Abstract: Quadrature coils for magnetic resonance imaging (MRI apparatus) are in the form of loops constructed of foil bands of conductive material with their respective axes forming an angle with each other to provide the quadrature phase signals. Trapezoidal cutouts are in each loop to allow for entry of the head of a human being or other large specimen. The angle between the coils is adjusted to compensate for the cutouts to provide and maintain the quadrature phase signals. Inductive coupling between the coils is minimized by three rectangular trim foils which are parallel to the main magnetic field and placed adjacent to the coils.

Abstract: A first temperature sensor is carried by the drill pipe on a radially extensible arm for positioning the sensor at or near the face of the well bore for measuring the true temperature of the face. A second temperature sensor at an intermediate position on the arm measures the temperature of the drilling fluid near the location of the first sensor. The first sensor takes a plurality of readings over a predetermined period of time to detect changes in surface temperature. Both sensors transmit their measurements to a microprocessor, which employs the laws of multidimensional and transient heat transfer by conduction to calculate the true formation temperature.

Abstract: A formation tester is set forth. The device utilizes a snorkel extending from the formation tester to obtain a pressure test and collect samples from a formation of interest. The apparatus includes multiple sample storage containers, thereby cooperating with an equalizing valve to selectively isolate the snorkel from fluid and fluid pressures in the well. A control valve system in a hydraulic circuit operate backup shoes and a snorkel seal until testing is over to assure sealing against well fluid invasion in unconsolidated formation. A speed up sequence for both the backup piston and cylinder arrangement as well as the pad setting piston and snorkel arrangement is illustrated.

Abstract: Magnetic structural arrangement of an installation for nuclear magnetic resonance tomography with superconducting background field coils and normally conducting gradient coils. The magnetic structural arrangement contains superconducting coils cooled by a cryogenic medium for generating a homogeneous magnetic background field, normally conducting coils within the inner space bounded by the background field coils for developing magnetic field gradients, and at least one cooled radiation shield of an electrically and thermally conducting material which is disposed between the gradient coils and the background field coils. In such a structural arrangement the danger exists that eddy currents set up in the radiation shield distort the gradient fields and/or these gradient fields generate undesired heat in the region of the background field coils.

Abstract: Samples of mud are taken periodically at the surface at one or several locations where the mud does not contain cuttings anymore. The mud samples are analyzed on the rig site to determine the successive values, as a function of time or depth, of a parameter representative of the weight of the fine solids present in the mud. In one aspect of the invention the weight of the fine solids present in the mud is determined by measuring the weight of the liquid phase of the mud and the weight of the electrolyte dissolved in a known weight of mud. Preferably the weight of the liquid phase is determined by drying to constant weight a given weight of mud and the weight of electrolyte is determined by chemical analysis of the mud filtrate using an ion chromatography system on the rig site.

Abstract: A magnetic resonance imager includes a quadrature coil assembly (20) for transmitting radio frequency signals into and receiving magnetic resonance signal from an examination region. The quadrature coils assembly includes a first coil (22) and a second coil (24). A shunt path (32, 64, 74, 84, 94, 98, 100, 112, 114, 122) provides a current path by shunting at least a portion of one of the coils. A variable impedance (34, 66, 76, 86, 96, 110, 120) adjusts the amount of current flow through the shunt path and the current flow through the bypassed coil portion. More specifically, adjusting the impedance changes the magnetization vector generated by the coil assembly in a transmit mode and adjusts their relative isolation in a receive mode. The quadrature coils are mounted such that they are offset by about, but not quite, 90.degree.. The variable impedance is adjusted until the offset is brought precisely to 90.degree..

Abstract: In a gradient coil system for a magnetic resonance apparatus arc conductors of notably X coils and Y coils are stacked axially or radially so as to form rigid stacks. The arc conductors are interconnected by means of electrical conductors and the stacks are also interconnected, so that a rigid, self-supporting coil system is obtained. Because the coil system is composed of rigid elements, is comparatively open and does not require a coil former, the production of noise in a magnetic resonance apparatus comprising such a coil system is substantially reduced and field disturbances due to coil deformations are also reduced.

Abstract: Downhole Torque and Rate of Penetration are utilized to develop indications of formations having high porosity or of the development of an undergauge bit. Downhole torque is normalized by dividing it by the product of downhole weight on bit and bit size to produce Dimensionless Torque while Rate of Penetration is normalized by dividing it by the product of downhole weight on bit and rotary speed. The values of Dimensionless Torque and Normalized Rate of Penetration are compared to "normally" expected values of these quantities. Deviations from the normal values are taken as an indication of the occurrence of bit penetration of a highly porous formation or of the development of an undergauge or damaged bit.

Abstract: In an nuclear magnetic resonance imaging system for acquiring a tomographic image of an object of interest at a high speed by use of time-varying gradient magnetic fields, a weighting factor is used in reconstructing an image through the calculation of a correlation of data of a detected nuclear magnetic resonance signal with data of a reference signal, thereby controlling the point spread function and/or the signal-to-noise ratio in each point on the reconstruction image. Also, the effect of relaxation, chemical shift and/or static magnetic field inhomegeneity, which would otherwise degradate the image quality, can be corrected. Further, a velocity of the object of interest at each point on the reconstruction image can be measured.

Abstract: A magnetic resonance spectrometer in which, at least in the receiving branch, the received spin resonance signal is transposed by successive mixing processes into a transposed signal having a higher frequency range than the baseband. The transposed signal is converted into a digital signal by an analog-to-digital converter.

Abstract: In NMR images, which are constructed from resonance signals, for example with Fourier zeugmatography, due to coherent interferences, for example, as a result of "leak-through" of NMR signals from one sequence to a next sequence of resonance signals, artefacts can occur in the images, which, depending upon the kind of interference, become manifest in the image as interference lines, ghost images or conspicuous dots. A method is disclosed of reducing the influence of these interferences by smearing the artefacts out over the image as noise. For this purpose, the phase of the reference signals is randomly modulated between measuring cycles of the resonance signals. The reference signal is used to form excitation pulses for producing resonance signals in a body and further in synchronous detection of the resonance signals.

Abstract: An apparatus for obtaining, in the course of a single scan, NMR image data for a plurality of selected planes in an object, oriented at different angles, utilizes a slice pointer for outputting a signal indicating a particular plane to a multiplier and offset parameter RAM which provides multiplier and offset terms corresponding to the angle of the plane. A generator provides a generic gradient waveform to an arithmetic unit which combines this waveform with the multiplier and offset parameters from the RAM to create waveforms, which when applied to the gradient coils of an NMR apparatus, rotate the slice selector and the readout gradients, thereby permitting image data to be obtained in planes having different angles. A method in accordance with the apparatus of the present invention is also disclosed.

Abstract: An RF shield, for use between a set of gradient coils and an RF coil, is hollow formed of a single conductor sheet divided into first and second opposed halves, each having a set of conductive streamline portions with a series of nonconductive cut lines formed therebetween. Each of the cut lines is parallel to the RF current and is of a generally oval shape. Each of the shield conductor loops is further separated into a "C"-shaped conductive portion, along at least one radial line, and the C portions are then connected so as to continue shielding the RF current, yet pass gradient magnetic fields in all three mutually orthogonal directions of a Cartesian coordinate system.

Abstract: The apparatus (1) is constituted by: device (3) for creating a homogeneous main magnetic static field (HO) orientated along a determined direction (Oz) in which static field there is placed the body (2) to be examined; devices for creating magnetic field gradients in a space of the body to be examined along three directions of the space; radio frequency excitation device (E) and a device (R) for the detection of the nuclear magnetic resonance signals produced by the body to be examined.

Abstract: For use in a measuring while drilling (MWD) apparatus, a variable drilling fluid flow orifice including circular valve seat and valve element in the fashion of a plug is disclosed. The plug is positioned on a stem which connects with a piston in a chamber, the chamber divided into two portions. Pressure is applied on both sides of the piston to provide a pressure balance. Moreover, the flow to the chamber is determined by a pump connected with a first valve means. The first valve means has two outlet lines which connect through first and second feed lines to the piston and chamber. The pump is isolated within a housing surrounded by an annular fluid flow path for drilling fluid. In the housing, a sealed chamber is included for hydraulic fluid for operation of the pump, and the first valve means is controlled by an electrical solenoid connected with a valve stem for moving valve elements of the first valve means to control fluid flow and thereby move the plug in the circular valve seat.

Abstract: Methods and apparatus are disclosed for determining oil saturation in sponge coring using solvents which dissolve substantially all of the oil but none of the sponge. Two classes of such solvents are specified. One is aprotic, and the resultant concentration of oil in it is measured by proton NMR spectroscopy. The other has no C--H bonds, and the resultant concentration of oil in it is measured by infrared spectroscopy.

Abstract: The invention relates to a volume selective magnetic resonance spectroscopy method. Volume selection is performed after excitation by means of three layer-selective 180.degree. rf pulses which excite the nuclear magnetization in three mutually perpendicular layers. The distance between the three selective 180.degree. rf pulses can be chosen to be as small as possible.

Abstract: Counter Rotating Current (CRC) pairs of loop-gap resonators are combined with planar pairs of loop-gap resonators to form networks of NMR local coils. A first embodiment is a quadrature probe in which a planar pair is sandwiched between the loop-gap resonators of the CRC pair. In a plurality of other embodiments, CRC pairs, planar pairs, and other types of local coils are arranged adjacent to one another to form networks of NMR local coils with an enlarged net region of sensitivity. In a further embodiment of the invention, an excitation coil operated in an excite/receive mode is combined with intrinsically isolated local detectors to form an NMR detection network.

Abstract: Magnetic coils (12) create a generally uniform magnetic field through an examination region (10). A radio frequency transmitter applied RF pulses to an RF antenna (26). A gradient field controller (30) generates gradient excitation current pulse profiles which pass through an eddy current calibration circuit (50) to gradient coils (38). A radio frequency receiver (92) receives magnetic resonance signals from the examination region, which signals are Fourier transformed (94) into an image representation (96). The eddy current calibration circuit (50) modifies the current pulse profiles in order to compensate for eddy currents, i.e. to remove the effect of eddy currents such that the resultant gradient magnetic field has a selected profile. An automatic calibration circuit (60) adjusts the decay constant or center frequency of a band pass filter (56) and the gain of an amplifier (58).

Abstract: A magnet system (1) for a nuclear magnetic resonance (NMR) imaging apparatus comprising a magnetic core arrangement (7, 13, 15) shaped to provide two or more discrete gaps (3, 5) of different sizes in which objects to be imaged may be placed, the magnetic field across each gap being produced by a single drive coil arrangement (9) associated with the core arrangement. A system providing gaps of different sizes, for different types of NMR examination is thus provided at relatively low cost compared with using a separate magnet system for each type of examination.