Potential Effects of Oil and Gas Development of the Monterey Shale on California's Lands and Waters

The petroleum industry has been extracting oil and gas from conventional formations for over 100 years in California, but thus far has been unable to tap economic quantities of oil that may be locked in the source rock (also known as shale) layers of the Monterey Formation that lies beneath extensive regions of California. Advances in horizontal drilling and multi-stage hydraulic fracturing technology have significantly increased the production of oil and natural gas from shale formations in other US locations. Attempts to apply that technology to produce commercial quantities of oil and gas from the wide spread but heavily fractured and seismically altered Monterey shale formation in California have not been successful to date. Moreover, it is not clear whether significant quantities of oil are still trapped in the source rock of the Monterey formation. However, if commercial quantities of petroleum resources are present and if it becomes technically and economically feasible to extract it in the future, this could result in major impacts to agricultural and natural areas of California that provide important habitat for wildlife and environmental services for people.
To understand how oil development of the Monterey source rock could impact nature in California, The Nature Conservancy set out to map the areas where the geologic conditions may be most favorable for oil production from the Monterey Shale. Next, we evaluated the ecosystem impacts of intensively developing these Monterey source rock oil plays. This map combines datasets related to protected and public lands, habitat and land cover, groundwater-dependent ecosystems, freshwater biodiversity with a dataset showing the estimate extent of the Monterey formation and its equivalents, the estimated extent of potential source rock, and the potential source rock with a 5km buffer where potential development would occur, and the location of oil and gas wells that are currently using a version of hydraulic fracturing techniques. While the map is intended to give users a better understanding of potentially significant adverse effects on species, habitats, freshwater, and groundwater-dependent ecosystems, it is unlikely that large-scale oil and gas production from source rock in the Monterey formation will occur without some as-yet unforeseen technological advance.