Abstract: A method and apparatus of monitoring subsurface formations containing at least one fluid reservoir and traversed by at least one well, by means of at least one sensor responsive to a parameter related to fluids, comprising the steps of:lowering the sensor into the well to a depth level corresponding to the reservoir;fixedly positioning said sensor at said depth while isolating the section of the well where the sensor is located from the rest of the well and providing fluid communication between the sensor and the reservoir.

Abstract: An apparatus for production logging of a well utilizing artificial lift in a wellbore comprises coiled tubing extending into the wellbore, the coiled tubing having gas injector means provided on its remote end and including means for electrical communication from the surface to the injector means; production logging tool means located within the wellbore at a distance so as to separate the logging tool from the injector means and connector means interconnecting the logging tool and the injector means for maintaining a fixed separation between the logging tool and the injector means and for effecting electrical communication from the production logging tool to the electrical communication means located within the injector means.