## Breadcrumb

-  Publications 
-  Articles 

#           Multimineral petrophysics of thermally immature Eagle Ford Group and Cretaceous mudstones, U.S. Geological Survey Gulf Coast 1 research wellbore in central Texas      

      December 14, 2021    

Traditional petrophysical methods to evaluate organic richness and mineralogy using gamma-ray and resistivity log responses are not diagnostic in source rocks. We have developed a deterministic, nonproprietary method to quantify formation variability in total organic carbon (TOC) and three key mudrock mineralogical components of nonhydrocarbon-bearing source rock strata of the Eagle Ford Group by developing a set of log-derived multimineral models calibrated with Fourier transform infrared spectroscopy core data from the research borehole U.S. Geological Survey Gulf Coast 1 West Woodway. We determined that bulk density response is a reliable indicator of organic content in these thermally immature, water-bearing source rocks. Multimineral findings indicate that a high degree of laminae-scale mineralogical heterogeneity exists due to thinly interbedded carbonate cements amid clay-rich mudstone layers. The lower part of the Eagle Ford Group contains the highest average TOC content (4.7 wt%) and the highest average carbonate volume (64.1 vol%), making it the optimal target in thermally mature areas for source-rock potential and hydraulic-fracture placement. In contrast, the uppermost portion of the Eagle Ford Group contains the highest average volume of clay minerals (42.6 vol%), which increases the potential for wellbore stability issues. Petrophysical characterization reveals that porosity is approximately 30% in this relatively uncompacted formation. In this thermally immature source rock, water saturation is nearly 100% and no free hydrocarbons were observed on the resistivity logs. No evidence of borehole ellipticity was observed on the three-arm caliper log, and horizontal stresses are presumed to be directionally uniform in the vicinity of this near-surface wellbore. This shallow wellbore has a temperature gradient of 1.87°F/100 ft (16.3°C/km) and is likely influenced by earth surface heating.

## Citation Information

## Related Content

                  -              Data           
                  -              Connect           

March 9, 2022

####                 Wireline geophysical logging curves and infrared spectral data for the USGS Gulf Coast #1 West Woodway research wellbore, McLennan County, Texas              

Energy Resources Program, Central Energy Resources Science Center

#### Lauri Burke, Ph.D.

##### Research Geophysicist

Central Energy Resources Science Center

lburke@usgs.gov

303-236-1912

#### Justin Birdwell

##### Research Engineer and Geochemist

Central Energy Resources Science Center

jbirdwell@usgs.gov

303-236-1534

#### Stanley Paxton

##### Physical Scientist

Central Energy Resources Science Center

spaxton@usgs.gov

303-236-5563

## Related Content

March 9, 2022

####                 Wireline geophysical logging curves and infrared spectral data for the USGS Gulf Coast #1 West Woodway research wellbore, McLennan County, Texas              

Energy Resources Program, Central Energy Resources Science Center

#### Lauri Burke, Ph.D.

##### Research Geophysicist

Central Energy Resources Science Center

lburke@usgs.gov

303-236-1912

#### Justin Birdwell

##### Research Engineer and Geochemist

Central Energy Resources Science Center

jbirdwell@usgs.gov

303-236-1534

#### Stanley Paxton

##### Physical Scientist

Central Energy Resources Science Center

spaxton@usgs.gov

303-236-5563

### Study Area

### Contact

####               Central Energy Resources Science Center          

Denver Federal CenterBldg. 25Denver, CO80225United States

### Explore Search

                  - United States
                  - texas

View All **