Drilling Through Hydrates
Often the presence of in situ gas hydrates, presents serious drilling hazards to offshore petroleum drilling. Drilling for petroleum without prior indication of the presence of hydrates, either with the use of analog data at offset wells or with the help of bottom-simulating reflectors of seismic data creates challenges for drilling teams (Collett 1971). This is because the failure for accounting for the presence of hydrates, in drilling processes results in dangerous well problems and accidents. A significant issue of drilling for petroleum with hydrates is the lack of stability of the well or flow of minor gases, which cause collapses (Nimblett, Shipp, and Strijbos 1). It is therefore, paramount that offshore drilling operations factor in solving hydrate problems.
Prior to the advent of technologies like the bottom-simulating reflector, oil-drilling processes usually struck gas hydrates with devastating effects. The recognition of hydrates prior to drilling was a major challenge since accuracy and precision of the hydrate location were not a guarantee. The other challenge of drilling with hydrates is by traditional tools like the use of gamma rays only and the use of resistivity logging-while-drilling (LWD) tools. These tools prevent or limit the driller’s knowledge of the petro-physical properties of the marine sediments, therefore, increasing the uncertainty of the presence of hydrates (Iyoho et al. 6). The other issue with drilling with hydrates is that even with the seismic detection of hydrates, drilling and logging performance does not offer accurate characteristics of hydrates. Therefore, given the various issues of each hydrate detection tool there is a call for robust geo-hazard analysis methods, which integrate petro-physical and geophysical modeling, pore pressure evaluation, and seismic interpretation.
Apart from physical characteristics of the marine sediments, drilling through gas hydrates can create serious problems. This is because the direct drilling with normal pressurized gas trap does create blowout or safety problems due to the physical strength of the reservoir (Nimblett, Shipp, and Strijbos 1). Drilling directly through gas hydrates causes technical problems, since it penetrates the hydrate’s stability zone on the side of the culmination gas trap. This increases the chances for a blowout to occur. Apart from blowouts, drilling through hydrates without considering the hydrate sediments thermodynamic stability conditions can create serious problems (Iyoho et al. 7). Drilling through warm hydrate fluids can cause existing hydrates to detach from sediments, causing a buildup of gases and consequently a blowout of the oil well. Moreover, any hydrate that melts during the drilling process can become loose, creating little structural support for the well, as the seafloor ends up unstable (Iyoho et al. 6). Additionally, hazards can occur while drilling through hydrates like the formation of gaseous hydrates like hydrocarbon flowing into the reservoir, leading to serious operational, safety, and control problems of the drilling well (Iyoho et al. 8). Therefore, fluid hydrates cause shifts in the well or seafloor leading to structural damages that have great operational and control problems.
In conclusion, it is evident that hydrates in offshore drilling are a major challenge as they occur naturally in the marine sediments. Traditional use of gamma rays and resistivity logging is not enough to detect hydrates. Mean while, seismic tools indicate sediment frequency but do not indicate the physical materials. The direct or indirect drilling of hydrates is a major hazard as gaseous or liquid hydrates shift, causing structural damage to the well or sea floor. Structural damages resulting from fluid flow causes serious operational, safety and control issues in well management.
Works Cited
Collett, Timothy S. Energy Resource Potential of Natural Gas Hydrates. The American Association of Petroleum Geologists 86.11 (2002): 1971-1992.
Iyoho, Ann W., Meize, Roy A., Millheim, Kaiser K., and Crumrine, Michael J. Lessons from integrated analysis of GOM drilling performance. SPE Drilling and Completion 20.1 (2005): 6-16.
Nimblett, Jillian N., Shipp Craig R., and Strijbos Floris. Gas Hydrates as a Drilling Hazard: Examples from Global Deepwater Settings. Offshore Technology Conference, May 2-5 2005, Houston, Texas.
