Oscillating oil drops, resonant frequencies, and low-frequency passive seismology

Abstract

A recent passive seismic technology in the oil industry, sometimes referred to as hydrocarbon microtremor analysis (also low-frequency spectroscopy), claims high correlation in some instances between the presence of hydrocarbons and low-frequency spectral anomalies (elevated spectral energy levels) computed from passively recorded seismic data. These observations have been reported for a number of different geographic locations. One of the difficulties in assessing this method is the lack of a physical basis for explaining the empirically observed effects. A potential explanation that has appeared in the literature can be referred to as the resonant amplification model. The main idea of the model is that, because of capillary effects, an oil drop in a rockpore will oscillate at a resonant frequency when driven by the ambient noise field of the earth. This resonance phenomenon is interpreted as a possible source of the spectral anomaly. I examined this model by numerical simulation but was unable to reproduce the amplification effect. I then considered one of the main input parameters, the resonant frequency itself. By computing resonant frequencies using theoretical models from the literature, I found that the resulting values are too high to be consistent with the frequency range of hydrocarbon microtremor analysis. Furthermore, I found that such resonances only exist for little or no viscous damping. When realistic damping is considered, there is no oil-drop resonance effect. The model, at least in its current form, does not appear to provide a promising direction for establishing a physical basis for hydrocarbon microtremor analysis.

Time Reverse Modeling of Hydrocarbon Detection for Passive Seismic Source Localization: A Case Study of Synthetics and Real Data From the South Sumatra Basin, Indonesia

“…The amplitude spectrum is exhibited at the interval of 1-6 Hz. This situation is consistent with that previously expressed by Broadhead [15] and tested by Ali MY [16], that the oil that resonates with ambient noise in the earth will emit energy back at a similar frequency in which the amplitude of these oscillations is greater than the resonant frequency. In the current study, the TRM was applied to the interval frequency of 1-6 Hz; to localize the source emits the signals.…”

Changes in permeability caused by transient stresses: Field observations, experiments, and mechanisms

“…However, the theoretical model of Beresnev [2006] and Beresnev and Deng [2010] suggests that the mobilization can be achieved at a continuum of frequencies, not only at resonance, as long as the leading meniscus is transported to the neck of the constriction. The resonance frequencies calculated from the two approaches [ Hilpert et al , 2000; Beresnev , 2006] are nearly identical [ Broadhead , 2010].…”

Theoretical and experimental study of resonance of blobs in porous media

“…Our model can be used to expand on the comment by Broadhead (2010) that oil blobs in media with a pore size smaller than 1 mm typically do not exhibit resonance due to too much damping. However, Broadhead (2010) did not examine the effects of wettability that is quite variable in oil reservoirs (Morrow, 1990).…”

“…Holzner et al (2009) attribute a high correlation between the presence of hydrocarbon reservoirs and lowfrequency spectral anomalies computed from passively recorded seismic data to the resonance of hydrocarbon blobs. However, Broadhead (2010) tests various resonance amplification models to show that the resonant frequency of blobs is too high to fall in the frequency range of a hydrocarbon microtremor. To summarize, it is important to know how liquid blobs respond to excitation as a function of frequency and whether resonance actually occurs in subsurface porous media.…”