14 September 2015

Copsa Mica eruption

July 13, 1933 - The beginning of the largest fire at a gas well in the Romanian history. The developing of Copsa Mica gas exploitation led to decision of Sonametan to drill in 1933 new gas wells (wells 4 and 5). Market studies conducted by Sonametan stood at decision to supply Sibiu with gas for consumption. The exploration drilling of well no. 5 Copsa Mica had the purpose to explore the Copsa Mica gas dome and to determine by mechanical coring and electric logging the sequence of layers, their gas content and possibly water. The drilling of this well started on March 10, 1933 and Rotary drilling system was used. The first column of 508 mm was fixed at 20.7 meters depth. The second column of 360 mm was fixed at 109.8 meters. Cementation was executed in good condition. The drilling continued to the depth of 764.4 m when analyses indicated a pressure increase in Copsa Mica dome. Gas pressure at the depth of 764 meters was about 100 bars. Given the shallow depth at which these pressures are encountered, this kind of gas domes pose a great difficulty for drilling. In order to maintain the layer pressure, during drilling, it was necessary to use a drilling fluid with a specific weight. Mud was brought from  Bazna to prepare the drilling fluid but in the absence of a special mixer that wasn’t done properly . That viscous mud quickly gasify. Given the high pressures encountered as a safety measure and to protect the well in case of eruption the decision was made on the 24th June, at a depth of 741 meters, to ask The Ministry the changing of working program by cementing the column immediately. This would had avoided the formation of a crater next to the wellhead, 17 days later. Degradation of drilling fluid properties led to increase of gas pression in the well. At July 11, the pressure reached 50 bars and the gas came out violent at 750 meters north of the well. The pressure in well dropped to 25 bars. Cementation resisted, or crater would be formed in the well. A huge amount of sand and marls was projected 100 meters into the air. On a circular area with a diameter of about 200 meters, the land was covered with sand and gray marl typical Pontian, white striped calcareous andesitic, tuff, conglomerate and finally vegetal elements from the valley. The next morning, the main crater looks roughly elliptical. Next to the main crater more secondary craters were formed. From the main crater eruption took place with intermittent bursts which made the impression that earth was boiling. On the next day, July 13, 1933, at 15.45, after a spark, ignited gas was burning with a flame height of 100-150 meters. Occasionally violent eruptions took place throwing masiv amounts of marl and sandstone. The water from  the crater, or after rains formed dark clouds of smoke which sometimes enveloped the flame. The aim was to stop the eruption by pumping into the well heavy drilling fluid, but with no results. Pressure in the well decreased and stabilized at 5 bars. The main crater was gradually approaching the well. Similar operations performed in August, September and October 1933, were unsuccessful. The material placed in the well was driven by gas, pulverized and thrown up great distances around the crater. In January 1935, the crater was 205 meters from the borehole no. 5 and on  9 May, 1935, the crater moved 80 meters towards the well. On August 28, 1935, after a rainfall, the crater again moved towards the well no. 5 by 45 m reducing the distance between  these at 75 meters. In 1940 engineer Popovici had the idea of ​​pumping water into the well. The  gas pressure dropped and led to decrease the flame height from 42 meters to 4 meter. In order to extinguish the fire there were  pumped about 2000 wagons of mud through four 16” pipelines. The large amount of mud burst into the crater quenching the flames. 

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