Through casing sensor placement

A method, comprising:

• determining a downhole location where one or more sensors can be positioned in a borehole through a subterranean formation;
• drilling a hole through a casing of the borehole using a drilling system at the downhole location;
• positioning the one or more sensors through in the hole and within the subterranean formation, wherein the one or more sensors are separated from the casing of the borehole;
• establishing a power coupling and a communication coupling between the one or more sensors and one or more devices located within an inner diameter of the casing;
• filling sealant into the hole to form a fluid seal between the inner diameter of the casing and an outer diameter of the casing, wherein the one or more sensors have a first side facing the casing, and the first side of each sensor in the one or more sensors has one or more flow paths allowing the sealant to flow through at least a portion of each sensor in the one or more sensors;
• and
• enabling a collection of sensor data from the one or more sensors at a downhole controller or a surface controller.

A sensor placement system, comprising:

• a transceiver, capable of communicating with a surface controller;
• a drilling system, located downhole a borehole through a subterranean formation, wherein the drilling system is capable of drilling a casing hole through a casing of the borehole and drilling into the subterranean formation;
• one or more sensors, capable of communicating with the transceiver, being positioned within the subterranean formation and separated from the casing of the borehole, and are coupled to a power source located within the borehole and communicatively coupled to a communication device located within the borehole;
• a sealant injection system, capable of injecting a sealant into the casing hole to fluidly seal an inner diameter of the casing and an outer diameter of the casing, wherein the one or more sensors have a first side facing the casing, and the first side of each sensor in the one or more sensors has one or more flow paths allowing the sealant to flow through at least a portion of each sensor in the one or more sensors;
• and
• wherein the drilling system, the transceiver, and the sealant injection system are part of a downhole tool.