海洋天然气水合物钻井难点及对策研究

Research on Challenges and Solutions of Marine Natural-gas Hydrates Drilling

天然气水合物是一种具有巨大开采潜力的未来能源,其中储集于海洋的天然气水合物占其总储量的90%以上。天然气水合物储层的钻井技术相对不成熟是目前限制水合物商业开发的主要因素之一。分析了海洋天然气水合物及储层的特点,指出钻井时温度、压力对水合物储层的稳定性具有重要影响。海洋天然气水合物储层钻井时主要面对水合物分解导致的气侵、井壁稳定以及钻井液性能维护等难点。钻进水合物储层前需要预估风险,钻井液技术是目前海洋水合物钻井所采取的主要技术,包括对钻井液温度、密度、添加剂等各方面的控制。未来可能广泛应用控压钻井技术和套管钻井技术钻进海洋水合物储层。

Natural-gas hydrates is a fuel of great potential for future and 90%of them are stored under marine seabed.The relatively undeveloped drilling technology for natural-gas hydrates is one of the key factors that limit its commercial exploitation.This paper analyzed the features of natural-gas hydrates as well as hydrate-bearing layer and pointed out that the pressure and temperature have great influence on the stability of natural gas hydrates sediments.The main challenges facing marine natural gas hydrates drilling are hydrate dissociation while drilling,borehole stability and drilling fluid property control.The risks should be evaluated before drilling through the hydrate-bearing layers.Drilling fluid technology is currently the main solution of drilling through hydrate-bearing layers which include controlling its density,temperature and adding chemical additives and so on.Managed pressure drilling and drilling casing may be applied widely for drilling marine natural-gas hydrates in the future.