Device and method for measuring the relative permeability of propped fractures in shale considering probability distribution

Patent metadata

Field	Value
Publication number	US-12092592-B2
Application number	US-202218148661-A
Country	US
Kind code	B2
Filing date	Dec 30, 2022
Priority date	Nov 5, 2022
Publication date	Sep 17, 2024
Grant date	Sep 17, 2024

Abstract

The present invention discloses a device and method for measuring the relative permeability of propped fractures in shale considering probability distribution, comprising a gas cylinder, a water pump, a booster pump, a rock slab holder, a differential pressure sensor, a directional X-ray source, an X-ray detector, an X-ray shielding box, a tee, a liquid meter, a gas meter, an electronic balance, and a vacuum pump; the inlet of rock slab holder is respectively connected with the gas cylinder and the water pump by the pipe, the outlet is connected with the liquid meter and the vacuum pump by the tee, and the differential pressure sensor is connected with both ends of the rock slab holder; the booster pump is connected with the rock slab holder by the pipe; the inlet of the gas meter is connected with the liquid meter, and the outlet is connected to the external atmosphere.

First claim

What is claimed is:

1. A method for measuring the relative permeability of propped fractures in shale considering probability distribution, comprising using a device for measuring the relative permeability of propped fractures in shale considering probability distribution, comprising a displacement system, a CT scanning imaging system and a metering system; wherein
the displacement system comprises a gas cylinder ( 1 ), a water pump ( 5 ), a booster pump ( 14 ), a rock slab holder ( 8 ), and a differential pressure sensor ( 9 ); the CT scanning imaging system comprises a directional X-ray source ( 7 ), an X-ray detector ( 10 ), and an X-ray shielding box ( 16 ); the metering system comprises a tee, a liquid meter ( 17 ), a gas meter ( 18 ), an electronic balance ( 11 ), and a vacuum pump ( 23 );
an inlet of the rock slab holder ( 8 ) is respectively connected with the gas cylinder ( 1 ) and the water pump ( 5 ) by a pipe, an outlet of the rock slab holder is connected with the liquid meter ( 17 ) and the vacuum pump ( 23 ) by the tee, and the differential pressure sensor ( 9 ) is connected with both ends of the rock slab holder ( 8 ); the booster pump ( 14 ) is connected with the rock slab holder ( 8 ) by the pipe;
the directional X-ray source ( 7 ), the X-ray detector ( 10 ), the rock slab holder ( 8 ), and the electronic balance ( 11 ) are all placed in the X-ray shielding box ( 16 ), the rock slab holder ( 8 ) is placed on the electronic balance ( 11 ) and located between the directional X-ray source ( 7 ) and the X-ray detector ( 10 );
an inlet of the gas meter ( 18 ) is connected with the liquid meter ( 17 ), and an outlet of the gas meter is connected to the external atmosphere;
a gas source control valve ( 2 ), a gas flow meter ( 3 ) and a gas pressure sensor ( 4 ) are installed between the gas cylinder ( 1 ) and the rock slab holder ( 8 );
the method specifically comprising the following steps:
Step 1: preparing two cuboid shale slabs of the same size, stacking them together, and laying proppants on the contact surface of the stacked slabs to form a whole shale slab;
Step 2: putting the whole shale slab into the rock slab holder ( 8 ), applying confining pressure on the upper, lower, left and right sides of the whole shale slab with the booster pump ( 14 ), and measuring the mass (denoted as m 1 ) of the whole shale slab with proppant by the electronic balance ( 11 );
Step 3: turning on the directional X-ray source ( 7 ), adjusting CT scanning parameters according to a shale rock slab size and a fracture size and determining a set of appropriate scanning parameters;
Step 4: determining the attenuation coefficient of pure substance with the scanning parameters set in Step 3;
filling the rock slab holder ( 8 ) with air and pressurizing to a specified fluid pressure acquiring CT projection images of pure air continuously after the pressure is stabilized; averaging multiple projection images to obtain the X-ray projection result of pure air, which is denoted as projection image A; then, conducting the same measurement for the gas and liquid used in relative permeability test and a standard block made of the same material as the proppant respectively to obtain the corresponding X-ray projection results, denoted as projection image B, projection image C and projection image D respectively; then, calculating the difference of attenuation coefficients of pure substances by the following equation;

(

μ
gas

-

μ
air

)

⁢
L

=

-
ln

⁢

I
B

I
A

⁢

(

μ
liquid

-

μ
air

)

⁢
L

=

-
ln

⁢

I
C

I
A

⁢

(

μ
proppant

-

μ
air

)

⁢
L

=

-
ln

⁢

I
D

I
A

where I A , I B , I C and I D are the intensity of each pixel point in the projection images A, B, C and D, respectively; L is the inner length of the holder cavity of the rock slab holder; μ air , μ gas , μ liquid and μ proppant stand for the attenuation coefficients of X-ray passing through air, experimental gas, experimental liquid and proppant successively;
Step 5: putting the whole shale slab into the rock slab holder ( 8 ), and applying confining pressure on the upper, lower, left and right sides of the slab with the booster pump ( 14 ); injecting air and pressurizing to the fluid pressure p required for the relative permeability experiment;
acquiring the CT projection images continuously after the pressure is stabilized, averaging multiple projection images to obtain the X-ray projection result of the rock slab, denoted as projection image E;
Step 6: calculating the porosity and pore volume in the propped fractures of the shale rock slab;

(

μ
proppant

-

μ
air

)

⁢
ϕ
⁢
L

=

-
ln

⁢

Assignees

• Univ Southwest Petroleum

Inventors

• Li Zhenglan
• Duan Yonggang
• Wei Mingqiang
• Fang Quantang
• Luo Le
• Ren Keyi
• Meng Lei
• Li Shuxin
• Nie Zhihong

Classifications

• G01N33/24

  Earth materials (G01N33/42 takes precedence) · CPC title

• G01N2223/419

  computed tomograph · CPC title

• G01N2223/04

  and measuring absorption · CPC title

• G01N15/082

  Investigating permeability by forcing a fluid through a sample · CPC title

• G01N2223/616

  earth materials · CPC title