Mini-well temperature profiling process

In a process in which an elongated electrical resistance heater is installed and operated within a well for substantially uniformly heating an interval of subterranean earth formations which interval is longer than about 100 feet and is heated to a temperature between about 600.degree. C. and a temperature damaging to the well or earth formation, an improvement for installing and operating the heater and measuring the pattern of temperature with depth along the heater, comprising:

• positioning a spooled electrical heater and a spooled tubular stainless steel measuring conduit having an internal diameter of from about 5/16ths to 9/16ths inch at the well site and unspooling the heater and conduit substantially simultaneously into the well while periodically attaching the heater to the conduit so that the conduit supports the weight of the heater;
• interconnecting a flexible weighting member, a thermocouple and a metal-sheathed cable for telemetering thermocouple responses, with those elements having outer diameters small enough to slide freely within the measuring conduit;
• arranging the telemetering cable and a means for spooling and unspooling the metal-sheathed cable so that (a) the gravitational force on the weighting means is capable of pulling the thermocouple and cable downward within the measuring conduit means while the cable is being unspooled and substantially straightening the bends imparted to the cable by the spooling means drum and (b) the correlation between the gravitational force on the weighing means and the diameter of the spooling means is such that the cold working of the cable is not more than about 0.3 percent;
• arranging the metal-sheathed cable spooling means for unattended automatic operation capable of moving the thermocouple through the interval being heated at a rate of about 3 to 2000 inches per minute capable of maintaining a substantial thermal equilibrium between the thermocouple and the temperature within the well;
• and
• operating the heater while measuring the pattern of temperature with depth throughout the interval.