Abstract: A method for detecting formation resistivity outside of metal casing using time-domain electromagnetic pulse in a borehole, the method including steps of a) providing a borehole large power pulse transmitting source, recording an induced electromotive force ?, and full time digital recording a transmitted waveform and a received signal; b) conducting transmission-reception and superimposing received signals to improve signal to noise ratio; c) calculating corresponding casing response according to known casing parameters and recorded current waveform of the transmitting source to obtain a relative induced electromotive force ??f; d) correcting relative induced electromotive force value; e) carrying out one-dimensional inversion and converting the observation signal into radial variation information of the formation resistivity; f) obtaining a two-dimensional image of the longitudinal and radial resistivity distribution of outer cased formation resistivity for measured well sections; and g) determining residua

Abstract: A method for detecting formation resistivity outside of metal casing using time-domain electromagnetic pulse in a borehole, the method including steps of a) providing a borehole large power pulse transmitting source, recording an induced electromotive force ?, and full time digital recording a transmitted waveform and a received signal; b) conducting transmission-reception and superimposing received signals to improve signal to noise ratio; c) calculating corresponding casing response according to known casing parameters and recorded current waveform of the transmitting source to obtain a relative induced electromotive force ??f; d) correcting relative induced electromotive force value; e) carrying out one-dimensional inversion and converting the observation signal into radial variation information of the formation resistivity; f) obtaining a two-dimensional image of the longitudinal and radial resistivity distribution of outer cased formation resistivity for measured well sections; and g) determining residua

Abstract: A high-power electromagnetic pulse transmitting device for use in a downhole, the device including a ground instrument and a downhole instrument. The ground instrument, with an industrial control computer as the core, includes a depth/magnetic mark/GPS signal recording module, a Manchester coding and decoding module, and a cable drive module, wherein the depth/magnetic mark recording and the Manchester coding and decoding modules communicate respectively through two serial ports with the industrial control computer, and the cable drive module communication for the downhole instrument through four cables by means of phantom power supply. The downhole instrument includes, in turn, from front to rear: an AC voltage boosting module, a rectifier, an energy storage capacitor, a transmitting coil, and a data acquisition module, and further includes a high-voltage discharge switch and a computer-manipulated controller. Power supply of the downhole instrument is provided by the ground instrument through cables.