315 results about "Nuclear magnetic resonance logging" patented technology

The invention relates to a nuclear magnetic resonance ground water detection system with reference coils and a detection method. All-waveform data of nuclear magnetic resonance signals in a transmitting/receiving coil and noise signals in the reference coils are synchronously acquired through a plurality of paths of A/D acquiring units; the distribution of optimal positions and quantity of the reference coils is realized through calculating the maximum correlation of the noise signals and the nuclear magnetic resonance signals, which are acquired by the reference coils; and under the condition of unknown signal and noise statistical properties, noise in the nuclear magnetic resonance signals obtained by the transmitting/receiving coil is maximally offset by adopting a variable step adaptive algorithm, the nuclear magnetic resonance signals are extracted under the interference of multi-field source complex strong noise, thus the problems of multiple interferences of nuclear magnetic resonance detection near villages and in neighboring regions of cities and difficulty of separating multiple kinds of interference noise data are effectively solved, the interference resistance of instruments is improved, and a reliable detection device and method are provided for searching underground water near villages and in neighboring regions of cities.

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 discloses a method for calculating tight sandstone reservoir permeability based on hole feature parameters. The method includes the steps of calculating hole structural parameters through a rock core mercury penetration experiment, establishing a permeability well logging interpretation model through a first characteristic function which is established through the hole structural parameters, converting nuclear magnetism T2 spectrum into a pseudo capillary pressure curve through correlations existing between nuclear magnetism T2 spectrum distribution and mercury penetration hole diameter distribution, and calculating the reservoir permeability according to a second characteristic function which is established through the pseudo capillary pressure curve. In practical application, the quantitative, continuous and high-precision pseudo capillary pressure curve is obtained through nuclear magnetic resonance well logging information under the condition that laboratory mercury penetration information does not exist, and finally, calculation of the reservoir permeability is conducted according to the second characteristic function which is established through the pseudo capillary pressure curve.

A nuclear magnetic resonance well logging apparatus, comprising an antenna for inducing a radio frequency magnetic field in earth formations surrounding the apparatus and for detecting nuclear magnetic resonance signals from the earth formations; and a magnet for inducing a static magnetic field within the earth formations. The magnet is formed from a powdered, electrically conductive permanent magnet material. The grain size of the magnet material small enough with respect to the frequency of the radio frequency magnetic field to substantially prevent intragranular power loss of the radio frequency magnetic field. The magnet is formed from electrically isolated blocks of the magnet material each having a thickness less than a skin depth of the radio frequency magnetic field within the magnet material. The boundaries between the blocks are oriented to interrupt flow of eddy currents in the magnet resulting from the radio frequency magnetic field. In a preferred embodiment, the magnet material comprises powdered, epoxy resin-bonded Samarium-Cobalt.

A laboratory NMR methodology (and corresponding laboratory apparatus) defines a sample volume. The method stores downhole tool data corresponding to a hydrocarbon-bearing sample collected from a given subsurface formation. The downhole tool data includes parameters pertaining to magnetic fields used by a downhole tool during a suite of NMR measurements of the given subsurface formation. The sample is positioned in the sample volume of the laboratory apparatus, which applies a static magnetic field in the sample volume. Furthermore, the laboratory apparatus applies a suite of NMR measurements to the sample volume to thereby determine a property of the sample. The NMR measurements of the suite each include a pulse sequence of oscillating magnetic field in conjunction with a pulsed-mode gradient field. The pulsed-mode gradient field is based on the stored downhole tool data corresponding to the sample. A laboratory NMR methodology for optimizing downhole NMR measurements is also described.

The invention relates to a method for determining T2cutoff value by nuclear magnetic resonance logging (NMRL) T2 spectra, comprising the steps of: 1. classifying NMRL T2 spectra by shape characteristics; 2. fitting and obtaining centrifugal spectrum according to different types of logging T2 spectra; 3. making area integration on the centrifugal spectrum and obtaining area of centrifugal spectrum; 4. calculating areas of logging T2 spectra; 5. accumulating the areas of logging T2 spectra, and as the accumulated area is equal to or closest to the area of centrifugal spectrum, the corresponding T2 value is a T2cutoff value. Thus, the invention determines T2cutoff value of each depth point by directly using NMRL T2 spectra.

An objective oriented NMR logging method selects pulse sequences over a plurality of frequencies from a set of building blocks. The building blocks include trainlet sequences wherein each trainlet comprises an excitation pulse and a plurality of refocusing pulses, the total length of a trainlet being typically less than 10 ms. Another building block is a short CPMG or modified CPMG sequence and yet another building block is a regular CPMG or modified CPMG sequence. The modified CPMG sequences may have refocusing pulses with a tipping angle less than 180° to reduce the power consumption. Based on the logging objective (formation evaluation or FE, FE plus hydrocarbon typing, FE plus gas evaluation) the building blocks are combined at a plurality of frequencies with different wait times and TEs.

Disclosed is a non-lineal statistical independent component (ICA) analysis methodology for calculating T2 or T1 distributions of nuclear magnetic resonance logs. In one aspect, the invention employs a classical blind source separation (BSS) approach with the input data (T2 or T1 distributions) being considered not only horizontally (in relaxation time units), but also vertically (in depth). The statistical variations are used for separating the principal independent components and their corresponding weighting matrix. The result of such ICA based BSS is an efficient separation of T2 components correlative to the presence of particular conditions (e.g., clay bound water, heavy oil, capillary bound water, free water, mud filtrate (water and oil), and noise). Individual saturation of estimated fluids can be calculated from the weighting matrix generated in accordance with the invention. In accordance with a further feature of the invention, it is contemplated that independent component analysis techniques may be applied to the underlying time domain data prior to its transformation to a T2 distribution. This advantageously results in “de-noising” of the signal, leading to more precise and accurate results following analysis of the T2 distribution.

The invention discloses a method for determining the 100% pure water spectrum through the nuclear magnetic resonance logging spectrum T2. The method includes the following steps that firstly, the relation between the irreducible water saturation Swi of a reservoir stratum in an exploratory area and the geometric mean value T2g of the spectrum T2 is built according to known rock physical experiment characteristics, then the irreducible water saturation Swi of the logging spectrum T2 and the geometric mean value T2g of the spectrum T2 are calculated point by point by means of a bulb tube thin film model, the nuclear magnetic resonance centrifugal spectrum is built, and the 100% pure water nuclear magnetic resonance spectrum is built on the basis of the nuclear magnetic resonance centrifugal spectrum. A significant difference exists between a nuclear magnetic single and a 100% pure water nuclear magnetic signal when the reservoir stratum contains oil and gas, and accurate identification is carried out on fluid of the reservoir stratum by means of the difference. The 100% pure water spectrum is built through nuclear magnetic resonance logging information so that the real pore structure of the reservoir stratum can be reflected; in addition, by contrasting the difference between the actually measured nuclear magnetic resonance spectrum and the built pure water spectrum, the property of the fluid of the reservoir stratum is effectively identified, so that the problem that fluid identification during nuclear magnetic resonance logging is difficult due to crude oil properties and observing modes is solved, the application of the nuclear magnetic resonance logging information is improved, and the geological problem solving capacity is enhanced.

The invention provides a nuclear magnetic resonance logger probe while drilling and a nuclear magnetic resonance logger while drilling. The nuclear magnetic resonance logger while drilling comprises a probe framework, wherein a slurry pipe penetrates through the center of the probe framework; in the probe framework, a first annular magnet and a second annular magnet are sleeved on the slurry pipe and all axially magnetized, and one ends of the first magnet and the second magnet, which have the same polarity, are correspondingly arranged; an antenna for forming a pulsed magnet field is fixedly embedded at a middle position on the peripheral side wall of the probe framework; and at least one pair of annular focusing magnet is coaxially sleeved on the slurry pipe and between the first magnet and the second magnet, and two focusing magnets which form each pair of focusing magnet are symmetrical to each other by the middle section of the antenna, and are radially magnetized. The nuclear magnetic resonance logger probe while drilling can increase the vertical extension length of a sensitive area, so the measurement signal to noise ratio and the precision of the measurement result are improved.

The invention discloses a reservoir layer evaluation method by utilizing nuclear magnetic resonance logging interpretation parameters, relating to the geology logging interpretation evaluation technology field of petroleum geological exploration; oil saturation So and mobile fluid saturation BVM parameters are chosen, a formula M1=BVM*So is utilized to obtain the M1 parameter which reflects the oil characteristics of the reservoir layer and the total energy; by utilizing the formula SMo=BVM-SMw, the mobile oil saturation SMo parameter is calculated, and then the formula M2=SMO*phi is utilized to obtain the M2 parameter which reflects the recoverable oil volume of the recoverable oil volume, and then the fluid type is determined according to the numeric range of the M1 and M2 values; by adopting the method, different oil grades of the reservoir layer can be effectively and quantitatively divided in a refining way, the undetermined factors of the interpretation parameters caused by block, horizon and oil-containing characteristics are eliminated, and the reservoir layer evaluation method has general applicability to a clastic rock oil-containing bed series.

The invention discloses a method for identifying a thickened oil reservoir by utilizing nuclear magnetic resonance well logging and belongs to the field of reservoir fluid identification.The method comprises the steps that a well having nuclear magnetic resonance well logging data is processed to obtain a standard T2 distribution spectrum; the nuclear magnetic porosity of the reservoir is calculated, and a nuclear magnetic T2 spectrum cutoff value method is utilized to calculate irreducible water saturation SBVI; a spectrum coefficient method is utilized to calculate irreducible water saturation SSBVI; finally, reservoir fluid identification factors are calculated; a fluid identification chart is established according to the fluid identification factors, and accordingly a reservoir fluid is accurately judged.The method utilize the characteristic that the two calculated irreducible water saturations have remarkable difference when thickened oil exists in the reservoir to effectively identify the reservoir, can adopt a method of utilizing the nuclear magnetic T2 spectrum cutoff value method and the spectrum coefficient method to calculate the difference of the irreducible water saturations to achieve accurate and reliable identification of the thickened oil reservoir in a thickened oil distribution area and is an effective fluid identification method for exploration and evaluation of large-area thickened oil reservoirs of our country at present.

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.

The invention discloses a method for constructing pseudo capillary pressure curves by using NMR (nuclear magnetic resonance) logging. The method comprises the steps as follows: according to NMR logging data measured actually and limited capillary pressure data, seven different relaxation time is set; NMR T2 spectra are divided into eight parts; the percentage content of porosity components of the eight parts is calculated; a transformation model between the mercury-injection saturability and the percentage content of the NMR porosity components under different mercury-injection pressures is built; according to the transformation model, the mercury-injection saturability under different mercury-injection pressures is calculated; according to the calculated mercury-injection saturability and the mercury-injection pressure corresponding to the mercury-injection saturability, the pseudo capillary pressure curves are constructed; and according to the pseudo capillary pressure curves, pore throat radius distribution is obtained, evaluation parameters of a pore structure of a reservoir stratum are calculated, and the purpose of constructing the pseudo capillary pressure curves by using NMR logging data accurately and carrying out continuous quantitative evaluation on the pore structure of the reservoir stratum is achieved.

The invention discloses a glutenite reservoir oil saturation calculation method based on nuclear magnetic resonance. The method includes the steps that glutenite cores of different lithological characters and pore structures are selected, and the porosity phi, the cementation index m, the saturation index n and the nuclear magnetic T2 spectrum of the glutenite cores are measured; the nuclear magnetic T2 spectrum is extracted to reflect the character parameters of the pore structures; through correlation among the cementation index m, the saturation index n and the character parameters of the pore structures, a saturation interpretation model based on the nuclear magnetic T2 spectrum is built; the cementation index m and the saturation index n of a reservoir are calculated through the nuclear magnetic T2 spectrum; the cementation index m and the saturation index n are substituted into the saturation interpretation model to obtain the oil saturation So through calculation. By means of the glutenite reservoir oil saturation calculation method, the quantitative, continuous and highly accurate cementation index m and the saturation index n can be obtained through nuclear magnetic resonance logging data under the condition that no laboratory rock electrical data exist, and the calculated oil saturation is made to be more accurate.

The invention discloses a calibration device for a nuclear magnetic resonance well logger, which comprises a circulation system, a shielding dial drum and a lithologic medium placing board, wherein the circulation system consists of a mixing vessel, a vacuum valve and a Faraday dial drum; the Faraday dial drum is provided with an instrument outer cylinder which is used for placing a detecting instrument and a corresponding probe; the shielding dial drum is sleeved outside the instrument outer cylinder and used for circulating flow of a calibration solution; the lithologic medium placing board is arranged inside the shielding dial drum and used for placing solid lithologic media; a skylight for placing and taking the solid lithologic media is also arranged on the shielding dial drum; and a skylight cover is arranged on the skylight. The calibration device for the nuclear magnetic resonance well logger not only effectively reduces the volume of the calibration device and shields interference of an external electromagnetic field but also can conveniently and flexibly replace the lithologic media, accurately calibrate the investigation depth and the sensitivity on the lithologic media with various porosities, and provide accurate scale data for the nuclear magnetic resonance well logger.

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.

The invention relates to a determination method for a T2 cut-off value in a T2 spectrum of nuclear magnetic resonance logging, in particular to a method for constructing a T2 cut-off value according to the pore structure characteristics reflected by T2 spectrum intensity at each time point, of a T2 spectrum of nuclear magnetic resonance logging. The determination method disclosed by the invention is capable of saving the time and cost of demarcating the T2 cut-off value in the original lots of experimental analysis for a rock core, does not need to establish an empirical formula on the basis of T2 spectrum classification to evaluate the T2 cut-off value, and realizes dynamic and automatic evaluation for the T2 cut-off value. The method realizes scientific, simple and rapid evaluation for the T2 cut-off value.

The invention provides a method and device for determining oil gas saturability. The method comprises the following steps of obtaining a long-echo distance measurement echo string and a short-echo distance measurement echo string; determining a stratum water dispersion coefficient according to actual stratum information at set experiment temperature under set experiment pressure; calculating water dispersion relaxation time according to the stratum water dispersion coefficient; and adding the water dispersion relaxation time under a long-echo distance and the water dispersion relaxation time under a short-echo distance to a short-echo distance spectrum T2, calculating and constructing an echo string, determining the property of fluid in a reservoir stratum according to the long-echo distance measurement echo string and the constructed echo string, and calculating the oil gas saturability of the reservoir stratum. According to the method and the device, the problem that extremely rich regional experience is needed for a conventional nuclear magnetic resonance shifted spectrum method is solved; the use range of a nuclear magnetic resonance well measurement fluid identification method is expanded.