Abstract: System and method for characterizing formation properties based on NMR measurements. NMR clay measurements of this invention distinguish between interstitial pore water and the water adsorbed by the clay minerals. The measurements can be used to determine the quantity of adsorbed water in different clays and correct previously available data obtained using conventional density and neutron porosity logs. A new petrophysical parameter wetness clay is defined as an intrinsic parameter for clays, and its value is computed for members of the smectite group of clays, such as montmorillonite. The wet clay values for the density, neutron logs based on the adsorbed water in clays are used to enhance the quality and accuracy of the overall log interpretation.

Abstract: A well logging system and method are disclosed for detecting the presence and estimating the quantity of gaseous and liquid hydrocarbons in the near wellbore zone. The system uses a gradient-based, multiple-frequency NMR logging tool to extract signal components characteristic for each type of hydrocarbons. To this end, a new data acquisition method is proposed in which measurements at different frequencies are interleaved to obtain, in a single logging pass, multiple data streams corresponding to different recovery times and/or diffusivity for the same spot in the formation. The resultant data streams are processed to determine mineralogy-independent water and hydrocarbon saturations and porosity estimates. Gas and oil saturations are used to obtain accurate estimates of the water content, permeability and other parameters of interest.

Abstract: A well logging system and method for detecting the presence and estimating the quantity of gaseous and liquid hydrocarbons in the near wellbore zone. The system uses a gradient-based, multiple-frequency NMR logging tool to extract signal components characteristic for each type of hydrocarbons. To this end, a new data acquisition method is proposed in which measurements at different frequencies are interleaved to obtain, in a single logging pass, multiple data streams corresponding to different recovery times and/or diffusivity for the same spot in the formation. The resultant data streams are processed to determine mineralogy-independent water and hydrocarbon saturations and porosity estimates. Gas and oil saturations are used to obtain accurate estimates of the water content, permeability and other parameters of interest.

Abstract: A simple, pore-level model for diffusion and NMR relaxation of oil-water mixtures in water wet pores has been developed. In addition to lending physical insight into the relaxation time behavior of mixed pore fluids, the model can be used to generate a practical tool for interpreting diffusion log data, i.e., a T2 vs. D cross plot. Locating points on the cross plot simultaneously yields the near wellbore water saturation and the rock pore size. For light oils, T2 is shown to be mainly a pore size indicator whereas D is controlled mainly by Sw. The pore size "resolution" decreases as oil viscosity and/or Sw decreases. A preliminary verification of the model has been made with limited core data and the results of applying the model to interpreting NMR log data are encouraging.

Abstract: An improved system for using magnetic resonance techniques to obtain information relating to geologic structures is disclosed. The system of the present invention uses values of the total porosity of a formation and the porosity obtained via NMR pulse echo techniques to derive additional information relating to the underlying geologic structures, including resistivity and water saturation. Independent estimate is provided to account for the presence of clay mineral content.

Abstract: An improved system for using magnetic resonance techniques to obtain information relating to geologic structures. The system of the present invention uses values of bulk-volume irreducible water and porosity obtained via the magnetic resonance techniques to obtain additional information relating to geologic structures, including water saturation.

Abstract: An improved system for using nuclear magnetic resonance techniques to obtain information relating to geologic structures. The system of the present invention employs a variable sampling window which increases sampling efficiency by allowing the system to optimize the sampling interval, thereby maximizing the amount of data which can be obtained in a series of data samples.

Abstract: The disclosure is directed to an apparatus and method for determining the bound-water-filled porosity of formations surrounding a borehole. Bound-water-filled porosity is the fraction of the formation unit volume (matrix plus fluid) which is occupied by bound water, bound water being the portion of the total water which is adsorbed or bound to, or impermeably held by, the matrix. In one embodiment, means are provided for deriving a first quantity which is a measure of the attenuation of microwave electromagnetic energy passed through the formations of interest. This first quantity may be, for example, the attenuation constant determined for the microwave electromagnetic energy passing through the formations. Means are provided for generating a second quantity which is substantially proportional to the square of the first quantity. The second quantity is indicative of the bound-water-filled porosity of the formations.

Abstract: In accordance with illustrative embodiments of the present invention, measurements of a plurality of earth formation parameters are combined to produce a new parameter representative of characteristics of the formation. This new parameter is then utilized to determine the permeability of the formation.

Abstract: The determination of a "composite" parameter of the formation water in formations surrounding a borehole, for example the composite conductivity of the formation water, is used in the disclosure to obtain a relatively accurate determination of formation characteristics, such as water saturation. The determined values are meaningful even in shaly regions of the formations. In contrast to past approaches which attempted to determine the volume and distribution type of shale or clay present in the formations and then introduce appropriate factors which often involve substantial guesswork, the disclosed technique determines a composite water parameter, for example a composite water conductivity, which represents the conductivity of the bulk water in the formations, including both free water and bound water. Bound water trapped in shales is accounted for in this determination so unlike prior techniques, the shales can be considered as having a porosity.

Abstract: The disclosure is directed to an apparatus and method for determining the water-filled porosity of formations surrounding a borehole. Alternatively, where porosity is known from other logging information, the disclosed techniques can be utilized for determining the conductivity of the water in formations surrounding a borehole or for determining water saturation. The formations are assumed to comprise a matrix, which may be any subsurface solid material, and fluids contained in the matrix, such as in pore spaces or interstices therein. In accordance with one embodiment, means are provided for deriving a first quantity which is representative of the attenuation of microwave electromagnetic energy propagating between spaced locations in the borehole, the first quantity being, for example, the attenuation constant, .alpha..

Abstract: The disclosure is directed to an apparatus and method for determining the bound-water-filled porosity of formations surrounding a borehole. Bound-water-filled porosity is the fraction of the formation unit volume (matrix plus fluid) which is occupied by bound water, bound water being the portion of the total water which is adsorbed or bound to, or impermeably held by, the matrix. In one embodiment, means are provided for deriving a first quantity which is a measure of the attenuation of microwave electromagnetic energy passed through the formations of interest. This first quantity may be, for example, the attenuation constant determined for the microwave electromagnetic energy passing through the formations. Means are provided for generating a second quantity which is substantially proportional to the square of the first quantity. The second quantity is indicative of the bound-water-filled porosity of the formations.

Abstract: The disclosure is directed to an apparatus and method for determining the water-filled porosity of formations surrounding a borehole. Means are provided for deriving a first quantity which is a measure of the travel time of microwave electromagnetic energy propagating over a predetermined distance in the formations, this first quantity being designated as t.sub.p1. Means are also provided for deriving a second quantity which is a measure of the attenuation of the microwave electromagnetic energy propagating over the predetermined distance in the formations, the second quantity being the attenuation constant, .alpha., in the preferred embodiment. Further means, responsive to the second quantity, are provided for generating a third quantity, designated t.sub.pwl, which is representative of the travel time of microwave electromagnetic energy propagating over the predetermined distance in water having a lossiness determined from the second quantity.