Production methods: a primer
Predictions for California’s oil industry emissions are also complicated by the lack of clarity about which production methods will be used, and at what depth. Some of these variables could make the Monterey Shale output cleaner than current California crudes, while others would make it dirtier. Here is a summary:
- Depth. While oil is found less than 2,000 feet deep in fields like Midway-Sunset, companies must drill to between 6,000 feet and 15,000 feet to tap shale oil in the Monterey. The additional depth requires extra energy for drilling, well completion, pumping and all other activities, all adding up to an approximately 1.3 percent increase in total carbon intensity per 1,000 feet. However, deeper oil tends to be somewhat lighter and less viscous than shallower oil, as explained by Richard Behl, the geologist at CSU Long Beach. “What controls the gravity of oil is what type of organisms were buried there before oil formed …. whether the oil was collecting in reservoir rocks that over geological times was exposed to bacteria and degraded its composition,” Behl said. “A lot of shallower deposits are very heavy, but much of the Monterey Shale deposits are more deeply buried, so it probably will be lighter. It’s too speculative to say by how much, however.”
- Fracking. Fracking has long been used in California oil production, with the first occurrence in the Whittier oilfield in 1953. However, oil industry officials say that because of the complex nature of the Monterey Shale, fracking may be ineffective in many areas and other techniques such as acidizing may be more effective. However, no information is available about energy intensity of the fracking process. Stanford’s Adam Brandt says he is only now starting the months-long process of crunching that data for the ARB. Because fracking is currently unregulated and no reporting of the practice is required, state regulators do not know what proportion of the state’s oil is produced through fracking.
- Steam injection. This method – the injection of hot water vapor downhole – is a common way of melting extra-heavy crude that is too tar-like to be easily extracted through conventional drilling. Steam injection is by far the most energy-intensive and water intensive method used in California oil extraction. In 2007, 23 of the state’s 153 oilfields used steam injection, according to ARB data. A similar method is hot water flooding, which injects hot water instead of steam. Steam generation represents 41 percent of the California oil and gas industry’s GHG emissions, while combined heat and power (which includes hot water heating and other drilling-related electricity use) causes another 22 percent, according to the ARB.
“When you see high values for carbon intensity at California oilfields, it’s almost always due in large part to steam injection or waterflooding,” said Brandt. He said the methods for extracting the Monterey Shale’s crude will be similar to anyone following the national debate over the Keystone XL pipeline. “You have extra-heavy crude, and the only way to get it out is via a process very similar to the ‘in situ’ production of the tar sands,” he said, referring to the Canadian practice of pumping steam down into the oil-bearing strata and waiting for the heat to melt the tar-like, compacted sands into a liquid that can be pumped up to the surface.
For the most part, Brandt noted, steam injection and hot waterflooding currently are used in relatively shallow depths in California, to a maximum of approximately 5,000 feet. While it is likely these methods will be adapted to the Monterey Shale, there is no guarantee they will be used at a greater rate than currently.
- Acidizing. As discussed in Next Generation’s two-part report about acidizing, oil companies operating in California say that many areas of the Monterey Shale do not respond well to fracking and instead give better results through the process of acidizing, which includes matrix acidizing and acid fracking. In these methods, large volumes of hydrofluoric acid are injected into the substrata to dissolve the rock and open up fractures so that the oil can flow. As with fracking, this practice is largely unregulated, so no information is available about what proportion of the state’s oil is extracted via acidizing, and no research has been carried out about the carbon intensity of acidizing.
- Clean tech. State regulators have created a system of incentives to support the use of “clean distributed generation technologies” to replace the natural gas that fires the steam flooding process and other oil well activities. These include a complex variety of low-carbon technologies – microturbines, fuel cells, and a thermal oxidizer integrated with a microturbine. One especially promising method is solar thermal enhanced oil recovery, with two test projects currently underway – Berry Petroleum with GlassPoint Solar in McKittrick, Kern County, and Chevron’s partnership with BrightSource Energy near Coalinga. In both cases, an array of solar concentrating mirrors tracks the sun, captures rays, then shines the concentrated light to heat the water into steam, which is then pumped down into the oil reservoir. This method is estimated to cut CO2 emissions of oil extraction by up to 80 percent. All these projects are experimental, with no guarantee that they will prove successful or be used widely in the Monterey – or in other shale formations around the country or world.