A method for monitoring a high-resistivity reservoir rock formation

摘要

A method for monitoring a high-resistivity reservoir rock formation ( 2 ) below one or more less resistive formations ( 3 ). The method includes transmitting an electromagnetic signal (S) propagating from near a seafloor or land surface ( 1 ) by means of an electromagnetic transmitter ( 5 ) powered by a voltage signal generator (G). The electromagnetic signal (S) propagates from the seafloor ( 1 ) and is guided along a conductive string ( 7 ) to the high-resistive formation ( 2 ), and propagates as a guided-wave electromagnetic signal (S 2 ) at a relatively higher speed (V 2 ) inside the high-resistivity formation ( 2 ) than a propagation speed (V 3 ) in the less resistive formations ( 3 ). The guided-wave electromagnetic signal (S 2 ) gives rise to an upward refracting electromagnetic signal (R 3 ) having the relatively lower propagation speed (V 3 ) in the less resistive formations ( 3 ) and having an exit angle nearer to the normal (N) to the interface between the high-resistivity formation ( 2 ) and the lower-resistivity formation ( 3 ), and gives rise to a steeply rising refraction wave front (F 3 ). The refracted electromagnetic wave front (F 3 ) includes refracted electromagnetic signals (R 3 ) detected along an array of sensor antennas ( 6 a, 6 b, 6 c, . . . , 6 k, . . . , 6 n) positioned along the seafloor. The array having a direction away from the transmitter ( 5 ).