Measurement device and support for use in a well

A measurement device to be permanently installed in a well for monitoring and/or studying a fluid reservoir through which at least one well passes, said device comprising:

• electrical power supply and measurement processing means;
• means for measuring the resistivity of the geological formation surrounding said reservoir;
• connection means connecting said measurement means to said electrical power supply and measurement processing means;
• and
• at least one support for measurement means to be permanently installed in a well in order to monitor and/or study a fluid reservoir through which said well passes, said support comprising a cylindrical tube and a jacket surrounding said cylindrical tube, whereby said jacket comprises:
• i. at least a first recess for receiving means for measuring the resistivity of the geological formations surrounding said reservoir, and
• ii. at least an axial recess for receiving connection means leading to power supply and measurement-processing means, said axial recess being such that said connection means are flush with the external surface of said jacket
• and whereby said measurement means and said connection means are being housed in the first and axial recesses in the jacket such that said measurement and connection means are flush with the external surface of said jacket and said axial recess extending over the entire length of the support.