Abstract: To discriminate optically between the various phases in a three-phase fluid, a light beam (F) of non-zero divergence is injected into a detector block (10) made of a material whose refractive index is greater than the refractive indices of all three phases of the fluid. The block (10) has a sensitive zone (18) and a total reflection zone (20) such that incident rays (Ri) parallel to the axis (12) of the block strike the sensitive zone (17) at an angle of incidence (.THETA.i) and are returned parallel to the axis (12) by the total reflection zone (20). The angle of incidence (.THETA.i) is such that a first phase gives rise to almost total reflection, a second phase gives rise to almost total transmission, and a third phase gives rise to partial transmission and partial reflection.

Abstract: A well logging apparatus is disclosed which employs slot antennas having a plurality of conductive probes traversing the slot. Also disclosed are a logging apparatus having electrically isolated antenna probes and a logging apparatus with an improved means for generating and applying a reference signal used in phase detection.

Abstract: A method and apparatus for investigating earth formations surrounding a borehole operates by selectively heating a region of the formations, and measuring the thermal response to obtain useful information concerning the characteristic length scales of the pores in the heated region. The thermal response is obtained indirectly by measuring the electrical conductivity response. The invention can be utilized to obtain, inter alia, indications of porosity, permeability, and the distribution of pore geometries. In accordance with an embodiment of the method of the invention, the following steps are performed: heating a region of the formations with a series of pulses of microwave electromagnetic energy; measuring the conductivity characteristic of the region which result from the heating pulses; and determining a property of the region of the formations from the measured conductivity characteristic.

Abstract: A system and method are disclosed for wireless two-way communication in a cased borehole having tubing extending therethrough. A downhole communications subsystem is mounted on the tubing. The downhole subsystem includes a downhole antenna for coupling electromagnetic energy in a TEM mode to and/or from the annulus between the casing and the tubing. The downhole subsystem further includes a downhole transmitter/receiver coupled to the downhole antenna, for coupling signals to and/or from the antenna. An uphole communications subsystem is located at the earth's surface, and includes an uphole antenna for coupling electromagnetic energy in a TEM mode to and/or from the annulus, and an uphole receiver/transmitter coupled to the uphole antenna, for coupling the signals to and/or from the uphole antenna. In accordance with a feature of the invention, the annulus contains a substantially non-conductive fluid (such as diesel, crude oil, or air) in at least the region of the downhole antenna and above.

Abstract: A method for determining the fluid mobility or permeability of subsurface formations using borehole measurements of the tube wave. The slowness of an hypothetical tube wave travelling in an elastic, nonpermeable medium is computed based on various measured parameters such as the formation matrix density, fluid density and fluid acoustic slowness. This elastic model slowness is subtracted from the measured tube wave slowness of a selected formation traversed by the borehole, and the difference is used to determine the formation permeability.

Abstract: A detector for detecting the acceleration, the velocity or the displacement of a point is described. The detector includes a light source, at least two photoelectric elements spaced apart from each other over a predetermined distance and a focusing optical system disposed between the light source and the photoelectric elements; the combination being particularly suited for use as an optical seismic detector for detecting and mapping an underground stratum structure.

Abstract: Well logging techniques are set forth for obtaining improved measurements of formation dielectric permittivity, conductivity, and water-filled porosity. The effects of dielectric and conductivity frequency dispersion are considered and utilized. In a disclosed embodiment, an estimated low frequency conductivity of a formation surrounding a borehole is determined using the following steps: deriving a measured value of formation high frequency conductivity from a logging device which traversed the borehole; determining a formation conductivity dispersion ratio as a function of the measured conductivity; and determining an estimated low frequency conductivity from the measured value of high frequency conductivity and the dispersion ratio.

Abstract: A well logging apparatus is disclosed which employs slot antennas having a plurality of conductive probes traversing the slot. Also disclosed are a logging apparatus having electrically isolated antenna probes and a logging apparatus with an improved circuit for generating and applying a reference signal used in phase detection.

Abstract: A method and apparatus are disclosed for determining hydraulic properties of formations surrounding a borehole. In one embodiment, trial values of hydraulic properties such as vertical and horizontal permeability are selected and used to obtain computed formation pressure responses that are compared to measured pressure responses taken at a source and two observation probe positions. Trial values can then be modified to bring the computed pressure responses closer to the measured ones. An improved technique is also disclosed for obtaining the computed pressure responses.

Abstract: An electromagnetic logging apparatus is disclosed which utilizes vertical magnetic dipole antennas for propagation logging, preferably at a frequency greater than 100 MHz. Slot antennas having conductive probes which are perpendicular to the borehole axis, and also perpendicular to a borehole radius, are employed to obtain the desired vertical magnetic dipole antenna characteristics. The depth of investigation is improved as compared to devices of this type which employ horizontal magnetic dipole antennas. Also, the antennas are tuned in a manner which provides advantageous operation.

Abstract: Well logging techniques are disclosed which use and/or measure formation textural parameters. A disclosed formation textural model is bimodal in nature, and includes fractions of spherical grains and of platey grains having a single aspect ratio. This model is used in obtaining improved well logging recordings.

Abstract: Measurement-while-drilling apparatus includes a 14 MeV neutron accelerator, a near-spaced neutron detector which primarily senses source neutrons and whose output is proportional to source strength, one or more intermediately-spaced epithermal neutron detectors eccentered against the drill collar wall and primarily responsive to formation hydrogen concentration, and a third far-spaced radiation detector, either gamma ray or neutron, primarily responsive to formation density. The intermediately-spaced and far-spaced detector outputs, normalized by the near-spaced detector output, are combined to provide measurements of porosity, density and lithology and to detect gas. A thermal neutron detector and/or a gamma ray detector may also be provided at intermediate spacings to provide additional information of interest, such as standoff measurements and spectral analysis of formation composition. Tool outputs are related to the angular or azimuthal orientation of the measurement apparatus in the borehole.