Wireless passive pressure sensor for downhole annulus monitoring

A method of measuring absolute pressure in an annulus, the method comprising:

• arranging an inductor in a downhole environment, the inductor including primary windings and secondary windings that are wound around different cores;
• arranging a capacitor in the annulus, the capacitor being coupled to the secondary windings and the capacitor including at least one plate that is flexible;
• disposing a controller coupled to the primary windings;
• introducing, using the controller, an input signal to the primary windings;
• receiving, using the controller, a return signal from the primary windings, the return signal resulting from the input signal being transferred through the secondary windings to the capacitor and back from the capacitor directly to the secondary windings, through the secondary windings to the primary windings;
• and
• determining the absolute pressure based on the return signal, wherein the annulus is formed by a first casing and a second casing within the first casing, and the arranging the inductor includes winding the primary windings around an outer surface of a tubing inside the secondary casing and winding the secondary windings around an outer surface of the secondary casing, and the disposing the controller includes conveying the controller into the tubing by a carrier.