Apparatuses and methods for determining properties of subterranean layers

A method of determining values of one or more properties of n layers of a borehole formed in the Earth's crust, the method comprising:

• supporting, in the borehole adjacent one or more of the layers, a plurality of at least (2n-1) sensor members having geometric factors, the geometric factors being mutually differing, known or calculable as defined with reference to a system comprising n layers;
• causing transmission of electromagnetic energy along, and/or reflection of electromagnetic energy at, each sensor member the sensor members being capable of detecting such transmitted and/or reflected electromagnetic energy;
• and
• calculating values of properties of such layers based on such energy values detected at each sensor member.

A method of determining the value of a parameter of a borehole system comprising a borehole having supported therein, apparatus comprising two sensors that are capable of generating outputs indicative respectively of differing mixtures of values of a first parameter of the borehole system and a further parameter of the borehole system, the first parameter being representative of a single physical characteristic of the borehole system and the further parameter taking account of up to two further physical characteristics of the borehole system, the method including:

• causing transmission of electromagnetic energy along, and/or reflection of electromagnetic energy at, each sensor member the sensor members being capable of detecting such transmitted and/or reflected electromagnetic energy;
• operatively connecting the sensors to processing apparatus;
• and
• using the processing apparatus to convert the sensor outputs to a value of the first parameter that is compensated for the further parameter.