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Two-dimensional nuclear magnetic resonance rapid inversion algorithm based on LSQR-RSVD

An inversion algorithm and nuclear magnetic resonance technology, applied in the field of two-dimensional nuclear magnetic resonance fast inversion algorithm, can solve problems such as unfavorable multi-dimensional nuclear magnetic resonance logging to promote real-time inversion, increase hardware cost, reduce computing efficiency, etc., and reduce computing time. and hardware costs, reduce memory requirements, and speed up inversion

Inactive Publication Date: 2019-08-20
CHINA UNIV OF PETROLEUM (EAST CHINA)
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Problems solved by technology

However, at present, the calculation efficiency of multi-dimensional NMR logging inversion is greatly affected by the number of echo trains and inversion parameters. With the increase of echo trains and inversion parameters, the calculation efficiency will be significantly reduced, and the memory usage will increase at the same time. It will increase the cost of hardware, which is not conducive to the promotion of multi-dimensional NMR logging and the realization of real-time inversion of multi-dimensional NMR logging while drilling

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[0029] Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

[0030] A fast two-dimensional NMR inversion algorithm based on LSQR-RSVD, the process is as follows figure 1 shown, including the following steps:

[0031] Step 1: Construct a two-dimensional model of fluid subject to Gaussian distribution, including oil-water model and gas-water model.

[0032] Specifically, for porous media, 2D NMR echo trains can be acquired by a CPMG pulse sequence with an echo interval of TE, a wait time of Tw, and a diffusion coefficient of D under a gradient field. 2D NMR signal can be written as: b(t,T E , T w )=∫∫f(x,y)K 1 (x)K 2 (y)dxdy+ε, for (T2,D), (T1,T2), (T1-D) different inversion targets, K 1 (x)K 2 (y) can be the kernel function of the inversion parameters respectively, for T 2 -D inversion, x=T 2 , y=D, to T 2 -T 1 Inversely speaking, x=T 2 , y=T 1 , to T 1 -D inversion terms, According to ...

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Abstract

The invention discloses a Two-dimensional nuclear magnetic resonance rapid inversion algorithm based on LSQR-RSVD, and belongs to the technical field of nuclear magnetic resonance inversion. The method comprises the following steps: designing and generating a forward modeling model suitable for two-dimensional nuclear magnetic inversion; setting a certain number of iterations to invert the forwardmodeling model by using the LSQR; setting the sub-matrix dimension of the RSVD algorithm, and performing inversion by taking the output of the LSQR as the input of the RSVD algorithm; and calculatingthe inversion time, the occupied memory and the relative error and generating a two-dimensional spectrum. The invention provides a novel fast two-nuclear magnetic resonance spectrum inversion methodbased on random singular value decomposition (RSVD). A calculation result of a non-negative least squares (LSQR) is taken as an inversion initial value of the RSVD, so that the memory requirement canbe remarkably reduced and the inversion speed can be increased when two-dimensional nuclear magnetic inversion is carried out, the inversion precision can be ensured, the calculation time and the hardware cost are effectively reduced, the design is reasonable, and a good effect is achieved.

Description

technical field [0001] The invention relates to the technical field of nuclear magnetic resonance inversion, in particular to a two-dimensional nuclear magnetic resonance fast inversion algorithm based on LSQR-RSVD. Background technique [0002] Nuclear magnetic resonance (NMR) logging technology has unique advantages in pore fluid identification, porosity calculation and permeability analysis. In order to accurately evaluate the properties of formation fluids and make up for the limitations of one-dimensional NMR logging in practical applications, two-dimensional NMR logging has become the focus of research. [0003] At present, the two-dimensional NMR inversion methods mainly include the joint inversion method of NMR multi-echo series data, the traditional singular value (SVD) and improved singular value decomposition algorithm, the two-dimensional NMR inversion algorithm based on SIRT, the genetic-based Algorithm and Least Squares Decomposition (LSQR) inversion hybrid al...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F17/10
CPCG06F17/10
Inventor 李海涛胡旭飞邓少贵张凤姣韩均安袁习勇
Owner CHINA UNIV OF PETROLEUM (EAST CHINA)
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