Abstract: A self-contained, battery powered well logging instrument is pumped down the interior of a drill pipe string having a catcher sub at its lower end. When the logging instrument latches into the catcher sub, the pumped fluid circulation is blocked, after which increased pump pressure switches a valve assembly to recreate circulation and energize the logging instrument to the standby position. An accelerometer in the logging instrument detects the upward movement of the instrument and switches the circuitry from standby to the record mode. The output from a clock controlled by the downhole accelerometer is recorded along with the logging information and is synchronized with pipe footage measurements and with a similar such accelerometer and clock at the earth's surface which are responsive to the movement of the pipe string at the earth's surface. The recorded logging samples are thus related to true depth by correlating with the data simultaneously recorded at the earth's surface.

Abstract: A self-contained, battery powered well logging instrument is pumped down the interior of a drill pipe string having a catcher sub at its lower end. When the logging instrument latches into the catcher sub, the pumped fluid circulation is blocked, after which increased pump pressure switches a valve assembly to recreate circulation and energize the logging instrument to the standby position. An accelerometer in the logging instrument detects the upward movement of the instrument and switches the circuitry from standby to the record mode. The output from a clock controlled by the downhole accelerometer is recorded along with the logging information and is synchronized with pipe footage measurements and with a similar such accelerometer and clock at the earth's surface which are responsive to the movement of the pipe string at the earth's surface. The recorded logging samples are thus related to true depth by correlating with the data simultaneously recorded at the earth's surface.

Abstract: A well logging instrument comprises a focus section having a focus upper guard, a center electrode and lower focus guard. The bottom section of the instrument includes a pad device having electrodes on its borehole wall-engaging surface and adapted to be urged against the borehole wall and also having a plurality of pressure relief holes formed therein to reduce differential pressure which might otherwise build up between the surface of the pad and the borehole wall. The remote electrode of the focus portion of the instrument is the armor surrounding the logging cable. The lower focus guard serves a dual function in that it is also the mini-focus remote electrode. Means are provided for measuring the potential between the focus guard and the cable armor and also between the microguard and the lower focus guard, both measurements then being sent up the logging cable to the surface electronics.