Determining geologic properties of a rock sample
Techniques for determining a geologic property of a rock sample include (i) measuring, using nuclear magnetic resonance (NMR), a volume of a fluid retained within a solid matrix of a processed rock sample; (ii) measuring, using a gas porosimeter, a volume of gas space of the processed rock sample; (iii) measuring, with an Archimedes assembly, a first mass value in air of the processed rock sample and a second mass value in a liquid of the processed rock sample; and (iv) determining, based at least on the measured volume of the fluid, the measured volume of the gas space, and the measured first and second mass values, at least one of a bulk volume, a bulk density, a grain density, or a porosity of the processed rock sample.
1 . A method of determining a geologic property of a rock sample, comprising:
(i) measuring, using nuclear magnetic resonance (NMR), a volume of a fluid retained within a solid matrix of a processed rock sample;
(ii) measuring, using a gas porosimeter, a volume of gas space of the processed rock sample;
(iii) measuring, with an Archimedes assembly, a first mass value in air of the processed rock sample and a second mass value in a liquid of the processed rock sample; and
(iv) determining, based at least on the measured volume of the fluid, the measured volume of the gas space, and the measured first and second mass values, at least one of a bulk volume, a bulk density, a grain density, or a porosity of the processed rock sample.
2 . The method of claim 1 , wherein the processed rock sample is free from chemical cleaning subsequent to removal of the processed rock sample from a subterranean formation.
3 . The method of claim 1 , wherein the processed rock sample comprises a plurality of drill cuttings or a plurality of crushed rock pieces.
4 . The method of claim 3 , wherein the plurality of drill cuttings are rinsed and at least partially dried to remove excess fluid from an outer surface of the plurality of drill cuttings prior to step (i).
5 . The method of claim 3 , wherein each of the plurality of drill cuttings or each of the plurality of crushed rock pieces have an outer dimension in a range of between 0.5 and 3 mm.
6 . The method of claim 1 , wherein step (ii) comprises measuring the volume of the gas space of the processed rock sample to determine a volume of the solid matrix with the gas porosimeter using a Boyle's law technique with an inert gas.
7 . The method of claim 6 , wherein the inert gas comprises nitrogen, helium, or argon.
8 . The method of claim 1 , wherein step (i) comprises measuring, using NMR, the volume of the fluid retained within the solid matrix with at least one of T 1 or T 2 measurements of the processed rock sample.
9 . The method of claim 1 , wherein the first mass value comprises a mass of the processed rock sample measured in air by the Archimedes assembly, and the second mass value comprises a mass of the processed rock sample measured in liquid by the Archimedes assembly.
10 . The method of claim 9 , wherein the liquid comprises water or oil.
11 . The method of claim 9 , wherein step (iv) comprises determining the bulk volume based on the first mass value in air, the second mass value in the liquid, and a density of the liquid.
12 . The method of claim 11 , wherein determining the bulk volume based on the first mass value, the second mass value, and the density of the liquid comprises solving:
V
B
=
M
A
-
M
F
ρ
F
,
where V B is the bulk volume of the processed rock sample, M A is the first mass value in air, M F is the second mass value in the fluid, and ρ F is the density of the liquid.
13 . The method of claim 11 , wherein step (iv) comprises determining the bulk density of the processed rock sample based on the first mass value of the processed rock sample, the density of the fluid retained within the solid matrix, the volume of the solid matrix, and the bulk volume.
14 . The method of claim 13 , wherein determining the bulk density of the processed rock sample based on the first mass value of the processed rock sample, the density of the fluid retained within the solid matrix, the volume of the solid matrix, and the bulk volume comprises solving:
ρ
B
=
M
A
-
V
NMR
*
ρ
liq
V
B
,
where ρ B is the bulk density of the processed rock sample, M A is the first mass value in air, ρ liq is the density of the fluid retained within the solid matrix, V NMR is the volume of the fluid retained in the solid matrix, and V B is the bulk volume.
15 . The method of claim 11 , wherein step (iv) comprises determining the grain density of the processed rock sample based on the first mass value, the density of the fluid retained in the solid matrix, the volume of the solid matrix, and the volume of the fluid retained in the solid matrix.
16 . The method of claim 15 , wherein determining the grain density of the processed rock sample based on the first mass value, the density of the fluid retained in the solid matrix, the volume of the solid matrix, and the volume of the fluid retained in the solid matrix comprises solving:
ρ
g
=
M
A
-
V
NMR
*
ρ
liq
V
g
-
V
NMR
,
where ρ g is the grain density of the processed rock sample, M A is the first mass value in air, ρ liq is the density of the fluid retained within the solid matrix, V NMR is the volume of the fluid retained in the solid matrix, and V g is the volume of the solid matrix.
17 . The method of claim 11 , wherein step (iv) comprises determining the porosity of the processed rock sample based on the volume of the solid matrix, the volume of the fluid retained in the solid matrix, and the bulk volume.
18 . The method of claim 17 , wherein determining the porosity of the processed rock sample based on the volume of the solid matrix, the volume of the fluid retained in the solid matrix, and the bulk volume comprises solving:
ϕ
=
V
g
-
V
NMR
V
B
,
where
Φ is the porosity of the processed rock sample, V NMR is the volume of the fluid retained in the solid matrix, V g is the volume of the solid matrix, and V B is the bulk volume.
19 . A system for determining a geologic property of a rock sample, comprising:
a gas porosimeter configured to determine a grain volume of a solid matrix of a processed rock sample that comprises the solid matrix and a fluid retained within the solid matrix;
an Archimedes assembly configured to measure a first mass value of the processed rock sample in air and a second mass value of the processed rock sample in a liquid;
a nuclear magnetic resonance (NMR) measurement device configured to determine one or more NMR measurements of the processed rock sample; and
a control system configured to perform operations comprising:
(i) determining a volume of the fluid retained within the solid matrix from the one or more NMR measurements;
(ii) identifying a measured volume of gas space of the processed rock sample from the gas porosimeter;
(iii) identifying a measured first mass value of the processed rock sample in air and a measured second mass value in the liquid of the processed rock sample from the Archimedes assembly; and
(iv) determining, based at least on the measured volume of the fluid, the measured volume of the gas space, and the measured first and second mass values, at least one of a bulk volume, a bulk density, a grain density, or a porosity of the processed rock sample.
20 . The system of claim 19 , wherein the processed rock sample is free from chemical cleaning subsequent to removal of the processed rock sample from a subterranean formation.
21 . The system of claim 19 , wherein the processed rock sample comprises a plurality of drill cuttings or a plurality of crushed rock pieces.
22 . The system of claim 21 , wherein the plurality of drill cuttings are rinsed and at least partially dried to remove excess fluid from an outer surface of the plurality of drill cuttings prior to step (i).
23 . The system of claim 21 , wherein each of the plurality of drill cuttings or each of the plurality of crushed rock pieces have an outer dimension in a range of between 0.5 and 3 mm.
24 . The system of claim 19 , wherein the measured volume of the gas space of the processed rock sample is measured with the gas porosimeter using a Boyle's law technique with an inert gas.
25 . The system of claim 24 , wherein the inert gas comprises nitrogen, helium, or argon.
26 . The system of claim 19 , wherein the measured volume of the fluid retained within the solid matrix is measured using at least one of T 1 or T 2 measurements of the processed rock sample with the NMR.
27 . The system of claim 19 , wherein the first mass value comprises a mass of the processed rock sample measured in air by the Archimedes assembly, and the second mass value comprises a mass of the processed rock sample measured in liquid by the Archimedes assembly.
28 . The system of claim 27 , wherein the liquid comprises water or oil.
29 . The system of claim 27 , wherein the operation (iv) comprises determining the bulk volume based on the first mass value in air, the second mass value in the liquid, and a density of the liquid.
30 . The system of claim 29 , wherein the operation of determining the bulk volume based on the first mass value in air, the second mass value in the liquid, and the density of the liquid comprises solving:
V
B
=
M
A
-
M
F
ρ
F
,
where V B is the bulk volume of the processed rock sample, M A is the first mass value in air, M F is the second mass value in the liquid, and ρ F is the density of the liquid.
31 . The system of claim 29 , wherein the operation (iv) comprises determining the bulk density of the processed rock sample based on the first mass value of the processed rock sample, the density of the fluid retained within the solid matrix, the volume of the solid matrix, and the bulk volume.
32 . The system of claim 27 , wherein the operation of determining the bulk density of the processed rock sample based on the first mass value of the processed rock sample, the density of the fluid retained within the solid matrix, the volume of the solid matrix, and the bulk volume comprises solving:
ρ
B
=
M
A
-
V
NMR
*
ρ
liq
V
B
,
where ρ B is the bulk density of the processed rock sample, M A is the first mass value, ρ liq is the density of the fluid retained within the solid matrix, V NMR is the volume of the fluid retained in the solid matrix, and V B is the bulk volume.
33 . The system of claim 29 , wherein the operation (iv) comprises determining the grain density of the processed rock sample based on the first mass value, the density of the fluid retained in the solid matrix, the volume of the solid matrix, and the volume of the fluid retained in the solid matrix.
34 . The system of claim 33 , wherein the operation of determining the grain density of the processed rock sample based on the first mass value, the density of the fluid retained in the solid matrix, the volume of the solid matrix, and the volume of the fluid retained in the solid matrix comprises solving:
ρ
g
=
M
A
-
V
NMR
*
ρ
liq
V
g
-
V
NMR
,
where ρ g is the grain density of the processed rock sample, M A is the first mass value in air, ρ liq is the density of the fluid retained within the solid matrix, V NMR is the volume of the fluid retained in the solid matrix, and V g is the volume of the solid matrix.
35 . The system of claim 29 , wherein the operation (iv) comprises determining the porosity of the processed rock sample based on the volume of the solid matrix, the volume of the fluid retained in the solid matrix, and the bulk volume.
36 . The system of claim 35 , wherein the operation of determining the porosity of the processed rock sample based on the volume of the solid matrix, the volume of the fluid retained in the solid matrix, and the bulk volume comprises solving:
ϕ
=
V
g
-
V
NMR
V
B
,
where Φ is the porosity of the processed rock sample, V NMR is the volume of the fluid retained in the solid matrix, V g is the volume of the solid matrix, and V B is the bulk volume.