Patent ID: 9598945
Date: 2017-03-21
CPC Classifications: E21B,H01Q,Y10T

Claim:
1. A coaxial antenna for radio frequency (RF) in-situ heating of a subterranean formation, the formation having a 1 st relative electrical permittivity and an electrical conductivity, the antenna having at least an antenna section comprising: an outer conductor having a longitudinal axis and having a circular cross-section having an inside diameter perpendicular to the longitudinal axis, and further having at least one aperture; an inner conductor that is coaxial to the outer conductor and having a circular cross-section having an outside diameter; and an annular space defined by the inside diameter of the outer conductor and the outside diameter of the inner conductor, the annular space containing a dielectric material having a 2 wherein a ratio b/a of the inside diameter of the outer conductor (b) and the outside diameter of the inner conductor (a) remains uniform along the longitudinal axis for a constant characteristic impedance, and wherein the b/a ratio ranges from 1.5 to 10; wherein the at least one aperture is arranged for the antenna to have a circumferential radiation of at least 180 degrees along the longitudinal axis; wherein the antenna has an operational RF power signal frequency from 5 kHz to 20 MHz; wherein the antenna has a radiation power from 0.5 kW/m to 50 kW/m per longitudinal length of the antenna, wherein the 1