Archive for the ‘Oil Prospects’ Category

Earlier this summer, I went up to the Humboldt County Public Library, enticed by a poster reading: “Petrolia 1865, California’s first oil field: A century of disappointment.” The speaker was Dr. Ken Aalto, an HSU professor emeritus who has studied Humboldt’s geology since 1974. The advertisement went on to explain that Aalto would be sharing a “tale of how Petrolia’s shear zone geology, at the noted Mendocino Triple Junction, kindled and dashed the hopes of oil explorers for a century.”

The Events room, off to the left just as you enter the Eureka library, was packed full as it has been every time I’ve been to one of these series of Saturday historical talks, which are presented jointly by the Humboldt Co. Historical Society and the Humboldt County Library. However, there were not too many Mattole faces there, so I am reporting on the presentation here, with the benefit of some of the diagrams and maps–and mostly, a paper–that Ken Aalto used in the slide show.

The clarity of the graphics on this blog site is not high; however, they make satisfactory illustrations of the general ideas, for the layperson. Luckily, I found Ken to be a generous man, and he allowed me to share any and all of the material he emailed me; so, if you would like to see any of these papers in greater detail, please let me know, and I can forward you a better copy, or more complete information. (Of course you would want to continue to give credit where it is due if you were to use his writing or maps anywhere else.)

I have been pretty ignorant of the science of our local geology, knowing little more than what I’ve read in local news reports around earthquake time, or in old-time descriptions of the oil-producing capabilities of the Mattole area. I confess that many of the words and coded designations on these maps make little sense to me. But it was the big question that drew me, and its answer was most satisfying. The question was, “With all this oil known to be around here, and with the new technologies that allow fracking to squeeze oil and gas out of previously impossible situations… are they going to try to start fracking around here?”

Dr. Aalto showed us several dozen slides, mainly of maps and diagrams of the earth beneath our feet. Some were of historical newspaper articles about the oil excitement, and a few were color photos of today’s landscape. His expert interpretation of these images was very interesting, if a bit hard to grasp and retain (for me!). However, he kindly sent me the paper he wrote, which seems to sum up his talk; and the abstract from it sums up the paper. So, here is the crystallized gist of the paper “PETROLIA, CALIFORNIA’S FIRST OIL FIELD–A CENTURY OF DISAPPOINTMENT,” by K.R. Aalto, Department of Geology, Humboldt State University, Arcata, CA  95521 (kra1@humboldt.edu); published by the Petroleum History Institute in the journal Oil-Industry History, v. 12, no. 1, 2011:

“ABSTRACT: The Petrolia oil field, the first to be developed in California in the 1860’s, attracted considerable interest and investment among oilmen because of the abundance of oil and gas seeps throughout that region. The ‘Union well’, first producing well drilled in California in 1865, yielded some thirty barrels of high quality oil, but production soon slowed to one barrel per day and the prospect was abandoned. However, over the next half-century exploration and drilling continued throughout the region with little or no success.
“Although touted as a potential major oil district, the highly deformed Franciscan Complex basement rocks, that were structurally imbricated with Neogene marine strata as part of an actively growing accretionary prism atop the subducting Farallon plate, did not provide adequate reservoirs. Rather, oil and gas seeped to the surface along shear zones. The tectonostratigraphic setting of California’s only oilfield unequivocally located in an active subduction zone precluded its success.”

Here is an excellently detailed schematic of the area's geology. If i orient myself as if i were underneath King Peak and looking northwest through the Earth, it makes sense.

An excellently detailed schematic of the area’s geology. If I orient myself as if I were under the ground south of King Peak and looking northwest through the Earth, it makes sense. Click on the image to make it full-screen.

Here is an overview of the Triple Junction area, showing the older Pacific Plate, to the south, pushing up into the Gorda/Juan de Fuca Plate, which is pushing underneath the continent (the North American Plate). Volcanoes east of us are one result of the pushing of the Pacific Plate under the westward-moving North American. We all know another result!

Here is an overview of the Triple Junction area, showing the older Pacific Plate, to the south, pushing up into the Gorda/Juan de Fuca Plate, which is pushing underneath the continent (the North American Plate). Volcanoes east of us are one result of the pushing of the Pacific Plate under the westward-moving North American. We all know another result!


In this zoom view, I put a little red dot where the town square of Petrolia sits, and highlighted the river in blue. It’s a blur if you blow it up too much (though you should click on it once), but as I said, I can email you a better copy if you are interested. There is also a key to all the colors and codes–it’s a humongous bunch of information, too big to put up here. One thing I find interesting about this map is the line of some sort of fracture going out northwest from Petrolia toward the ocean at McNutt Gulch. Several people have theorized that at one time, the Mattole River emptied out to the sea through that gulch, and that a massive uplift of “the Table” with its flat, straight lines and abrupt rises, diverted it south to its present bed.

These first three images are from USGS map series MF-2336, by R.J. McLaughlin, S.D. Ellen, M.C. Blake, Jr., A.S. Jayko, W.P. Irwin, K.R. Aalto, G.A. Carver, and S.H. Clarke, Jr., et. al.; from the year 2000.

Ken Aalto’s 2011 paper on our local geology (cited above) lays out the situation far better than I can. Allow me to copy directly from his document (and note that the definition of “terrane” as used here is “the area or surface over which a particular rock or group of rocks is prevalent”–Merriam-Webster):

“MODERN INTERPRETATION: Basement rock in the Petrolia area consists of penetratively deformed Franciscan Complex Coastal belt which is divided into several tectonostratigraphic terranes that include rocks ranging from Late Cretaceous to Middle Miocene age (Fig.1). The sandstones of these terranes are highly sheared, well cemented and discontinuous, thus their reservoir potential is low. Franciscan rocks are locally depositionally overlain and structurally imbricated with thin slabs and slivers of Miocene and younger non-accretionary marine strata (the Late Cenozoic overlap assemblage) originally deposited in forearc or marginal basin settings (Fig. 1; Aalto et al. 1995; Miller and Aalto, 1983). Miocene and younger source rocks are depicted as imbricate slices in an accretionary complex (Fig. 4; McLaughlin et al. 2000). H. D. MacGinitie recognized this structural style, noting that:
‘[t]he Tertiary outcrops are found as elongated strips following the structural trends [of the subjacent Franciscan Complex]. The strips are synclinal in nature and are usually overturned toward the south and bounded by overthrust blocks of the Mesozoic rocks on the north side.’ (MacGinitie 1943, p. 633).
“Source rocks, originating in forearc or marginal basin settings, are thrust beneath False Cape and Coastal terranes, and possibly provide a source for the oil presently leaking from seeps and wells within the Coastal terrane of the Petrolia area (Fig. 4; McLaughlin et al. 1999).
“MacGinitie (1943, p. 634) noted that the abundant oil and gas seeps of the Petrolia region commonly occurred ‘…in connection with major lines of faulting’ and that ‘…the source of the oil in the seeps and from the wildcat wells may be found in black, organic shale.’ However, he suggested that ‘…the folding and faulting have been so strong in the areas where oil indications occur that the majority of the structures are too broken to furnish satisfactory oil storage’
(MacGinitie, 1943, p. 635). Ogle (1953) determined that sandstone beds of Lower Wildcat Group (Fig. 3, part of the overlap assemblage) served as reservoir rocks in the gas fields developed near Eureka. Franciscan basement rocks did not appear to be suitable as reservoirs, although some sheared areas were permeable.
“In 1997, McLaughlin et al. (1999) collected some dozens of samples from active seeps and oil and gas wells of the Petrolia region. These have stable isotopic compositions similar to petroleum derived from Miocene source rocks elsewhere in California. In assessing possible source rocks among exposed Tertiary rocks, McLaughlin et al. (1999) concluded:
‘Fair to good petroleum generative potential is indicated for thermally immature Miocene shale and mudstone [of the Petrolia region], with TOC values of 1.1-1.8 wt %, HI>200, and Tmax values of about 420 degrees C.’ (Text from poster presented by McLaughlin et al., 1999).
“These data and regional structure suggest petroleum could very well have been generated from similar forearc source rocks that were structurally interleaved with the Franciscan Complex during growth of the modern accretionary prism, and which reached thermal maturity during thrust burial to several kilometers.”

Here is a good diagram from Ken Aalto's paper.

This diagram appeared in the Ken Aalto paper “Petrolia, California’s First Oil Field…”

And now, for the all-important…

“McLaughlin et al. (1999) concluded that:
‘[t]he oil systems of this area are unique in California in having reservoir rocks within the youngest part of the Franciscan Complex and in being the only California oilfield that is unequivocally associated with an active subduction zone setting.’
“Such a setting is unlikely to persist in geologic time due to the extensive structural dismemberment that accompanies the growth of the prism by the continuous stacking of thrust plates. Ongoing faulting and duplexing of oil-generative rocks engenders leakage to the surface and consequent destruction of hydrocarbons (Fig. 4). Reservoirs, whether created within duplexed younger sandstones or within zones with enhanced fracture porosity, are likely to be destroyed by ongoing deformation. Thus the richest oil fields in the world at Petrolia were never to be.”

Or, as Dr. Aalto put it at the end of his presentation, “There is no hope. There is never enough of a reservoir or a yield to be profitable.”
Thank you, Ken Aalto!


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On last Thursday, Dec. 2, i attended a double book-signing party at the Humboldt County Historical Society. Dennis and Gloria Turner were presenting their new, expanded, corrected, and updated Place Names of Humboldt County, which i will write about presently; and Marvin Shepherd with his wife Patsy were meeting and greeting and signing copies of his exciting new volume, The Sea Captain’s Odyssey: A Biography of Captain H. H. Buhne, 1822-1894.

Marv had visited the MVHS a couple of time in the last few years looking for material about Petrolia during the years of Buhne’s interest here. I was looking forward to his book mainly to see what he did with this Mattole information. However, now that i have the book in hand, i find it a hard-to-put-down read! Captain Buhne, for whom many a locality and landmark in Eureka is named, left his home in Flensburg, Denmark, in 1838, as cabin boy on a whaling ship, and thus began a lifetime of ambition, adventure, and attendant hardship. His main claim to fame in Humboldt has been piloting the first ship of American settlers over the Humboldt Bar in 1850, but there is a lot more to his story than this. Fans of Horatio Alger (as the author points out), Richard Henry Dana, and of course, of any early Humboldt history, will relish the Buhne saga. There is no shortage of dramatic life-or-death struggle here.

Marv’s book is very well-written, painstakingly researched, and set up so that both the casual reader and the historical researcher will enjoy it. I was impressed with his section on the oil frenzy in the Mattole and the investment in the excitement by Humboldt Bay businessmen– it felt like he was doing my work for me!

Marvin Shepherd kindly allowed me to print a few scans of pages of his brand-new book here. If you would like to purchase a copy, the best way for now is to visit the Humboldt County Historical Society at 8th and H Streets in Eureka (call 707-445-4342 to verify hours). Eventually Marv will have copies available online, and i will have a few at the MVHS office. Enjoy!

Scanning done by permission of author Marvin Shepherd. Sorry about the dark edge

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Here is the article by teacher Leslie Gould from earlier in 1907, promised in the Nov. 30 blog entry, below. I believe it was from the Humboldt Standard as well. (Click on it, and click again until it’s really big.)

From the Humboldt Room at Humboldt State University. Much gratitude to the HSU librarians, especially Joan Berman, for maintaining that place so beautifully and making so much available to us!

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