Research On Wellbore Stability In Gas Hydrae Formation

Gas hydrate is a ice-like crystalline compound, formed by water molecules and natural gas molecules under certain temperature and pressure conditions, also called clathrate hydrate or "fire ice". For the gas forming gas hydrate is mainly methane, it is also called methane hydrate. Natural gas hydrate distributes mainly in the marine continental margin sediments and permafrost environments, and most of found gas hydrate existed in the former. The research of gas hydrate has become the hotspot of the development of the geosciences research and the energy industry of the present age. The research is involved with many fields, such as the exploration of a new type of energy, greenhouse effect, global carbon cycle, climatic change, ancient ocean, the ocean geological calamity, oil gas transportation, the blockage in the pipeline, the renewal of ship energy and military defense, and may also have the profound influence on the development of geology, environmental sciences and the energy industry. So many countries in the world research gas hydrate broadly from their respective different attention aspects. Especially for the severity shortage of energy resources and the high oil gas price in the recent years, many countries pay more attention to gas hydrate, with the traits of high energy density, large reserves and wide-ranging distribution, and the exploration and the research of gas hydrate .For our country, the shortage of oil gas resources and the fast economy development make the gap of energy resources bigger and bigger. Experts predict petroleum crude will be imported 2 hundreds million tons in 2010, which costs hundreds million foreign exchange reserves. Moreover, the inconsequence of the energy configuration and the becoming effective of the Kyoto Protocol force us to find a new type of substituted clear energy .From the aspects of the security of our country energy strategy and the economy's persistent development, the extent of the exploration and the research of gas hydrate will be enlarged.In order to explore and exploit gas hydrate in the certain underground depth, drilling wells are absolutely necessary. The temperature and pressure characteristics of gas hydrate make the wells in these sediments different from the wells in the general oil gas sediments, and also make the wells confronted with the more difficult problems. Firstly, while drilling, the stratum stress near the borehole and the bottom of hole is released and depresses. At the same time, the heat energy generated by the friction of the bit cutting rocks and the friction of the drilling tools, the...