Abstract: A perforating apparatus adapted to be disposed in a wellbore includes a plurality of shaped charges, an electrical current carrying conductor, and a plurality of exploding foil or exploding bridgewire initiators disposed, respectively, between the plurality of charges and the current carrying conductor for simultaneously detonating thereby simultaneously detonating all of the plurality of shaped charges of the perforating apparatus in response to a current flowing in the conductor. Each of the shaped charges include a new secondary explosive primer disposed in the apex of the charge for detonating in response to a detonation of the exploding foil or exploding bridgewire initiator. The electrical conductor may include a flat cable having a plurality of such initiators spaced apart at predetermined intervals along the cable and adapted to wrap helically around the perforating apparatus until each of the initiators abut against a shaped charge of the plurality of charges in the perforating apparatus.

Abstract: The detonating bore in the rear wall of a shaped charge case is outwardly convex. A powdered explosive is compacted into the case through the open front opposite the detonating bore, causing the portion which enters the convex end of the bore from within the case to be less compacted and less dense, for increased sensitivity and more reliable detonation.

Abstract: A method and apparatus for autocalibrating the transfer function of a digital induction logging tool is disclosed. A plurality of test calibration signals of differing amplitudes are generated and periodically substituted for the normal formation signals. An expression for the transfer function of the tool using standard circuit analysis is obtained for the tool. From the tool output measurements taken for the various test calibration inputs, a linearization correction function is obtained for the tool transfer function as the tool is being used in normal logging operations.

Abstract: The method according to the present invention for determining the flowrate of a fluid flowing in a well comprises the steps of lowering in the well a logging sonde comprising at least one vortex street generating obstacle and a transducer responsive to pressure variations due to the generation of vortices, the transducer producing, for each depth in the well, a detection signal the useful component of which has a frequency f and an amplitude A, deriving from the detection signal a first signal indicative of frequency f, deriving from the detection signal a second signal indicative of the reduced amplitude Ar, defined as the ratio A/f.sup.

Abstract: A floating point analog-to-digital converter for use in a digital induction logging tool is disclosed. Floating point samples of phase quadrature components of the receiver signal are obtained. Each sample contains a digital word representing the exponent of a floating point number and digital word representing its magnitude. A voltage-to-frequency converter produces an output frequency proportional to the magnitude of the component signal. The resulting frequency signal is counted over a predetermined time inverval. At the completion of each time interval, the count is shifted until a predetermined magnitude is reached. The number of shift pulses required to reach this magnitude represents the exponent. The resulting shifted count represents its magnitude.