Does oil drilling cause sinkholes or earthquakes?

Dear EarthTalk: What, if any, fills the empty space underground created by the extraction of billions of gallons of oil? Could oil drilling be one of the causes of the increase in land colonization and sinkholes in oil-rich areas? Can it cause earthquakes? –– Linda Anderson, Sedona, Arizona
The crude oil (and natural gas) we drill for the world is, for the most part, stored in tiny pores in rock up to only about three miles deep in the Earth’s extremely dense crust. At such depths, the oil is there under a fairly high pressure. When removed, other liquids – usually water – move to take its place, equalizing the pressure in the process. Sometimes oil extractors pump water from one side of an oil field to push oil to wells on the other side, and the water replaces the oil accordingly.

In cases where other liquids do not enter, such as in the North Sea off the Netherlands, the porous rock layer which originally housed the oil may collapse after extraction, causing slight deposits of earth (called “land subsidence”) in the bedrock surface above, but usually no more than a few tenths of an inch per year.

Here in the United States, land subsidence induced by the high volume extraction of underground resources, including oil and gas, “is more common than most people realize,” according to the US Geological Survey (USGS), a government agency that collects, monitors, analyzes, and provides scientific understanding of natural resource conditions, problems, and issues. Flat coastal plains and wetlands near sea level are most exposed to this potential side effect.

Excessive pumping of groundwater, not oil or gas extraction, is the biggest source of land subsidence, according to the USGS, but the agency cites several cases throughout the 20th century that it says them, demonstrate how “the accelerated withdrawal of oil, gas and associated water from shallow unconsolidated reservoirs could lower land elevation, cause minor earthquakes and activate faults. [around oil fields]. “

Subsidence around large, mature oil and gas fields that coincide with faults could add enough stress to trigger small local earthquakes up to two kilometers from the offending wells. Most geologists agree, however, that oil and gas extraction is unlikely to contribute or cause major earthquakes, which are generated at much deeper depths than would be practical for drilling. oil or gas. The USGS suggests, however, that the continued withdrawal of oil and gas and the associated drop in groundwater pressure could even contribute to coastal sea level rise by lowering coastal land rise.

When it comes to sinkholes, modern oil wells tend to be much deeper than the depth where sinkholes can typically affect people. Nonetheless, in 1980, residents of the town of Wink, West Texas, woke up one morning to find a sinkhole 370 feet wide and 110 feet deep a few miles north of downtown. Geologists suspect that the sinkhole formed as a result of historic (and by today’s outdated standards) oil production practices in the area, in which extractors pumped salt water below the surface and left a void in which the layer of earth above finally collapsed. A second, even larger chasm opened nearby in 2002.

CONTACT: US Geological Survey, www.usgs.gov.

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