Methane Hydrate Drilling Technology

Most of the world's resources of hydrocarbons energy remain in the form of methane hydrates or clathrates. These exist naturally as frozen crystalline lattice consisting of molecules of water that have formed an open, cage-like lattice that encloses molecules of methane. For example, if one percent of the methane hydrates deposits in the Gulf of Mexico were to be commercially drillable and produce able, the United States would not be dependent upon foreign imports of oil and gas for the foreseeable future. However, and it must be mentioned early on, methane hydrates present a litany of drilling-related challenges to the conventional methods. To a great degree, this explains why there have been only a few attempts to drill for commercial quantities. Much has been discussed and learned about where methane hydrates of "commercial quantities" are located, reservoir thickness and depth, etc. Commercial quantities have been quantified onshore typically in artic permafrost regions and offshore on the slopes of continental shelves where pressure and temperatures are suitable and methane and water co-exist. Scientific expeditions such as those conducted by the Integrated Offshore Drilling Program (Texas A&M) have extensively mapped and quantified huge deposits, globally. However, little has been written about technologies that exist that appear to have unique potential to enable the safe and effective drilling and production of commercial quantities. In addition to hydrates being only quasi-stable, the crystalline structure packs methane so efficiently, depending upon the purity of the hydrate, it can contain between 70 and 164 times the volume of free gas at standard temperature and pressure vs. the volume of the hydrate prior to dissociation. Because hydrates will dissociate or release free gas upon a decrease of pressure, increase of temperature, or combinations thereof, premature dissociation around the wellbore and within annulus returns to the surface must be avoided during the drilling process. A primary purpose of this paper is to suggest that Managed Pressure Drilling (MPD) technology may be uniquely applicable to the successful drilling for commercial quantities. "MPD is an adaptive drilling process used to more precisely control the annular pressure profile throughout the wellbore. The objectives are to ascertain the downhole pressure environment limits and to manage the annular hydraulic pressure profile accordingly." Add to this IADC definition of Managed Pressure Drilling an ability to avoid a premature increase in temperature within the wellbore annulus - summarizes the context of this presentation. Given the "size of the prize" and with encouragement by the U.S. Department of Energy, the President of the United States, Japan and others that have announced commitments to developing the technology base to allow commercial production of methane from hydrates deposits by the year 2015, a purpose of this endeavor is to assist in launching serious discussion about methane hydrate drilling technology. MPD has been practiced onshore for at least the past two decades with good success.