Abstract

The West Tracy Gas Field, located in Section 13, T2S, R4E, San Joaquin County, California, is four miles west of the main Tracy Gas Field. Drilling in the West Tracy area began in 1959. Nahama and Weagant Energy Company discovered commercial gas production at West Tracy in 1993.

Seismic shot in the region revealed the geologic complexity as the West Tracy Gas Field is situated near the intersection of three thrust faults; the Stockton Thrust Fault, Vernalis Thrust Fault, and West Tracy Thrust Fault. Although the original wells drilled by Nahama and Weagant were Winters Sand plays based on seismic anomalies, the resulting gas production was discovered in deeper Lathrop Sands. These productive sands are found on the hanging wall of the Stockton Thrust Fault and footwall of the West Tracy Thrust Fault. The reservoir trap at West Tracy is similar to the trap found in the 352 BCF Lathrop Gas Field. Each well drilled at West Tracy, combined with existing 2-D seismic, illustrates the complexities of the area.

In addition to geologic complexities of the area, development efforts were slowed since the Lathrop Sands have low permeability and 716 BTU per cubic foot natural gas. Fracture stimulation of the Lathrop Sands was necessary to improve well deliverabilities. As a result of the stimulation treatment, gas deliverability increased from 640 to 2,500 MCFPD.