Abstract: An FM detector for demodulating frequency modulated signals includes an FM detector having an oscillator composed of a capacitor and a Schmitt Trigger. The oscillator is controlled by the input signal to the FM detector. The FM detector also includes a phase detector for mixing the input signal with an oscillator signal from the oscillator to provide an output signal. The frequency of the oscillator is set to the frequency of the input signal using components internal to the FM detector. A first switch is used to charge and discharge the capacitor in accordance with the state of the Schmitt Trigger. A second switch is used to set the frequency of the oscillator to the frequency of the input signal.

Abstract: The logging tool comprises a gas void fraction measurement section (37) consisting of a first set (37) of eight longitudinal electrodes (38) extending parallel to the longitudinal axis of the tool and positioned and regularly spaced around said longitudinal axis, a sleeve (40) made of dielectric material and located in contact and around the electrodes for obtaining an electric field pattern distributed essentially radially between the electrodes and the wall (12) of the borehole facing the electrodes (38), a centralizer (32) for substantially centralizing the tool in the borehole, and a circuit means (69-115) for measuring sequentially the capacitance between two adjacent electrodes for each pair of electrodes, said capacitance being characteristic of the gas void fraction of the fluid flowing in the wellbore. The logging tool comprises in addition a cross correlation gas velocity measurement section (28) which includes a second (48) and a third (50) set of electrodes.

Abstract: Formation fluid is received in and passed through a sonde supported by an armored well logging cable at a depth of interest in a well bore. Periodically, samples of the formation fluid are taken. Higher density portions of the fluid, which represent formation fluid and/or mud filtrate, are separated. The separated fluid is a sample from which the resistivity is measured. As sampling continues, the sample fluid becomes substantially formation fluid and an apparent R.sub.2 measurement is made. An electrical signal indicating the R.sub.2 at the depth of interest is sent to the surface for recording and further processing. R.sub.2 measurements can be taken at any desired number of depths of interest in the well bore.

Abstract: The infusion of fluid from the formation being drilled into a borehole is detected by modulating the drilling fluid stream in the drill pipe and detecting pressure variations commensurate with the modulation at the surface in the annulus between the drill pipe and wall of the well. The detected pressure variations are compared in phase and/or amplitude with their own near term past history or with the drilling fluid pressure variations in the drill pipe resulting from the modulation. Variations in phase or amplitude which can not be attributed to changes in the drilling operation will be indicative of fluid infusion.

Abstract: The infusion of fluid from the formation being drilled into a borehole is detected in an MWD system by modulating the drilling fluid stream in the drill pipe and detecting pressure variations commensurate with the modulation at the surface in the annulus between the drill pipe and wall of the well. Modulation to generate the pressure variations in the annulus is accomplished by the same pressure generating element used to generate pressure signals in the mud column for MWD measurements. The detected pressure variations are compared in phase and/or amplitude with their own near term past history or with the drilling fluid pressure variations in the drill pipe resulting from the modulation. Variations in phase or amplitude which can not be attributed to changes in the drilling operation will be indicative of fluid infusion.

Abstract: The method uses a tubular shaped and electrically conductive well casing that extends to a geological formation in an oil or gas well. The casing is used for both flowing fluid between the formation and the casing at the top of the well and for communicating data representative of a parameter in the well to the casing at the top of the wall. A tool carrying a switch and an electrical contact is inserted down the inside of the casing. The contact on the tool is connected to the inside of the casing. The flow of the fluid between the geological formation and the casing at the top of the well through the side of the casing above the tool is controlled. A parameter in the well adjacent the formation is sensed. The switch in the tool is operated for sequentially connecting together and disconnecting the contact to a return electrical path to the top of the well for causing changes in the conductance between the casing and the return path representative of data about the parameter.

Abstract: A high permeability ferrite core, which includes a gap between adjacent ends thereof, is combined with a magnetic coil encircling the core, and is located in a sub positioned in the drill string just above the drill bit of a borehole drilling rig. The core is positioned so that the gap thereof lies across a recess region formed in the outer wall of the sub. Drilling fluids flow along the outer surface of the sub on the return path from the drill bit to the mud pits located at the surface of the borehole. A constant current, or voltage, at a frequency within the range of 20 KHz-20 MHz is applied to the terminals of the coil encircling the core and the eddy currents developed in the gap region produce a measurable back emf at the coil terminals. The current produced by this emf voltage is indicative of the resistivity of the drilling fluid within the recess region in the wall of the sub and the fluctuations of the voltage accurately follow the variations in drilling fluid resistivity.

Abstract: In accordance with illustrative embodiments of the present invention, methods for processing well logging data comprises deriving measurements of a plurality of earth formations parameters and combining these measurements in a new manner to enable interpretation of shales and shaly sand type formations. More particularly, measurements of a plurality of the hydrogen index, bulk density, radially deep and shallow resistivity, spontaneous potential, acoustic travel time and natural formation radioactivity content are made and combined in a manner to produce data useful in evaluating shales and shaly sand type formations.

Abstract: A method of computer generating a subsurface characteristic model which is substantially consistent with readings taken in a well with a well logging device. A set of actual measurement values which represent readings taken over a given depth interval of a well is derived. An initial trial model of the subsurface characteristic under investigation is then selected. Next, a set of simulated measurement values is generated by applying the approximate response characteristic of the logging device to the discrete trial model. The simulated measurement values are compared with the actual measurement values and an error function is generated in accordance with the comparison, the error function reflecting the comparison taken over a substantial portion of the given depth interval. The model is then modified in a manner which tends to minimize the error function.

Abstract: In an in situ uranium leaching process, a method of detecting presence or absence of leach solution escaping from a desired leaching zone involves monitoring the electrical impedance of a zone just outside the desired zone to detect high ionic concentration indicative of leach solution. Electrical impedance is measured by locating monitor wells just outside the leaching zone and positioning pairs of current and voltage probes within the monitor wells and closest injection wells. Low frequency, constant current is generated by each pair of current probes between corresponding injection and monitor wells to develop a zone impedance-dependent voltage drop that is measured by each set of voltage probes and correlated to presence or absence of escaping leach solution. In an alternative embodiment, electrical impedances are measured between a single, central recovery well and a series of distributed, monitor wells to reduce the total number of probes required.

Abstract: A method and implementing apparatus for measuring in situ the electrical capacitance and resistance of soils and determining therefrom the density and fabric thereof. The apparatus includes a self-contained probe adapted to be driven into the soil to be measured. The probe has a soil sensor element and a measuring circuit such as a capacitance and resistance bridge. The measuring circuit employs radiofrequency current to enable direct measurement at the probe of the resistance and capacitance of the soil sample and of the pore liquid. A remote indicator and control unit in communication with the probe is provided with indicators such as meters or displays which provide direct readout of measured resistance and capacitance, and which may also enable the bridge in the probe to become balanced. Alternatively, the probe may include a computer for automatically balancing the bridge and calculating critical soil properties.