Method and apparatus for transmitting electromagnetic signals into the earth from a capacitor
First Claim
1. A method for transmitting an electromagnetic signal through an earth formation, including the steps of:
- (a) disposing capacitor plates having a largest dimension L, in direct contact with the earth formation to form an earth capacitor comprising the plates and a region of the earth formation near the plates;
(b) applying a short voltage pulse across the capacitor plates to transmit electromagnetic radiation into the earth formation, wherein for each frequency component of the electromagnetic radiation, the largest dimension L satisifies the relation Re[kL]<
1, where k is the wavenumber in the earth formation of said frequency component, wherein the short voltage pulse has frequency components in a broad band extending from below 1 MHz to above 100 MHz;
(c) detecting electromagnetic radiation that has propagated through the earth formation in response to application of the short voltage pulse; and
(d) processing only frequency components of the detected electromagnetic radiation, in a frequency window having an upper frequency less than 25 MHz, which have propagated into the earth formation to a penetration depth much greater than on the order of several hundred feet to image the earth formation.
2 Assignments
0 Petitions
Accused Products
Abstract
A method and apparatus in which a capacitor is disposed in direct contact with the earth, and a short voltage pulse is applied to the capacitor to transmit a pulse of electromagnetic radiation having a broad frequency band into the earth. In a preferred embodiment, a portion of the electromagnetic radiation that has propagated through the subsurface is detected and processed to image the subsurface. The size, L, of the transmitting capacitor should be sufficiently small to satisfy the relation Re[kL]<1, where k is the wavenumber in the earth formation of each frequency component of radiation transmitted into the earth. In a preferred embodiment, the voltage pulse applied to the transmitting capacitor has frequency components in a broad band from below 1 MHz to above 100 MHz, and the only frequency components of the detected electromagnetic radiation that are processed to image the subsurface have frequency in the range from about 500 KHz to 25 MHz.
68 Citations
21 Claims
-
1. A method for transmitting an electromagnetic signal through an earth formation, including the steps of:
-
(a) disposing capacitor plates having a largest dimension L, in direct contact with the earth formation to form an earth capacitor comprising the plates and a region of the earth formation near the plates; (b) applying a short voltage pulse across the capacitor plates to transmit electromagnetic radiation into the earth formation, wherein for each frequency component of the electromagnetic radiation, the largest dimension L satisifies the relation Re[kL]<
1, where k is the wavenumber in the earth formation of said frequency component, wherein the short voltage pulse has frequency components in a broad band extending from below 1 MHz to above 100 MHz;(c) detecting electromagnetic radiation that has propagated through the earth formation in response to application of the short voltage pulse; and (d) processing only frequency components of the detected electromagnetic radiation, in a frequency window having an upper frequency less than 25 MHz, which have propagated into the earth formation to a penetration depth much greater than on the order of several hundred feet to image the earth formation. - View Dependent Claims (2, 3, 4)
-
-
5. An apparatus for transmitting an electromagnetic signal through an earth formation, including:
-
a capacitor assembly having a largest dimension L, disposed in direct contact with the earth formation to form an earth capacitor comprising the capacitor assembly and a region of the earth formation near said capacitor assembly; a means for applying a short voltage pulse to the capacitor assembly to transmit electromagnetic radiation into the earth formation, wherein for each frequency component of the electromagnetic radiation, the largest dimension L satisifes the relation Re[kL]<
1, where k is the wavenumber in the earth formation of said frequency component, wherein the short voltage pulse has frequency components in a broad band extending from below 1 MHz to above 100 MHz; anda means for detecting electromagnetic radiation that has propagated through the earth formation in response to application of the short voltage pulse, including means for processing only frequency components of the detected electromagnetic radiation, in a frequency window having an upper frequency less than 25 MHz, which have propagated into the earth formation to a penetration depth much greater than on the order of several hundred feet. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
-
-
18. A method for transmitting an electromagnetic signal through an earth formation, including the steps of:
-
(a) disposing capacitor plates having a largest dimension L, in direct contact with the earth formation to form an earth capacitor comprising the plates and a region of the earth formation near the plates; (b) applying a short voltage pulse between the capacitor plate and ground to transmit electromagnetic radiation into the earth formation, wherein for each frequency component of the electromagnetic radiation, the largest dimension L satisifies the relation Re[kL]<
1, where k is the wavenumber in the earth formation of said frequency component, wherein the short voltage pulse has frequency components in a broad band extending from below 1 MHz to above 100 MHz;(c) detecting electromagnetic radiation that has propagated through the earth formation in response to application of the short voltage pulse; and (d) processing only frequency components of the detected electromagnetic radiation, in a frequency window having an upper frequency less than 25 MHz, which have propagated into the earth formation to a penetration depth much greater than the largest dimension L. - View Dependent Claims (19)
-
-
20. An apparatus for transmitting an electromagnetic signal through an earth formation, including:
-
a capacitor assembly having a largest dimension L, disposed in direct contact with the earth formation to form an earth capacitor comprising the capacitor assembly and a region of the earth formation near said capacitor assembly; a means for applying a short voltage pulse to the capacitor assembly to transmit electromagnetic radiation into the earth formation, wherein for each frequency component of the electromagnetic radiation, the largest dimension L satisifes the relation Re[kL]<
1, where k is the wavenumber in the earth formation of said frequency component; anda means for detecting electromagnetic radiation that has propagated through the earth formation in response to application of the short voltage pulse, including means for identifying frequency components of the detected electromagnetic radiation in a frequency window which have propagated into the earth formation to a penetration depth much greater than on the order of several hundred feet, wherein the means for applying the short voltage pulse to the capacitor assembly includes; a pulse generator; and a transmission line balun connected between the pulse generator and the capacitor assembly. - View Dependent Claims (21)
-
Specification