latch relay or storing the event on some other type of a memory (e.g., integrated circuit) of system  20 . Such a memory or latch relay is schematically illustrated by numeral  52 . 
   Since existing conventional H2S monitors may provide different sounding alarm signals, signal relay unit  44  includes a learning mode  54  for teaching unit  44  to recognize the sound of a particular alarm signal and to distinguish that sound from other extraneous or background sounds. When operating in learning mode  54 , signal relay unit  44  listens to alarm signal  46  and stores its various attributes, which may include, but are not limited to, pitch, volume, waveform, tone, pulsating pattern, etc. Afterwards, signal relay unit  44  is returned to its normal operating mode where unit  44  listens for the alarm signal it just learned to recognize while in its learning mode. Such a learning process is based on common voice recognition technology, which is practiced by Sensory, Inc. of Santa Clara, Calif. 
   In some cases, signal relay unit  44  can be taught to recognize several different audible alarm patterns. This allows unit  44  to be paired up with different models of H2S monitors without having to repeat the learning process for each individual H2S monitor. Signal relay unit  44  would then emit trigger signal  38  if any one of several known alarm patterns were detected. 
   Although the invention is described with reference to a preferred embodiment, it should be appreciated by those skilled in the art that other variations are well within the scope of the invention. Also, it should be noted that the various elements, such as those represented by numerals  16 ,  20 ,  22 ,  23 , and  36  are drawn out of scale to show more or less detail depending on the need. Therefore, the scope of the invention is to be determined by reference to the claims, which follow.