We identify remaining prospectivity in the Austin Chalk within an area of Wilson County, TX by integrating seismic inversion products, post-stack attributes, and publically available historical production data using multivariate statistical analysis. The resulting production prediction volume can then be used to optimize new well placement both laterally and vertically as well as allow for customized completions. By adopting these strategies the operator can avoid perforating and completing unproductive regions along the wellbore length resulting in significant cost savings with a negligible impact on production.
Using 58 post-stack seismic attributes and pre-stack inversion products, correlations can be generated between historical production metrics in the Austin Chalk and extracted seismic attribute values at the well bore. This approach typically identifies a number of attribute volumes that correlate reasonably well with production. Frequently the correlation coefficients for individual attributes would not be considered high enough to represent a sole or definitive indicator of production potential. For this reason we perform multivariate regression analysis on a portfolio of performance indicators combining multiple seismic attributes to produce production prediction volumes that are highly correlated to production. It is important to exercise caution when developing these production prediction models to minimize the number of attributes used in the model. This reduces the possibility of false correlations and of including redundant (co-linear) seismic attributes.
Using production data from 27 vertical wells, we generated a production prediction model using five variables drawn from the post-stack and inversion volumes as well as two directional component angle attributes. It had a correlation coefficient of 0.933 with historical Austin Chalk production. We validated the preferred model with a blind test using 16 horizontal wells by extracting the production prediction from the model along the producing interval of the well bore. Through this method of testing we achieve a correlation coefficient of 0.86 between the predicted and actual horizontal well production.
The Upper Cretaceous Austin Chalk occupies a swath from the south Texas border with Mexico, through East Texas, and into Louisiana and south Mississippi, and it contains several major fields (Figure 1). The Austin Chalk is underlain by the Eagle Ford Shale, which is believed to be a primary source of the hydrocarbons for the overlying Austin Chalk. Vertical fractures between the Austin Chalk and Eagle Ford are hypothesized as the conduits for hydrocarbon migration and formation pressure escape from the Eagle Ford into the overlying Austin Chalk (Figure 2).