Lithologic Framework Modeling of the Fruitvale Oil Field Investigating Interaction Between Wastewater Injection Wells and Usable Groundwater

Abstract:

The Fruitvale Oil Field lies in a populated area where oil production, water disposal injection wells, and drinking water wells lie in close proximity. The purpose of this project is to build a lithological framework of the area that can then be used to determine if water disposal from petroleum production has a chance of reaching usable groundwater aquifers.

Using the DOGGR database, data were collected from well logs. Lithologic data from drilling logs and cores were coded and entered into a relational database, where it was combined with the surface elevation and location coordinates of each well. Elevation data was acquired through ArcGIS using a USGS 24k 10 m DEM. Drillers logs that started at the surface, and were continuous, were sorted by the density of intervals recorded, in order to select high quality drillers logs for use in creating a model. About 900 wells were coded and approximately 150 wells were used in the model. These wells were entered into the modeling program (Rockworks), which allowed the wells to be visualized as strip logs and also as cross sections, and 2D fence models were created to represent subsurface conditions. The data were interpolated into 3D models of the subsurface. Water disposal wells, with the depths of the perforation intervals as well as injection volume, were added to the model, and analyzed.

Techniques of interpolation used in this project included kriging, which requires statistical analysis of the data collected. This allowed correlation between widely-spaced wells. Up scaling the data to a coarse or fine texture was also been found to be effective with the kriging technique. The methods developed on this field can be used to build framework models of other fields in the Central Valley to explore the relationship between water disposal injection and usable groundwater.