Subsea Wells Blowout Occurrence and Methods of Source Control

The article will be useful to the scientists and specialists in the oil and gas industry involved in the construction of offshore wells and the blowout response. The article provides a brief list of the implemented oil and gas projects on the shelf of the Russian Federation. The principle of two barriers, which must be observed throughout the entire life cycle of the well, is considered. The main reasons for the transition of kick into blowout are considered, and the most well-known cases of blowout of the offshore wells in the industry are given. According to the SINTEF Offshore Blowout database, the worldwide statistics of loss of well control from 2000 to 2015 are given. The reasons for the development of offshore fields with large-diameter wells are described, and the risk of increased complexity in controlling such wells in the event of blowout is noted. The peculiarities of subsea wells blowout are described. As is known, the blowout of a gas well is associated with the creation of a gas-water plume, which makes it difficult or completely deprives vertical access to the wellhead in shallow water during emergency rescue operations. The paper shows a model of gas-water plume in shallow water conditions, and describes the processes occurring when the gas plume floats up and its impact on ships (drilling rigs, supply vessels and etc.). An example is given related to the modeling a rising gas-water plume using computational fluid dynamics (CFD) at various sea depths and flow rates of a blowing well. The methods of well source control are considered, the current schemes for installing an capping stack at the wellhead of a subsea blowing well are described. The advantages and limitations of each well source control method are presented.