TURNING WIGGLES INTO OIL: 3D SEISMIC INCREASES PRODUCTION IN THE EASTERN SHALLOW OIL ZONE, ELK HILLS FIELD, CALIFORNIA

The Reservoir Management Team (RMT) of the Eastern Shallow Oil Zone (ESOZ) at Elk Hills is effectively utilizing cutting edge 3D seismic technology in an integrated multidisciplinary effort to maximize production and reserves in an established core asset. Although Elk Hills provides significant imaging challenges with its near surface air sands and steep hills, an interpretable result was obtained by optimizing acquisition parameters, particularly by increasing the fold. The seismic was just acquired in 1999, with interpretation beginning in early 2000. This work has already bolstered production, and has identified significant future potential in these reservoirs.

The ESOZ is an extremely large and prolific set of oil reservoirs with a long history of production. Discovered in the early 1900’s and later rolled into a government strategic petroleum reserve, the 13,000 acre area was developed in “fits and starts” directly correlated with the historical war and peace eras of the United States. To date about 1,500 wells have been completed, at depths from 1,800’ to 4,500’. Gravity drainage, enhanced by gas injection, is the primary drive mechanism. Complex faulting and multi-stacked sand/shale sequences sub-divide the five main reservoirs creating a significant challenge to optimizing performance.

The insights from the 3D seismic data have been employed on over 20 prospects through December 2000. The 3D data has accurately pin pointed fault locations, identified gas–liquid contacts, and ultimately reduced risk. As the interpretation progresses, the team continues to integrate the information, locating wells that will produce previously by-passed perched oil in areas once thought to be completely exploited. The team has already gained more valuable insights about the geology from wavelet character mapping and inversion. Seismic data is being integrated into a 3D reservoir model in order to better extrapolate reservoir properties between discrete petrophysical measurements in existing wells.