By Julia Wellner, Assistant Professor, Department of Earth and Atmospheric Sciences
Natural oil seeps have been known for millennia in places like Southern California’s doubly-named La Brea Tar Pits in downtown Los Angeles. There, Native Americans used the oily material seeping out of the ground for many purposes, including sealing wooden boats.
Move forward in time and to the other side of the country to where scientists realized in the middle of the 1800s that similar seeps in Pennsylvania and New York yielded material that could be turned into clean-burning kerosene. The timing was right as whale oil was becoming more difficult to obtain due to the extreme pressure on the populations that overhunting had created. Natural gas was also found near the surface and used for lighting but only in limited areas close to the source of the gas.
It wasn’t long after the discovery that these seeps leaked such useful materials, that more of it was needed. The history of oil drilling in the U.S. usually starts with the Drake Well in Titusville, Pa., drilled in 1859 seeking oil, which was found after drilling to depths that today would be considered essentially at the surface (tens of feet). There wasn’t much research done to pick the drilling sites near Titusville, and maybe that is why the first several wells were dry. They just drilled near the areas with seeps and hoped for the best.
We’ve gotten steadily better at finding and extracting fossil fuels in the ensuing 150 years, each advance depending both on what had been learned from previous drilling and on the technological and analytical advances developed in research laboratories.
After Titusville, the next big discovery was in 1901 at Spindletop, near Beaumont, Texas. There, drilling into a salt-formed trap led to the famous gusher that started the Texas and Gulf Coast oil rush. The high rate of production of oil from Spindletop only lasted a few years, though, and then started to decline as the reservoir was depleted. Around the same time, major oil fields were developed in and around Los Angeles, including at La Brea, again, following known seeps.
As production rates at each of these early fields started to decline, just as whale oil had before, exploration and drilling for new sources moved to areas without the obvious clues of seeps. This meant drilling into more deeply-buried reservoirs, or sites ever farther offshore in deeper and deeper water, or in regions distant from where anyone was living, or in sites that were all of the above.
Once seeps were no longer used as a guide for new drilling prospects, the science of geologists and geophysicists became more and more important. Geophysicists created tools for looking into the subsurface prior to drilling and for logging the details of the holes once drilled. Geologists interpreted these new datasets and developed prospects for new drilling sites.
King Hubbert was a geophysicist at the Shell research lab in Houston in the middle part of the last century. Working with a team of bright young geologists and other assistants, he developed the idea of the bell-shaped production curve for any given oil field: production would ramp up quickly after discovery, have a period of high production, and then rates would decline quickly. Applying this to all the petroleum resources on Earth at once became known as “peak oil.” A related idea, also from Shell, is the “creaming curve.” The creaming curve suggests that in the beginning of a field, or of exploration around the planet, the easiest and/or largest targets – the seeps and the mega-fields – will be produced first and then the harder to find or harder to produce reservoirs will be targeted, just like skimming the cream off the top of the milk.
Through advanced technologic developments, production is now possible in reservoirs thought useless a decade ago. We can see ever deeper into the Earth with details that tell us what is there.
There is ample literature about peak oil, whether it really exists, whether we have passed it or not or ever will, or if it is based on a set of arbitrary curves.