Schlumberger Technology Corporation

Pierre Eisenmann

Ollivier Faivre

Jan W Smits

Jean Claude Trouiller

Michel V Berard

Isabelle M Dubourg

Yoshinobu Jinzaki

A method of measuring the resistivity of drilling mud in a borehole passing through a terrestrial formation includes the steps of a) inserting a sonde into the borehole, the sonde having an elongate body provided with at least one annular current electrode (A , A&prime; ) and at least two annular guard electrodes (A, A&prime;, A , A&prime; , A , A&prime; ) situated on either side of the annular current electrode; b) performing computed focusing to simulate an operating mode in which at least one current I is emitted into the surrounding formation from the annular current electrode, the current I being focused in the formation by emitting two currents I and I&prime; from the two annular guard electrodes situated on either side of the annular current electrode; and c) producing a signal representative of the resistivity R of the drilling mud from the simulated operating mode. Apparatus for measuring the resistivity of drilling mud in a borehole includes the sonde, and electronic circuitry for performing computed focusing and computing a signal representative of the resistivity R of the drilling mud on the basis of the computed focusing.

Methods and apparatuses for measuring the resistivity of drilling mud in a borehole

The invention relates to a method of measuring the resistivity of a drilling mud by means of a sonde provided with an annular current electrode (A.sub.0) and with annular guard electrodes (A, A'), current I.sub.0 being emitted into the surrounding formation together with focusing currents I and I'. A signal representative of R.sub.m is produced in response to I.sub.0. Various apparatuses for implementing the method are described. Another method implements a technique of computed focusing. Corresponding apparatuses are also described.

Method/apparatus for measuring mud resistivity using a focused-electrode

The invention relates to a method of correcting the measurements of a pressure gauge for the influence of temperature transients. In a preferred embodiment, a correction term is added to the pressure value measured at an instant t, the correction term A.sub.O [T(t+.tau.)-T(t)] being proportional to the difference between the temperature T(t+.tau.) measured after a time interval of duration .tau. has elapsed from instant t, and the temperature T(t) at instant t. The invention is applicable to measurements in oil wells.

Method and apparatus for correcting a pressure measurement for the

A method of analyzing a mixture of hydrocarbon oils by using gel-permeation chromatography together with infrared detection. According to the method the signals from the infrared detector are combined to form fingerprints (M) which are characteristic of the samples being analyzed and which represent the molecular size distribution of the various hydrocarbon fractions in the samples. Then, the fingerprints are combined either to determine the concentration and the fingerprints of an unknown oil present in a mixture of two oils, or else the concentrations of n known oils in a mixture of the n oils.

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Paris, France

Pierre Eisenmann