Abstract: A method and apparatus for obtaining data for simultaneously measuring relative permeability (k.sub.r), static capillary pressure, dynamic capillary pressure (P.sub.c), and electrical resistivity (R.sub.t) of a core sample taken from a subterranean reservoir under simulated reservoir temperature and pressure. A core sample having a a simulated original water and oil saturation is waterflooded while (1) pressures at spaced points along the core are measured to determine k.sub.r, (2) capillary pressures of the oil and water are measured to determine P.sub.c ; and (3) R.sub.t is measured between points spaced on the core. At the same time, the core is scanned by microwaves to determine the water saturation existing in the core at the time a particular measurement is made.

Abstract: A system for determining the relative permeabilities of gas, water and oil in a core sample has a microwave emitter/detector subsystem and an X-ray emitter/detector subsystem. A core holder positions the core sample between microwave absorbers which prevent diffracted microwaves from reaching a microwave detector where they would reduce the signal-to-noise ratio of the microwave measurements. The microwave emitter/detector subsystem and the X-ray emitter/detector subsystem each have linear calibration characteristics, allowing one subsystem to be calibrated with respect to the other subsystem. The dynamic range of microwave measurements is extended through the use of adjustable attenuators. This also facilitates the use of core samples with wide diameters. The stratification characteristics of the fluids may be observed with a windowed cell separator at the outlet of the core sample.

Abstract: The present system is directed to an improved dipmeter system including plural sensors on isolated pads around a sonde. An independent output is formed from each of the sensor pads, and each output is provided to its own adjustable high pass filter. The several high pass filters delete low frequency constituents in the sensor signals. Then, the signals are provided to a dipmeter computer to determine depth with greater accuracy. As a variation, the high pass filters can be selectively adjusted to provide an adjustable frequency for the filters, and one version utilizes the derivative of the dipmeter signal as a function of velocity or time.

Abstract: A porous rock is saturated with a first fluid and electrical resistivity is measured along its length. A second fluid, immiscible with the first fluid, is injected into the porous rock at a first flow rate. This injection continues until displacement of the first fluid from the porous rock ceases and the pressure drop along the porous rock becomes constant, indicating a first residual fluid saturation equilibrium. The foregoing is repeated for a plurality of increasing second fluid injection flow rates to effect electrical resistivity measurements at decreasing residual fluid saturation equilibriums. The method may then be repeated substituting the second fluid for the first and vice versa to perform an imbibition experiment.

Abstract: A two-phase fluid, flow having a first fluid and an immiscible second fluid, is passed through a core sample. The core sample is scanned with X-rays to produce a display of fluid distribution within the core sample. Electrical resistivity is measured along the length of the core sample for those intervals having uniform first fluid distribution. The two-phase flow is continued to repetitively decrease the first fluid saturation in a plurality of drainage cycles with electrical resistivity being again measured for each drainage cycle. Thereafter, the two-phase fluid flow is continued to repetitively increase the first fluid saturation in a plurality of imbibition cycles with electrical resistivity being again measured for each imbibition cycle.

Abstract: A cylindrical core sample of a subterranean formation is place into a sleeve under confining pressure. At least one electrode array extends through the sleeve and makes contact with the core sample. The array is in a plane normal to the core sample and has an even number of electrodes equally spaced about the sleeve. A current is passed through the core sample and voltages are measured across each pair of electrodes that are spaced 180.degree. apart around the sleeve. Such measurements are utilized to identify the radial direction of any electrical anisotropy in the core sample, particularly under differing fluid saturation conditions.

Abstract: A transversely isotropic cylindrical core sample of a subterranean formation is fluid saturated and subjected to a confining pressure. Electrical potential is measured along the core sample and in a plurality of direction through the core sample which are normal to the cylindrical axis of the core sample at a plurality of spaced-apart positions along such axis. From these electric potential measurement tensor conductivity components normal to and lying within the bedding plane of the core sample are determined.

Abstract: A cylindrical core sample of a subterranean formation is fluid saturated and subjected to a confining pressure. Voltages are measured in a plurality of directions through the core sample which are normal to the cylindrical axis of the core sample at a plurality of spaced-apart positions along such axis and utilized to determine resistivities. These resistivities are compared to identify the radial direction of any electrical anisotropy in the core sample for differing fluid saturation conditions.

Abstract: Two types of dielectric logging tools are in use: the pad type which operates in the 100 to 1100 MHz frequency range and the mandrel type, which typically operates in the 10 to 100 MHz range. Although both types of tools make the same measurement, the lower frequency tools have a greater depth of investigation and therefore have different applications than the higher frequency pad device. However, logs measured with 10 to 100 MHz tools are more difficult to interpret because of the large frequency-dependent dispersion of the dielectric permittivity below 100 MHz. A model of the frequency dependence of the dielectric permittivity has now been developed that predicts permittivities in the 10 to 100 MHz range from the more easily obtained measurements in the 100 to 1300 MHz range. The predicted permittivities are used to calculate fit parameters for interpretation equations normally used for the higher frequency pad devices.

Abstract: A method for determining at wellsites the swelling-clay content of cement mixtures by high-frequency dielectric measurements including: grinding a cement mix sample to a size suitable for testing; washing the cement mix sample with a fluid having a water activity substantially less than water, which may contain a soluble cation; packing the washed cement mix sample into a sample cell suitable for dielectric measurement; measuring the dielectric constant at a preselected frequency; and comparing the measured dielectric constant of the cement mix sample to calibration curves.

Abstract: A material sample representative of a subsurface formation is tested for its dynamic interaction with a coring fluid. The material sample is subjected to a pressurized and agitating coring fluid to simulate a coring operation. Thereafter the material sample is x-ray scanned to identify the extent of coring fluid invasion during the dynamic interaction of the material sample and the coring fluid.

Abstract: A method for determining at wellsites the solids content of drilling fluids by high-frequency dielectric measurements including: preparing samples of the drilling fluid, of the drill cuttings from the formation, and of each solids-additives type added to the drilling fluid for uniform dielectric constant measurements at preselected frequencies and obtaining the solids content in accordance with the relationship between the dielectric constant measurements of the drilling fluid-solids, drill cuttings, and each of the solids-additives type. In accordance with the method of the invention two levels of determination are possible. These levels of determination depend upon whether the quantities of solids-additives type added to the drilling fluid are known.

Abstract: Resistivities are measured for a plurality of subsections of a porous rock following a fluid injection that alters the fluid saturation throughout the porous rock. The measured subsection resistivites are compared to identify an equilibrium in the altered fluid saturation throughout the porous rock when there is a fixed relationship between the measured subsection resistivities. Following the detection of fluid saturation equilibrium, the resistivity of the porous rock is measured.

Abstract: A core sample from a subterranean formation is shaped to provide a plurality of parallel, planar outer surfaces. Electrical resistivity is measured in each of the azimuthal directions through the core sample which are perpendicular to each of the pairs of parallel, planar outer surfaces for each of a plurality of differing fluid saturations within the core sample. A logarithmic plot is made of measured resistivity versus water saturation for each of the azimuthal directions through the core sample for which resistivity was measured. If the same logarithmic plot is obtained for all measured azimuthal directions, the core sample is identified as being electrically isotropic. If different logarithmic plots are obtained for at least 2 azimuthal directions the core sample is identified as being electrically anisotropic.

Abstract: Apparatus is provided for measuring resistivities along the length of a core sample of a porous rock under confining pressure and varying fluid saturations. A confining pressure sleeve surrounds the core sample. Resistivities are measured along the length of the core sample by a plurality of electrodes extending through such sleeve as fluid saturations vary.

Abstract: A method and system for determining fluid saturation within a fracture. The method comprises the steps of establishing a functional relationship between fluid saturation and capacitance for a multiple component fluid; introducing the fluid between the fracture faces of the fractured media; measuring electrical capacitance between the fracture faces; and determining fluid saturation from the capacitance measurement and the functional relationship. The method and system find utility with both simulated and natural fractures.

Abstract: For a formation zone of a well, a method for determining the relationship between bulk volume of oil .phi..sub.o as a function of total effective formation porosity .phi..sub.E and height h above the oil water contact from capillary pressure data of a core taken from the formation of the well is disclosed. The disclosed relationship of the form,.phi..sub.0 =C.phi..sub.E -K+g log hwhere C, K and g are constants derived from the capillary pressure data of the core and the relationship between h and the capillary pressure is affected by the relative densities of the connate water of the zone and the oil in the zone.According to an alternative embodiment of the invention, log data may be used to characterize a well according to the relationship.phi..sub.0 =C.phi..sub.E -K+g log hby using sets of data at different depths in the well with statistical regression methods, where the initial oil-water contact level may be determined from said log data.

Abstract: A method for determining at wellsites the swelling-clay content of shales and shaly sandstones earth formations whereby a sample of the formation is washed with a fluid having a water activity substantially less than that of water, which fluid may contain a soluble cation, and measurements of the sample's dielectric constant are made at a preselected frequency for subsequent comparison to calibration curves, thereby obtaining a measurement of the welling-clay content of the formation. The determinations of the swelling-clay content may be performed at different levels depending on the nature of the samples.

Abstract: A new functional parameter reprsentative of the geometrical distribution of matrix material and the variable geometrical distribution of hydrocarbon and water in pore spaces in a porous earth formation is determined and is used to evaluate, or to determine, water saturation of the formation from dielectric permittivity measurements.

Abstract: Logging means and methods are disclosed for distinguishing between dispersed and laminated clay in earth formations. A wireline apparatus is employed consisting of a multifrequency induced polarization logging tool operating at extremely low frequencies, combined with other logging tools which measure the total amount of clay in the formation. A determination is then made of the fraction of the total clay content in the formation which is due to laminated clay.

Abstract: A low-resistivity, hydrocarbon-bearing subsurface sand formation is logged with an electric logging system. Measurements are taken of formation porosity, water resistivity and formation resistivity. Core samples are taken from the formation water and electrical measurements are made on such core samples that reflect both a free-fluid pore network conductance and a rock matrix conductance. From the measurements, a formation water saturation corrected for rock matrix conductance is determined.

Abstract: For a formation zone of a well, a method for determining the relationship between bulk volume of oil .phi..sub.o as a function of total effective formation porosity .phi..sub.E and height h above the oil water contact from capillary pressure data of a core taken from the formation of the well is disclosed. The disclosed relationship of the form,.phi..sub.o =C.phi..sub.E -K+g log hwhere C, K and g are constants derived from the capillary pressure data of the core and the relationship between h and the capillary pressure is affected by the relative densities of the connate water of the zone and the oil in the zone. In a well which has been produced and no .phi..sub.E log exists, the original bulk volume of .phi..sub.o is determined from the R.sub.t log in cooperation with the core data relationship between .phi..sub.o, .phi..sub.

Abstract: A core holder is provided for making petrophysical measurements of core samples from a borehole. The core holder is designed to make resistivity measurements and fluid-flow tests under reproduced conditions of in-situ fluid saturation, reservoir pressure and reservoir temperature.

Abstract: A method of identifying complex lithologies of subsurface rock formations includes the excitation of at least a portion of the rock formation with a multi-frequency electric current. The voltage resulting in the rock is measured and the phase and amplitude of such voltage is determined for each of the included frequencies. The resistivities are determined for each of the frequencies and are plotted as a function of frequency. The complex lithology of the rock formation is characterized by such plot.

Abstract: A method for measuring soil salinity measures the low frequency permittivity of a soil sample at one or more frequencies below 2 megahertz and determines the salinity of the soil sample based on the measured real part of the permittivity. Apparatus for performing the method comprises a soil sample holder for laboratory measurements or a four electrode array for measuring soil salinity in situ. An electrical circuit measures the low frequency permittivity of the soil sample and converts the measured permittivity to the salinity of the soil sample. The salinity conversion can be performed by a read-only memory or a computer with the output being registered by display on a digital or analog display or storage in a data memory.

Abstract: An in-situ method of determining the pore size distribution, capillary pressure curve, and permeability of a formation using induced polarization logging measurements. The induced polarization (IP) voltage decay curve is measured opposite the formation of interest and the voltage decay curve is decomposed into a series of relaxation times related to the pore size distribution. The capillary pressure curve and the permeability are approximated from the pore size distribution. The measurements can also be made in the frequency domain using various frequencies to obtain the variation in phase shift with frequency. The variation in phase shift with frequency can be correlated with previous core measurements to obtain the pore size distribution, capillary pressure curve and formation permeability.

Abstract: A method for determining the productivity of a well site includes extracting a core with sponge coring techniques and measuring the parameters of the core. The parameters measured are porosity, permeability and percent mobile oil. A core factor is calculated which is the square root of the product of permeability and porosity and indicates the space available in the core for oil production. The core factor is multiplied by the percent mobile oil to provide a Production Index. The Production Index indicates the capacity of a given oil well to produce oil. With the Production Index data, perforations are selectively placed in various areas along the longitudinal axis of a well casing (38) to selectively allow communication between the interior of the well casing and a formation of interest. In this manner, only areas having high oil mobility are communicated within a given region of the formation of interest.

Abstract: Method and apparatus are provided for obtaining accurate dynamic measurements for passage of phase fronts through a core sample in a test fixture. Flow-through grid structures are provided for electrodes to permit data to be obtained before, during and after passage of a front therethrough. Such electrodes are incorporated in a test apparatus for obtaining electrical characteristics of the core sample. With the inventive structure a method is provided for measurement of instabilities in a phase front progressing through the medium. Availability of accurate dynamic data representing parameters descriptive of material characteristics before, during and after passage of a front provides a more efficient method for enhanced recovery of oil using a fire flood technique.

Abstract: A method and system for measuring rock electrical properties using time-domain spectroscopy. The rock to be measured is place in direct contact with the substantially flat face of a sample cell. A voltage pulse is launched into a coaxial line connected to the sample cell. The pulse propagates through the sample cell and reflects from the rock. The incident voltage pulse and reflected voltage signal are analyzed to determine the rock's conductivity as well as the rock's dielectric constant over a broad frequency range.

Abstract: A method of two dimensional chemical flood testing includes evacuating a porous medium contained in a test cell. The porous medium in the test cell is irradiated with a beam of microwave energy at a plurality of predetermined locations on said test cell. The microwave energy that has passed through the porous medium at each location is detected at the location. The porous medium in the test cell is filled with brine. The irradiating and detecting steps are repeated, the porous medium is then flooded with crude oil, or a substitute, and again the irradiating and detecting steps are repeated. The porous medium is flooded with brine and again the irradiating and detecting steps are repeated. A calibration curve for each location is derived from the detected microwave energy at the location from the prior irradiating and detecting steps.

Abstract: A method and system for regulating current flow through a core sample from a subterranean formation being tested for electrical impedance, including a variable-frequency current source, means for passing such current through the core sample, means for measuring such current flow, and means for regulating the current flow through the core sample so that it is dependent upon the amplitude of the current flow from the current source and is independent of non-linear variations in core inpedance responsive to the current flow through the core sample.

Abstract: A method of determining the oil and water relative permeabilities and the water saturation of a core of earthen material which includes providing two types of liquids to the core in a manner so that the liquids mix to form a two phase liquid which moves through the core. The core is irradiated with microwave energy while the liquid is in the core. A received energy signal is generated in accordance with the microwave energy that has passed through the core. A liquid pressure drop along a predetermined length of the core is sensed and a representative pressure drop signal is provided. The oil and water relative permeabilities and the water saturation of the core are derived in accordance with the flow rate of the liquid, the received energy signal and the pressure drop signal. The liquid flow rate may be either sensed or the liquid may be provided at a predetermined flow rate.

Abstract: A microwave core monitor includes a sample cell which contains a test core of an earth formation. A microwave transmitter irradiates the test core with a beam of electromagnetic energy at a microwave frequency. A microwave receiver provides an indication representative of a characteristic of a liquid, or the absence of a liquid, in the test core in accordance with electromagnetic energy that has passed through the core. The sample cell further includes microwave absorber rods which prevent portions of the beam of electromagnetic energy not passing through the test core from reaching the receiver.

Abstract: A method of determining the oil and water relative permeabilities and the water saturation of a core of earthen material which includes providing a two phase oil/water liquid to and through said core. The core is irradiated with microwave energy while the liquid is in the core. A received energy signal is generated in accordance with the microwave energy that has passed through the core. A liquid pressure drop along a predetermined length of said core is sensed and a representative pressure drop signal is provided. The oil and water relative permeabilities and the water saturation of the core are derived in accordance with the flow rate of the liquid, the received energy signal and the pressure drop signal. The liquid flow rate may be either sensed or the liquid may be provided at a predetermined flow rate.

Abstract: There is disclosed a battery-operated motor control circuit. An adjustable voltage reference (18, 26, 28) is coupled to the battery (10), with the output of the adjustable voltage reference being coupled to the positive input of an operational amplifier (34). The negative input of the operational amplifier (34) is coupled to ratio control means (60) for setting the gain of the operational amplifier (34) and thus setting the motor (54) to a selected speed. A transistor-pair amplifier (38, 40) is coupled to the output of the operational amplifier (34), with a negative feedback line (50) being coupled from the output of the transistor amplifier to the negative input of the operational amplifier. The motor is also coupled to the output of the transistor amplifier.

Abstract: A method of determining the oil and brine saturation distribution in an oil field by taking electrical current and potential measurements among a plurality of open-hole wells geometrically distributed throughout the oil field. Poisson's equation is utilized to develop fluid saturation distributions from the electrical current and potential measurement. Both signal generating equipment and chemical means are used to develop current flow among the several open-hole wells.