Methane Emissions from Abandoned Oil and Gas Wells in California.

California hosts ∼124,000 abandoned and plugged (AP) oil and gas wells, ∼38,000 idle wells, and ∼63,000 active wells, whose methane (CH) emissions remain largely unquantified at levels below ∼2 kg CH h. We sampled 121 wells using two methods: a rapid mobile plume integration method (detection ∼0.5 g CH h) and a more sensitive static flux chamber (detection ∼1 × 10 g CH h).