b'Seismic window Seismic windowrecorded naturally occurring seismic activity using high sensitivity, broad band seismometers to obtain measurements of spectral properties at several points across an oil discovery, which they then calibrated to well control. They found a low frequency anomaly at 3Hz was present at points above the hydrocarbon, and an impressive correlation between their DHI value and nett pay thickness. Sounds like the bees kneeswhat could possibly go wrong? Well heres a list ofFigure 1.Extract from page 23 of the Geological some of the problems: Survey of Western Australia Annual Review 2018 - 19. Michael MicenkoPassive seismic has been used in WA to aid mineral Associate Editor for PetroleumThe presence of artificial sources suchexploration for some time.mick@freogeos.com.au as traffic, production wells or pipelines can affect the data quality the earth can be extracted despite it Amplitude of the measured signalbeing low frequency data (0-10Hz).Passive seismic depends on the time of day possibly because of gravity induced forces likeAs I understand it, the passive seismic I was chatting at a networking lunchtides method involves using a 3 component recently, and the discussion turned toThe spectrogram is non-stationary inseismometer to continuously record passive seismic, or more specifically,time or space what most of us call seismic noise. This using passive seismic to distinguishnoise, generated in the ever moving hydrocarbons from water in a subsurfaceJust one of these problems has themantle by grain to grain interactions, reservoir. Passive seismic records datapotential to derail the method, and all threeis modified as it passes through the from naturally occurring seismic eventstogether appears to be insurmountable,overlying rocks before being recorded at rather than from a controlled source. Thebut Im assured the method works if thethe surface. If there is no change in the method is commonly used to monitorproper processing is applied. overlying strata the seismic signal does micro-seismic events, to map fracturenot change but if there is even a subtle lengths following hydraulic stimulation,This is all interesting but I had to ask about the source. What is the cause of thechange the signal is altered. The recorded or to record tele-seismic arrivals to mapdata is analysed and processed to obtain crustal structure, but using passiveapparently never ending and ubiquitous supply of low energy seismic events? Ita frequency spectrum that is compared seismic to differentiate fluid fill wasto a model and neighbouring events new. Or so I thought. But, after someappears the Russians had a theory where they considered the earth was not madeand an interpretation of the cause of any follow up, I found it had been used indifferences is made.Eastern Europe for at least 10 years andof simple solid layers but rather a system possibly for over forty years. Closer toof separate bodies under different stress conditions, some of which are close toThis innovative technique is still home, several surveys have been carriedexperimental but I believe a pilot project out in recent years by The Geologicala state of instability. In this state even a weak effect could trigger a change in themay be kicked off in Australia later this year.Survey of Western Australia to map the thickness of sedimentary overburdenproperties and energy state of the system. (Figure 1). The passive method is cheap,As a result of this instability real rocksReferenceenvironmentally friendly and can detectconstantly emit micro-seisms caused by hydrocarbons directly - just what wetemporary changes in stress resultingIrinyakov, E., Sergy Mikhailov, S., need in this day and age.from geodynamic and geochemicalKhabibullin, I., 2008. Application processes. A bit waffly but essentiallyof Low Frequency Passive Seismic A paper by Irinyakov, Mikhailov anddifferential movement of grains in theTechnology for Hydrocarbon Khabibulin (2008) describes theupper mantle creates a continuousExploration at Complicated successful use of low energy passivesource of micro-seismic events that canSubsurface Structures. SPE Russian seismic to prospect for hydrocarbons inbe recorded at the earths surface, andOil & Gas Technical Conference and complicated geological conditions. Theyinformation about the fine structure ofExhibition, Moscow. Russia 2008JUNE 2021 PREVIEW 44'