255 results about "Transverse Relaxation Time" patented technology

The invention discloses a nuclear magnetic resonance analyzer and a nuclear magnetic resonance measuring method. The analyzer comprises a radio frequency circuit, a magnet, a glass tube, a first coil and a second coil, wherein a sample to be measured is placed in the glass tube; the glass tube is fixedly arranged at a position opposite to the magnet and is placed in a magnetic field produced by the magnet; the first coil and the second coil are wound on the outer surface of the glass tube respectively and are connected with the radio frequency circuit; the first coil is placed at a uniform magnetic field produced by the magnet; and the second coil is placed at a gradient magnetic field produced by the magnet. Through the analyzer, distribution data of transverse relaxation time and longitudinal relaxation time of substances in the sample to be measured can be obtained, and distribution data of diffusion coefficients of the substances in the sample can be obtained.

A method and apparatus for obtaining a parameter of interest relating to a region proximate a nuclear magnetic resonance (NMR) logging tool suitable for subterranean well logging is disclosed. The nuclei of the region are subjected to a pulsed NMR technique and are productive of NMR logging data, the nuclei of the region characteristically having a longitudinal relaxation time T₁ distribution and an apparent transverse relaxation time T_2app distribution. In response to the NMR logging data, an R distribution is defined as R=T₁/T_2app, the T_2app and R distributions are processed as separate bins, along with the NMR logging data, according to a two-dimensional inversion model, and a signal intensity map of R versus T_2app is provided that is representative of the parameter of interest relating to the region. In response to a high-intensity signal on the map being within a first range of T_2app values and a first range of R values, the presence of a light hydrocarbon within the region is identified.

The invention provides a method for judging the wettability of a reservoir rock. The method comprises the following steps of: measuring free relaxation time of oil and water respectively; measuring transverse relaxation time of the oil and the water in saturated states respectively; measuring a nuclear magnetic resonance signal of the reservoir rock in the co-presence of an oil phase and a water phase by using nuclear magnetic resonance technology and recording an oil saturation value and a water saturation value in the co-presence of the oil phase and the water phase; dipping the rock core of the reservoir rock in the co-presence of the oil phase and the water phase in more than or equal to 20,000 ppm paramagnetic solution, waiting for at least 48 hours and separating the nuclear magnetic resonance signal of the reservoir rock in the co-presence of the oil phase and the water phase to obtain the transverse relaxation time of the oil and the water reflecting the size of an oil wet area and a water wet area; and calculating a wettability index in the co-presence of the oil phase and the water phase according to the free relaxation time of the oil and the water, the transverse relaxation time of the oil and the water in the saturated states, the transverse relaxation time of the oil and the water, the oil saturation value and the water saturation value so as to judge the wettability of the reservoir rock.

An optical pumping magnetometer is provided that is capable of improving the response of the magnetometer with respect to a magnetic field that varies with a period shorter than the transverse relaxation time of electron spin of an alkali metal atom.

Methods and pulse sequences for facilitating nuclear magnetic resonance (NMR) measurements in grossly inhomogeneous fields. Methods and pulse sequences according to the invention may be used to accurately measure variables such as transverse relaxation time, longitudinal relaxation time, and diffusion, without the need for data at long recovery time, thereby allowing for faster measurements. In addition, methods and pulse sequences according to embodiment of the invention may allow simultaneous encoding of information in both the amplitude and the shape of echoes, so as to allow a single-shot measurement of multiple variables, e.g., both transverse relaxation time (from the decay of echo amplitudes) and longitudinal relaxation time (from the echo shape). CPMG detection may be used to overcome the often limited signal-to-noise ratio in grossly inhomogeneous fields.

The invention discloses a method for identifying the quality of edible oil with low-field NMR (Nuclear Magnetic Resonance), suitable for identifying and measuring genuine edible oil and inferior drainage oil. The method rapidly and accurately identifies the genuine edible oil and the inferior drainage oil by using the difference between the relaxation time map data of the genuine edible oil and the inferior drainage oil as a main identification reference, using NMR signals of the genuine edible oil and the inferior drainage oil as main observation objects and using the comparison and the analysis of the transversal relaxation time map data of the genuine edible oil and the inferior drainage oil as main measures. The method of the invention has high measuring result accuracy, good repetition and stability, short duration, and the like, is beneficial to the realization of the one-site identification of the qualities of various kinds of edible oil and provides reliable oil quality information for detecting the qualities of various kinds of edible oil.

The invention discloses a method for measuring the oil content of drilling fluid through low-field NMR (Nuclear Magnetic Resonance), suitable for measuring the content of crude oil with different densities in the drilling fluid. The method comprises the step of measuring the oil content of the drilling fluid by using the transverse relaxation time of the crude oil and the drilling fluid and different diffusion coefficients as main identification criteria, using the signal strength of NMR of the crude oil and the drilling fluid as a main observation object and using the transverse relaxation analysis of the drilling fluid and the correlation analysis of the diffusion coefficients and transverse relaxation as main measures. The method of the invention has the advantages of high measuring result accuracy, good stability, short time consumption, and the like, is easy to realize the online measurement of the oil content of the drilling fluid and provides reliable storage information of an oil layer for logging operation.

The invention provides a transverse relaxation time measuring method. The method comprises the following steps of: acquiring an echo signal; fitting the echo signal to acquire a prior estimate value of the relaxation time; and calculating echo time interval according to the prior estimate value, and feeding the echo time interval to the fitting calculation to acquire a measurement value of the relaxation time. Through rough estimation on the relaxation by the fitting calculation, the transverse relaxation time measuring method and system realize optimization on the signal to noise ratio of the relaxation time in the echo signal, so that the accuracy of relaxation time measurement is effectively improved.

Many reservoirs of interest include heavy oil. In such reservoirs, parti at normal temperatures, many instruments commonly used for formation evaluation may not be able to distinguish between heavy oil and bound water in the formation. Passive or active heating is used to elevate the temperature of the fluids in the formation. At elevated temperatures, distinguishing between heavy oil and bound water is easier. Of particular interest is the increase in the resolvability of the transverse relaxation time T2 of NMR spin echo measurements. Additionally, the dielectric constant and the loss tangents of water and heavy oil show different temperature and frequency dependence.

The invention discloses a quick measurement method for different forms of water in sludge. The quick measurement method comprises the following steps of: (1) performing low-field nuclear magnetic resonance measurement on the sludge to obtain a transverse relaxation time T2 spectrum of different forms of water in the sludge; (2) stewing and settling activated sludge, preparing a standard sample by supernatant liquid at equal mass interval, and constructing a standard curve; (3) according to the obtained standard curve, matrixing the low-field nuclear magnetic resonance transverse relaxation time of the sludge to obtain three different forms of water, namely free water mass, interstitial water mass and surface combined water mass in the sludge; and (4) drying the sludge to be measured until the weight is balanced, subtracting the final mass from the initial mass, and calculating the fourth form of water in the sludge, namely the internal combined water mass. Compared with the conventional method, the quick measurement method for measuring the content of different forms of water in the sludge by a nuclear magnetic resonance technology has the advantages of short experiment time, harmlessness to experiment samples, precision of measurement and the like.

The invention discloses a method and a device for determining saturation exponent of tight sandstone. The method comprises: according to nuclear magnetic resonance transverse relaxation time T2 spectrum of a core in a water saturation state and nuclear magnetic resonance transverse relaxation time T2 spectrum of cores in different water saturation states after different centrifugal forces are applied, determining geometric mean value of the nuclear magnetic resonance transverse relaxation time T2, the geometric mean value of the nuclear magnetic resonance transverse relaxation time T2 of the cores in different water saturation states after different centrifugal forces are applied on the cores, and water saturation of the cores after different centrifugal forces are applied; and according to the geometric mean value of the nuclear magnetic resonance transverse relaxation time T2 of the core in a water saturation state, and the geometric mean value of the nuclear magnetic resonance transverse relaxation time T2 of the cores in different water saturation states after different centrifugal forces are applied, and the water saturation of the cores after different centrifugal forces are applied, determining saturation exponent of the cores. The method and the device can accurately and efficiently determine the saturation exponent of tight sandstones.

The invention provides a single-scanning quantitative magnetic resonance diffusion imaging method based on dual echo, and relates to a magnetic resonance imaging method. According to the method, two echoes with the same evolution time are generated through two small-angle excitation pulses with the same turning angle, so that the same transverse relaxation time is achieved; a displacement gradient is added after each excitation pulse to achieve central displacement of the two echo signals in a signal space, and a diffusion gradient is added after the first excitation pulse, so that diffusion reduction only exists in the first echo signal; accordingly, signals under different diffusion factors are obtained. The two echo signals are from one imaging slice, so that the two echo signals can be separated through priori knowledge of the two echo signals by matching sparse conversion with a corresponding separation algorithm. Finally, a quantitative ADC image is obtained by performing apparent diffusion coefficient calculation on two signals obtained through separation. Single-scanning quantitative ADC imaging is obtained through the method, and the quality of the obtained ADC image is good.

The invention provides a method and device for determining horizontal surface relaxation rate. The method comprises the step of carrying out CT scanning on a rock core sample to acquire a gray level image of the rock core sample, carrying out binarization processing on the gray level image to generate a binary image and extract a hole grillage, carrying out nuclear magnetic resonance measurement on the rock core sample to determine measured horizontal relaxation signals, carrying out relaxation simulation on the rock core sample according to the extracted binary image of the hole grillage and the preset surface relaxation rate to determine simulated horizontal relaxation signals, comparing whether the simulated horizontal relaxation time signals coincide with the components at the right-most ends of the measured horizontal relaxation time signals, and choosing the preset surface relaxation rate as the determined horizontal surface relaxation rate of the rock core sample to be outputted when the simulated horizontal relaxation time signals coincide with the component of the right-most ends of the measured horizontal relaxation time signals. The method and device for determining horizontal surface relaxation rate has the advantages of being more reliable in principle, simple in calculating process, easy to achieve, strong in actual operability and the like.

The embodiment of the invention provides a method and a device for obtaining transverse relaxation time distribution of a target storage layer. The method comprises the steps of setting corresponding experiment temperature and pressure according to temperature and pressure information of the target storage layer, and obtaining nuclear magnetic resonance intrinsic transverse relaxation time distribution of free state formation water of the target storage layer, nuclear magnetic resonance intrinsic transverse relaxation time distribution of crude oil of the target storage layer and nuclear magnetic resonance intrinsic transverse relaxation time distribution of formation water of the target storage layer; and calculating a hydrogen-containing index of the crude oil, a hydrogen-containing index of formation water, a diffusion coefficient of the crude oil and a diffusion coefficient of the formation water, then replacing intrinsic relaxation and diffusion relaxation comprehensive contribution of the crude oil by intrinsic relaxation and diffusion relaxation comprehensive contribution of the free state formation water, acquiring a rotating echo signal of the target storage layer under a complete water containing state, and performing inversion on the rotating echo signal to obtain the nuclear magnetic resonance transverse relaxation time distribution of the target storage layer under the complete water containing state.

The invention discloses a hydration degree measurement method for cement-based materials based on nuclear magnetic resonance, which belongs to the technical field of cement material measurement. The hydration degree measurement method disclosed by the invention adopts a nuclear magnetic resonance technique to test nuclear magnetic signals of the cement-based materials at different ages; a relation between transverse relaxation time and the nuclear magnetic signals is obtained by inverse analysis; furthermore, a ratio of nuclear magnetic semaphores of left and right peaks is taken as a nuclear magnetic signal ratio of gel pore water and capillary pore water, and then the hydration degree of the cement-based materials to be detected at the age is solved according to a Powers model. Compared with traditional methods including a muffle furnace method and the like, the hydration degree measurement method disclosed by the invention is a nondestructive testing method, can reduce operation steps of a test greatly and shorten a testing period greatly, and can be used for monitoring samples continuously so as to ensure that the errors of test results are small; meanwhile, the method disclosed by the invention does not need to calibrate nuclear magnetic resonance semaphores and sample water content and directly adopts the ratio of the nuclear magnetic semaphores of the left and right peaks, namely a microstructure factor, as a parameter to represent the hydration degree, and therefore, measurement procedures and errors are reduced.

A nuclear magnetic resonance quantitative analysis method for a rock micro-crack damage variable is provided; firstly, a sample is processed, the sample is soaked in distilled water, then nuclear magnetic resonance detection is carried out, CPMG pulse sequence detection is carried out on the sample, a spin echo train attenuated signal is obtained, the spin echo train attenuated signal is subjected to inversion, and a T2 spectrum distribution diagram and a spectral area value are obtained; a corresponding relation of the relaxation time T2 and the pore size r is analyzed; according to a fact that the spectral peak area is proportional to the micro-fracture pore number, a rock damage variable formula characterized by the nuclear magnetic resonance transverse relaxation time T2 spectra is established, and the quantitative analysis method is provided for identification of damage of rock materials.

A system provides B1- and B0-insensitive, blood flow and motion-robust T2-preparation and T2-preparation combined with inversion recovery. An MR imaging system discriminates between imaged tissue types based on transverse relaxation time (T2) or transverse relaxation time combined with longitudinal recovery time (T1). A signal generator generates a pulse sequence for T2 preparation or combined T2-preparation with inversion recovery comprising one or more B1 independent refocusing (BIREF-1) pulses for refocusing of magnetization of an anatomical region of interest being imaged, and different combinations of adiabatic or non-adiabatic tip-down and flip-back pulses. Multiple RF coils transmit RF pulses in response to the pulse sequence and acquire RF data in response to transmission of the RF pulses. A processing system processes the RF data to provide a display image indicating different tissue types with enhanced discrimination based on T2 relaxation time difference or combined T2 and T1 time difference.

The invention relates to the field of well logging technology and discloses a method, device and system for correcting measurement of nuclear magnetic resonance porosities. A first mapping relation among transverse relaxation time, a first porosity component and first porosity cumulation is obtained, so that a second mapping relation between a capillary radius and the transverse relaxation time is obtained and further a third mapping relation between the capillary radius and a second porosity component is obtained; according to the first mapping relation, the second mapping relation and the third mapping relation, the corresponding relation between the first porosity component and the second porosity component is obtained, and the component ratio of the second porosity component to the first porosity component is calculated; according to the component ratio, the correction computation is performed on the measurement data of nuclear magnetic resonance porosities, so that the accuracy of the existing measurement of nuclear magnetic resonance porosities is improved.