Abstract: Molecular structures of organic molecules in a geological formation are determined. The organic molecules may include kerogen, coal, and/or other organic molecules. In particular, the technique implmented may operate to convert nuclear magnetic resonance data into a multi-dimensional space that permits identification of molecular structures through comparisons of intensity information across the multi-dimensional space with a cutoff map of the space. This may not only simplify the identification of molecular structures of the organic molecules, but also use exact mathematical model for mixture samples to derive both structural and dynamic parameters plus their variation.

Abstract: The present invention enables the use of a global optimization method for performing joint-inversion of multiple petrophysical data sets, using forward models based on first principle of physics, to generate a 3D rock representation of a subsurface rock structure. The resulting 3D rock representation captures the internal structure, and honors the measured petrophysical properties, of the subsurface rock structure. The 3D rock representation can then be used to predict additional properties not considered in the inversion, to further characterize the subsurface rock structure.

Abstract: A computer-implemented method and system for processing subsurface logs to enhance the continuity of physical property measurements. The method includes obtaining a set of measurement signals along a spatial or time domain from at least one sensor tool moving through a borehole which has traversed through a subsurface region. The method additionally includes performing a global inversion of the set of measurement signals along the spatial or time domain to determine a set of physical properties of the subsurface region having a smooth variation along the spatial or time domain, wherein the set of physical properties can be utilized to determine characteristics of the subsurface region.

Abstract: A computer-implemented method enables a proton density distribution to be obtained. In one embodiment, the method comprises acquiring nuclear magnetic resonance data from porous media; inverting the nuclear magnetic resonance data via a global optimization algorithm to determine a proton density distribution within the porous media; and outputting the determined proton density distribution.

Abstract: The present invention provides a method for obtaining a multi-dimensional proton density distribution from a system of nuclear spins. A plurality of nuclear magnetic resonance (NMR) data is acquired from a fluid containing porous medium having a system of nuclear spins. A multi-dimensional inversion is performed on the plurality of nuclear magnetic resonance data using an inversion algorithm to solve a mathematical problem employing a single composite kernel to arrive at a multi-dimensional proton density distribution. Ideally, the mathematical problem can be cast in the form of a Fredholm integral of the first kind wherein a two or more kernels can be reduced to a single composite kernel for ease of solution. Preferably, a series of conventional CPMG pulse sequences, using a conventional NMR tool, can be used to excite the system of nuclear spins.

Abstract: Novel pulse sequences are used to probe the properties of porous media, such as are found in subterranean formations and core samples. This use allows diffusion effects to be uncoupled from the overall T2 relaxation time of the sample. Properties such as internal field gradient and distribution of diffusion coefficients may be determined. A series of pulse sequences are applied to the media to be evaluated. The series of pulse sequences include first and second windows. The first windows include pulse sequences have varying characteristics, such as increasing echo spacing, while the second windows preferably utilize similar pulse sequences which have very small echo spacing. Apparent internal field gradient distribution and apparent diffusion coefficient may be determined as a function of T2 relaxation time.

Abstract: The present invention provides a method for obtaining a multi-dimensional proton density distribution from a system of nuclear spins. A plurality of nuclear magnetic resonance (NMR) data is acquired from a fluid containing porous medium having a system of nuclear spins. A multi-dimensional inversion is performed on the plurality of nuclear magnetic resonance data using an inversion algorithm to solve a mathematical problem employing a single composite kernel to arrive at a multi-dimensional proton density distribution. Ideally, the mathematical problem can be cast in the form of a Fredholm integral of the first kind wherein a two or more kernels can be reduced to a single composite kernel for ease of solution. Preferably, a series of conventional CPMG pulse sequences, using a conventional NMR tool, can be used to excite the system of nuclear spins.

Abstract: A high vertical resolution antenna design is provided for use in an NMR measurement apparatus. Multiple coils are situated along the length of a magnet. A primary coil is energized to cause an oscillating magnetic field in a portion of earth formation surrounding a borehole. A secondary coil having smaller dimensions than the primary coil is operated to receive spin echoes from a depth of investigation associated with the secondary coil. A distance sufficient to minimize electrical coupling separates the coils. The separation distance can be reduced by selecting a secondary coil with orthogonal polarization to the primary coil. Alternatively, a cross coil configuration can be implemented where the orthogonal secondary coil at least partially overlaps the primary coil, thereby reducing the overall length necessary for the polarizing magnet.

Abstract: A high vertical resolution antenna design is provided for use in an NMR measurement apparatus. Multiple coils are situated along the length of a magnet. A primary coil is energized to cause an oscillating magnetic field in a portion of earth formation surrounding a borehole. A secondary coil having smaller dimensions than the primary coil is operated to receive spin echoes from a depth of investigation associated with the secondary coil. A distance sufficient to minimize electrical coupling separates the coils. The separation distance can be reduced by selecting a secondary coil with orthogonal polarization to the primary coil. Alternatively, a cross coil configuration can be implemented where the orthogonal secondary coil at least partially overlaps the primary coil, thereby reducing the overall length necessary for the polarizing magnet.

Abstract: Novel pulse sequences are used to probe the properties of porous media, such as are found in subterranean formations and core samples. This use allows diffusion effects to be uncoupled from the overall T2 relaxation time of the sample. Properties such as internal field gradient and distribution of diffusion coefficients may be determined. A series of pulse sequences are applied to the media to be evaluated. The series of pulse sequences include first and second windows. The first windows include pulse sequences have varying characteristics, such as increasing echo spacing, while the second windows preferably utilize similar pulse sequences which have very small echo spacing. Apparent internal field gradient distribution and apparent diffusion coefficient may be determined as a function of T2 relaxation time.

Abstract: The present invention relates generally to a nuclear magnetic resonance apparatus and method for substantially eliminating the effects of phase coherent acoustic ringing in borehole logging. A series of cycles of measurement pulse sequences are applied to the formation surrounding the borehole. Each pulse sequence includes an RF excitation pulse and several RF refocusing pulses. Spin echoes are received that contain spurious ringing signals from the excitation and refocusing pulses. Spin echo signals from corresponding spin echoes of each cycle are combined and substantially cancel the spurious ringing from the excitation and refocusing pulses of the pulse sequences.

Abstract: A downhole NMR measurement apparatus for use in a borehole includes at least one magnet, at least one RF transmission coil, at least one gradient coil and circuitry. The magnet(s) establish a magnetic field in a region of a formation that at least partially surrounds the measurement apparatus. The RF transmission coils(s) transmit RF pulses pursuant to an NMR pulse sequence into the region to, in combination with the magnetic field, induce the generation of spin echo signals from a resonance volume within the region. The gradient coil(s) establish a pulsed gradient field in the resonance volume, and the circuitry is coupled to the gradient coil(s) to control the generation of the pulsed gradient field to phase encode the spin echo signals for purposes of high resolution imaging of the formation.

Abstract: A method for reducing ringing in nuclear magnetic resonance measurements is disclosed. The method includes inducing a static magnetic field in a sensitive volume to orient nuclear magnetic spins of nuclei in the sensitive volume. The nuclear spins are reoriented by a first selected angle. An amplitude of the static magnetic field is then adjusted to cause a first selected phase shift in a spin echo signal measured subsequently to the reorienting by the first angle. The spins are then reoriented by a second selected angle, and a first spin echo signal is detected. After a selected wait time, reorienting by the first selected angle is repeated. Adjusting the amplitude of the static magnetic field is then repeated to cause a second selected phase shift in a subsequently measured spin echo. The first and second selected phase shifts have a difference between them of an odd numbered multiple of 180 degrees. Reorienting by the second selected and detecting a second spin echo signal are then repeated.

Abstract: The present invention relates generally to an apparatus and method for measuring nuclear magnetic resonance properties of an earth formation traversed by a borehole by generating gradient-echoes. The measurement can be made while drilling or using a wireline tool. The apparatus applies a static magnetic field, B.sub.a, in a volume of the formation which polarizes the nuclei of hydrogenous connate fluids within the formation. The apparatus applies a second magnetic field, B.sub.b, in a volume of the formation. The magnetic fields B.sub.a and B.sub.b are substantially orthogonal in the volume of the formation. A change in the polarity of the magnetic field, B.sub.b, reverses the direction of precession of the nuclei thereby generating a train of gradient-echoes. Each gradient-echo signal is transformed into the frequency domain and the signal frequency is mapped to a radial position in the volume of the formation in order to generate an image of the formation.

Abstract: The present invention relates generally to a method for eliminating ringing while measuring nuclear magnetic resonance properties of an earth formation traversed by a borehole. The measurement can be made while drilling or using a wireline tool. During a first time period of a single pulse sequence, the measurement includes the desired spin-echoes and the undesired effects, that is, ringing, measurement noise, and baseline shift. During a second time period of the single pulse sequence, the spin-echoes are eliminated but not the undesired effects. Using the signal collected during the second time period, the signals measured during the first time period are corrected to eliminate the ringing component, measurement noise, and baseline shift.