DOWNLOAD: Quick-Desorption™ Automated Shale Gas Desorption and Tight Rock Analysis: Sorption Isotherms Performed on Rotary Sidewall Cores (PDF)

Quick-Desorption™ Complete Shale Analysis

A industry-leading evaluation procedure was developed to perform most of the shale analysis tests on rotary sidewall samples or vertical plugs cut on location from the center of a full diameter core. This analysis works exceptionally well with rotary sidewalls due to the reduced trip time lifting the samples from reservoir temperature and pressure minimizing the lost gas. Due to the sample dimension the desorption is much faster than full diameter (days versus months). Only one sidewall sample is required for this procedure.

1 Measured gas
A fully automated laboratory is present on location when the rotary sidewall samples are taken.  The cores are cut from top to bottom and retrieved from the coring tool ASAP to minimize the lost gas. The wire line trip out time is recorded and used in the USBM lost gas calculation. Vertical plug samples can be cut, in the center of a conventional core, at  the well site and used for Quick-Desorption and Shale Evaluation. The portable laboratory returns to our laboratory facility while collecting desorption data at constant reservoir temperature. The desorption is conducted until the gas production ends.

2 Lost gas and matrix permeability
The linear portion of the desorption curve is used to determine lost gas and the diffusion parameter for the plug samples.

3 Bulk density, micro fracture porosity and permeability at confining stress
Bulk density and micro fracture permeability and porosity measurements are performed at reservoir confining stress on the wet shale sample (if a straight cylinder can be shaped from the recovered core material). If the sample quality is poor, only the bulk density is measured. 

4 Residual gas
The shale is grinded to about 45 mesh using special mills. Another desorption is performed at reservoir temperature on the granular sample to measure the residual gas and the diffusion parameter.

5 Total gas
Total gas is calculated by adding measured, lost and residual gas.

6 Geochemistry
A small portion of the sample is collected to perform TOC and Rock-Evaluation. The plug end trims are also available for further geochemistry and/or petrography analysis (TS, XRD, SEM).
 
7 Gas filled porosity
The gas filled porosity is measured on the crushed sidewall sample by gas expansion into the “as received” shale. 

8 Water and oil saturations, total porosity, and grain density
The samples are extracted to measure the water and oil saturations. The total porosity and the grain density are also measured.

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Shale Evaluation using Sorption Isotherms

Only one sidewall sample is required for this new test procedure.

 
1. Rotary sidewall samples are preserved at the well site and shipped to our laboratory in Midland, Texas therefore there are not any field expenses associated with this procedure. The preservation consists in surface mud cleaning with a wet towel, the samples are wrapped in ceran wrap and aluminum foil. A few drops of water are added to each glass jar before the samples are sealed to prevent evaporation during transportation.

2. The samples are trimmed photographed in UV and white light.

3. Microfracture analysis. The as received samples are loaded at reservoir stress and the porosity and permeability of the gas filled microfractures are measured. The bulk density and matrix permeability is also measured.

4. Residual gas measurement. The sidewall samples are ground to approximate 45 mesh. A complete desorption isotherm is performed at reservoir temperature to determine the residual gas and the diffusion parameter.

5. The gas filled porosity is measured by helium expansion into as received samples.

6. Sorption isotherms at reservoir temperature with methane are measured on each sample. These isotherms are normally close to the desorption isotherms (not measured in the field).

7. Cut fluorescence. A small fraction of the ground sample is photographed in UV without and with a cut solvent to document the cut fluorescence.

8. Geochemistry. A small portion of the sample is collected to perform TOC and Rock-Evaluation. The plug end trims are also available for further geochemistry and/or petrography analysis (TS, XRD, SEM).

9. Water and oil saturations, total porosity, and grain density.
The samples are extracted to measure the water and oil saturations. The total porosity and the grain density are also measured.

10. Helium Sorption isotherms at reservoir temperature are performed on each sample to determine free and adsorbed gas proportions.

DOWNLOAD: Quick-Desorption™ Automated Shale Gas Desorption and Tight Rock Analysis: Sorption Isotherms Performed on Rotary Sidewall Cores (PDF)

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