Shale oil analysis method and apparatus for continuously characterizing saturation of adsorbed oil and free oil

Patent metadata

Field	Value
Publication number	US-11086044-B2
Application number	US-201916729606-A
Country	US
Kind code	B2
Filing date	Dec 30, 2019
Priority date	Sep 17, 2019
Publication date	Aug 10, 2021
Grant date	Aug 10, 2021

Abstract

A shale oil analysis method and apparatus for continuously characterizing saturation of adsorbed oil and free oil, comprising: obtain NMR T2 spectrum, NMR porosity, oil saturation and wettability indexes of a core samples, determine a lower limit value for the saturation calculation of the absorbed oil based on the NMR T2 spectrum, the NMR porosity, the oil saturation and wettability indices; determining a lower limit value for the saturation calculation of the free oil according to the bulk relaxation T2 spectrum of the crude oil of the well interval or an adjacent well interval and the NMR T2 spectrum of the core samples; calculating the saturation of the absorbed oil and the free oil, and analyzing the shale oil in the well interval to be analyzed. The solution realizes the quantitative and continuous characterization of the adsorbed oil and the free oil of the shale oil via well logs.

First claim

The invention claimed is:

1. A shale oil analysis method for continuously characterizing saturation of absorbed oil and free oil, wherein the method comprises steps of:
acquiring NMR log data of a well interval to be analyzed;
performing a NMR measurement, a saturation measurement and an Amott wettability measurement on a core sample acquired from a “sweet spot” in the well interval to be analyzed, to obtain a NMR T 2 spectrum, a NMR porosity, an oil saturation and a wettability index of the core sample, and determine a lower limit of a saturation calculation of adsorbed oil based on the NMR T 2 spectrum, the NMR porosity, the oil saturation and the wettability index of the core sample;
acquiring a bulk relaxation T 2 spectrum of crude oil in the well interval to be analyzed and a well interval having a same depth as a depth of the well interval to be analyzed in an adjacent well, and determining a lower limit of a saturation calculation of free oil according to the bulk relaxation T 2 spectrum of the crude oil and the NMR T 2 spectrum of the core sample;
continuously and quantitatively calculating the saturation of the absorbed oil and the free oil in the well interval to be analyzed, according the NMR log data of the well interval to be analyzed, the lower limit of the saturation calculation of adsorbed oil and the free oil; and
analyzing the shale oil in the well interval to be analyzed, according to the saturation of the absorbed oil and the free oil in the well interval to be analyzed.

2. The shale oil analysis method for continuously characterizing saturation of absorbed oil and free oil according to claim 1 , wherein the core sample comprises a first core sample and a second core sample, wherein the first core sample and the second core sample are samples obtained by splitting a core plunger sample drilled in a direction parallel to a bedding into two;
said performing a NMR measurement, a saturation measurement and an Amott wettability measurement on a core sample acquired from a “sweet spot” in the well interval to be analyzed, to obtain a NMR T 2 spectrum, a NMR porosity, an oil saturation and a wettability index of the core sample, and determine a lower limit of the saturation calculation of adsorbed oil based on the NMR T 2 spectrum, the NMR porosity, the oil saturation and the wettability index of the core sample comprises:
performing the NMR measurement on the first core sample at a formation temperature, to obtain a NMR T 2 spectrum and a NMR porosity of the first core sample;
selecting the second core sample corresponding to the first core sample which has a NMR porosity greater than a preset threshold value and a bulk relaxation peak on the NMR T 2 spectrum that satisfies a preset condition, and performing the Amott wettability measurement on the second core sample, to obtain a wettability index of a corresponding second core sample;
performing the saturation measurement on the first core sample which has the NMR porosity greater than the preset threshold value and the bulk relaxation peak on the NMR T 2 spectrum that satisfies the preset condition, to obtain an oil saturation and a water saturation of the first core sample; and
selecting a NMR T 2 spectrum of the first core sample corresponding to the second core sample with the wettability index representing a weakly oil-wet property and an oil-wet property according to the wettability index of the corresponding second core sample, and determining a pore percentage according to the NMR T 2 spectrum of the corresponding first core sample, a T 2 transverse relaxation time corresponding to a point at which the pore percentage is equal to the water saturation of the corresponding first core sample being the lower limit of the saturation calculation of adsorbed oil.

3. The shale oil analysis method for continuously characterizing saturation of absorbed oil and free oil according to claim 1 , wherein determining a lower limit of the saturation calculation of free oil according to the bulk relaxation T 2 spectrum of the crude oil and the NMR T 2 spectrum of the core sample comprises:
selecting the NMR T 2 spectrum of multiple first core sample corresponding to multiple second core sample with the wettability index representing a strongly oil-wet property according to the wettability index of the corresponding second core sample, comparing the NMR T 2 spectrum of the corresponding multiple first core sample with the bulk relaxation T 2 spectrum of the crude oil, when it is recognized that a last peak of the NMR T 2 spectrum of the corresponding multiple first core sample is the bulk relaxation spectrum and the time corresponding to a left valley of the NMR T 2 volume of the corresponding multiple first core samples is the same, determining the time corresponding to the left valley as the lower limit of the saturation calculation of free oil.

4. The shale oil analysis method for continuously characterizing saturation of absorbed oil and free oil according to claim 1 , wherein lower limit of the saturation calculation of adsorbed oil is determined according to the following formula:

S

absorption
⁢

⁢
oil

=

∑

i
=

T

2
⁢
cut
⁢

⁢
1

T

2
⁢
cut
⁢

⁢
2

⁢

P
i

∑

i
=
0.3

3000

⁢

P
i

⁢

;

where, S absorption oil denotes the saturation of the absorbed oil; P i denotes pore volume corresponding to the ith relaxation time component, dimensionless and decimal; T 2cut1 denotes the lower limit of the saturation calculation of adsorbed oil, in the unit of ms;
The lower limit of the saturation calculation of free oil is determined according to the following formula:

S

free
⁢

⁢
oil

Assignees

• Petrochina Co Ltd

Inventors

• Zhi Dongming
• Kuang Lichun
• Wang Xiaojun
• Sun Zhongchun
• Qin Zhijun
• Wang Wei
• Zhang Ni
• Mao Xinjun
• Ouyang Min
• Chang Qiusheng

Classifications

• E21B49/00

  Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells · CPC title

• G01N13/04

  Investigating osmotic effects · CPC title

• G01V3/32 Primary

  operating with electron or nuclear magnetic resonance · CPC title

• G01N13/00

  Investigating surface or boundary effects, e.g. wetting power; Investigating diffusion effects; Analysing materials by determining surface, boundary, or diffusion effects (scanning-probe techniques or apparatus G01Q) · CPC title

• G01V3/38

  Processing data, e.g. for analysis, for interpretation, for correction · CPC title