The seismoelectric effects induced from the coupling of the seismic wave field and the electromagnetic field depend on the physical properties of the reservoir rocks. We built an experimental apparatus to measure the ...The seismoelectric effects induced from the coupling of the seismic wave field and the electromagnetic field depend on the physical properties of the reservoir rocks. We built an experimental apparatus to measure the seismoelectric effects in saturated sandstone samples. We recorded the seismoelectric signals induced by P-waves and studied the attenuation of the seismoelectric signals induced at the sandstone interface. The analysis of the seismoelectric effects suggests that the minimization of the potential difference between the reference potential and the baseline potential of the seismoelectric disturbance area is critical to the accuracy of the seismoelectric measurements and greatly improves the detectability of the seismoelectric signals. The experimental results confirmed that the seismoelectric coupling of the seismic wave field and the electromagnetic field is induced when seismic wave propagating in a fluid-saturated porous medium. The amplitudes of the seismoelectric signals decrease linearly with increasing distance between the source and the interface, and decay exponentially with increasing distance between the receiver and the interface. The seismoelectric response of sandstone samples with different permeabilities suggests that the seismoelectric response is directly related to permeability, which should help obtaining the permeability of reservoirs in the future.展开更多
Water-saturated porous media often exhibit a seismoelectric effect due to the existence of an electrical double layer and a relative flow of pore fluid. Here we consider the seismoelectric waves in an open borehole su...Water-saturated porous media often exhibit a seismoelectric effect due to the existence of an electrical double layer and a relative flow of pore fluid. Here we consider the seismoelectric waves in an open borehole surrounded by water-saturated porous formation which exhibits discontinuity of electrochemical properties at a cylindrical interface. We carefully analyze the seismoelectric interface response since these signals show sensitivity to contrasts in electrochemical properties across an interface. Both coupled and approximate methods are used to compute borehole seismoelectric fields. The simulation results show that the radiated electromagnetic wave from the electrochemical interface is generated due to the change of salinity in pore fluid in the porous formation. However, the elastic properties of the formation remain unchanged across such an electrochemical interface. As a result it is difficult to recognize such a change in electrochemical properties using only elastic waves. Therefore, the seismoelectric interface response is potentially used to detect the changes of the electrochemical properties in the formation.展开更多
The shear-horizontal(SH) waves excited by the shear source in a borehole are easy to analyze due to the simple waveform. The borehole-side structures make the formation properties discontinuous. We consider a cylindri...The shear-horizontal(SH) waves excited by the shear source in a borehole are easy to analyze due to the simple waveform. The borehole-side structures make the formation properties discontinuous. We consider a cylindrical double layer structure and study the borehole shear-horizontal and transverse-electric(SH-TE) seismoelectric waves. We first derive the expressions of the basic field quantities, and simulate the acoustic field and electric field using the real axis integral method. Compared with the wave fields of an infinitely homogeneous porous medium outside the borehole, the cylindrical layered structure makes the multi-mode cylindrical Love waves and their accompanying electric fields excited.Next, in order to study the interface response law of the inducing electric fields, we use the secant integral method to calculate the interface converted electromagnetic waves and analyze the causes of each component. It is found that an interface response occurs each time the SH wave impinges the interface in the layered porous medium. The results show that the SH-TE mode has a potential application for borehole-side interface detection in geophysical logs.展开更多
We designed a new downhole electrokinetic logging tool based on numericalsimulations and petrophysical experiments. Acoustic and electric receivers cannot be arrangedat the same depth, and the proposed composite elect...We designed a new downhole electrokinetic logging tool based on numericalsimulations and petrophysical experiments. Acoustic and electric receivers cannot be arrangedat the same depth, and the proposed composite electrokinetic logging tool offers a solutionto this problem. The sound field characteristics of the detectors were tested in a water tank inthe laboratory. Then, we calculated the sound pressure of the radiated acoustic field and thetransmitting voltage response of the transmitting transducers; in addition, we analyzed thedirectivity and application of the acoustic transmitting probe based on linear phased array.The results suggest that the sound pressure generated at 1500 mm spacing reaches up to 47.2k Pa and decreases with increasing acoustic source frequency. When the excitation signalsdelay time of adjacent acoustic transmitting subarrays increases, the radiation beam of themain lobe is deflected and its energy gradually increases, which presumably enhances theacoustoelectric conversion efficiency.展开更多
基金supported by the National Science and Technology Major Project(No.2016ZX05018-005)the New Methods,New Technology Research of Geophysical Prospecting(No.2014A-3612)
文摘The seismoelectric effects induced from the coupling of the seismic wave field and the electromagnetic field depend on the physical properties of the reservoir rocks. We built an experimental apparatus to measure the seismoelectric effects in saturated sandstone samples. We recorded the seismoelectric signals induced by P-waves and studied the attenuation of the seismoelectric signals induced at the sandstone interface. The analysis of the seismoelectric effects suggests that the minimization of the potential difference between the reference potential and the baseline potential of the seismoelectric disturbance area is critical to the accuracy of the seismoelectric measurements and greatly improves the detectability of the seismoelectric signals. The experimental results confirmed that the seismoelectric coupling of the seismic wave field and the electromagnetic field is induced when seismic wave propagating in a fluid-saturated porous medium. The amplitudes of the seismoelectric signals decrease linearly with increasing distance between the source and the interface, and decay exponentially with increasing distance between the receiver and the interface. The seismoelectric response of sandstone samples with different permeabilities suggests that the seismoelectric response is directly related to permeability, which should help obtaining the permeability of reservoirs in the future.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.40974067,41474098,and 11134011)the State Key Laboratory of Acoustics,China(Grant No.SKLA201608)
文摘Water-saturated porous media often exhibit a seismoelectric effect due to the existence of an electrical double layer and a relative flow of pore fluid. Here we consider the seismoelectric waves in an open borehole surrounded by water-saturated porous formation which exhibits discontinuity of electrochemical properties at a cylindrical interface. We carefully analyze the seismoelectric interface response since these signals show sensitivity to contrasts in electrochemical properties across an interface. Both coupled and approximate methods are used to compute borehole seismoelectric fields. The simulation results show that the radiated electromagnetic wave from the electrochemical interface is generated due to the change of salinity in pore fluid in the porous formation. However, the elastic properties of the formation remain unchanged across such an electrochemical interface. As a result it is difficult to recognize such a change in electrochemical properties using only elastic waves. Therefore, the seismoelectric interface response is potentially used to detect the changes of the electrochemical properties in the formation.
基金Project supported by the Natural Science Foundation of Jilin Province of China(Grant No.20180101282JC)the National Natural Science Foundation of China(Grant Nos.40974067 and 42074139)。
文摘The shear-horizontal(SH) waves excited by the shear source in a borehole are easy to analyze due to the simple waveform. The borehole-side structures make the formation properties discontinuous. We consider a cylindrical double layer structure and study the borehole shear-horizontal and transverse-electric(SH-TE) seismoelectric waves. We first derive the expressions of the basic field quantities, and simulate the acoustic field and electric field using the real axis integral method. Compared with the wave fields of an infinitely homogeneous porous medium outside the borehole, the cylindrical layered structure makes the multi-mode cylindrical Love waves and their accompanying electric fields excited.Next, in order to study the interface response law of the inducing electric fields, we use the secant integral method to calculate the interface converted electromagnetic waves and analyze the causes of each component. It is found that an interface response occurs each time the SH wave impinges the interface in the layered porous medium. The results show that the SH-TE mode has a potential application for borehole-side interface detection in geophysical logs.
基金supported by the National Science Foundation of China(No.61102102,11134011,11204380 and 11374371)Major National Science and Technology Projects(No.2011ZX05020-009)+1 种基金Science and Technology Project of CNPC(No.2014A-3912 and 2011B-4001)Petro China Innovation Foundation(No.2014D-5006-0307)
文摘We designed a new downhole electrokinetic logging tool based on numericalsimulations and petrophysical experiments. Acoustic and electric receivers cannot be arrangedat the same depth, and the proposed composite electrokinetic logging tool offers a solutionto this problem. The sound field characteristics of the detectors were tested in a water tank inthe laboratory. Then, we calculated the sound pressure of the radiated acoustic field and thetransmitting voltage response of the transmitting transducers; in addition, we analyzed thedirectivity and application of the acoustic transmitting probe based on linear phased array.The results suggest that the sound pressure generated at 1500 mm spacing reaches up to 47.2k Pa and decreases with increasing acoustic source frequency. When the excitation signalsdelay time of adjacent acoustic transmitting subarrays increases, the radiation beam of themain lobe is deflected and its energy gradually increases, which presumably enhances theacoustoelectric conversion efficiency.
