Method and apparatus for testing the integrity of the electrical insulation of a well logging sonde

Apparatus for testing the integrity of the electrical insulation of a logging sonde having a plurality of electrodes in order to measure the electrical resistivity of earth formations traversed by a borehole, said sonde being adapted to be lowered into said borehole, comprising:

• an enclosure capable of containing under high pressure a fluid introduced therein;
• means connecting said sonde to said enclosure for positioning selected ones of said electrodes within said interior;
• a supply of conductive fluid, said fluid having an electrical resistivity which is low relative to the electrical resistivity of air;
• means communicating with the interior of said enclosure for introducing said fluid from said supply into said enclosure, between said sonde and said enclosure;
• means for pressurizing the interior of said enclosure after the introduction of fluid therein, said sonde thereby being at least partly immersed in pressurized conductive fluid, and said enclosure and said connecting means being so constructed and arranged that electrical conduction paths are capable of being established through said fluid and said enclosure;
• and
• means for effecting electrical communication between respective ones of said electrodes and the environment exterior of said enclosure in order to accommodate a measurement of parameters associated with operation of said sonde within said enclosure and said fluid such as to permit the derivation therefrom of an indication of the integrity of said electrical insulation.

A method for testing the integrity of the electrical insulation of a logging sonde having a plurality of electrodes in order to measure the electrical resistivity of earth formations traversed by a borehole, said sonde being adapted to be lowered into said borehole, comprising the steps of:

• positioning said sonde in the interior of an enclosure capable of containing a fluid introduced therein, by connecting said sonde thereto such that selected ones of said electrodes are disposed within said interior;
• providing a conductive fluid within said enclosure, between said sonde and said enclosure;
• effecting electrical communication between respective ones of said electrodes and the environment exterior of said enclosure;
• coupling selected ones of said electrodes to a source of electrical energy, electrical conduction paths thereby being established through said enclosure;
• and
• measuring the electrical energy detected by other selected ones of said electrodes such as to permit the derivation therefrom of an indication of the integrity of said electrical insulation.

A method for testing the integrity of the electrical insulation of a logging sonde having a plurality of electrodes in order to measure the electrical resistivity of earth formations traversed by a borehole, said sonde being adapted to be lowered into said borehole, comprising:

• positioning said sonde in the interior of an enclosure capable of containing under high pressure a fluid introduced therein, by connecting said sonde thereto such that selected ones of said electrodes are disposed within said interior;
• providing a supply of a conductive fluid, said fluid having an electrical resistivity which is low relative to the electrical resistivity of air;
• introducing said fluid from said supply into said enclosure, between said sonde and said enclosure;
• pressurizing the interior of said enclosure after the introduction of fluid therein, said sonde thereby being at least partly immersed in pressurized low resistivity fluid;
• and
• effecting electrical communication between respective ones of said electrodes and the environment exterior of said enclosure for establishing electrical conduction paths through said fluid and said enclosure and for accommodating measurement of parameters associated with operation of said sonde within said enclosure and said fluid such as to permit the derivation therefrom of an indication of the integrity of said electrical insulation.

Method for testing a logging sonde equipped with electrical insulation for the electrical elements thereof and respective current sending and current return electrodes, comprising the steps of:

• placing said sonde within a sealed enclosure having a wall of known high electrical resistivity;
• filling said enclosure with a fluid of low electrical resistivity capable of having electrical conduction paths established therein;
• placing said fluid under high pressure;
• measuring the electrical resistivity of said wall by means of said sonde operating in a shallow investigation mode, conduction paths traversing said fluid and said wall thereby being established;
• and
• comparing the value obtained in said wall resistivity measuring step with the known electrical resistivity of said wall, leakage currents tending to produce a decrease in a measurement current obtained in said wall resistivity measuring step thereby being capable of detection.

An apparatus for testing the integrity of the electrical insulation of a logging sonde having a plurality of electrodes for measuring the electrical resistivity of earth formations traversed by a borehole, comprising:

• an enclosure capable of containing under high pressure a conductive fluid introduced therein;
• means for retaining said sonde within said enclosure to form an intervening space therebetween capable of being occupied by said conductive fluid under pressure;
• means for providing a current path for current originating from and returning to said sonde, said current path traversing at least a portion of said conductive fluid and at least a portion of said enclosure;
• means for highly pressurizing said conductive fluid;
• and
• means for effecting electrical communication with said electrodes from the environment exterior of said enclosure such that electrical parameters associated with operation of said sonde after pressurization of said conductive fluid are measurable, an indication of the integrity of said electrical insulation thereby being capable of determination.