Patent ID: 9625601
Date: 2017-04-18
CPC Classifications: G01N,G01R,G01V

Claim:
1. A constant gradient field nuclear magnetic resonance (NMR) rock sample analysis method, characterized in that it comprises: 1) in a constant gradient field generated by a magnet, according to a saturated fluid in a sample under test, designing parameters comprising an echo train k, a pulse interval tau, the number of 180° pulses Ne, and a waiting time RD in a CGMF-CPMG pulse sequence to perform NMR measurement to acquire measurement data; the value of k is between 2 and 8, the value of tau is distributed between 150 μs and 20000 μs, the value of Ne is distributed between 128 and 30720, and the waiting time is distributed between 2000 ms and 12000 ms; 2) converting NMR data measured in Step 1) into a two-dimensional NMR spectrum D-T 3) performing measurement and inversion on a constant gradient field standard sample using Step 1) and Step 2) to obtain the two-dimensional NMR spectrum D-T 4) measuring the rock sample using Step 1) and Step 2), acquiring a fluid two-dimensional NMR spectrum D-T 5) computing the porosity, permeability, oil saturation, movable fluid saturation, crude oil coefficient of the rock sample according to the two-dimensional NMR spectrum D-T a) performing volume integration through the two-dimensional NMR spectrum of the rock sample, introducing a constant gradient field NMR calibration line according to Step 3), and computing the NMR porosity of the rock sample; b) computing the permeability of the rock sample according to the NMR porosity and irreducible water saturation: wherein, K c) identifying fluid types rapidly according to the two-dimensional NMR spectrum explanation template established in Step 4), distinguishing oil and water; selecting the area of oil in the two-dimensional NMR spectrum with a mouse, computing, by the system, automatically the ratio between the volume integral of the selected area and the total volume integral of the two-dimensional NMR spectrum, and acquiring oil saturation; similarly, obtaining oil, gas and water saturation, respectively; d) comprehensively judging and selecting a movable fluid area according to a movable fluid T e) when the rock sample contains crude oil with a high viscosity, measuring that the NMR signal of a unit volume of rock sample is small, causing offsets of different degrees to parameters of the porosity, permeability, movable fluid saturation and oil saturation of a rock sample, wherein calibration is required; the crude oil coefficient is ratio between the signal of a unit volume of constant gradient field NMR standard sample and the NMR signal of a unit volume of crude oil: 6) the slicing thickness of the constant gradient field NMR rock sample analyzer being 0.3 cm, and according to Step 1) to Step 5), performing single slice scanning on a rock sample to acquire partial oil and water saturation of a rock sample; at the same time, repeating Step 1) to Step 5) to perform continuous slice scanning on the rock sample to acquire axial oil and water saturation distribution and movable fluid saturation distribution of the rock sample, so as to perform better realtime reservoir evaluation and fluid identification.