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Micro-tremor Analysis in Seismic Reflection Data

for Identification of Oil and Gas Reservoirs

Tatiana Chichinina , tichqvoa@yahoo.comInstituto Mexicano del Petróleo (IMP)

Eugeny Hogoev IPGG Russian Academy of Sciences

Alfonso Reyes-Pimentel UNAM

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EAGE – Amsterdam – 19 of June 2014

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The method is based on the phenomenon of natural

seismic emission associated with Micro-Tremors of

Hydrocarbon reservoirs in the subsurface of the Earth.

This Hydrocarbon Microtremor is also called by Lambert

et al. (2013 ) as “Ambient Wavefield Modification caused

by a Hydrocarbon reservoir”.

Lambert M.-A., Saenger E.H., Quintal B., and Schmalholz S.M., 2013, Numerical simulation of ambient seismic wavefield modification caused by pore-fluid effects in an oil reservoir, GEOPHYSICS, 78, T41–T52.

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• Method.

• Frequency band of micro-tremors.

• Updated Method with application to field data.

• Physical reasons of micro-tremors .

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• Method

• Frequency band of micro-tremors.

• Updated Method with application to field data.

• Physical reasons of micro-tremors .

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The advantage of the method (proposed by Vedernikov, 2001) is that the input data for the analysis can be extracted from the conventional seismic reflection data.

Thus, the method is of easy field-data acquisition compared to other passive seismic methods.

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Additional part of seismogram used for the analysis of micro -tremors

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Long offsets and early times

• The methodology consists of the use of raw seismic records at early times and far offsets.

These portions of the seismic traces contain information prior to the arrival of the waves generated by artificial source.

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Spectral analysis of micro-tremors linked to the presence of hydrocarbons

The end result is spectral amplitude values of micro-tremors for different frequency ranges shown along the seismic line, that is to say depending on the position of the receiver.

You can note that the maximum intensity of the amplitude spectrum is observed in in the frequency interval from 10 Hz to 20 Hz.

Bh1

[10 Hz ; 20 Hz]

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• Method

• Frequency band of micro-tremors

• Updated Method with application to field data

• Physical reasons of micro-tremors

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In other methods of Hydrocarbon Microtremor Analysis (HyMA), It has been observed that natural micro-tremor response in areas of oil and gas reservoirs exhibit certain characteristic behavior, with the maximum amplitude-spectrum energy at lower frequencies, in the interval from 1.5 Hz to 6 Hz. This frequency range of the Micro-Tremors is the same for different oil-gas fields . Note that in those methods there are no any sources used for excitation of artificial waves such as reflected waves in our case.

In our method, which we present here, we use conventional seismic data, which is reflected waves originated from the excitation by artificial sources such as vibrators or explosions.

That is why the frequencies of Micro-Tremors are lifted up to 20 Hz comparing with the frequencies in the methods of Passive Seismic Exploration.

EAGE – Amsterdam – 19 of June 2014

Se ha observado la prevalencia de ciertas frecuencias en los espectros de microsismos debido a la presencia de hidrocarburos.

Dangel et al. (2003) Journal of Volcanology and Geothermal Research

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The HMT frequency band is from 1.5 Hz to 4 Hz

State of the artIn different (other) methods of analysis of the Hydrocarbon Micro-Tremors (HMT),

the HMT frequency band is from 1.5 Hz to 4 Hz

United Arab Emirates(UAE)

UAESwitzerland

The frequency band is from 1.5 Hz to 5 Hz

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•Saenger E.H., Schmalholz S.M., Lambert M.-A., Nguyen T.T., Torres A., Metzger S., Habiger R.M., Müller T., Rentsch S. and Méndez-Hernández E., 2009, A passive seismic survey over a gas field: Analysis of low-frequency anomalies. Geophysics, 74, p. O29-O40.

Case Study in México, Burgos gas/oil field

Saenger et al., 2009

Hydrocarbons No hydrocarbons

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Natural micro-tremor spectral response of oil and gas

reservoir

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Holzner, et al., 2005,

2006Hydrocarbon Microtremor

Analysis (HyMAS)

The ever-present seismic background noise of the earth acts as the driving force for the generation of hydrocarbon indicating signals. The seismic background noise spectrum is modified in a different way when interacting with geological structures containing hydrocarbon filled pores compared with interaction with similar structures not containing hydrocarbons .

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•   Selection of the appropriate portions of traces from CRP gathers,•  Application of rejection criteria for removing noisy records, •  Implementation of Fast Fourier Transform, •  Estimation of mean value of Amplitude Spectra in each frequency range, in function of the position of the receiver,--with the subsequent amplitude smoothing, as it shown here: before smoothing and after..  

Processing flow of the Analysis of the spectrums of micro-tremors:

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[0; 20 Hz]

Before smoothing After smoothing

In the method presented here, the micro-tremor anomalies lie in the frequency range from 0 Hz to 20 Hz.

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Microtremors after excitation with a seismic vibrator Serdyukov and Kurlenya (2007)

Serdyukov S.V., Kurlenya M.V., 2007, Seismic stimulation of oil reservoirs // Russian Geology and Geophysics. v. 48, №11, p. 959-966. [in Russian].

From 11 Hz to 16 Hzfrom 22 Hz to 30 Hz

Hydrocarbon-microtremors’ frequencies after excitation

by seismic vibrator

Ampl

itud

e s

pect

rum

Frequency

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After stimulation with vibrator, not only the frequency growth is observed, but also the intensity of hydrocarbon micro-tremors’ emission.

5 minutes after excitation

Before excitation

Ampl

itud

e sp

ectr

um

Receiver coordinate along seismic line [m]

Vedernikov et al. 2001

Hydrocarbon microtremors’ amplitudes: before and after excitation with vibrator

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Vedernikov et al. 2001

5 minutes after excitationBefore excitation

Vedernikov G.V., Zharkov A.V., Maksimov L.A., 2001, Results on the analysis of the Earth hydrocarbon tremors: Geofizika. Special issue on 30 years of “Sibneftegeofizika”, p.96-98 [in Russian].

Stimulation experiment of hydrocarbon microtremors with vibrators

Tecnologías Innovadoras para la exploración y desarrollo de yacimientos no convencionales en México

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Stimulation of hydrocarbon micro-tremors after vibrator

(vibro-seisms) excitation

Vedernikov et al. 2001

Vedernikov G.V., Zharkov A.V., Maksimov L.A., 2001, Results on the analysis of the Earth hydrocarbon tremors: Geofizika. Special issue on 30 years of “Sibneftegeofizika”, p.96-98

[in Russian].

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• Method

• Frequency band of micro-tremors

• Updated method with its application to field data

• Physical reasons of micro-tremors

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Long offsets and early times

Additional part of seismogram is used for the analysis of micro-tremors

The new approach:Long offsets and late times

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To improve the method, we propose using the late-time portion of seismic traces, additionally to the earliest-time portion.

We consider that in the seismic records at large times of arrival (that is several seconds , for example 3.5 sec in this case), the artificial-wave energy has been attenuated to such a degree that the dominant response provides us pure natural micro-seismic response. This enables us separating natural hydrocarbon micro tremors from reflected waves…

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Comparison

Input data: The earliest-timeportions of seismic traces Input data: The late-time

portions of seismic traces

The new approach

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Amplitude-spectrum map of micro- tremors

Zoomed fragment (b).

Well Bh-1

Pair of intersected seismic profiles (W-E and N-S)

Spectrum

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• Method

• Frequency band of micro-tremors

• Updated Method with application to field data

• Physical reasons of micro-tremors

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Why hydrocarbon reservoirs have the micro-tremor-emission spectrum of low frequency?

What is the physical reason of it?

Why the micro-fractures saturated with oil or gas cause the low-frequency micro-tremors’ emission ?

And water-saturated fractures do not cause it... Why?

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There were performed numerous efforts to understand the causes of this phenomenon of microseisms related to oil and gas. Nowadays there is no unique theory which perfectly explains all the aspects of this phenomenon. However in spite of absence of a unified theory, various methods of MicroTremor spectral analysis are rapidly developed for seismic exploration of oil and gas.The ever-present seismic background noise of the earth acts as the driving force for the generation of hydrocarbon indicating signals. The seismic background noise spectrum is modified in a different way when interacting with geological structures containing hydrocarbon filled pores compared with interaction with similar structures not containing hydrocarbons .

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Current investigations which combine the macroscopic aspects of Krauklis wave* propagation, as well as the microscopic poro-mechanical amplification mechanism, are expected to provide major steps towards the complete understanding of the occurrence of Hydrocarbon Microtremor signals (Holzner et al, 2005).

-------------------------------------------------------------------------------------------------(*) Korneev (2008, 2010, 2011), Korneev et al (2004, 2009, 2012) on Krauklis wave .

R. Holzner, P. Eschle, H. Zürcher, M. Lambert, R. Graf, S. Dangel and P.F. Meier, 2005,Applying microtremor analysis to identify hydrocarbon reservoirs First Break, V. 23, No 5, May 2005

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Lambert et al. (2013) consider a possible mechanism causing Hydrocarbon Microtremor signals, which can be understood within the framework of a poro-mechanical amplification mechanism driven by the ever present seismic background noise that resonantly enhances low frequency seismic signals due to the interaction of liquid hydrocarbons, and pore-rock material. The resulting oscillations are transmitted from the reservoir to the surface almost without attenuation or scattering losses due to the low frequency.

Lambert M.-A., Saenger E.H., Quintal B., and Schmalholz S.M., 2013, Numerical simulation of ambient seismic wavefield modification caused by pore-fluid effects in an oil reservoir, GEOPHYSICS, 78, T41–T52.

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Following Lambert et al (2013), poroelastic effects within an oil reservoir may be a plausible explanation for low-frequency ambient wavefield modifications observed at oil fields.

Wave-induced fluid flow at the mesoscopic scale in an oil reservoiris a physical mechanism that can cause significant attenuation contrast to the surrounding rocks. As a physical consequence of this model, ambient wavefield modifications are generated by the reservoir.

Above the oil-saturated reservoir

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Kuznetsov , Dyblenko, Chirkin et al. 2007

Acoustic emission after stimulation by ultrasonic excitation

in oil saturated rock and water- saturated rock

Kuznetsov O.L. , Dyblenko V.P. , Chirkin I.A. et al , 2007, Specific features of geomechanical-stress accumulation and anomalous seismic-acoustic emission in oil and gas-saturated rocks : Geofizika , 6, 8-15

WaterOil

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Acoustic emission stimulated by ultrasonic pulses

Oil-saturated rocks

Water sarurarted rocks

Dry rocks

0 20 40 60 80 100 t [s]Time

Ener

gy

E

0

2

4

6

8

10

Application of mechanical loading

After stimulation

III III

Kuznetsov , Dyblenko, Chirkin et al 2007 Stimulation by

ultrasonic wave

pulses

Dr. Irek Fayzullin hypothesizes that the primary mechanism of hydrocarbon micro-tremor (HMT) is the “in-situ” effect of "disclosure-closing" of microcracks in the subsurface of the earth.

The potential elastic energy of the micro-tremor emission is accumulated at the ends of each crack in the form of stress anomalies. Through this mechanism, the potential energy is transformed into kinetic energy, i.e.–into the micro-tremor emission; the maximum energy is released at the moment of crack closing.

Every day, some of fractures are "active ", i.e. they are closing and disclosing to the state of unstable equilibrium.

D'yakonov B.P., I.S. Fayzullin, 2009, Response of fractured (consisted of block units) media to seismic-acoustic excitations and/or natural microseisms. Part I. Evolution of cracks under variable manmade and natural loading: Geofizika, № 3, p. 5-11.

(*) Fayzullin I.S. , Kutsenko N.V. , 2004, The feasibility of using the scattered waves for the study of fractured geomedium. Numerical simulation: Geofizika, № 5, p.5-9.

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(a)– horizontal section (b) – vertical section

During the micro-fracures’ growth, these micro-fractures are opening, and then they are closing in the subsequet stage of rock compaction, and this can be the main cause of microtremors. (D'yakonov and Fayzullin, 2009)

Micro-tremors occur due to the fractures´ growth with its subsequent decrease in growth and partial closing. Thus the increase and decrease of fractures´ growth takes place due to in-situ temporal stress variations . That is in-situ stress-induced rock compaction and de-compaction variations, which can be considered as the main cause of micro-tremors.

Kouznetsov, Chirkin, et al 2006

Seismic monitoring of the open-fracture variation in reservoir rocks due to Linisolar Tides.

Why the micro-fractures saturated with oil or gas cause the low-frequency micro-tremors’ emission ?

And water-saturated fractures do not cause it... Why?

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The process of the microtremors´ (MT) emission occurs constantly in the subsurface and it never attenuates. It is differentiated in space and time by the average energy, variance and frequency of events of the MT emission .

In turn, these statistics parameters are dominantly determined by such factors as dynamic state of stress, in-situ geo-mechanical properties and the type of saturation fluid (gas, water, or oil) in microfractures .

The fluid type effects to the MT-emission frequency, which is different due to different magnitude of fluid-penetration rate, that is different penetration ability for filtrating into the cavity of closing crack for each fluid (e.g. oil or water).

Presence of fluid results in acceleration of the process of disclosure of fracture and its transition into unstable state .

A speed of penetration of fluid in crack is determined by the phase-permeability coefficient. The higher is the phase-permeability coefficient of fluid, the more frequent is the act of microtremors´ emissions, and so the higher MT-emission frequency is observed.

D'yakonov B.P., I.S. Fayzullin, 2009, Response of fractured (consisted of block units) media to seismic-acoustic excitations and/or natural microseisms. Part I. Evolution of cracks under variable manmade and natural loading: Geofizika, № 3, p. 5-11.

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The coefficient of permeability of the fluid phase of water is larger than this coefficient of oil. And so the water opens and enters into the closed microcracks more quickly compared to the case of oil saturated cracks ...

Therefore, the maximum of microtremors’ spectrum over oilfields shifts towards more lower frequencies compared to the frequencies over water-filled cracks.

That is, in other words, the water-saturated cracks make the cycle of opening -closing and making claps (while doing this) more frequently, in comparison with the oil-filled cracks. That is in contrast with water-filled cracks, the oil-filled cracks will clap less frequently (rarely).

This can explain why oil reservoirs have low-frequency anomalies of the microtremor emission of lower frequency than that of water-saturated cracks.

http://ts.sbras.ru/ru/Pages/articles.aspx?Nomer=1_10

D'yakonov and Fayzullin, 2009

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After stimulation (excitation) by a vibrator, the so-called “Back-Scattered” seismic waves (also called as “Diffracted” waves) are generated, which are originally caused by populations (ensembles) of open fractures.

Special data-processing sequence (method SLBO) is developed, in which this type of wave is separated; these are back-scattered waves, which are related to the micro-tremor emission of hydrocarbons (also known as hydrocarbon microtremor (HM)).

A technology SLBO is developed, which provides reliable 3D imaging of the fractures’ spatial distribution in subsurface, as well as direct hydrocarbon indicator; the latter is a new development (namely the method “СЛОНГ-SLONG”(*).

Spectral attributes estimated from these micro-tremors are related to the direct hydrocarbon indicators.

Fayzullin I.S. , A.V. Seregin, A.V. Volkov, 2013, On the connection of the energy of the scattered waves to the physical characteristics of rocks. Seismic side-scanning method (SLBO): Geofizika, № 4.

Back-scattered waves

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Fayzullin I.S., Chirkin I.A., 1998, Seismic-acoustic method for studying fractured rocks: Geoinformatika, № 3, p.24-27 .

Fayzullin I.S., Kutsenko N.V., 2004, The feasibility of using the scattered waves for the study of fractured geomedium. Numerical simulation: Geofizika, № 5, p.5-9.

D'yakonov B.P., I.S. Fayzullin, 2009, Response of fractured (consisted of block units) media to seismic-acoustic excitations and/or natural microseisms. Part I. Evolution of cracks under variable manmade and natural loading: Geofizika, № 3, p. 5-11.

Fayzullin I.S., B.P. D'yakonov, R.S. Khisamov, R.KH. Muslimov, N.V. Kutsenko, 2006,  On the impact of seismic-acoustic excitation on flooded oil reservoirs: Tekhnologii seysmorazvedki, № 3.

Fayzullin I.S., A.V. Seregin, A.V. Volkov, 2013, On the connection of the energy of the scattered waves to physical characteristics of rocks. Seismic side-scanning method (SLBO): Geofizika, № 4.

Literature

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http://www.gradient-geo.com/m_phyisic.htm

Resonance model of seismic waves between the ground surface and the oil reservoir

Spectrum Birialtsev et al., 2006

Shabalin et al. 2013

Frequency

Ground surface

Oil reservoir

Resonance of low-frequency (long -wavelength) P waves

Birialtsev E. V., Plotnikova I.N., Khabibulin I.R., Shabalin N.Y., 2006, The analysis of microseism spectrum for prospecting of oil reservoir in Republic Tatarstan, EAGE Conference, Saint Petersburg, Russia.

Shabalin N.YA., Birialtsev E. V., Ryzhov V.YA., 2013, Passive methods in low-frequency seismic exploration– Myths and Realities . Pribory i sistemy razvedochnoy geofiziki, 2 (44), p. 46-53. [in Russian].

Method of low frequency seismic surveys in oil and gas exploration

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OIL

WaterNote the difference in the case of the layer with water saturation

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Resonance model of seismic waves between the ground surface and the oil reservoir

Birialtsev et al., 2006

Shabalin et al. 2013

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A mechanism of condensation and evaporation of oil- droplets on the surface of the micro-crack cavity and/or gas bubbles in fluid infill of crack is developed by Kuznetsov et al., 2003.

Kuznetsov O.L., Grafov B.M., Suntsov A.E., and Arutyunov S.L., 2003, ANCHAR technology: the method background. Spetsialniy vypusk “Tehnologii seysmorsvedki –II”, Geofizika, p. 103-107.

Tecnologías Innovadoras para la exploración y desarrollo de yacimientos no convencionales en México

Holzner et al., 2009, Communications in Nonlinear Science and Numerical Simulation, 14, 160-173. 46

Schematic representation of a simple bi-conical pore geometry which enableslow frequency oscillations of the contained liquid along z-direction

Seismic waves propagation through solids exhibiting a resonance frequency.

Rheological model for coupling between elastic deformation and

fluid oscillations

Modification of spectra

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Frehner et al., 2009

oil

-- May be electric resonant circuit formed by oil reservoir (the capacitor)?

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Capacitor

What is the physical reason of Hydrocarbon Micro-Tremors?

Glikman hypothesis in the paper of Kulikov S.A., Gatiyatullin N.S., and Kulikova E.R

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Thank you

tichqvoa@yahoo.com

http://chichinina.rusiamexico.com