Rancho San Francisco No. 66

In 1948, RSF 66 was drilled to 14,509 feet and, for a while, became the world's deepest producing well (but not the deepest well drilled). See the complete well records for RSF 66 here.

The following was stated in the February 1949 issue of the Petroleum Engineer):

"For the first time in the history of the oil industry commercial production was found deeper than 14,000 ft and before the year was out five separate fields had production at these new record depths." (p. B-7)
"As the end of the year [1948] came, Barndall No. 66-9 RSF picked up a new deep sand in the Newhall-Potrero field, California, reaching to 14,505 ft, according to company report, and producing 50 bbl a day of 28 gravity oil on gas lift." (p. B-26)

In September of 1949, the world's deepest producing well became Standard Oil's Mushrush 5 well in the Wasco Field in Kern County, California. It began producing at a depth from 15250-15530 feet.

Well name note: On the Rancho San Francisco lease in the Newhall-Potrero oil field the dash numbers in the well name indicated what oil zone was to be, or was, drilled to. There would eventually be seven zones (called 1, 3, 4, 5, 6, 7, & 9). For RSF 66, the Division of Oil and Gas "Notice of Intention to Drill New Well" form dated August 22, 1947, the well was called RSF 66-6. The "-6" meant that they planned to drill into the 6th oil zone of the field. Later in the well records the well became RSF 66-7 because they drilled into the 7th zone. By the 1980's, well records just call the well RSF 66. Nowhere in the well records was the well called RSF 66-9. The "9" would have meant that they drilled to the 9th zone, which they did. I leave off the dash number when mentioning any of the RSF wells on this website.