Abstract: A method for tuning a nuclear magnetic resonance (NMR) tool having an operating frequency and equipped with an antenna, is disclosed comprising: (a) transmitting a rf magnetic field to a sample under investigation; (b) receiving an NMR signal from the sample within a detection window; (c) determining mistuning of said antenna relative to said operating frequency; (d) analyzing the received echo signal to determine mistuning of the received signal from the operating frequency. The mistuning of the received signals from the operating frequency may be determined by analyzing any changes in phase of the echo along the echo signal. The antenna tuning process may be automated by measuring calibrated signal amplitudes at more than one frequency and identifying a maximum amplitude. The system tuning may be maintained by repeating (a) through-(d) while operating the tool and implementing a feedback loop.

Abstract: The present invention relates to a method and apparatus for determining the presence of magnetic materials in a media, such as an earth formation. More specifically, the method of the present invention correlates a diffusion-relaxation calibration function representative of magnetic materials with a 2-D function developed using diffusion-editing to determine the presence and relative content of magnetic materials in a media.

Abstract: The present invention discloses a diffusion edited pulse technique that allows information about a fluid to be extracted, comprising: a) obtaining a fluid sample; b) generating a sequence of magnetic field pulses in the fluid, the sequence comprising an initial magnetic field pulse, a first portion that follows the initial magnetic field pulse, and a second portion that follows the first portion; c) detecting magnetic resonance signals using the second portion of the sequence; d) modifying the first portion of the sequence, and repeating steps (b) and (c); and e) extracting information about the fluid by determining relaxation and diffusion characteristics and their correlation based on the signals detected in steps (c) and (d). Also disclosed is a logging tool equipped with a processor to implement the diffusion edited pulse technique.

Abstract: The present invention relates to a method and apparatus for determining the wettability of a porous media, such as bone, plant, food, wood or molecular sieves, etc., having two or more fluids. The method of the present invention correlates a diffusion-relaxation calibration function representative of at least one fluid in the porous media with a 2-D function developed using diffusion-editing to determine wettability of the porous media.

Abstract: In one embodiment of the present invention, a method of measuring the molecular displacement of a fluid is disclosed comprising: (a) applying a strong magnetic field gradient to the fluid; (b) applying a sequence of oscillating magnetic field pulses to the fluid wherein the sequence includes a first portion followed by a second portion, wherein the first portion spatially modulates the magnetization state of the fluid and the second portion monitors the evolution of the modulation; (c) detecting magnetic resonance signals from the fluid; and (d) analyzing the detected signals to determine the molecular displacement of the fluid. This method may be used to determine the diffusion of the fluid or the restricted diffusion of the fluid through the porous media if the fluid is within a porous media (such as earth formation, bone, wood or other material). Also disclosed is a logging tool configured to implement this methodology.

Abstract: The present invention relates to a method and apparatus for determining the presence of magnetic materials in a media, such as an earth formation. More specifically, the method of the present invention correlates a diffusion-relaxation calibration function representative of magnetic materials with a 2-D function developed using diffusion-editing to determine the presence and relative content of magnetic materials in a media.

Abstract: A method for determining downhole reservoir wettability includes acquiring a first set of NMR measurements of formation fluids in earth formations at a selected axial depth; inverting the first set of the NMR measurements to produce a first distribution of a spin relaxation parameter for a fluid component in the formation fluids; acquiring a second set of NMR measurements of a formation fluid sample removed by a formation fluid testing tool at the selected axial depth, the formation fluid sample being kept at a substantially same pressure and temperature as those of the formation fluids in the earth formations at the selected axial depth; inverting the second set of NMR measurements to produce a second distribution of the spin relaxation parameter for the fluid component in the formation fluid sample; determining the reservoir wettability from a comparison of the first and second distributions of the spin relaxation parameter.

Abstract: A method for determining downhole reservoir wettability includes acquiring a first set of NMR measurements of formation fluids in earth formations at a selected axial depth; inverting the first set of the NMR measurements to produce a first distribution of a spin relaxation parameter for a fluid component in the formation fluids; acquiring a second set of NMR measurements of a formation fluid sample removed by a formation fluid testing tool at the selected axial depth, the formation fluid sample being kept at a substantially same pressure and temperature as those of the formation fluids in the earth formations at the selected axial depth; inverting the second set of NMR measurements to produce a second distribution of the spin relaxation parameter for the fluid component in the formation fluid sample; determining the reservoir wettability from a comparison of the first and second distributions of the spin relaxation parameter.

Abstract: In one embodiment of the present invention, a method of measuring the molecular displacement of a fluid is disclosed comprising: (a) applying a strong magnetic field gradient to the fluid; (b) applying a sequence of oscillating magnetic field pulses to the fluid wherein the sequence includes a first portion followed by a second portion, wherein the first portion spatially modulates the magnetization state of the fluid and the second portion monitors the evolution of the modulation; (c) detecting magnetic resonance signals from the fluid; and (d) analyzing the detected signals to determine the molecular displacement of the fluid. This method may be used to determine the diffusion of the fluid or the restricted diffusion of the fluid through the porous media if the fluid is within a porous media (such as earth formation, bone, wood or other material). Also disclosed is a logging tool configured to implement this methodology.

Abstract: The present invention discloses a diffusion edited pulse technique that allows information about a fluid to be extracted, comprising: a) obtaining a fluid sample; b) generating a sequence of magnetic field pulses in the fluid, the sequence comprising an initial magnetic field pulse, a first portion that follows the initial magnetic field pulse, and a second portion that follows the first portion; c) detecting magnetic resonance signals using the second portion of the sequence; d) modifying the first portion of the sequence, and repeating steps (b) and (c); and e) extracting information about the fluid by determining relaxation and diffusion characteristics and their correlation based on the signals detected in steps (c) and (d). Also disclosed is a logging tool equipped with a processor to implement the diffusion edited pulse technique.

Abstract: The present invention relates to a method and apparatus for determining the wettability of a porous media, such as bone, plant, food, wood or molecular sieves, etc., having two or more fluids. The method of the present invention correlates a diffusion-relaxation calibration function representative of at least one fluid in the porous media with a 2-D function developed using diffusion-editing to determine wettability of the porous media.

Abstract: Nuclear magnetic resonance methods for extracting information about a fluid in a rock are described. A system of nuclear spins in the fluid are prepared in a driven equilibrium, and a series of magnetic resonance signals generated from the fluid. The series of magnetic resonance signals is detected and analyzed to extract information about the fluid in the rock.

Abstract: Nuclear magnetic resonance logging methods that detect and analyze a steady state free precession (SSFP) signal are described. In some embodiments, Carr-Purcell-Meiboom-Gill (CPMG) spin echoes are detected along with the SSFP signals. From the SSFP signal, either alone or in combination with CPMG signals, information about a region of an earth formation, such as porosity, bound fluid volume and diffusion, may be extracted.

Abstract: NMR methods for extracting information about a fluid in rock and logging apparatuses for implementing such methods in a borehole environment are provided. The methods involve generating at least two different magnetic field pulse sequences. The magnetic field pulse sequences include a first portion and a second portion. A magnetic field pulse sequence is generated, and magnetic resonance signals are detected using the second portion of the sequence. The first portion of the sequence is modified, and again the sequence generated and magnetic resonance signals detected using the second portion. The magnetic resonance signals are analyzed, and information about, for example, diffusion coefficient, viscosity, composition, saturation in a rock, pore size, pore geometry and the like, extracted from the analyzed signals.

Abstract: Nuclear magnetic resonance logging methods that detect and analyze a steady state free precession (SSFP) signal are described. In some embodiments, Carr-Purcell-Meiboom-Gill (CPMG) spin echoes are detected along with the SSFP signals. From the SSFP signal, either alone or in combination with CPMG signals, information about a region of an earth formation, such as porosity, bound fluid volume and diffusion, may be extracted.

Abstract: A method for determining a characteristic of formations surrounding an earth borehole, includes the following steps: (a) providing a logging device that is moveable through the borehole; (b) producing, from the logging device, a static magnetic field in the formations; (c) transmitting, into the formations, from the logging device, a magnetic pulse sequence and receiving, during the pulse sequence, magnetic resonance spin echo signals; the magnetic pulse sequence having a portion of a pulse acquisition sequence with relatively long pulse spacing times tE,1 and another portion of the pulse acquisition sequence with relatively short pulse spacing times tE,2; and (d) repeating step (c) with pulse spacing times tE,2 that are different than tE,2;(e) deriving respective T2 distributions from the spin echo signals obtained during the another portion of the pulse acquisition sequence of step (c) and during the another portion of the pulse acquisition sequence of step (d); and (f) determining the characteristic of the

Abstract: Nuclear magnetic resonance measurements on a fluid in a rock and methods of analyzing nuclear magnetic resonance data are described. At least one nuclear magnetic resonance measurement is performed, and nuclear magnetic resonance data from each of the measurements are acquired. The data are compressed and analyzed to extract information about the fluid in the rock.

Abstract: Nuclear magnetic resonance methods for extracting information about a fluid in a rock are described. A system of nuclear spins in the fluid are prepared in a driven equilibrium, and a series of magnetic resonance signals generated from the fluid. The series of magnetic resonance signals is detected and analyzed to extract information about the fluid in the rock.

Abstract: Nuclear magnetic resonance measurements on a fluid in a rock and methods of analyzing nuclear magnetic resonance data are described. At least one nuclear magnetic resonance measurement is performed, and nuclear magnetic resonance data from each of the measurements are acquired. The data are compressed and analyzed to extract information about the fluid in the rock.

Abstract: A high speed, NMR, porosity measuring technique and instrument, is described. The instrument is configured with a long prepolarization region of up to approximately six feet disposed ahead of a short detection region of about six inches. The prepolarization region comprises permanent magnets. The detection region comprises homogeneous magnets and rf antenna. This tool design makes possible the acquisition of NMR porosity measurements at 1800 ft./hr., or more, with wait times between successive detection measurements of approximately one second.