Experimental studies of electrokinetic conversions in fluid‐saturated borehole models

Abstract

Experimental and theoretical studies show that there are electromagnetic (EM) fields generated by seismic waves with two kinds of conversion mechanisms in a fluid‐saturated, porous medium. Within a homogeneous formation, the seismic wave generates a seismoelectric field that exists only in the area disturbed by the seismic wave and whose apparent velocity is that of the seismic wave. At an interface between differing formation properties, the generated seismoelectric wave is a propagating EM wave that can be detected everywhere. An electrode, used as a receiver on the ground surface, can detect the propagating EM wave generated at an interface, but cannot detect the seismoelectric field generated in a homogeneous formation. When the electrode is in a borehole and close to a porous formation, it can detect both the EM waves and the seismoelectric field. In this paper, electrokinetic measurements are performed with borehole models made of natural rocks or artificial materials. Experimental results show that the Stoneley wave and other acoustic modes, excited by a monopole source in the borehole models, generate seismoelectric fields in fluid‐saturated formations. The electric components of the seismoelectric fields can be detected by an electrode in the borehole or on the borehole wall. The amplitude and frequency of the seismoelectric fields are related not only to the seismic wave, but also to formation properties such as permeability, conductivity, etc. Comparison between the waveforms of the seismoelectric signals and acoustic logging waves suggests that seismoelectric well logging may explore the different properties of the formation. Electroseismic measurements are also performed with these borehole models. The electric pulse through the electrode in the borehole or on the borehole wall induces Stoneley waves in fluid‐saturated models that can be received by a monopole transducer in the same borehole. These measurement methods (seismoelectric logging or electroseismic logging) might directly apply to well logging to investigate formation properties related to the pore fluid flow.

Laboratory measurements and theoretical modeling of seismoelectric interface response and coseismic wave fields

“…[3][4][5][6][7] Furthermore, a wide range of field and laboratory validations of the coseismic field and the interface response was presented in the literature. [8][9][10][11][12][13][14][15][16][17][18][19][20][21] Several of these works compare either field measurements 15,17 or laboratory measurements 20 with a seismoelectric wave propagation model, corroborating that the coseismic and interface response fields are predicted by the theory.…”

Coupled seismic and electromagnetic wave propagation

“…From research based on this electrokinetic theory, one can distinguish two seismoelectric effects: (1) a coseismic (electric) field is coupled to seismic waves and therefore propagates with seismic wave velocity (e.g., Pride & Haartsen, 1996) and (2) a seismic wave that traverses an interface with a contrast in electrical or mechanical properties produces EM-waves that propagate outside the support of the seismic waves with much higher EM-wave speeds (e.g., Pride & Haartsen, 1996;Haartsen & Pride, 1997). These effects have been verified experimentally in the laboratory (e.g., Zhu et al, 1999Zhu et al, , 2000Zhu & Toksöz, 2003;Block & Harris, 2006;Bordes et al, 2006) and in the field (e.g., Long & Rivers, 1975;Butler et al, 1996;Mikhailov et al, 1997;Beamish, 1999;Garambois & Dietrich, 2001;Dupuis et al, 2007;Haines et al, 2007). Also, the coseismic magnetic fields associated with a Stoneley wave (Zhu & Toksöz, 2005) and with a shear wave have been measured (Bordes et al, 2006(Bordes et al, , 2008.…”

“…Full-waveform electroseismic simulations were performed by White & Zhou (2006); Hu et al (2007); Guan & Hu (2008) and Zyserman et al (2010). A wide range of field and laboratory measurements of the coseismic and interface response fields was presented (see e.g., Martner & Sparks, 1959;Thompson & Gist, 1993;Butler et al, 1996;Mikhailov et al, 1997;Beamish, 1999;Zhu et al, 1999;Mikhailov et al, 2000;Zhu et al, 2000;Garambois & Dietrich, 2001;Zhu & Toksöz, 2003, 2005Block & Harris, 2006;Bordes et al, 2006;Dupuis & Butler, 2006;Haines et al, 2007;Dupuis et al, 2007;Strahser et al, 2007;Liu et al, 2008;Zhu et al, 2008a,b;Dupuis et al, 2009). Zhu & Toksöz (2005) and Bordes et al (2006Bordes et al ( , 2008 reported on coseismic magnetic field measurements associated with a Stoneley wave and a shear wave, respectively.…”

“…The inverse effect was also measured. Electroseismic measurements were performed by Zhu et al (1999Zhu et al ( , 2008a; and Thompson et al (2007).…”

“…Both coseismic and interface response effects are visible in full-waveform numerical simulations (e.g., Haartsen & Pride, 1997;Garambois & Dietrich, 2002;Haines & Pride, 2006;Jardani et al, 2010;. Furthermore, a wide range of field and laboratory validations of the coseismic field and the interface response was presented in the literature (e.g., Long & Rivers, 1975;Thompson & Gist, 1993;Butler et al, 1996;Mikhailov et al, 1997;Beamish, 1999;Zhu et al, 1999Zhu et al, , 2000Garambois & Dietrich, 2001;Zhu & Toksöz, 2003;Block & Harris, 2006;Bordes et al, 2006;Haines et al, 2007;Dupuis et al, 2007Dupuis et al, , 2009). Several of these works compare either field measurements (i.e., Mikhailov et al, 1997;Haines et al, 2007) or laboratory measurements (i.e., Zhu et al, 2000) with a seismoelectric wave propagation model, corroborating that the coseismic and interface response fields are predicted by the theory.…”