Los Angeles Basin, New Oil from Old Fields
Authors: Hill James M. 
Published: December 2007

During the months of February and March of 1995, Vortex Energy and Minerals, a Canadian company, operating under the name of the local operator Casex, redrilled the Turf Club #2 well located within the boundaries of the Potrero Oil Field, Los Angeles Basin California. During drilling the well found a new, undrained fault block within the old Potrero Field. The first sidetrack of the Casex Turf #2 well was directionally drilled almost 3300 feet north of the surface location. The prospect concept was a subsurface north-trending anticline defined mainly on topography. During drilling the well encountered strong oil and gas shows, and after logging dipmeter information indicated strong north dip, which was counter to the original prospect concept. The strong shows suggested commercial oil production might be present to the south. The well was then plugged back and redrilled almost 1,600 feet south of the original sidetrack to a total drilled depth of 10,500 feet. This hole encountered stronger shows of oil and gas, and pipe was run to 10,500 feet. Testing of the Miocene O'Dea and Pliocene Repetto sands zones produced mostly water. The final production test within the Pliocene Pico Formation flowed at rates approaching almost 1000 barrels of 26 degree gravity oil per day. The Turf #2 well began commercial oil production in February of 1996, from two Pico oil sands located between 2848 and 2916 feet drilled depth. The new fault block encountered by the Casex Turf #2 well is extensional in nature, located in the eastern portion of the old Potrero Field and is estimated to be about 10 acres in size. The Turf #2 well penetrated only the uppermost parts of the productive Pico section, and additional sands, productive in the old field, should be found deeper in the section.

Introduction

The first commercial production from the Potrero Field was found on April 11, 1928, when Associate Oil drilled a well which flowed at a daily rate of 1049 barrels of high quality, 42.7 degree gravity oil (Johnson, 1962). The Potrero Field is one of the smaller oil and gas accumulations located along the very oil-prolific Baldwin Hills-Newport Inglewood fault trend, which extends from West Newport Beach to the south, northward to Beverly Hills. This trend is displayed on figure 1 (Woodford, et al., 1954). This fault zone is made up of a series of faults, many of which have pronounced surface expression. They are strike slip in nature with the major type of movement being right lateral with a dip-slip or reverse component (Harding, 1973).

A combination of compression and shear forces has formed numerous anticlinal structures along the fault trend (Harding, 1973). These structures are located along the southwestern portion of the Los Angeles Basin. Large quantities of oil have been produced from the basin, mostly from a thick section of upper Miocene and lower Pliocene deep water turbidite sands. To the east of this fault trend the rocks dip down eastward into the Los Angeles Basin.

The Casex Turf #2 side-track and redrill was the first well to be drilled within the old Potrero Field boundary in over 14 years. The project took almost 5 years to permit and finally went forward as a redrill of the original Turf #2 well, which was a redrill of the old Turf #1 that was drilled in 1940. Although Vortex Energy and Minerals, a Canadian company, was in control of the project, permit problems required Casex be the designated operator of the well.

The Original Prospect

The original prospect was mapped by, F. J. Noble, C. W. Hatten and J. E. Kilkenny as a doubly plunging, northwest-trending anticline located to the northeast of the Potrero Field, east of the Newport-Inglewood fault trend. Topography played a major role in the play concept as many of the oil and gas fields along this trend have a strong topographic expression. The play was billed as the last undrilled topographic high in the Los Angeles Basin. P. 677^