WO2013055366A1

WO2013055366A1 - Geological seismic sensing node stimulus event summary information

Info

Publication number: WO2013055366A1
Application number: PCT/US2011/056403
Authority: WO
Inventors: Anton Nicholas Clarkson; Neel Banerjee
Original assignee: Hewlett-Packard Development Company, L.P.
Priority date: 2011-10-14
Filing date: 2011-10-14
Publication date: 2013-04-18

Abstract

A self-contained geological seismic sensing node comprises a geological seismic sensing element to sense seismic data representing seismic reflections occurring in response to predefined seismic stimulus events. The node transmits summary information of the sensed geological seismic data to a recipient external to the sensing node.

Description

GEOLOGICAL SEISMIC SENSING NODE STIMULUS EVENT SUMMARY INFORMATION

BACKGROUND

[0001] Geological seismic sensors or nodes are sometimes used to detect and map underground resources such as oil, natural gas, mineral deposits and the like. Raw seismic data continuously produced by such nodes is stored and time indexed at the node and is continuously streamed to a collection center. The time indexed nature of the raw data and its continuous transmission may burden transmission, power and analytical resources.

BRIEF DESCRIPTION OF THE DRAWINGS

[0002] Figure 1 is a schematic illustration of an example geological seismic sensing system.

[0003] Figure 2 is a schematic illustration of an example geological seismic sensing node of the system of Figure 1.

[0004] Figure 3 is an example timeline of sensed geological seismic data, pre-and post- seismic stimulus event notifications and seismic stimulus events.

[0005] Figure 4 is a flow diagram of an example method for storing seismic data at the seismic sensing node of Figure 2.

[0006] Figure 5 is a diagram of an example layout of seismic data elements stored in a memory of the seismic sensing node of Figure 2.

[0007] Figure 6 is a diagram of another example layout of seismic data elements stored in a memory of the seismic sensing node of Figure 2.

[0008] Figure 7 is a flow diagram of another example method for storing seismic data at the seismic sensing node of Figure 2.

[0009] Figure 8 is a diagram of another example layout of seismic data elements stored in a memory of the seismic sensing node of Figure 2. [0010] Figure 9 is a flow diagram of an example method for generating summary information for a seismic stimulus event.

[0011] Figure 10 is a flow diagram of an example method for transmitting summary information for a seismic stimulus event.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

[0012] Figure 1 schematically illustrates an example geological seismic sensing system 20. Seismic sensing system 20 stores and indexes seismic data at each node based upon predefined source-stimulus events rather than utilizing a time based index. As a result, retrieval and analysis of the geological seismic data is improved in terms of power consumption, retrieval latency and storage efficiency. In some examples, seismic data not associated with a stimulus event is discarded, preserving valuable storage space and conserving the energy associated with storing that data in non-volatile storage. Seismic sensing system 20 transmits summary information based upon the data captured from a source-stimulus event, rather than a continuous stream of raw seismic data, reducing transmission load.

[0013] Seismic sensing system 20 comprises seismic stimulator source 22, geological seismic sensing nodes 24, 25 and data collection center 28. Seismic stimulator 22 comprises a device configured to generate and apply a predefined geological seismic stimulus to ground 30 in discrete events. As shown by Figure 1, the seismic stimulus creates seismic waves 32. As indicated by arrows 34, the seismic waves reflect off of underground geological structures or formations and these reflections are sensed by sensor nodes 24, 25. Examples of seismic stimulator 22 include, but are not limited to, dynamite impulses, accelerated weight drops or seismic vibrator vibrations, such as seismic vibrator vehicles, such as a VIBROSEIS seismic vibrator, which produces frequency swept seismic signals or chirps.

[0014] Geological seismic sensing nodes 24, 25 comprise individual self-contained sensing units dispersed at spaced locations in contact with ground 30 over a geological area which is to be examined for the existence of a resource 32. Each sensing node 24, 25 is configured to sense seismic data representing seismic reflections in the ground 32 occurring in response to predefined seismic stimulus events produced by seismic stimulator 22. In the example illustrated, each sensing node 24, 25 includes one or more accelerometer sensing elements having sensitivity levels of less than 200 ng/VHz with a dynamic signal range of less than lg to detect weak motion events In one example, the sensing elements of each sensing node 24, 25 have sensitivity levels of less than 200 ng/VHz with a dynamic signal range of at least 1 g. In other examples, each sensing node may alternatively comprise a geophone. As shown by Figure 1, sensor nodes 24 may be placed in contact with the surface of ground 30. Other sensor nodes, such as sensor node 25, may be placed below the surface of ground 30.

[0015] Each sensing node 24, 25 is further configured to store the sensed seismic data. In particular, each sensing node 24, 25 is configured to determine whether an individual piece of data is part of a series of samples occurring in response to a seismic stimulus produced by seismic stimulator 22 representing seismic reflections from the stimulus in ground 30. Each node 24, 25 may determine whether sensed raw seismic data is associated with a particular predefined seismic stimulus event generated by stimulator 22 by one of various methods. According to one example method, each node 24, 25 is provided with a calendar or time schedule of forthcoming predefined seismic stimulus events. In one example, the stimulus event calendar may be provided in the memory of each node 24, 25 upon manufacture, configuration or deployment. In another example, the stimulus event calendar or schedule may be communicated via a wired or wireless fashion to each of nodes 24, 25.

[0016] In yet another example, node 24, 25 may receive a notification of an

immediately forthcoming seismic stimulus event or a recently transpired seismic stimulus event. Such notification may be transmitted or communicated to each node 24, 25 in a wired or wireless fashion. In yet another example, such notification may be provided by an acoustic ground coupling, wherein the notification is represented or formed by the generation of seismic signals in ground 30 which are sensed by nodes 24, 25. For example, in embodiments where seismic stimulator 22 comprises a seismic vibrator source, the seismic vibrator source may communicate with each of nodes 24, 25 by generating and emitting one or more predefined signal patterns proceeding or immediately after a seismic vibrator chirp notifying nodes 24, 25 of the forthcoming stimulus event or a recently transpired stimulus event. The signal patterns produced by the seismic vibrator source may additionally provide information regarding the upcoming or transpired stimulus event. For example, the signal patterns may indicate a start time of a stimulus event, stop time of a stimulus event, a time until next stimulus event or time since the end of a last stimulus event. In such an example, each node 24, 25 includes circuitry or computer readable program instructions followed by processor to recognize the signal patterns to translate and determine the stimulus event information from the signal patterns. In other implementations, the nodes 24, 25 could also be signaled through an audible method such as with accelerometers sensitive to airborne pressure waves.

[0017] Accordingly yet another example, each node 24, 25 may include circuitry or processor instructions provided as part of a computer or processor readable medium that analyzes the raw seismic data to identify the start and end of a seismic stimulus event based upon the raw seismic data. In one example, the determination of the occurrence of the stimulus event may be achieved using a predefined profile of a stimulus event, wherein the times at which a raw seismic data matches or approximates the profile are the times identified as during which the seismic stimulus event is taking place. In another example, the determination of the occurrence of the stimulus event may be based upon other techniques.

[0018] In embodiments where nodes 24, 25 are individually capable of determining a beginning and an end of a seismic stimulus event, node 24, 25 may be additionally configured to communicate their determinations to other of nodes 24, 25. As a result, a particular node 24, 25 which may have misdiagnosed notification signals and may not be aware of a seismic stimulus event, may be made aware of the seismic stimulus event from another of the nodes 24, 25. Such internode communication may be used to confirm or validate an individual node's determination of a start or stop time of a forthcoming or completed seismic stimulus event. In one example, one of nodes 24, 25 may be provided with a seismic stimulus event schedule, wherein the particular node is responsible for communicating the schedule to other nodes in the network of nodes which are not provided with the schedule.

[0019] Once a particular node 24, 25 determines that a seismic stimulus event is about to take place, is in the process of taking place or has fully taken place, the node 24, 25 assigns the previous, current and future data captured resulting from the predefined stimulus event generated by seismic stimulator 22 in a data structure that represents that stimulus event occurrence. Because each piece of raw seismic data is indexed based upon the predefined seismic stimulus event generating the seismic data, rather than merely being indexed based upon time, more efficient and potentially more accurate retrieval and analysis of the sensed geological seismic data is achieved. In one example, sensed seismic data not identified as belonging to or occurring as a result of a predefined seismic stimulus event produced by seismic stimulator 22 is discarded, conserving memory or storage space. The discarded data not tied to a seismic stimulus event also is not used in calculations or processing which improves the accuracy of the analysis as the process only analyzes data that has resulted from a stimulus event.

[0020] As further schematically illustrated by Figure 1, each of sensor nodes 24, 25 is configured to communicate with data collection center 28. According to one example, each of sensor nodes 24, 25 may communicate with data collection center 28 via a cable or other wired connection. In another example, each of nodes 24, 25 may communicate with data collection center 28 via a wireless connection. Each sensor node 24, 25 uses such communication avenues to communicate seismic information to data collection center 28.

[0021] According to one example, each node 24, 25 is further configured to perform analysis of the sensed geological data and to transmit results of such analysis to data collection center 28. The analyzed results or "quality control" (QC) information indicate whether the survey is operating correctly (nodes 24, 25are seeing seismic stimulus events). By reporting QC information back in terms of stimulus events, survey control is enabled to make faster more accurate decisions on how to proceed with the survey based on nodes clearly informing them that they saw the seismic event and providing summary data which informs survey control with how "well" they saw the event.

[0022] In one example, the data is transmitted to an intermediate survey control station which forwards the data to the data collection center 28. Each node 24, 25 is configured to transmit summary information of the sensed geological seismic data to data collection center 28. In one example, the summary information is transmitted to data collection center 28 in addition to the transmission of raw seismic data, reducing analytical load of data collection center 28. In another example, the summary information is transmitted to data collection center 28 in place of raw seismic data. As a result, network or transmission loads are reduced, consuming less transmission bandwidth.

[0023] The summary information communicated to data collection center 28 may include various selected pieces of information regarding seismic reflections sensed by a particular node 24, 25. In one example, the summary information may comprise a summary of all raw seismic data that is sensed during a predefined time period. In another example, the summary information may comprise a summary of sensed raw seismic data that has been identified or determined to be associated with a predefined seismic stimulus event produced by stimulator 22.

[0024] According to one example, the summary information may comprise one or more selected pieces of the actual raw seismic data which satisfies some predefined criteria. In other words, the summary information comprises selected portions of the sensed geological seismic data while other portions of the sensed geological seismic data are not part of the summary information. For example, the summary information may comprise a selected piece of raw seismic data that has been determined to constitute a minimum amplitude value, a peak amplitude value or a median amplitude value.

[0025] The summary information may also or alternatively comprise a mathematical summary which is calculated using or based upon the raw seismic data, either all the raw geological seismic data or just the raw geological seismic data tagged to a predefined stimulus event. For example, the summary information may comprise a root mean squared value of the sensed geological seismic data or degree of fit between the sensed geological seismic data and a predefined profile. In addition to including selected pieces of raw seismic data or including mathematical calculations or summaries based upon such raw seismic data, the summary information may include information such the time at which a stimulus event started, the time at which the stimulus event ended, the length of the stimulus event or the like.

[0026] Data collection center 28 receives information from nodes 24 and analyzes such data to identify and potentially map the existence of resource 32 in ground 30. In another example, some or most of the analysis may alternatively be subsequently performed at another analytical center. In the example illustrated, data collection center 28 communicates with each of nodes 24, 25 in a wired or wireless fashion. In the example illustrated, data collection center 28 receives the aforementioned summary information through the wired or wireless connection during a survey based upon the determined starting and ending points of a stimulus event, wherein upon completion of the survey, the nodes 24, 25 or memory storage portions of such nodes 24, 25 are removed, collected and transported to the data collection center 28 or transported to a facility remote from the original selected sensing locations of nodes 24, 25 that transmits information indexed or assigned from nodes 24, 25 to data collection center 28. The information stored on the memory storage device of the collected nodes 24, 25 is indexed based upon or assigned to specific determined are identified stimulus events. This information is then extracted from the collected nodes 24, 25 (or memory storage devices of such nodes) for analysis.

[0027] Data collection center 28 (schematically shown) comprises communication device 40, memory 42, output 44 and processing unit 46. Communication device 40 comprises a device configured to facilitate wireless communication between data collection center 28 and nodes 24, 25. In another example, communication device 40 may alternatively be configured to facilitate wired communication between data collection 28 and nodes 24, 25.

[0028] In yet other examples, data collection center 28 may not be configured to communicate with nodes 24, 25, wherein nodes 24, 25, or memory storage portions of nodes 24, 25, are physically removed, collected and transported to data collection center 28 or transported to a facility remote from the original selected sensing locations of nodes 24, 25 that transmits information from nodes 24, 25 to data collection center 28. In such an embodiment, communication device 40 may be configured to extract raw seismic data and other information regarding identified seismic events from the collected nodes 24, 25 or the collected memory storage portions of nodes 24, 25. In such an embodiment, nodes 24, 25 may not transmit the above-described summary information, but instead individually store the summary information for later extraction. According to yet other examples, such notice 24, 25 may not generate such summary information, but instead store raw seismic data indexed based upon determined are identified predefined seismic stimulus events.

[0029] Memory 42 comprises one or more persistent storage devices configured to store data and serve as a non-transient tangible computer readable medium containing code or instructions to be carried out by processor 46. Memory 42 may be used to store seismic information and data received from nodes 24, 25. Memory 42 contains instructions directing processor 46 to analyze such information to identify and potentially map the existence of resource 32.

[0030] Output 44 comprises one or more devices facilitating the output of data and the output of results generated from such data. Output 44 may include one or more monitors or displays. Output 44 may include one or more printers. Output 44 may include one or more portable memories are storage devices upon which data and results may be recorded. Output 44 may comprise a communication device to communicate with other data collection centers or a central collection center.

[0031] Processor 46 comprises one or more processing units configured to analyze the seismic data received or extracted from nodes 24, 25 following instructions contained in memory 42. Processor 46 analyzes such data to identify and potentially map the existence of resource 32 in ground 30. For purposes of this application, the term

"processing unit" shall mean a presently developed or future developed processing unit that executes sequences of instructions contained in a memory. Execution of the sequences of instructions causes the processing unit to perform steps such as generating control signals. The instructions may be loaded in a random access memory (RAM) for execution by the processing unit from a read only memory (ROM), a mass storage device, or some other persistent storage. In other embodiments, hard wired circuitry may be used in place of or in combination with software instructions to implement the functions described. For example, processor 46 may be embodied as part of one or more application-specific integrated circuits (ASICs). Unless otherwise specifically noted, the controller is not limited to any specific combination of hardware circuitry and software, nor to any particular source for the instructions executed by the processing unit.

[0032] Figure 2 schematically illustrates geological seismic sensing node 124, one example of an individual geological seismic sensing node 24. As shown by Figure 2, node 124 comprises housing 126, sensing element 128, memory 130, communication device 132, GPS 133 and processing unit 134. Housing 126 comprise one or more structures surrounding a substantially enclosing the remaining components of node 124 such that node 124 comprises a self-contained geological seismic sensing unit. Housing 126 may have a variety of sizes, shapes and configurations.

[0033] Sensing element 128 comprises one or more elements configured to contact ground 30 (shown in Figure 1) when resting upon a surface to ground 30 (as in the case of nodes 24) or when buried below the surface of ground 30 (as in the case of node 25). In the example shown, sensing element 128 includes a prong or probe 136 configured to be inserted through the surface of ground 30 into ground 30 to facilitate more intimate direct contact with ground 30. As shown by broken lines, in another example, sensing element 128 may include one or more surface pads or pucks 138 which contact ground 30. In one example, sensing element 128 includes an accelerometer for sensing seismic reflections resulting from a predefined seismic stimulus produced by seismic stimulator 22 (shown in Figure 1). In the example shown, seismic sensing element 128 has sensitivity levels of less than 200 ng/VHz with a dynamic signal range or signal level of at least 1 g. In yet other embodiments, seismic sensing element 128 may have other configurations and may use other sensing technologies. [0034] Memory 130 comprises one or more persistent storage devices configured to store data and serve as a non-transient tangible computer readable medium containing code or instructions to be carried out by processing unit 134. In the example shown, memory 130 comprises a random access memory for temporary storage of data and a more permanent storage device. Memory 42 may be used to store seismic information and data received from nodes 24, 25. Memory 42 contains instructions directing processing unit 134 to determine or identify the forthcoming or prior occurrence of a predefined seismic stimulus event and to assign raw seismic data to such identified stimulus events. Memory 42 further contains instructions directing processing unit 134 to generate summary information from the raw sensed seismic data that has been assigned to or tagged with a stimulus event, wherein the summary information may be stored or communicated to data collection center 28 (described above). In one example, memory 42 further contains instructions directing processing unit 134 to discard raw sensed seismic data determined to be unrelated or not resulting from the occurrence of a predefined geological seismic stimulus event. In another example, the summary information may alternatively be generated from all raw seismic data, rather than being limited to raw seismic data specifically tagged to a stimulus event.

[0035] Communication device 132 comprises one or more devices configured to communicate with data collection center 28 in a wired or wireless fashion. For example, communication device 132 may comprise a wired port (USB port or the like) or wireless transceiver. In another example, communication device 132 may be omitted, wherein node 124 is physically extracted and collected or wherein memory 130 or selected portions a memory 130, such as a memory card, are physically extracted, collected and transported to a data collection center 28.

[0036] Global positioning system (GPSS) comprises a space-based global navigation satellite system (GNSS) that provides location and time information. GPS 133 communicates with a satellite to provide processing unit 134 location and time information, wherein processing unit 134 may utilize such information in the analysis of sensed seismic data. In other examples, GPS 133 may be omitted where other mechanisms are used for time or location information.

[0037] Processing unit 134 comprises one or more processing units configured to carry out instructions contained in memory 130. As described above, processing unit 134, following instructions contained in memory 130, determines or identifies a predefined seismic stimulus event and stores raw seismic data in memory 130 with an index or other identifier indicating which identified stimulus event resulted in the particular piece of seismic data. Processing unit 134 may additionally analyze the raw seismic data to generate summary information, or the summary information may be stored or transmitted to data collection center 28. In the example illustrated, processing unit 134, and its circuitry, are remotely located within housing 126 from sensing element 128. As a result, node 124 experiences less noise and improved sensitivity.

[0038] Figures 3-6 describe one example mode of operation of node 124 in which node 124 stores seismic data (D) based upon determined seismic stimulus events (SE). Figure 3 is a timeline 200 of data sensing, stimulus notifications and predefined geological seismic events. Figure 4 is a flow diagram outlining a method 210 of operation for node 124 (or any of nodes 24, 25). Figures 5 and 6 illustrate different examples of storage of sensed seismic data in memory 130 by node 124.

[0039] As shown by Figure 3, sensing element 128 senses a series of pieces of raw seismic data Di-D_N over time. During such time, node 124 further receives stimulus event notifications S_N. In the example shown, node 124 receives notification of an upcoming start of a first predefined seismic stimulus event SEi between the reception of Data D₃ and D₄ and receives notification of an upcoming start (a pre-notification) of a second predefined seismic stimulus event SE₂ between the reception of Data D₉ and Di₀. Node 124 further receives notification following the completion (a post notification) of the first seismic stimulus event SEi between the reception of Data D₇ and D₈ and receives notification following the completion of the second seismic stimulus event SE2 between the reception of data Di₃ and Di₄. As noted above, node 124 utilizes such notification to determine the time during which a predefined, artificially or man-made generated seismic stimulus event occurred and to further determine which of data pieces or elements D were the result of the stimulus event. As a result, node 124 is given both the starting and ending points or time of a seismic stimulus event. In other examples, node 124 may alternatively determine the time of a seismic stimulus event including its starting and ending points using either the pre-notification or the post notification and an expected length or predefined length or duration of a stimulus event. Node 124 may alternatively determine the time of a seismic stimulus event as well as its starting and ending points using one of a pre-notification or post notification in combination with the analyzed characteristics of data D. In still other examples, both of such notifications may be omitted, wherein node 124 is provided with a schedule containing the starting and ending times of multiple stimulus events which are to take place or which have taken place.

[0040] As shown by step 216 of method 210 illustrated in Figure 4, sensing element 128 of node 124 senses seismic data D which occurs over time as shown in Figure 3. Node 124 senses or receives such seismic data in a continuous or periodic fashion. As indicated by step 218, processing unit 134 stores the received seismic data D in memory 130 as it is received. As indicated by step 220, for each data element D, processing unit 134 determines whether the data element D occurred during a period of time during which a predefined geological seismic stimulus event was taking place. In other words, processing unit 134 determines whether the data element D represents reflections of a geological seismic wave introduced by seismic stimulator 22. As noted above, this determination may occur using either a calendar or schedule of stimulus events stored or received by node 124, one or both of pre-or post-notifications received by node 124 or based upon analyzed characteristics of the seismic data itself.

[0041] As indicated by step 222, if processing unit 134 determines that a data element D occurred during an applied seismic stimulus event SE, processing unit 134 associates the data element D and the identified stimulus event SE in memory 130. Processing unit 134 assigns the data element D to the identified stimulus event SE in memory 130. In one example, such association or assignment may occur during a stimulus event, such as when processing unit 134 knows ahead of time when the stimulus event is to start and when the stimulus event will end or is expected to end. According to another example, such association or assignment may occur after completion of the stimulus event, such as when processing unit 234 receives a post stimulus event notification or when analysis of the seismic data itself identifies the period of time over which the seismic event occurred after completion of the seismic event. For times when a seismic event has not yet been identified, seismic data stored during such time is not associated with any particular seismic event.

[0042] Figure 5 illustrates one example by which data elements D]-D_]4 may be associated with identified stimulus events SE in memory 130. As shown by Figure 5, data elements D are serially stored in memory 130 with those data elements D occurring during a seismic stimulus event SE having an additional identifier. In the example illustrated, data elements D₄-D₇ are associated with stimulus event SEi while data elements Dio-D_]3 or associated with stimulus event SE₂.

[0043] Figure 6 illustrates another example by which data elements Dj may be associated with identified stimulus events SE in memory 130. As shown by Figure 6, data elements D are clustered or grouped together at different locations or portions within memory 130 based upon whether they are associated with a stimulus event. In the example illustrated, a first portion 226 of memory 130 includes all data elements D which have been associated with a stimulus event SE with a second different and remote portion 228 of memory 130 that includes those data elements D which have not been associated with any stimulus event. Data elements within portion 226 are further grouped or clustered based upon the particular stimulus event to which they are associated. In the example illustrated, data elements D₄-D₇ are associated with stimulus event SE] in portion 226 while data elements Dio-D_]3 are associated with stimulus event SE₂ in portion 226. Data elements Di-D₃ and D₈-D₉ are stored and grouped together in portion 228. In some embodiments, the grouping of unassigned data elements in portion 228 may facilitate less intensive review of such data elements or the discarding of such elements to enhance data analysis efficiencies at data collection center 28 (shown in Figure 1). [0044] Figures 7 and 8 describe another example method 310 for a mode of operation of node 124 in which node 124 stores and discards seismic data (D) based upon determined seismic stimulus events (SE). As shown by step 316 of method 310 illustrated in Figure 7, sensing element 128 of node 124 senses seismic data D which occurs over time as shown in Figure 3. Node 124 senses or receives such seismic data in a continuous or periodic fashion. As indicated by step 318, processing unit 134 temporarily stores the received seismic data D in memory 130 as it is received.

According to one example, processing unit 134 temporarily stores seismic data D in a temporary storage or temporary memory such as a random access memory. As indicated by step 320, for each data element D, processing unit 134 determines whether the data element D occurred during a period of time during which a predefined geological seismic stimulus event was taking place. In other words, processing unit 134 determines whether the data element D represents reflections of a geological seismic wave introduced by seismic stimulator 22. As noted above, this determination may occur using either a calendar or schedule of stimulus events stored or received by node 124, one or both of pre-or post-notifications received by node 124 or based upon analyzed characteristics of the seismic data itself.

[0045] As indicated by step 322, if processing unit 134 determines that a data element D occurred during an applied seismic stimulus event SE, processing unit 134 associates the data element D and the identified stimulus event SE in memory 130. Processing unit 134 assigns the data element D to the identified stimulus event SE in memory 130. In one example, such association or assignment may occur during a stimulus event, such as when processing unit 134 knows ahead of time when the stimulus event is to start and when the stimulus event will end or is expected to end. According to another example, such association or assignment may occur after completion of the stimulus event, such as when processing unit 234 receives a post stimulus event notification or when analysis of the seismic data itself identifying the period of time of the seismic event is completed after completion of the seismic event. For times when a seismic event has not yet been identified, seismic data stored during such time is not associated with any particular seismic event.

[0046] As indicated by step 324, if processing unit 324 determines that a particular data element D is not associated with any predefined geological stimulus event, processing unit 324 discards the data element D. In one example, the discarding of a data element D may occur immediately after capture, such as when processing unit 134 knows ahead of time when the stimulus event is to start and when the stimulus event will end or is expected to end. According to another example, such discarding of data elements D may occur after completion of the stimulus event, such as when processing unit 234 receives a post stimulus event notification or when analysis of the seismic data itself identifies the period of time of the completed seismic event after completion of the seismic event. In some embodiments, data elements D may not be immediately discarded, but stored in a highly compact fashion (stored in a more compact fashion as compared to the storage of data determined to be associate with a stimulus event, wherein the non-associated data may be more complex and difficult to later retrieve from compact storage) for later confirmation that the seismic data D is indeed not associate with a stimulus of vent, wherein such data D will be discarded upon such confirmation.

[0047] Figure 8 illustrates one example by which data elements Di may be associated with identified stimulus events SE in memory 130. As shown by Figure 8, data elements D are serially stored in memory 130 with those data elements D occurring during a seismic stimulus event SE having an additional identifier. In the example illustrated, data elements D₄-D₇ are associated with stimulus event SE] while data elements Dio-Di₃ or associated with stimulus event SE₂. Those data elements D[-D₃ and Dg-D₉ are not stored in memory 130.

[0048] In one example, volatile (RAM) and non-volatile (FLASH) memories are structured for event-based data storage and the data structures used in such a method. Such an example takes full advantage of event-based sensing systems and discards data that is directly not attributed to a time period resulting from a physical stimulus event. The example method is also conceptual and does not limit itself to all constraints found in many systems. [0049] Volatile Memory Organization: In an event-based sensor node volatile memory is used to temporarily store sensor data in a linear temporal fashion as it's generated by the sensing element. As the sensor node detects, or is notified by external intelligence of a defined stimulus event, the node processor commits the sensor values attributable the stimulus event to non-volatile memory along with timing and statistical summary information which describes the event. The size of the volatile temporal storage buffer is determined by the data generation rate of the sensing element and the worst case processing time (to detect a stimulus event) or worst case external notification time. If the constraints of the previous sentence are met, the volatile memory buffer can be implemented as a circular buffer which automatically overwrites sensor values that were not attributable to a stimulus event (events that were attributable to a stimulus event have been tagged and transferred to non-volatile memory prior to buffer wrap around). Such an organization ensures that only sensor readings attributable to a stimulus event are stored in non-volatile memory.

[0050] Non-Volatile Memory Organization: In example system there are two primary no n- volatile storage elements: the event record, which a temporal list of all defined stimulus events that have been detected and recorded, and the shot data record which is a collection of metadata, raw seismic data, timing information, and statistical summary data.

[0051] Event Record: The event record is a data structure stored in no n- volatile memory which records the following information: a shot number assignment (this can either be arbitrary to each individual node or synchronized across all sensors); the start and end time of the data records resulting from the defined stimulus event; and the address (or sector/block address) of the shot data record (raw and calculated data associated with this event). The event record is organized temporally and serves as an indexing tool to access shot records based on occurrence time. Additional metadata, such as the total number of stored shots contained in the event record can be stored along with the event record to aide in efficient searching of the event record. Each element in the event record is a fixed length which enables efficient indexing and temporal searching given that the elements are organized in a linear time fashion. If the event record is corrupted while deployed it can be regenerated by reading the metadata from each shot data record to rebuild the event record. Detecting corruption could be as simple checksum value which is calculated prior to each new write to the event record.

[0052] Shot Data Records: The shot data records are of variable length (depending on the duration of the stimulus event and ground propagation speeds) and contain the raw sensor data, timing data, and calculated summary data. Each shot data record contains metadata which: identifies the shot (by the shot number assignment generated when the data was stored); specifies the time over which the shot occurred; contains the memory address of the location in the shot data record in which the predefined statistical summary information is stored; and the overall size of the shot data record. The remainder of the shot data record contains the raw sensor values, any application specific annotations to indicate a missed data point or non-consistent time interval between data points, and the statistical summary of the shot that was calculated as the shot was stored into non- volatile memory from the volatile memory buffer.

[0053] Figure 9 is a flow diagram illustrating a method 410 according to which node 124 may operate when calculating summary information using raw seismic data sensed by sensing element 128 (shown in Figure 2). As shown by step 412, sensing element 128 collects a plurality data elements D over time. As indicated by step 414, processing unit 134 determines whether a predefined seismic stimulus event is taking place. As indicated by step 416, processing unit 134 may utilize one or more predefined profiles for data elements D in a predefined seismic stimulus event. As indicated by step 418, processing unit 134 determines the start of a seismic stimulus event in the current or previous sample. As indicated by step 420, processing unit 134 continues until the end of a seismic stimulus event is detected. As indicated by step 422, once the end of the seismic stimulus event has been detected by processing unit 134, processing unit 134, following instructions contained in memory 130, calculates or generates a statistical summary information of the identified predefined artificial or man-made seismic stimulus event. Thereafter, processing unit 134 in their stores the summary information for subsequent transmission to data collection center 28.

[0054] Although method 410 describes a method wherein the start and end of a predefined seismic stimulus event is determined based upon how a collection of data elements D in a sample corresponds to a predefined profile for a seismic stimulus event, in other examples, method 410 may return the start and end of a seismic stimulus event in other manners. For example, the occurrence of a seismic stimulus event and the determination of what data elements D are associated with the seismic stimulus event may be determined using pre-event seismic notifications, post-event seismic notifications or schedules of seismic events.

[0055] Figure 10 illustrates one example method 510 by which sensor node 124 may communicate or transmit summary information to data collection center 28 (shown in Figure 1). As indicated by step 512, sensor node 124 receives a poll from data collection center 28 via a wired or wireless network with communication device 132. As indicated by step 514, upon receiving a request from data collection center 28, processing unit 134 determines whether any identified or determined complete stimulus events with their associated data elements D remains unreported. As indicated by step 516, if processing unit 134 determines that there are unreported seismic stimulus events, processing unit 134 transmit the calculated or generated summary information for the under reported seismic stimulus events to data collection center 28.

[0056] If processing unit 134 determines data elements D for all completed seismic stimulus events have been reported, processing unit 134 then determines whether sensor node 124 is in the middle of storing or recording data elements D during an ongoing seismic stimulus event as indicated by step 518. As indicated by step 520, if sensor node 124 is not currently in the process of recording or storing data elements D from an ongoing seismic stimulus event, node 124 responds to the poll from data collection center 28 by transmitting a status update regarding node 124. Alternatively, as indicated by step 522, if sensor node 124 is in process of recording or storing data elements D from an ongoing seismic stimulus event (a start of seismic stimulus event has been identified and end and of the same side stimulus event has not yet been identified), processing unit 134 responds to the poll from data collection center 28 indicating that a predefined seismic stimulus event is currently being detected by node 124.

[0057] In other examples, the transmission of summary information may be triggered in other manners. For example, in other examples, processing unit 134 may alternatively report summary information to collection center 28 on a predefined schedule. In another example, processing unit 134 may alternatively initiate the transmission of the summary information to data collection center 28 automatically in response to determining an estimated completion of a predefined seismic stimulus event.

[0058] Although the present disclosure has been described with reference to example embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the claimed subject matter. For example, although different example embodiments may have been described as including one or more features providing one or more benefits, it is contemplated that the described features may be interchanged with one another or alternatively be combined with one another in the described example embodiments or in other alternative embodiments. Because the technology of the present disclosure is relatively complex, not all changes in the technology are foreseeable. The present disclosure described with reference to the example embodiments and set forth in the following claims is manifestly intended to be as broad as possible. For example, unless specifically otherwise noted, the claims reciting a single particular element also encompass a plurality of such particular elements.

Claims

WHAT IS CLAIMED IS:

1. A geological seismic sensing system comprising:

a self-contained geological seismic sensing node comprising: a geological seismic sensing element to sense geological seismic data representing reflections in ground occurring in response to predefined seismic stimulus events;

a memory;

a communication device; and

a processing unit configured to store sensed geological seismic data sensed by the sensing element in the memory and configured to transmit summary information of the sensed geological seismic data to a recipient external to the sensing node using the communication device.

2. The system of claim 1, wherein the geological seismic sensing element comprises an accelerometer.

3. The geological seismic sensing system of claim 1, wherein the node further comprises a global positioning system.

4. The system of claim 1, when the communication device is wireless.

5. The system of claim 1, wherein the processing unit is configured to continuously store the geological seismic data in the memory and wherein the processing unit is configured intermittently transmit the summary information.

6. The system of claim 1, wherein the summary information comprises a mathematical summary of the geological seismic data sensed by the sensing element.

7. The system of claim 6, wherein the summary information comprises a degree of fit between the sensed geological seismic data and a predefined profile.

8. The system of claim 6, wherein the processing unit is configured to apply a criterion, wherein the summary information comprises selected portions of the sensed geological seismic data, other portions of the sensed geological seismic data not being part of the summary information.

9. The system of claim 8, wherein the processing unit determines a peak seismic amplitude value from the geological seismic data and wherein the summary information includes the determined peak seismic amplitude value.

10. The system of claim 8, wherein the summary information comprises information indicating when a predefined seismic stimulus event started and when the predefined seismic stimulus event ended.

1 1. The system of claim 8, wherein the processing unit determines a root mean squared value of the sensed geological seismic data and wherein the summary information includes the root mean squared value.

12. The system of claim 1, wherein the summary information is based upon only the data that occurs during a predefined seismic stimulus event.

13. A geological seismic sensing system comprising:

a self-contained geological seismic sensing node comprising: a geological seismic sensing element to sense geological seismic data representing reflections in ground occurring in response to a predefined seismic stimulus event;

a memory;

a communication device; and

a processing unit configured to store sensed geological seismic data sensed by the sensing element in the memory and configured to intermittently transmit data based on occurrence of the predefined seismic stimulus event to a recipient external to the sensing node using the communication device.

14. The system of claim 13, wherein the processing unit is configured to intermittently transmit summary information to the recipient external to the sensing node using the communication device.

15. A method comprising:

sensing geological seismic data at a first frequency; and

transmitting summary information based upon the sensed geological seismic data at a second frequency less than the first frequency.

16. The method of claim 15, wherein the summary information comprises information different from the sensed geological seismic data and based upon the sensed geological seismic data.

17. The system of claim 15, wherein the summary information comprises selected portions of the sensed geological seismic data, other portions of the sensed geological seismic data not being part of the summary information.