Schlumberger Technology Corporation

Other

William E Kenyon

Paul L Baker

Terizhandur S Ramakrishnan

Pabitra N Sen

Edmund J Fordham

Robert L Kleinberg

Martin D Hurlimann

Francois M Auzerais

Douglas D Griffin, Ii

Masafumi Fukuhara

Elizabeth B Dussan V

Weng C Chew

David Furse Allen

David J Wilkinson

Mark Flaum

Jayanth R Banavar

Lawrence M Schwartz

Peter I Day

Max Lipsicas

Sung K Park

Abdurranhman Sezginer

A method for determining a characteristic of formations surrounding an earth borehole, includes the following steps: (a) providing a logging device that is moveable through the borehole; (b) producing, from the logging device, a static magnetic field in the formations; (c) transmitting, into the formations, from the logging device, a magnetic pulse sequence and receiving, during the pulse sequence, magnetic resonance spin echo signals; the magnetic pulse sequence having a portion of a pulse acquisition sequence with relatively long pulse spacing times t and another portion of the pulse acquisition sequence with relatively short pulse spacing times t ; and (d) repeating step (c) with pulse spacing times t that are different than t ;(e) deriving respective T distributions from the spin echo signals obtained during the another portion of the pulse acquisition sequence of step (c) and during the another portion of the pulse acquisition sequence of step (d); and (f) determining the characteristic of the formations from the respective T distributions.

Well logging technique and apparatus for determining pore characteristics of earth formations using magnetic resonance

Carbonate formations yield unreliable, down hole NMR results. Inter alia, these results must be corrected for temperature. The invention features several methods for obtaining more reliable NMR results for rock petrophysical parameters in carbonate rock formations based upon adjusting T.sub.2 data with respect to temperature.

Method for estimating rock petrophysical parameters using temperature

In this invention a new interpretation methodology has been developed. A pore structure model is used to compute the relaxation behavior. This model is then used as the kernel of a best-fit inversion scheme against the measured data, in contrast to inverting for a T.sub.2 distribution that relies on regularization. Parameters of the model are obtained by 'best fitting' the model with the data. The method considers a geometrical or physical model comprising both intergranular and intragranular porosity (microporosity). The NMR relaxation is computed by one of the several methods. The model is compactly represented by a set of physical parameters that are iterated upon until a match with relaxation data is obtained in the best fit sense. The result is obtained in terms of these physical parameters, and then integrated with other types of measurements.

Method for estimating pore structure in carbonates from NMR measurements

Apparatus for obtaining horizontal and/or vertical permeability measurements through a probe having an elongate aperture. The invention uses the elongate aperture in the probe to orient fluid flow in an earth formation horizontally or vertically. The elongate aperture is approximated through the use of a single elongate opening or through the use of a group of aligned openings of varying shapes. Measurements can be taken at different orientations by including additional probe openings along more than one axis.

Apparatus for determining horizontal and/or vertical permeability of an

Borehole NMR logging apparatus and methods, and methods for the interpretation thereof. A logging tool is provided which produces a strong, static and homogeneous magnetic field B.sub.0 in a Volume of an adjacent formation on one side of the tool to measure nuclear magnetic resonance characteristics thereof. In the preferred embodiment, the tool has an RF antenna mounted on the outside of the metal body of the tool, directing focussed oscillating magnetic fields B.sub.1 at said Volume to polarize or tip the magnetic moments of hydrogen nuclei of fluids within rock pores. The same antenna can be used to receive signals of proton precession in the Volume of interest immediately after transmission of the RF polarizing field B.sub.1. Extremely rapid damping of the antenna between the transmitting and receiving modes of operation is accomplished by a Q-switch disclosed herein. The invention provides for the direct measurement of NMR decay having transverse relaxation time T.sub.2 behavior, and further provides for the fast repetition of pulsed measurements from within a borehole. An additional magnet array may be mounted offset from the first magnet configuration to prepolarize a formation before it is measured in order to pre-align a larger number of protons than the single magnet configuration could do by itself. Additional features of the invention are disclosed which increase the Signal/Noise ratio of the measured data, and improve the quality and quantity of borehole NMR measurements, per unit of time spent. Disclosed interpretation methods determine fluid flow permeability and longitudinal relaxation time T.sub.1 -type parameters by directly comparing the measured decay signals (such as T.sub.2 and T.sub.2 * type decay) to a representation which responds to both the decay time t.sub.dec and the imposed polarization period prior to such decay, t.sub.pol. The parameters of amplitude and T.sub.1 are determined and combined with certain preferred methods to generate robust values of formation characteristics such as fluid flow permeability. Other related methods are disclosed.

Borehole measurement of NMR characteristics of earth formations, and

A head restraint system for vehicles including an extensible support provided with energy absorbing devices which limit the rearward angular displacement of the occupant's head. The support is secured to each side of the interior of a vehicle so that the support is positioned horizontal to the top of a seat back and substantially in the same vertical plane as the seat back.

Head restraint for vehicles

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.

Method for determining low frequency conductivity of subsurface

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.

Method and apparatus for obtaining properties of subsurface formations

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, a corrected dielectric permittivity of a formation surrounding a borehole is determined using the following steps: deriving a measured value of formation dielectric permittivity from a logging device which traversed the borehole; deriving a measured value of formation conductivity from a logging device which traversed the borehole; determining a formation dielectric permittivity dispersion value as a function of the measured conductivity; and determining a corrected formation dielectric permittivity from the measured value of dielectric permittivity and the dispersion value.

Method and apparatus for determining dielectric permittivity of

A borehole investigating device takes measurements of a subsurface earth formation and provides signals forming sonic, formation density or similar logs of the borehole. Additionally, the investigating device measures the dip of seismic signal reflectors traversed by the borehole and provides corresponding dip signals. A seismic section which may or may not include the borehole is selected, and the log and dip signals are combined with signals defining the location of the seismic section with respect to the borehole, to thereby provide synthetic logs for each of a number of virtual boreholes which coincide with selected virtual and/or actual shotpoints of the seismic section. The synthetic log signals are then combined to form a truly two-dimensional synthetic seismogram for the selected seismic section. The synthetically derived signals may be corrected in accordance with a selected geological model of the formation.

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Ridgefield, CT, United States of America

William E Kenyon