Drilling through gas hydrates formations: possible problems and suggested solution
Amodu, Afolabi Ayoola
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Gas hydrate research in the last two decades has taken various directions ranging from ways to understand the safe and economical production of this enormous resource to drilling problems. as more rigs and production platforms move into deeper waters to its environmental impact on global warming and cooling. Gas hydrates are ice-like structures of a water lattice with cavities, which contain guest gases. Gas hydrates are stable at low temperatures and high pressures. The amount of energy trapped in gas hydrates all over the world is about twice the amount found in all recoverable fossil fuels today. This research identifies the problems facing the oil and gas industry as it drills in deeper waters where gas hydrates are present and suggests solutions to some of the problems. The problems considered in this research have been approached from a drilling point of view. Hence, the parameters investigated and discussed are drilling controlled parameters. They include rate of penetration, circulation rate and drilling fluid density. The rate of penetration in offshore wells contributes largely to the final cost of the drilling process. These 3 parameters have been linked in the course of this research in order to suggest an optimum rate of penetration. The results show the rate of penetration is directly proportional to the amount of gas released when drilling through gas hydrate. As the volume of gas released increases, the problems facing the drilling rigs, drilling crew and environment is seen to increase. The results also show the extent of risk to be expected while drilling through gas hydrate formations. A chart relating the rate of penetration, circulation rate and effective mud weight was used to select the optimum drilling rate within the drilling safety window. Finally, future considerations and recommendations in order to improve the analyses presented in this work are presented. Other drilling parameters proposed for future analysis include drill bit analysis with respect to heat transfer and the impact of dissociation of gas hydrate around the wellbore and seafloor stability.