Schlumberger Technology Corporation

Services Petroliers Schlumberger

Schlumberger Holdings Limited

Schlumberger Oilfield Assistance Limited

Eni S.p.a.-agip Division

Jean-Claude Trouiller

Bernard Vivet

Emmanuel Legendre

Ollivier Faivre

Bronislaw Seeman

Laurent Jammes

Dylan H Davies

Marie-Therese Gounot

Pascal Rothnemer

Olivier Faivre

Patrizio Gossenberg

Maria Teresa Galli

Henri Gruel

Mauro Gonfalini

Mauro Eni SpA - Agip Division Gonfalini

Laurent c/o Schlumberger Beijing Geoscience Jammes

Patrizio Eni SpA - Agip Division Gossenberg

Maria Teresa Eni SpA - Agip Division Galli

Pascal Schlumberger Rothnemer

Methods for evaluating the properties of formations surrounding a borehole, include the steps of measuring electrical properties of the formation from within the borehole; deriving a model of parameters of the formation surrounding the borehole; and estimating the properties of the formation using the model to interpret the measured electrical properties. In one aspect of the invention in which the formation includes a series of distributed beds, each bed having specific properties. Another aspect includes grouping similar beds, assigning one or more properties to all of the beds in a group, and using the assigned properties to estimate the properties of the formation for measurements relating to the beds of that group. Another aspect includes making several different measurements of formation electrical properties and simultaneously estimating the formation properties from the different measurements to provide a joint inversion. A still further aspect includes the use of a complex model incorporating electrical properties with other petrophysical information to estimate the properties of the formation from the electrical measurements.

Method for evaluating formation properties

The apparatus includes an array of azimuthal current electrodes (Aaz.sub.i) that are circumferentially spaced apart from one another on a body together with two annular guard electrodes (A2) disposed on opposite sides of the array of azimuthal current electrodes (Aaz.sub.i). Measurement currents (Iaz.sub.i) are emitted by the current electrodes (Aaz.sub.i) and focusing currents are emitted by the guard electrodes (A2). Azimuthal monitor electrodes (Maz.sub.i) are associated with respective ones of the azimuthal current electrodes (Aaz.sub.i). Two annular monitor electrodes (M3, M4) are disposed on opposite sides of the array of azimuthal current electrodes (Aaz.sub.i). For focusing purposes, a servo-control system controls the emission of the currents so as to substantially cancel the potential difference detected between the short circuited monitor electrodes (M3, M4) and each of the azimuthal monitor electrodes (Maz.sub.i). In response to the measurement currents (Iaz.sub.i), output signals (Raz.sub.i) are generated representative of the resistivity of the formations in a plurality of directions around the axis of the borehole. A high resolution output signal (Rhr) is also generated as a function of the sum of the measurement currents (Iaz.sub.i).

Method and apparatus for evaluating formation resistivity using focused

A logging method for measuring the resistivity of formations having a borehole passing therethrough, in which a logging sonde is suspended inside the borehole by means of a cable, the sonde comprising electrodes for injecting alternating currents into the formations, these electrodes comprising a central electrode A.sub.0 and focusing electrodes, together with a return electrode B and a potential reference electrode N, one of which is placed above the sonde and the other of which is placed at the surface, and producing a resistivity log from the current I.sub.0 emitted by the central electrode and the potential difference between the sonde and the reference electrode. The method further comprises the step of producing a second log of the resistivity with the return and potential reference electrodes being placed as for the first log and under conditions such that the investigation depth is different from that applicable to the first log. The invention is applicable to correcting the Groningen effect.

Logging method and apparatus for measuring the Grondingen

The invention relates to a logging method and apparatus for determining the electrical resistivity of an earth formation traversed by a borehole. The resistivity is determined using a measuring pad which has a central electrode operable to deliver a measuring current. The measuring current is focused radially by means of two focusing systems: an active focusing system which focuses the measuring current in a first direction; and a passive focusing system which focuses the measuring current in a second direction perpendicular to said first direction.

Method and apparatus for measuring the resistivity of earth formations

Illustrative embodiments of the present invention include a transducer for acoustic well logging, comprising a cylindrical hollow body which is capable of vibrating radially and longitudinally with respect to its axis, and an hemispherical cap coupled to one end of the hollow body. A transducer of this type has a directivity pattern in the range of angles of about 15.degree. to 75.degree. to its axis. This range includes substantially all the acoustic waves whose angles of incidence at the interface between the drilling mud and the formations fall in the range of limit refraction angles typically encountered for the drilling mud commonly used and the various different kinds of formations usually investigated.

Acoustic transducer

Acoustic well-logging methods and apparatus are provided for investigating earth formations traversed by a borehole. Acoustic waves are transmitted from different points in the borehole and received at other points in the borehole, and a reception signal is generated representative of the received acoustic waves. The time interval between the instant the measurement waves are transmitted and the instant the instantaneous amplitude of the reception signal exceeds a given detection threshold for the first time is measured as a function of depth and the value of the detection threshold is adjusted during each measurement sequence in accordance with the amplitude of the noise received during the next preceding listening interval.

Acoustic well logging with threshold adjustment

In accordance with an illustrative embodiment of the present invention, there is shown a substantially rigid member having interruptions in the longitudinal continuity of the member to provide tortuous paths for the passage of acoustic energy along the member. A plurality of masses are periodically spaced along the interior of the member and are each mechanically integral with opposite sides of the member at locations chosen to enable the member and masses to cooperate as a mechanical filter. By so doing, the structure made of the member and masses will have good acoustic delay and attenuation characteristics as well as good mechanical characteristics.

Apparatus for use in investigating earth formations

In accordance with an illustrative embodiment of the present invention, an acoustic logging transducer array includes cylindrical transmitter and receiver transducers whose axes are aligned perpendicular to the longitudinal axis of a longitudinally extending support member in a borehole. The transducers are eccentered in the borehole with the receiving transducers mounted in a pad member which is supported near the borehole wall.

Acoustic well logging methods and apparatus

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Saint Remy les Chevreuse, France

Jean-Claude Trouiller