Passive Seismic Spectroscopy is a low-frequency seismo-acoustic spectroscopy for hydrocarbon reservoir detection and monitoring.
The spectroscopy analysis result is a Direct Hydrocarbon Indicator (DHI) presented in form of a surface map of the probable hydrocarbon distribution (or absence). The figure at the top of the page shows several areas in orange – to – red colours: they represent, from the passive seismic spectroscopy perspective, the highest hydrocarbon potential within the area of interest.
Geodynamics Worldwide, by using ultrasensitive acoustic sensors (Broad Band Sensors), has the ability to detect the areas where the probability of presence of hydrocarbons is higher, minimizing the uncertainty of the subsurface fluid system. This technology, applied in more than 100 locations worldwide, has ultimate benefit to oil companies and petroleum authorities throughout the life of their hydrocarbon assets.
Different surveys over different oil and gas fields have established the presence of spectral anomalies in a low-frequency window (1 – 10 Hz), also known as micro-tremors.
By using high-sensitivity broadband seismometers, Geodynamics Worldwide has the ability to detect the areas where the probability of presence of hydrocarbons is higher, reducing the uncertainty of the subsurface fluid system. This technology, applied so far in more than 100 locations worldwide, has ultimate benefit to oil companies and petroleum authorities throughout the life of their hydrocarbon assets.
Different surveys over different oil and gas fields have established the presence of spectral anomalies in a low frequency window (1 – 10 Hz).
The usage of low-frequency seismic waves avoids the problems of velocity inversions, thin layering, lateral heterogeneity, such as in basalt and evaporitic settings or very complex geology. Passive seismic can be virtually applied in any environmentally sensitive place, as it leaves no traces and has no negative impact on local flora and fauna. The passive seismic acquisition does not require any explosions, vibrations or similar.
Typical fields of application are:
- Exploration: fluid content of structural and stratigraphic hydrocarbon traps on green fields
- Exploration: prospect ranking
- Field development: field appraisal, field delineation, identification of development wells
- Field monitoring: determination of water front, water fingering, hydrocarbon fluid barriers
- Time lapse field monitoring and assessment of the hydrocarbon recovery scheme
Field survey is carried out by a team of 3 – 6 operators as well as a full set of seismometer units. Depending on the survey design, the number of seismometere units displaced in the field varies. A grid of data points is designed to cover the target area. Spacing of the grid begins from 250 m and can reach up to 2 km. Each data point is designated by one seismometer unit and the acquisition time goes from 60 min to 24 hours. Depending on client’s objectives, the passive seismic survey can have various settings with different outputs. The main one is the spectroscopic analysis.
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Holzner, R., Eschle, P., Zurcher, H., Lambert, M., Graf, R., Dangel, S., and Meier, P.F. 2005] Applying microtremor analysis to identify hydrocarbon reservoirs. First Break
Lambert M.-A., Schmalholz S.M., Saenger E.H. and Steiner B. 2009.Low-frequency microtremor anomalies at an oil and gas field in Voitsdorf, Austria. Geophysical Prospecting 57, 393–411.
Nguyen T. T., Saenger. E. H., Schmalholz S.M., Artman B. 2008. Earthquake triggered modifications of microtremor signals above and nearby a hydrocarbon reservoir in Voitsdorf, Austria. 70th EAGE Conference and Exhibition.
Riahi, N., Goertz, A.,Birkelo, B., Saenger E. K. 2013. A statistical strategy for ambient seismic wavefield analysis: investigating correlations to a hydrocarbon reservoir.Geophysical Journal International: 192, 148–162.
Saenger, E. H., Schmalholz, S. M., Lambert, M. A., Nguyen, T. T., Torres, A., Metzger, S., Habiger, R. M., Muller, T., Rentsch, S. and Mendez-Hernandez, E.  A passive seismic survey over a gas field: Analysis of low-frequency anomalies. Geophysics 74(2), O29-O40.