Snubbing Field Operations - Potential Trapped Air and Explosive Hydrocarbon Mixtures on Surface
Date
2013-06-20
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Abstract
Snubbing is a widely used drilling, completion and work-over method. It is especially useful in HPHT reservoirs and in unconventional reservoirs such as the Marcellus, Haynesville, Bakken oil and Eagle Ford shale plays. During some operations, though very infrequent, powerful explosions have occurred on surface which have resulted in injuries to personnel and the destruction of surface equipment.
It is shown in this thesis that these explosions, could be internal explosions, that, based on the literature describing Low Temperature Oxidation (LTO) reactions, which occur in conjunction with in-situ combustion processes; in the presence of a trapped pocket of air which is in contact with immobile hydrocarbon liquids and in the case of gas wells, with natural gas.
There are three mechanisms that create this explosion. This first mechanism requires the presence of a trapped pocket of air to persists for a sufficient time for LTO reactions to create oxidized species, heat and volatile vapor products and bring the interface into the flammability zone. Subsequently, the second mechanism involves a rapid temperature rise from the fast compression of the pocket of air and immobile hydrocarbon sufficient enough to auto-ignite the volatile vapors and start a burn, the final mechanism involves this burn exhausting the oxygen supply within the air pocket and looking for oxygen internally from LTO oxidized species created prior ignition. Once the combustion reaction draws oxygen internally from these species, a powerful explosion occurs similar to conventional explosives.
This thesis also identifies the location and potential volume of trapped pockets of air on surface snubbing equipment that could lead to the explosion described above.
Furthermore a theoretical low pressure (8 MPa) snubbing simulation was conducted to illustrate the power of the LTO initiated explosion from a small trapped pocket of air (0.150L). This simulation shows the explosive pressure rise of the explosion and also illustrate the strength and damage potential of an explosive detonation shockwave resulting from the explosion described above.
Finally, this thesis recommends methods to reduce the likelihood of an internal explosion within snubbing surface equipment during operations.
It is hoped that the outcomes and recommendations within this thesis will reduce the likelihood of explosions during snubbing operations and ultimately save lives.
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Education--Administration, Engineering--Chemical, Engineering--Petroleum, Engineering--Operations Research
Citation
Prebeau-Menezes, L. J. (2013). Snubbing Field Operations - Potential Trapped Air and Explosive Hydrocarbon Mixtures on Surface (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27808