System and method of pore type classification for petrophysical rock typing

Patent metadata

Field	Value
Publication number	US-10324229-B2
Application number	US-201514919890-A
Country	US
Kind code	B2
Filing date	Oct 22, 2015
Priority date	Oct 23, 2014
Publication date	Jun 18, 2019
Grant date	Jun 18, 2019

Abstract

Embodiments of a method of pore type classification for petrophysical rock typing are disclosed herein. In general, embodiments of the method utilize parameterization of MICP data and/or other petrophysical data for pore type classification. Furthermore, embodiments of the method involve extrapolating, predicting, or propagating the pore type classification to the well log domain. The methods described here are unique in that: they describe the process from sample selection through log-scale prediction; PTGs are defined independently of the original depositional geology; parameters which describe the whole MICP curve shape can be utilized; and objective clustering can be used to remove subjective decisions. In addition, the method exploits the link between MICP data and the petrophysical characteristics of rock samples to derive self-consistent predictions of PTG, porosity, permeability and water saturation.

First claim

What is claimed is:

1. A method of pore type classification, the method comprising:
a) selecting a plurality of core plugs from a reservoir;
b) acquiring a dataset from the plurality of core plugs, wherein the dataset comprises mercury injection capillary pressure (MICP) data, porosity, permeability, and grain density data for each core plug of the plurality of core plugs, and wherein a MICP device houses each core plug of the plurality of core plugs in order to acquire the MICP data for the core plug;
c) parameterizing, using a computer, the dataset using a Gaussian error function and the MICP data to derive a plurality of curve fit parameters, wherein the Gaussian error function comprises a formula comprising:

V

P
c

=

V

P
∞

2

⁢

(

1
+

2

π

⁢

∫
0
x

⁢

e

-

t
2

·

⁢
dt

)

where V P c is pore volume at a given capillary pressure and

x
=

1
S

⁢

log
⁡

(

P
c

P
m

)

,

where S is a pore system shape factor, P m is a modal pressure of the pore system, and V p ∞ is a bulk volume of the pore system;
d) clustering, using the computer, the plurality of curve fit parameters to create one or more pore type groups for the plurality of core plugs with the MICP data;
e) extrapolating the one or more pore type groups to a different plurality of core plugs without any MICP data; and
f) propagating the one or more pore type groups of the plurality of core plugs with the MICP data and the different plurality of core plugs without any MICP data to a well log domain to classify a rock type from the reservoir, wherein the rock type is used to model the reservoir.

2. The method of claim 1 , further comprising correcting and performing quality control on the dataset.

3. The method of claim 1 , wherein the plurality of core plugs represents a statistically representative number of samples for a depositional rock type.

4. The method of claim 1 , wherein the plurality of core plugs represents a statistically representative number of samples from a petrophysical space.

5. The method of claim 1 , wherein (c) further comprises:
c1) choosing an initial model with a number of modes, N, wherein N is an integer;
c2) executing a solution with the N number of modes to minimize a difference between the MICP data and predicted MICP data generated by the Gaussian error function;
c3) if an individual mode of the N number of modes does not satisfy an acceptance criteria, then this mode is removed from the N number of modes, and remaining modes of the N number of modes from the solution form a new starting model with N=N−1 modes;
c4) repeating (c2) and (c3) until a final solution is obtained where all modes meet the acceptance criteria.

6. The method of claim 1 , wherein (b) further comprises, for each core plug of the plurality of core plugs:
b1) acquiring plug computed tomography (CT) scan to identify heterogeneities, and identify suitable part of the core plug for sub-coring;
b2) sub-coring the core plug based on b1) to a plug size capable of being housed in the MICP device;
b3) measuring the porosity, the grain density, and the permeability of the core plug using accepted American Petroleum Institute (API) techniques; and
b4) acquiring the MICP data of the core plug.

7. The method of claim 6 , wherein the plug size is 1 inch×1 inch.

8. The method of claim 1 , wherein the reservoir comprises a carbonate formation.

9. The method of claim 1 , further comprising calculating one or more petrophysical properties for each of the one or more pore type groups.

10. The method of claim 9 , wherein the calculating the one or more petrophysical properties for each of the one or more pore type groups comprises using a Monte-Carlo approach to determine one or more probabilistic representations within each of the one or more pore type groups and using the one or more probabilistic representations to calculate the one or more petrophysical properties.

11. The method of claim 9 , wherein calculating the one or more petrophysical properties for each of the one or more pore type groups comprises using averaged MICP data from each of the one or more pore type groups.

12. The method of claim 11 , further comprising, for each of the one or more pore type groups, generating a MICP synthetic curve based on a range of observed pore system parameters, and using the MICP synthetic curve to generate a calibrated permeability and an associated water curve.

13. A system comprising:
an interface for receiving a dataset for a plurality of core plugs from a reservoir, wherein the dataset comprises mercury injection capillary pressure (MICP) data, porosity, permeability, and grain density data for each core plug of the plurality of core plugs, and wherein a MICP data is acquired using a MICP device that houses each core plug of the plurality of core plugs in order to acquire the MICP data for the core plug;
a memory resource;
input and output functions for presenting and receiving communication signals to and from a human user;
one or more central processing units for executing program instructions; and program memory, coupled to the one or more central processing units, for storing a computer program including program instructions that, when executed by the one or more central processing units, cause the computer system to perform a plurality of operations for pore type classif

Assignees

• Chevron Usa Inc

Inventors

• Theologou Paul
• Skalinski Mark
• Mallan Robert K

Classifications

• G01N33/241

  for hydrocarbon content · CPC title

• G01N15/0886 Primary

  Mercury porosimetry · CPC title

• G01N2223/649

  porosity · CPC title

• G01V99/005 Primary

  Physics · mapped topic

• G01N2015/0813

  Measuring intrusion, e.g. of mercury · CPC title