Abstract: Method of determining the permeability of an underground medium from NMR logs of the permeability of rock fragments from the medium, based on prior calibration of the permeability resulting from these measurements, from direct measurements on rock fragments such as cuttings for example. The method mainly comprises measuring permeability (k) from rock fragments, measuring the signal produced by a device allowing NMR analysis of the rock fragments previously saturated with a protonated liquid (brine for example), obtaining optimum values for the parameters of a relation giving the permeability as a function of the NMR signal, and applying this relation to the well zones that have already been subjected to NMR logging but for which no direct permeability measurements are available. Applications: evaluation of a hydrocarbon reservoir for example.

Abstract: A method and device for measuring the resistivity anisotropy of rocks exhibiting layerings of different conductivity such as laminations is disclosed. The method comprises setting a sample saturated with a first fluid into a petrophysical measurement device allowing the sample to be subjected to drainage operations by injection under pressure of a second fluid. Pairs of electrodes (E, E?) are pressed against the peripheral wall thereof, allowing application of an electric current and detection of the potential differences that appear between distinct application points in response to the application of the electric current. During these operations, at least one injection pressure stage is established for the second fluid, and continuous and precise measurements of the variations in the complex electric impedance of the sample at several frequencies are performed during a displacement stage of the saturating fluid.

Abstract: The invention relates to a nuclear magnetic resonance method of detecting and monitoring the flocculation kinetics of high molecular weight fractions of a complex fluid. The inventive method applies the following to the fluid: a first static polarization magnetic field and, subsequently, at least a second oscillating pulsed magnetic field which generates a nuclear magnetic resonance for the nuclei considered and the acquisition of relaxation signals from the nuclei in the fluid. Moreover, the method detects, in the relaxation signals, a first part P1 which is representative of the relaxation of the flocculated fractions in the fluid and a second part P2 which is representative of the relaxation of the liquid fraction of the fluid; and determines the flocculation rate of the fractions by comparison with values M<sb>x</sb>(t=0) and M<sb>x1</sb>(t=0) which were extrapolated at the start of the acquisition times of the two parts.

Abstract: A method for determining the variations of the resistivity index (RI) of a family of rock samples of complex pore structure with at least two pore networks, as a function of the water saturation (Sw), and in the presence of a non-oil conducting fluid. The volume fraction (f1, f2, f3) occupied by each pore network and the distribution of the pore throats in the various pore networks are determined for each sample of the family. The values of coefficients relating the variation of its electrical resistivity as a function of its water saturation (Sw) are experimentally determined on a sample of the family used as a reference sample. The resistivity index (RI) of all the samples of the family is then determined on the basis of the variation of parameters describing the layout of the pore network, and using the values of the coefficients measured on the reference sample.

Abstract: A method for determining the variations of the resistivity index (RI) of a family of rock samples of complex pore structure with at least two pore networks, as a function of the water saturation (Sw), and in the presence of a non-oil conducting fluid. The volume fraction (f1, f2, f3) occupied by each pore network and the distribution of the pore throats in the various pore networks are determined for each sample of the family. The values of coefficients relating the variation of its electrical resistivity as a function of its water saturation (Sw) are experimentally determined on a sample of the family used as a reference sample. The resistivity index (RI) of all the samples of the family is then determined on the basis of the variation of parameters describing the layout of the pore network, and using the values of the coefficients measured on the reference sample.

Abstract: A device for connecting, by means of a shielded cable, electrodes to a measuring device, located on either side of a wall (18) separating an enclosure under pressure from the outside environment. The device comprises a rigid protector sleeve (16) made of an insulating material that tightly runs through the wall and extends to the immediate vicinity of the electrode, into which shielded cable (C) is passed. A tube (23) made of a conducting material is arranged in rigid sleeve (16) and in electric contact with the cable shield. A plug (24) is secured to rigid sleeve (16), connected to electrode (15) and electrically linked to core (21) of the shielded cable inside metal tube (23). An electric connector (20) is associated with rigid sleeve (16) outside wall (18) for connection of a shielded wire connected to the measuring device. This device can be used in a system measuring the electrical resistivity of a sample in a frequency range that can reach several ten MHz.

Abstract: A method for faster determination of physical parameters (capillary pressure curves and relative permeabilities for example) of a geologic sample initially saturated with a first fluid placed in a vessel and subjected to centrifugation in the presence of a second fluid. The equilibrium saturations are determined before complete stabilization is reached through analytic modelling involving exponential functions, best adjusting to an effective production curve, for each speed stage. A database, obtained by means of various simulations, is used to obtain the relative permeability curves corresponding to the centrifuged sample. The method can be applied for measurement of petrophysical characteristics.

Abstract: Thermostat-controlled containment cell for a sample, suitable notably for a measuring device such as a nuclear magnetic resonance (NMR) spectrometer, NMR type measuring device including the cell, and method for implementing it.

Abstract: The beaver control screen has a cone-shaped screen having a base, an apex and a horizontal axis. A first set of spaced-apart rods extends from the base to the apex and are disposed in a first conical layer. A second set of rods is disposed in a second conical layer inside the first conical layer and extends toward the apex over a distance of about one-half the length of the first conical layer. The first and second conical layers are set at different angles with the horizontal axis such that a distance between a rod in the first layer and an adjacent rod in the second layer is a same distance along the adjacent rod. At the apex of the screen, the rods in the first conical layer are alternately affixed to the outside edge and to the inside edge of an annular plate.

Abstract: Device for connecting, by means of a shielded cable, electrodes to a measuring device, located on either side of a wall (18) separating an enclosure under pressure from the outside environment.

Abstract: The invention is a device for separating a mixture of fluids (conducting fluid, non-conducting fluid, gas), suited to measure the volumes of the various fluids by means of a capacitive measuring process.

Abstract: Method and device for measuring the resistivity index curve (Ir) of a solid sample such as a geologic sample independently of the capillary pressure curve (Pc). Multi-frequency complex impedance measurements are carried out for a sample subjected to a radial confining pressure, during operations of drainage or imbibition of a first, initially saturating fluid, through a semipermeable membrane permeable to this first fluid, placed at a first end of a containment cell, by injection of a second fluid under pressure at the opposite end thereof. One or more injection pressure stages are applied and the continuous variations of the resistivity index (Ir) as a function of the average saturation (Sw) variation are measured without waiting for the capillary equilibria to be reached. Electrodes pressed against the sample on the periphery thereof are used, these electrodes having a given longitudinal extension in relation to the length of the sample and being connected to an impedance meter.

Abstract: The invention is a process and device for performing successive drainage and imbibition phases of a first electrically-conducting fluid and a second fluid of lower density than the first fluid, in a porous sample (1) by means of a centrifuge. Each sample is placed in a main chamber (3) of an elongate vessel (2) fastened to the end of an arm of the centrifuge, together with a spacer (6) whose volume is so selected that, on the one hand, the interface between the two fluids does not come into contact with the sample in operation and, on the other hand, the volume of chamber (3) remaining free around the sample and the associated spacer is greater than, but preferably close to the pore volume of the sample, so as to maximize the displacement amplitude of the interface for a given variation of the volume of fluid displaced. A capacitive sonde (11) in an auxiliary cavity (4), connected to an outer measuring device, is used for measuring the displacements of the interface.

Abstract: Device intended for measurements on a porous rock bar in the presence of fluids including a containment cell comprising an elongate body (2) closed at the opposite ends thereof by end pieces (6, 7) and sources of pressurized fluids allowing displacement under pressure, within the sample, of a first wetting fluid and of a second fluid. One or more selectively wettable rigid membranes consisting each of a relatively thin layer of a porous ceramic on a support layer made from a porous material are pressed against the ends of the sample. The membranes can for example be made by sintering of metallic grains of unequal size (the grains are much coarser for the support layer). Such membranes have good resistance to high temperatures of the order of several hundred .degree.C. Electrodes (E1) connected to a measuring device (24) are used to determine physical characteristics of the bar. The device can be used for oil reservoir engineering notably.

Abstract: The device includes a cell for a sample, delimited lengthwise by two end pieces (7, 8) and laterally by a deformable sheath (17). The end pieces are traversed by channels (14) which place their grooved inside faces in communication respectively with two sources (14, 15) at an adjustable pressure delivering respectively a first and a second fluid. Between the inside faces of the end pieces and the sample, two semipermeable membranes (12, 13) are disposed, which are permeable respectively to the first and to the second fluid. Electrodes (18, 19) are placed inside sheath (17) in contact with the sample and connected to a system (24) for measuring the electrical conductivity of the sample. The cell is placed in a body (1) associated with pressure means (28) for applying a confinement pressure to sheath (17) and membranes (12, 13). The device is designed to operate at relatively high temperatures.

Abstract: The process mainly consists in placing a sample previously imbibed with a first fluid into a vessel or bucket containing another fluid of different density and in applying a centrifugal force by rotating the bucket at the end of an arm, so as to study the displacements of the fluids in the sample during at least two distinct phases. During the first phase, the rotational speed is increased so as to drain the first fluid from the sample. During the second phase, the rotational speed is progressively decreased. In order to avoid a discontinuity and to allow an imbibition of the sample, it is important to keep the two fluids in permanent contact with the sample. The amount of fluid produced in the bucket by centrifugation may be determined. The fluid produced may also be transferred into a variable chamber, for example inside the same bucket or a second rotating bucket.