Methane emission to the atmosphere from the first gas-producing well in Transylvania

Historically, the Transylvanian basin is one of the most important natural gas-producing areas in Europe. The existence of commercial gas reserves was incidentally discovered in the early 1900's while drilling for potassium salts in the Miocene deposits that fill the basin. Well #2 Sarmasel, that was positioned close to an area with natural gas emissions, has intercepted very shallow strata containing gas. Drilling had to be stopped on 22 April 1909, after 5 months of work, at a depth of 300 m, due to overwhelming technical difficulties related to the high pressure of gas. Thus, this date marks the beginning of the gas extraction in Transylvania. The well has been left open until 23 June 1910, when a first attempt at closure was made. Twenty hours after closure, gas was observed escaping in a neighbouring field, which required the reopening of the well. A second closure attempt occurred on 31 July 1911, subsequent to the external encasement of the well for the initial 120 meters of depth. No gas leak was detected, and the closure seemed to be effective at this stage. On 29 October 1911, a powerful gas eruption occurred in the fields east of the well, accompanied by considerable gas emissions in the surrounding area, local seismic activity, saline water leakage, and the appearance of several craters located between 100 and 400 meters from the well. The well was reopened once again, until the end of 1913, when it was connected to the pipeline conveying gas to consumers. More than 1.3×10⁹ m³ of gas has been released to the atmosphere during a span of four years. An additional 556×10⁶ m³ of gas was supplied to consumers from 1913 to 1935, when the well was capped. The total volume is around 2 billion cubic meters of gas from a single, 300-meter-deep well! The main crater generated by the 1911 outburst, despite being filled with soil post-explosion, persists in emitting gas that sustains a perpetual fire. 

Our research demonstrated that Sarmasel is a case of ongoing, prolonged gas leakage caused by manmade activities (drilling and gas extraction) conducted over a century ago, functioning in conjunction with, and likely intensified by, a natural seepage process. Sarmasel can thus be regarded as a hybrid leakage-seepage system. This study exemplifies the risk of generating fugitive emissions when drilling occurs within a natural seepage system.
Acknowledgments: This work was supported by the Project DTIE21-EN3485 funded by UNEP and by the Project 14/11.11.2023—ENGAGE, PNRR-III-C9-2022—I8, supported by the EU through the Romanian Govt.