Method for determining a matrix permeability of a subsurface formation
A method for determining a matrix permeability of a subsurface formation, including the steps: acquiring a core from the subsurface formation, imposing a fluid to the core until the core is saturated with the fluid, conducting a pressure-pulse decay (PD) method on an upstream and a downstream side of the core by applying a pressure-pulse on the upstream and the downstream side of the core, and determining the matrix permeability from decays of the pressure-pulses on the upstream side and downstream side, respectively.
1. A method for determining a matrix permeability of a subsurface formation, comprising the steps:
acquiring a core from the subsurface formation,
imposing a fluid to the core until the core is saturated with the fluid,
conducting a pressure-pulse decay (PD) method on an upstream and a downstream side of the core by applying a pressure-pulse on the upstream and the downstream side of the core, and
determining the matrix permeability from decays of the pressure-pulses on the upstream side and downstream side.
2. The method of claim 1 , further comprising applying a confining pressure to the core to ensure proper sealing of the core.
3. The method of claim 2 , wherein the confining pressure is higher than the pressure of the fluid at any time.
4. The method of claim 2 , wherein the confining pressure is applied before the PD method.
5. The method of claim 2 , wherein the confining pressure is performed by a confining pressure pump.
6. The method of claim 2 , wherein a pore pressure of the fluid is smaller than the confining pressure.
7. The method of claim 2 , further comprising stopping the confining pressure after the PD method.
8. The method of claim 2 , wherein the confining pressure is constant.
9. The method of claim 1 , wherein the pressure-pulse is a fraction of the saturation pressure of the core.
10. The method of claim 1 , wherein the fluid is a liquid.
11. The method of claim 1 , wherein the fluid is a gas.
12. The method of claim 11 , wherein the gas comprises a noble gas.
13. The method of claim 11 , wherein the gas comprises nitrogen.
14. The method of claim 11 , wherein the gas is pressured.
15. The method of claim 11 , wherein the gas is imposed with the saturation pressure of the core.
16. The method of claim 1 , wherein the core is saturated in eight to sixteen hours.
17. The method of claim 1 , wherein the core is saturated in eight to twenty four hours.
18. The method of claim 1 , wherein the pressure-pulse on the upstream and downstream side is applied on the core simultaneously.
19. The method of claim 1 , wherein the matrix permeability on the upstream side is determined using the following equation:
log
(
P
D
u
)
≈
log
(
f
1
)
-
φ
1
1
2
4
k
mpfu
c
μ
ϕ
m
L
2
t
.
20. The method of claim 1 , wherein the matrix permeability on the downstream side is determined using the following equation:
log
(
P
D
d
)
≈
log
(
f
2
)
-
φ
1
2
2
4
k
mpfd
c
μ
ϕ
m
L
2
t
.