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Twenty-five years ago the first deep wildcat well to explore the large subsurface San Emidio anticline was abandoned, with no promising indications of commercial oil production. Anticipated upper Miocene reservoir rocks continued to elude five more exploratory efforts during the ensuing twenty-three years. Reef Ridge sands were found to be thin or not present, and Stevens sands generally silty and impermeable. First commercial Reef Ridge production was proven in July, 1958, when Richfield Oil Corporation K.C.L. "H" No. 34-9 was completed flowing 350 b/d clean 30° gravity oil and 46 mcf gas through a 12/64^Prime bean from the interval 11,451-11,558 feet. Development of the H-33 pool commenced with completion of K.C.L. "H" No. 83-9 at a rate of 440 b/d clean 31° g avity oil and 50 mcf gas through an 8/64^Prime bean from the interval 12,702-12,838 feet. Current daily production from both zones in twenty-two wells is about 7,000 b/d gross.
Characterized by a lack of structural complexity, the area has several well defined lithologic units that record contrasting environments of sedimentation. Overlying and sealing the stratigraphically closed Reef Ridge reservoir sand is the impervious, well bedded Reef Ridge shale, youngest Miocene formation present. Gross lithologic characteristics allow subdivision of the Reef Ridge sand interval into an upper member of massive, moderately sorted, contiguous sands and a lower member of poorly bedded, generally less permeable sands. Between Reef Ridge and H-33 sands is 300 feet of impermeable upper Mohnian siltstone. H-33 reservoir sands are fine-grained, moderately to well sorted and divisible into an upper series of thin-bedded lenticular sands and a lower massive unit.
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