Abstract: A technique for producing measurements of physical characteristics of subsurface media near a borehole penetrating the earth is disclosed that uses multiple transducers positioned along a borehole tool. A number of transducers of a first type, such as transmitters, are separated from each other along the tool by a preselected separation, and a number of transducers of a second type, such as receivers, are separated from each other by the same separation and are positioned on the tool at a preselected distance from the transducers of the first type. The technique contemplates the use of appropriate circuitry for producing measurements, using different combinations of transducers, of physical characteristics of the subsurface media at different positions along the borehole.Furthermore, different combinations of measurements produced at different borehole positions may be compared or combined to produce improved measurements that are compensated for borehole effects and other errors.

Abstract: A method which determines output parameters (such as porosity .phi. or water saturation S.sub.w of formations) from a set of logging measurements taken at each level of a borehole is proposed.Measurement and response equation uncertainties of each logging apparatus are determined at each measurement level. Assumed values of the output parameters are chosen and, applying the response equations, calculated values of the measurements are determined. The calculated values of the measurements and the actual measurements are then compared to determine deviations which are weighted by factors calculated from the previously determined uncertainties. An incoherence function is determined from the weighted deviations and a number of "a-priori" constraints. Minimization of the incoherence function gives the most probable output parameters whose uncertainty is in turn calculated.

Abstract: A depth measurement system produces independent signals, each presumably corresponding to the same movement of a wireline if produced under ideal wireline measurement conditions. The system utilizes the signals to provide an accurate and repeatable signal under varying wireline measurement conditions and is particularly suitable for driving a recorder for depth recording and merging measurements from tools lowered in the borehole on different runs and to detect slippage between the wireline and a tangential wheel used to provide one of the signals. Slidably mounted measurement wheels insure tangential engagement of opposite sides of the wireline with equal pressure. Low-load signal generators each responsive to the rotation of the opposing wheels provide independent signals, each ideally corresponding to the movement of the wirline engaged between them. Magnetic marks written on the wireline are sensed and provide yet another independent signal.

Abstract: The disclosure is directed to an apparatus and method for determining the water-filled porosity of formations surrounding a borehole. Alternatively, where porosity is known from other logging information, the disclosed techniques can be utilized for determining the conductivity of the water in formations surrounding a borehole or for determining water saturation. The formations are assumed to comprise a matrix, which may be any subsurface solid material, and fluids contained in the matrix, such as in pore spaces or interstices therein. In accordance with one embodiment, means are provided for deriving a first quantity which is representative of the attenuation of microwave electromagnetic energy propagating between spaced locations in the borehole, the first quantity being, for example, the attenuation constant, .alpha..

Abstract: The disclosure is directed to an apparatus and method for determining the bound-water-filled porosity of formations surrounding a borehole. Bound-water-filled porosity is the fraction of the formation unit volume (matrix plus fluid) which is occupied by bound water, bound water being the portion of the total water which is adsorbed or bound to, or impermeably held by, the matrix. In one embodiment, means are provided for deriving a first quantity which is a measure of the attenuation of microwave electromagnetic energy passed through the formations of interest. This first quantity may be, for example, the attenuation constant determined for the microwave electromagnetic energy passing through the formations. Means are provided for generating a second quantity which is substantially proportional to the square of the first quantity. The second quantity is indicative of the bound-water-filled porosity of the formations.

Abstract: An apparatus and method for determining the amount of adsorbed fluid in formations surrounding a borehole. In accordance with the present invention, means are provided for deriving a first quantity which is a function of the dielectric constant of the formations as measured by passing electromagnetic energy of a first frequency through the formations. Means are also provided for deriving a second quantity which is a function of the dielectric constant of the formations as measured by passing electromagnetic energy of a second frequency through the formations. Finally, means are provided for determining the amount of adsorbed fluid in the formations as a function of the difference between the first and second quantities.

Abstract: A method and apparatus are described for preferentially exciting and for extracting late arrivals at low frequencies in an acoustic investigation of a borehole. The late arrival may be the Stoneley wave whose amplitude is derived by measuring the energy in a predetermined frequency band of a waveform produced with a low frequency transmitter-receiver system. The transmitter produces a highly damped acoustic pulse whose frequency spectrum is selected to preferentially excite a late arrival such as the Stoneley wave and/or tube wave with wavelengths which are significantly greater than the diameter of the borehole while preserving measurable earlier arrivals at higher frequencies. A receiver system is used which provides a generally flat frequency response including low frequencies to produce waveforms of both the earlier arrivals at high frequencies and late arrivals at low frequencies with sufficient extractable amplitudes throughout a wide range of borehole and formation conditions.

Abstract: An apparatus and method for investigating a borehole with energy transmissions whose directivity is varied in real time during the investigation is described. A plurality of transmitters are employed on a well logging tool with at least one receiver located ahead of the transmitters. The transmitters are repetitively activated to transmit a wave of energy to the receiver which produces a received wave. A parameter of the received wave is derived and used to vary the relative delay of activation of the transmitters to direct the beam of energy in a manner whereby the parameter is effectively enhanced for a subsequent investigation. A real time control is provided over the directivity of the energy transmissions to preferentially emphasize a particular segment of a received wave.

Abstract: A depth measurement system particularly suitable for automatically driving a recorder under varying wireline measurement conditions for repeatedly depth recording measurements from borehole tools produces different measurements at generally the same point on the wireline which would correspond if measurement conditions were ideal, but are subject to non-repeatable variations. Accordingly, these signals are automatically utilized to provide a repeatable signal. In one form, the signals correspond to magnetic marks and to incremental movement of the wireline, the latter produced by mechanically coupled devices subject to slippage, variations in circumference, etc. The incremental signals are counted and compared with the number expected for such intervals, a low count indicating slippage or the like and used to provide an appropriate alarm and/or an automatically slippage corrected signal particularly suitable for driving a recorder.

Abstract: Illustrative embodiments of the present invention include methods and apparatus for producing indications of the presence of hydrocarbons in subsurface earth formations. In one embodiment, two different pore volume indications are derived and comparably displayed. The first is primarily dependent upon the hydrogen content of the fluid in the pore space of the formation and may be derived from count rate ratios obtained between two epithermal neutron responsive detectors differently spaced from a neutron source. If thermal neutron or neutron captured gamma ray responsive detectors are used, compensation is provided for thermal neutron absorption effects. The second pore volume indication is produced directly from a measurement of the thermal neutron absorption characteristic of the formation and a value for the water component of the formation.

Abstract: An apparatus and method for determining the amount of adsorbed fluid in formations surrounding a borehole. In accordance with the present invention, means are provided for deriving a first quantity which is a function of the dielectric loss factor of the formations as measured by passing electromagnetic energy of a first frequency through the formations. Means are also provided for deriving a second quantity which is a function of the dielectric loss factor of the formations as measured by passing electromagnetic energy of a second frequency through the formations. Finally, means are provided for determining the amount of adsorbed fluid in the formations as a function of the difference between the first and second quantities.