"user manual"
Contents
1. www firstbreak org 2011 EAGE first break volume 29 July 2011 Wifi options for real time recording long distance transmission espns central location and recording on the line but it delays the time at which users get to see some data If the ground units are limited in storage capacity this presents further challenges to the operator who will have to collect them up merely to download data while deploying fresh boxes in the same place In permanent and passive a rule is that accessing the data should not interfere with on going acquisition and fortunately there are a few cableless systems which do allow data to be downloaded while it is being recorded thus not messing with the monitoring process However different surveys call for different ideal methods of harvesting so for greatest efficiency data security and HSE OGG PS OUR se Real time monitoring of deployed hardware and passive data in central location Cunee SOP L125 NIT US AOA W 2011 EAGE www firstbreak org special topic Passive Seismic exposure data collection must be flexible too Some recorders allow the user to plug a laptop or tablet PC directly into the ground unit and copy the data while it is still deployed and acquiring data Some users prefer not to have to carry computers into the field and want to harvest via removable USB stick also without disturbing acquisition Both can be accommodated Some surveys can be more effici2. equipment as unsuitable Experience has already revealed that it can be disastrous not to know what is happen ing out there when operations call for leaving out equipment for days if not months or indefinitely On an active survey it is not considered a luxury to be sure that ground units power supplies and sensors are always working properly and neither should it be necessary in passive where there is no second chance to log an event Traversing huge areas on foot in inappropriate and noisy vehicles just to assure oneself the job is being done properly is somewhat impractical It may be true that shootblind hardware used to be the lower cost route but this is mostly no longer the case In terms of hardware purchase and even more so in operational savings doing things cost effectively now means using equipment which can remotely monitor what s going on by use of built in mesh radio networking MRN These MRNs only have to get their messages which include QC status and remote control commands to an adjacent ground unit which then passes them along disseminating over the entire operation using the licence free 2 4 GHz band MRNs are the opposite of what earlier wireless systems were in land seismic where they had to transmit the entire width of the spread requiring lots of power Even so off the shelf MRN technology in the past was not well suited to some passive operations where channel densities were 94 fir
3. a b ay j i ie 1 7 i 1 r E Pa a d a A P J a 2 sik K 1 g f t d i a i A 7 i 1 p Pt i b Fa tag re ne al Use of Wifi for seismic system control and data retrieval 2001 SSC archive 96 first break volume 29 July 2011 Stylised representation of universal hardware ideal for passive permanent and active recording old in the seismic domain To ensure Wi Fi connectivity over large distances with irregularly spaced data collectors more modern technology must be used possibly along with some judiciously placed repeaters However the quantity can be fairly low with proper planning Some systems now even allow Google Earth imagery to find lines of sight Repeater tower densities as low as one every 20 40 km may be achievable and even fewer if data can be hopped from station to station This is not to say that all passive acquisition which requires real time recording happens over large distances The monitoring of fracing can take place over relatively small areas and here cableless equipment which has the ability to be hardwired together for the purpose enables one set of equipment to be easily adapted to take on all RTR roles Such are the requirements of the universal recorder Future seismic Most who study novel instrumentation and the plethora of new geophysical techniques believe that we are currently in an era of very rapid change What we may consider as state of th
4. and better equipped with their own tools and a workshop which will probably be larger than is found on many active operations with similar channel counts Workers may also need their own transportation and ideally there should be a field co ordinator as well as a shop co ordinator to run things smoothly These key people should understand such things as budgeting procurement and scheduling in a way which is not usually found on an active crew This may be an extra expense and one which will be reduced by using more capable passive hardware but do not expect to get the best results without such a small core of qualified and properly equipped staff Cable or cableless system System robustness Analog to digital convertor Low frequency system limit System dynamic range Survey aerial extent Data rate Continuous recording Equipment remote control Equipment monitoring Data return real time Download speed in field data harvesting Channel density Geometry System memory capacity requirement Removable storage media Sensor types Data format Operation Personnel Operation Duration Universal dual operations Either Medium 24 bits 3 Hz Limited lt 00 sq km Low High Occasionally required Useful but not essential Useful but not essential Useful but not essential E Low High intermittent Useful but not essential Medium High Usually regular Zero low Sometimes useful but not usually ava
5. ca tions is much the same as the next and in active recording hardware there is a good deal of truth in this A few decibels better here or microvolts there is not going to make much difference on a land crew especially compared to such simple things as planting the geophones properly Take a look at the specs of the designed purely for active systems and you might find it hard to fit a cigarette paper between them This is partly because many manufacturers use the same chip sets and partly because developers know that these figures are accepted as both sufficient for the industry and obtainable with most decent engineers Why bother with anything more In passive recording equipment specifications and functionality differ between systems far more and these differences can most definitely affect the final result in greater ways than in active recording Take for example the frequency range of an instrument While Nyquist s theorem sample rate sets the upper limit of recoverable frequency I know of no hardware which has the slightest difficulty in digitizing the highest frequencies which mother earth deigns 92 first break volume 29 July 2011 to propagate through the bits of the planet we are generally interested in so both made for active and made for passive products serve their causes well here Yet when it comes to low frequencies some hardware limits the response to 3 Hz which is far from ideal for passive There can be se
6. ch superior performance especially in terms of noise the ability to use different recording systems and to be used in arrays better cost and robustness Also as passive generally requires use of cableless recorders where power is at a premium any transducer such as a MEMS accelerometer which requires extra power should also be seen as a distinct drawback Extent of operations Before we go further investigating what other features are important for perfecting passive we must think about the different sort of environments where these various operations may take place Few would claim that the average active crew has life easy but compared to the extremes where passive may have to perform it is definitely active recording which gets the easier ride Let us consider the simple areal extent of passive and permanent surveys Here the terrain across which deployed equipment may have to be continuously monitored main tained and perhaps even provide real time data has already reached hundreds of square kilometres and is only going to fom Bae A Z Sensor testing with Wifi pass by download poe special topic Passive Seismic get larger The most extensive such operation this author is familiar with is about five times larger than the biggest live patch ever switched on for an active land survey Addition ally passive work often takes place in areas of much higher cultural activity and this presents an extra set of problems
7. d geotechnical applications hazards and geothermal I would add hazard safety monitoring microseismic recording and as imperfectly defined as it is the related topic of permanent monitoring Ei Vie ipa m H m EE Far a p Bi Aisn l ae Seems HEI lP riamn ie E miary ia 29 n Howe Bhag Beers cee be ic in deker iE ora L OF iris oni ui ET ice Emi Aaka H E himp i CHP cee Oe arr J ate a Cly mams gt U kia sere CH mra P 4 i Mr ad r x I ik _ EACT Gree Sresnce RY matics otorert ote O7s90_ aco 2 FDS rgheath btconnect com 2011 EAGE www firstbreak org too Like any new field terminology is rather messy since there can be overlap between these operations permanent monitoring projects can be passive operations also In fact in some people s minds anything which is not out and out active exploration comes under the heading of passive and I shall go along with that here Passive reality The potential benefits of recording without controlled sources appear to have taken some by surprise including even a few oilfield service companies and geophysical contractors This has lead to cases where survey planners have not had time to get to grips with all the practicalities which can determine the operation s success from both the economic and data quality points of view After all whereas there s a lot of different hardware available not much of it wa
8. e art today almost certainly will become antiquated at a rate few have ever experienced before Thus the notion of future seismic is something that should be of interest to us all and passive is starting to make its presence felt here too though not in the way many predicted Source control flexibility is one area where future seismic aficionados have recently started looking resulting in for example a new generation of vibroseis controller active passive recording is probably next in line There have already been surveys which used standard hardware to record actively during the day and are then left switched on at night to gather passive data often with mixed results given the limitations of the hardware used So can the latest generations of passive equipment help take geophysics further into the future Clearly as passive systems have at last surpassed active record www firstbreak org 2011 EAGE first break volume 29 July 2011 Cableless equipment now offers hardwire options as universal system ers in specifications and functionality it may well be time for geoscientists to consider what may be gained undertaking the active passive job properly and even more regularly Field operations Although the latest passive equipment may be employed on almost any active or non active survey this does not mean that the greatest crew efficiencies come from running all operations in the same way As different as the ideal
9. e ratio of the smallest signal an instrument can deal with to the largest one it can simul taneously handle without over scaling In active recording many insist on this being as high as possible while devising surveys which then fail to make full use of the range But in passive permanent monitoring the first of these values is especially important because such surveys may use sensors deployed in lower noise environments buried or be part of a downhole tool whose outputs are made available at the surface Then passive operations often have to accept high level inputs where sensors output high voltages due to vehicular traffic There are also some advantages to con necting multiple geophones in series to increase the output of the array Both extremes of signal must be sampled well at the same time so one can be removed while the other is processed Typical 24 bit over sampling based instruments struggle with this but at least one recorder Sigma from iSeis can han dle the task as it has a 32 bit convertor with the necessary characteristics One may thus conclude that when planning a passive rather than an active survey specifications do make a definite difference www firstbreak org 2011 EAGE first break volume 29 July 2011 There is also a lot of work underway in regard to sensors both single and multi component and so far it seems that the simple analogue variety offers the most benefits to this field These include their mu
10. ehaviour of CO in the subsurface including monitoring modelling mapping and predictions For more information about this event check our website www eage org WWW eage org 98 Submit your abstract now www firstbreak org 2011 EAGE
11. emory card A three component survey under the same conditions is going to use up close on 40 GB Many of us get rather blas about data capacity as mobile phones with dozens of gigabytes storage are common but some seismic instruments run out of memory address space at 2 or 4 GB This used to be enough for many types of active survey but clearly not sufficient to take on much else Data handling harvesting We have looked at some of the features that passive needs compared to active and how they impose greatly differing requirements on the hardware and its deployment It has been seen that cableless systems with high memory capacity and an ability to remotely control monitor at least system basics are the best tool for the job We now jump forward a few hours or days or months confident that everything has been working well during this time and realize that we need to get our hands on some of this data At this stage we assume that if real time recording is an option offered for that particular cableless system it was not being used and we have to go about data collection in some other way In active work equipment fairly regularly gets picked up by the line crew and moved forward For such surveys using some types of cableless equipment this is when ground units have to be rounded up in some staging area and data down loaded Not only does this require more equipment ground units cannot simultaneously be in harvest mode at some
12. ent by not having to touch the ground box at all and make use of internal omni directional Wi Fi for transmitting data to the harvesting device as it passes by The downside of this is that range can be rather limited and data rate is affected by quality of connection which is in turn governed by range So the option of an external Wi Fi either of omni or semi directional design permits further levels of harvesting flexibility which can make all the differ ence considering passive data volumes and problems of access As Wi Fi can be power hungry so an MRN is useful to turn on off the Wi Fi when it is not needed thus saving valuable battery energy Even in something as obvious to exploration geophysics as data collection we see some major differences between what is acceptable for passive versus active Real time recording It has been shown that cableless instruments are the only solution to many types of passive permanent work But what if the user wants real time recording RTR to be able to sit in some central location which may even be in a different country and have all data appear before him The number of cableless recorders with any sort of RTR option can just about be counted on the fingers of one hand However almost all of these were designed for active work and may struggle to cope in some passive operations especially given the low channel density uneven geometries and huge survey areas Here the first things to realize i
13. first break volume 29 July 2011 special topic Passive Seismic Time to consider the practicalities of passive seismic acquisition Bob Heath casts a critical eye over current passive seismic acquisition equipment and opera tions and suggests that experience with past new technology evolution in land seismic may offer some valuable lessons and pitfalls to avoid assive acquisition appears to be all the rage Geophysical societies hold workshops on the theme and many magazine column inches are devoted to it Some even say that it is the fastest growing sector in exploration But is this field really ready for the big time Is the industry prepared to do passive properly to get the most out of it In some ways passive only seems to be where active acqui sition was at the dawn of the 3D land seismic era lots of expectation theories and ideas but rather less in terms of hardware well suited to the job or an understanding of all the practicalities This article is an attempt to convert the theoretical into getting the best from real projects It discusses how choice of equipment and method of deployment affect passive acquisi tion today every bit as much as it did for active exploration a quarter century ago and hopes that some of the same mistakes can thus be avoided So what is passive acquisition At its most recent work shop the EAGE provided a non exhaustive list reservoir monitoring CO2 sequestration mining an
14. ilable Limited SEGD or SEGY Usually dependent on large crew of labourers Limited Not possible 2011 EAGE www firstbreak org Cableless essential for most applications Maximum robustness required 32 bits lt 1Hz Maximum possible May have simultaneously to handle low noise and high input from serial sensor arrays Can be gt 1 000 sq km Low Medium Almost always required Mostly essential Essential Essential in some contracts Low High continuous Essential if not real time Low Medium Usually irregular Zero to functionally unlimited Very useful Large varieties of types frequencies sensitivites configurations surface and downhole SEGD or SEGY More dependent on low no s of individual technicians Can be unlimited Ideal passive system also good for active Table 1 Main differences between active and pas sive systems and operations considerations 97 special topic Passive Seismic Passive permanent may also require someone who is concerned with maintenance nitty gritty As much as it affects active operations things like weather damage and animals pulling at cables can be on going issues for non active and this is why it is essential to have equipment which can provide full spread monitoring whatever the terrain There will also be various passive housekeeping duties which will not be so important to the active for example where solar panels are used they need to be kep
15. in terms both of initial equipment deployment and ongoing operations However it is not just the survey s physical extent or terrain challenges but also the lower average channel density of passive recording and the totally irregular layout patterns which make life awkward This is because sym metrical geometries and within certain limits high channel densities make it far simpler for most hardware to work well nowadays compared to sparsely or irregularly deployed equipment Indeed there are some systems which can only work when the layout is neat and regular So if we want to perform surveys in wide expanses of tricky terrain with almost random and low channel densities it is clear that our hardware options are going to be limited The traditional land market is monopolized by instru ments which rely on twisted pair digital telemetry spread cables Although now stretched to the limit of what they can achieve in engineering terms cable based recording has been perfected enough such that logistically simple active surveys ty i Accidents happen needs Passive hardware needs to be more robust than active recording hardware OBB a 1081497 AEETI ap mop os 1453 Se S NSOCE Eas M x a Very large stationary array over difficult terrain with RTR capability Google Earth imagery can be used for planning purposes 2011 EAGE www firstbreak org 93 special topic Passive Seismic can be undertaken with a
16. n amount of drama which most contractors have learned to cope with And because of cable s dominance for some it was originally the technology of choice for passive too But it is obvious that the component which makes such hardware viable in active recording the spread cable is what makes it unsuited for routine pas sive permanent jobs and thus cabled systems are the first equipment type to drop off the list in this new frontier In fairness they were never designed for this sort of work so our expectations should never have been too great That leaves us with cableless cablefree or wireless technologies the terms can be synonymous here and the features they offer for passive s progress Monitoring So what type of cableless kit is ideal to take on all that passive has to throw at it That may be easier to answer by considering what is inappropriate The problem is while none of these systems by definition rely on cable telemetry most wireless product developers made no attempt to design in any feature which would allow the smallest amount of data to be returned from remote units deployed across even small survey areas Such limited hardware which can also not hear commands from the central system is often referred to as shoot blind For very short term or limited areal extent passive work this may not be much of a hindrance But to avoid potential embarrassment elsewhere these shortcomings tend to mark out such
17. passive recorder is now from the generally used active recorder field operations differ even more Active seismic often needs armies of juggies who are there to put down and a little while later pick up geophones and other hardware Taking a line crew who may be expert at traditional surveys and expecting them to do just as well first time out on a passive operation is a lot to expect Passive special topic Passive Seismic operations tend to need a small crew of individuals who have been instructed in the essential differences between active and passive operations system manufacturers should be able to say what these are and who can also work as a small team A few jacks of all trades rather than dozens of masters of none Daily logistics are everything to a passive crew because there is no source crew to manage thereby controlling the data flow The data simply arrive every moment of every day whether the crew is ready or not To cope battery manage ment should be one of the things at the top of the daily to do list not necessarily because of fear of batteries running down a good system lets you monitor this remotely but to prevent surprises And where RTR is not being used it is good idea to set up a harvesting routine on a daily basis too for the same reason By using simple spreadsheets to manage logistics it is possible to increase accountability and avoid equipment based panics The operatives need to be well trained
18. s designed specifically for the purpose and some certainly is not being used as per the user manual In fact devising equipment suited to a set of passive operations which is far wider than anything encountered in active recording has been no simple matter So let us look at what is necessary to make sure that passive permanent surveys pay the biggest dividends and as Passive recording includes mining and hazard eval uation Sigma Observer software 91 special topic Passive Seismic Onsite training Sigma passive operation Texas 2011 quickly as possible and not make the mistake of the early land active recording 3D pioneers who took a decade or more to learn things the hard way Specifications Whereas all geoscientists are happy thinking in scientific terms the most important unit when it comes to this new field is not velocity or frequency but is the dollar In the past passive equipment was often rather expensive to buy costly to use and generally designed for a few rather specific tasks Fortunately there is now hardware which can be considered universal able to be used on almost all active and passive operations prices have dropped and with the right training can be much lower cost to use too So before we get too carried away with the details of the technology the fact that there is a new commercial reality is the first thing we can celebrate Many may think that one set of seismic system specifi
19. s that various types of passive permanent recording now go on globally so any hardware which must be useable around the world will have to pay attention to various RF challenges VHF communica a Fecending ieta Cortnsstion 7 DSTO 1215182124 270 1996 19 245 4851 4 57696904 67775 PERL ST OIRO ait a f mp I fle del i i NE i i He Ht ii i i wi Y i F g oF dit in i Hi Xf dal Wide jil a cof i J 4 fik re hie a 1 i i j i tr xi i al ie HH i dist H WR ON KY D DO ME E N E N a EHD A Tetai OIM MES 95 special topic Passive Seismic tion would not be appropriate for the transmission task given power requirements bandwidth limitations and licensing difficulties It seems that the 2 4 GHz band is the only truly licence free one anywhere on Planet Earth Of course this band has its problems such as absorption which only gets worse by going to higher microwave frequencies 2 4 GHz is the devil we know and it is what must be used to turn a cable less system into an internationally capable real time recorder Here the same longer range omni directional external Wi Fi as used for pass by downloading can be used for real time or something a bit more directional Using Wi Fi to control remote equipment and return data is at least 10 years i i E i rdr pn ne N w a7 ii i i u Jae ki a i e 7 Au P L F P ria J a 4 i rz M i i m i i ak a P
20. st break volume 29 July 2011 especially low However through recent enhancements of the protocol and occasionally some judicious use of simple MRN relays it has become much more passive friendly What MRNs offer in terms of communications bandwidth is still rather limited and cannot be used for sending back the full seismic record in real time The technology for doing so will be considered later Enhanced MRNs are already quite capable of providing remote control functionality and the throughput to monitor large numbers of channels and multiple test functions such as sensor GPS reception which can come and go in some places which is why it is essential to have some alternative when GPS reception is not available ground unit i tests battery power and so on These are all things which the passive operator needs to know Indeed some recent opera tions demonstrated that they are of inestimable benefit to the passive environment The alternative is to see nothing and keep one s fingers crossed If we are still considering systems with no real time recording option the final issue in this section is how much data storage each ground unit needs especially taking into account that passive often uses fairly high sample rates To put some rough figures on this a single channel sampling every millisecond operating 24 7 for a month and output ting 4 bytes per sample plus some overhead will take up a significant fraction of a 16 GB m
21. t clean from road dust etc Then there is the obvious when using passive systems with in field data harvesting one must consider how man made noise can be controlled Simple planning procedures can make a big difference All in all it is possible to use run of the mill equipment and crews in a passive operation but do not expect to get the most from either The main differences are summarized in Table 1 for easy reference There is no doubt that the proper use of the most modern hardware offers immensely valuable and new Opportunities for those who know how to take advantage as well as hazards for those who are not so well prepared As Alexander Pope said A little learning is a dangerous thing but by spending time to get better acquainted with EAGE EUROPEAN ASSOCIATION OF GEOSCIENTISTS amp ENGINEERS first break volume 29 July 2011 what is now possible the industry does not need to repeat the mistakes of the past Acknowledgements I wish to offer my thanks to John Giles Scott Burkholder and Dan Braden of iSeis for their input and practical advice I want to acknowledge the valuable input of Jim O Donnell of BC Geophysics and his personal communications about life at the sharp end of passive and Satish Pullammanappallil of Optim Finally I thank Delta Geophysical for their thoughts on and photos of advanced multi disciplinary passive operations Further reading Hanssen P 2011 Passive Seismic Methods for H
22. veral reasons for this but generally it is either because few in active seismic care about anything this low or because most man made sources do not give out much energy in the long wavelength section of the seismic spectrum This then engenders the attitude if we can t produce it why make the extra effort to build an instrument which listens for it However much non active work not only feels at home with lower frequency but positively excels there For exam ple using sensors and instruments which are capable of lt 1 Hz allows us to tap into passive surface and body waves to image the subsurface geology in a way which active does not Also presence of partially saturated hydrocarbon reservoirs is associated with spectral anomalies in the range of 1 6 Hz in microtremors When measured at the surface the spectral energy is elevated above a hydrocarbon reser voir compared with spectral energy measured at positions away from a reservoir 1 3 5 or 1 6 Hz and the spectral ratio between vertical and horizontal components V H can show anomalies in the presence of hydrocarbons The polarization of the waves might also provide information about the time variability of the microtremor phenomena related to hydrocarbon reservoirs So any recorder which wants to describe itself as good for passive applications needs to have the functionality to cope with all this Let us also consider instantaneous dynamic range This can be considered as th
23. ydrocarbon Exploration EAGE Third Passive Seismic Workshop Athens Greece Hauer G Hons M Stewart R and Spiewak S 2008 Laboratory Com parison of the Performance of Analog Geophones and MEMS Accel erometers 70 EAGE Conference amp Exhibition Extended abstracts Hons M Stewart R Hauer G Lawton D and Betram M 2008 Accelerometer Versus Geophone Response A Field Case History 70 EAGE Conference Exhibition Extended abstracts Heath R 2010 Weighing the role of cableless and cable based systems in the future of land seismic acquisition First Break 28 6 69 77 Third EAGE CO Geological Storage Workshop Understanding the Behaviour of CO in Geologic Storage Reservoirs 26 27 March 2012 Edinburgh UK Geological storage of CO in the deep subsurface is probably the part of CCS which attracts the most attention from regulators as well as the public There is some concern that especially in deep saline aquifers CO injection may cause undue pressure build up and problems with displacement of saline formation water In order to properly monitor and predict the movement of a CO plume it is important to understand the behaviour of CO at all scale levels from regional to pore scale and at different time scales from day to day operations through everal decades of operations to centuries or millennia of required storage residence time In this workshop we plan to discuss all aspects of understanding the b
Download Pdf Manuals
Related Search