Measuring formation porosity and permeability

Patent metadata

Field	Value
Publication number	US-10260300-B2
Application number	US-201315101569-A
Country	US
Kind code	B2
Filing date	Dec 4, 2013
Priority date	Dec 4, 2013
Publication date	Apr 16, 2019
Grant date	Apr 16, 2019

Abstract

Values for porosity and permeability of core samples in a borehole are estimated by generating radial waves with an acoustic source in fluid around the core sample, and measuring pressure in the fluid. Moreover, the acoustic source operates at frequency close to a resonant frequency of the core sample. After the acoustic source no longer operates at the resonant frequency, pressure in the fluid attenuates over time. The pressure attenuation is recorded by the pressure measurements, along with the pressure in the fluid at the first harmonic (spectral component). The pressure attenuation and spectral component each are dependent on porosity and permeability of the core sample. Thus values for the porosity and permeability are determined based on the arithmetic relationships between pressure attenuation and the spectral component and porosity and permeability.

First claim

What is claimed is:

1. A method of estimating characteristics of a core sample in a borehole comprising:
(a) measuring values of pressure in a fluid surrounding the core sample that fluctuate in response to radial waves that propagate radially through the fluid and reflect from the core sample;
(b) identifying an attenuation of pressure in the fluid over time based on step (a);
(c) identifying a pressure in the fluid at a resonant frequency of the core sample; and
(d) estimating at least one of porosity or permeability of the core sample based on the values identified in steps (b) and (c).

2. The method of claim 1 , wherein the radial waves are at a frequency at about a resonant frequency of the core sample.

3. The method of claim 2 , wherein the step of identifying an attenuation of pressure in the fluid takes place after radial waves at the resonant frequency of the core sample no longer propagate through the fluid.

4. The method of claim 1 , wherein the fluid comprises a known fluid, and that is isolated from a wellbore fluid that is disposed in the borehole.

5. The method of claim 1 , further comprising generating the radial waves with an acoustic source that operates at about the first resonant frequency of the core sample, wherein the acoustic source is a tubular member that circumscribes the core and the fluid, and comprises a material selected from the group consisting of a piezoelectric material, a magnetostrictive material, and combinations thereof.

6. The method of claim 1 , wherein the resonant frequency is a minimal resonant frequency.

7. The method of claim 1 , further comprising obtaining the core sample with a coring tool, and wherein step (a) takes place in the coring tool.

8. A method of estimating characteristics of a core sample in a borehole comprising:
(a) obtaining the core sample with a coring tool in the borehole and immersing the core sample in a fluid;
(b) using a transmitter that operates at a resonant frequency of the core sample to generate radial waves in the fluid that propagate radially through the fluid and reflect from the core sample;
(c) identifying an attenuation of peaks of pressure in the fluid over time that are from the radial waves that propagate through the core sample;
(d) identifying a pressure in the fluid at the frequency of a resonant peak that is from at least one of the radial waves; and
(e) estimating at least one of porosity or permeability of the core sample.

9. The method of claim 8 , wherein the step of estimating at least one of porosity or permeability of the core sample is based on the steps of identifying of steps (b) and (c).

10. The method of claim 8 , further comprising the generation of radial waves at the resonant frequency is terminated prior to steps (c) and (d).

11. The method of claim 8 , wherein the resonant frequency of the core sample is estimated.

12. A system for estimating characteristics of a core sample in a borehole comprising:
a coring bit having an axial bore in which the core sample is selectively disposed;
a tubular transducer that circumscribes the axial bore and selectively oscillates at about a resonant frequency of the core sample;
an acoustic receiver disposed in the axial bore and immersed in a fluid that contacts the core sample, and that selectively receives radial waves generated by the tubular transducer that propagate radially through the fluid and reflect from the core sample; and
a processor for estimating a value for at least one of a porosity or permeability of the core sample based on a measurement of an attenuation of pressure of the radial waves received by the receiver and a pressure measured in the fluid at the resonant frequency of the core sample.

13. The system of claim 12 , further comprising springs for suspending the acoustic receiver in the fluid.

14. The system of claim 12 , further comprising a housing on which the coring bit is attached and which defines a coring tool, and a drill string attached to an end of the coring tool for rotating the coring bit.

15. The system of claim 12 , wherein the fluid is disposed in the axial bore when the coring bit is at surface, and wherein the fluid has known properties and is isolated from drilling fluid that is selectively circulated through the system.

Assignees

• Baker Hughes A Ge Co Llc

Inventors

• Dorovsky Vitaly Nikolaevich
• Perepechko Yury Vadimovich
• Podberezhny Maxim Yurievich

Classifications

• E21B25/00 Primary

  Apparatus for obtaining or removing undisturbed cores, e.g. core barrels or core extractors (core bits E21B10/02) · CPC title

• G01N15/08

  Investigating permeability, pore-volume, or surface area of porous materials · CPC title

• G01V1/50

  Analysing data · CPC title

• G01V2210/6244

  Porosity · CPC title

• G01V2210/1429

  Subsurface, e.g. in borehole or below weathering layer or mud line · CPC title