Methods and systems for determining gas permeability of a subsurface formation

Patent metadata

Field	Value
Publication number	US-10436696-B2
Application number	US-201816056596-A
Country	US
Kind code	B2
Filing date	Aug 7, 2018
Priority date	Dec 14, 2015
Publication date	Oct 8, 2019
Grant date	Oct 8, 2019

Abstract

Methods and systems for determining permeability, as a function of pore pressure, and porosity of a subsurface formation. The method includes positioning a sample in a sample assembly comprising of a gas and a pressure gauge, inside a pressure vessel comprising gas or liquid and a pressure gauge, measuring a first gas pressure, pi, of the sample inside the pressure vessel, applying a second gas pressure, po, to the pressure vessel, the second gas pressure being greater than the first gas pressure, measuring a third gas pressure, p, at time, t, at location, x, from the inlet of sample inside the pressure vessel, determining a total gas mass per unit volume of the subsurface formation, m, and determining the permeability, k, of the subsurface formation as a function of pore pressure based at least in part on the first gas pressure, the second pressure, the third gas pressure, and the gas density, with a single test run.

First claim

The invention claimed is:

1. An apparatus for determining gas permeability of a subsurface formation, comprising:
a first sleeve having a length, a diameter, a first open end, and a second open end;
a first end piece adapted to be inserted into the first open end and a second end piece adapted to be inserted into the second open end of the first sleeve;
a first hole formed through the first sleeve and into a body of a sample of the subsurface formation housed in the first sleeve;
a half sleeve disposed on the first sleeve, the half sleeve having a second hole corresponding to the first hole on the first sleeve;
a tubing comprising a pressure gauge, the tubing inserted through the first hole, the second hole, and into the body of the sample;
an anchoring device for securing the tubing to the first sleeve and half sleeve, thereby forming a sample assembly; and
a pressure vessel for receiving the sample assembly, the pressure vessel comprising at least two ports connecting the sample to at least one pump with at least one pressure gauge, at least one port for applying a confining pressure, and at least one port for measuring pressure located at a known location along the sample, wherein determining gas permeability of the subsurface formation comprises:
positioning the sample in the pressure vessel comprising a fluid and the at least one pressure gauge;
measuring a first pore gas pressure, p 1 , of a gas at a location, x, along the sample;
applying a predetermined second pore gas pressure, p 0 , to an inlet of the sample, the second pore gas pressure being greater than the first pore gas pressure;
measuring a third pole gas pressure, p, as a function of time, t, at a location, x, along the sample in the pressure vessel;
in a computer, determining a gas density or total gas mass per unit volume of the subsurface formation, m; and
in the computer, determining the gas permeability of the subsurface formation, k(p), based at least in part on the first pore gas pressure, the second pore gas pressure, the third pore gas pressure as a function of time, and the gas density.

2. The apparatus of claim 1 , wherein the first sleeve and the half sleeve comprise at least one of rubber and a polymeric material.

3. The apparatus of claim 1 , wherein an inner diameter of the half sleeve is smaller than the outer diameter of the first sleeve.

4. The apparatus of claim 1 , wherein a length of the half sleeve is equal to or less than the length of the first sleeve.

5. The apparatus of claim 1 , wherein the fluid inside the pressure vessel comprises gas, water, or oil.

6. The apparatus of claim 1 , wherein the tubing further comprises a temperature gauge.

7. The apparatus of claim 1 , wherein the pressure gauge is coupled to the pressure tap using a flexible line.

8. The apparatus of claim 1 , further comprising:
an inlet pump configured to pump gas from a first gas tank into the sample assembly inside the pressure vessel, an outlet pump configured to store gas from the sample assembly inside the pressure vessel into a second gas tank, and gas in the gas tanks, the sample, the pressure lines, and the pumps.

9. The apparatus of claim 1 , wherein the step of determining a transport parameter of the subsurface formation further comprises:
determining a transport parameter of the subsurface formation, D(p), using a first formula:

D
⁡

(
p
)

=

∫

p
i

p

⁢

λ
2

⁢

d
⁢

⁢
m

dp

⁢
dp

dp

d
⁢

⁢
λ

where λ is an independent variable calculated using the formula λ=xt −1/2 ; and
determining gas permeability k of the subsurface formation from D(p) using

D
⁡

(
p
)

=

k
⁢

⁢
ρ

μ

where μ stands for gas viscosity, and ρ for gas density.

10. The apparatus of claim 9 , wherein the step of determining gas permeability of the subsurface formation further comprises:
determining the total gas mass per unit volume of the subsurface formation, m, using a second formula:
m =ϕρ+(1−ϕ)ρ a

where ϕ is porosity of the subsurface formation, ρ is gas density of the gas, and ρ a is adsorbed gas mass per unit volume of the subsurface formation.

11. The apparatus of claim 10 , wherein the step of determining gas permeability of the subsurface formation further comprises:
determining the porosity 0 of the subsurface formation using a third formula:

ϕ
=

B
-

A
⁢

∫

p
i

p
0

⁢

λ
⁢

d
⁢

⁢

ρ
a

dp

⁢
dp

A
⁢

∫

p
i

p
0

⁢

Assignees

• Saudi Arabian Oil Co

Inventors

• Liu Hui-Hai
• Lai Bitao
• Zhang Jilin Jay
• Georgi Daniel
• Huang Xinwo

Classifications

• G01N33/24

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

• G01N15/0826 Primary

  and measuring fluid flow rate, i.e. permeation rate or pressure change · CPC title