天然气水合物钻探现状与钻井技术

钻井是天然气水合物勘探发现最直接的手段,也是天然气水合物开发的必要环节。天然气水合物,尤其是海域深水天然气水合物的勘探与开发对钻井技术提出了更高的要求。在总结全球天然气水合物钻探现状和钻井技术的基础上,对天然气水合物钻井面临的挑战和未来发展方向进行了分析。总结认为,全球已在多个冻土区和海域开展了天然气水合物勘探与试采,显示了较好的天然气水合物勘探开发前景；天然气水合物钻探通常与随钻测井(LWD)相结合,并以常规钻探设备、水基钻井液为主；天然气水合物试采井的完井方式各不相同,尚未形成有效的完井技术系列；天然气水合物的温度-压力特征、储层特征、埋深特征和力学特征等决定了天然气水合物钻井面临井筒稳定性、钻井液安全密度窗口窄等方面的挑战。未来,应进一步探索研究控压钻井、欠平衡钻井、套管钻井、隔热竖管钻井、深水浅软地层水平井钻完井、潜式钻探设备组合和经济环保高效型低温钻完井液等技术在天然气水合物钻井中的应用。

Current Status and Technology of Natural Gas Hydrate Drilling

Drilling is the most direct means of natural gas hydrate exploration and the necessary procedure of natural gas hydrate development. Natural gas hydrate, especially the exploration and development of marine natural gas hydrate, raises a higher demand to drilling technology. On the basis of summarizing the present drilling status and drilling technology of natural gas hydrate in the world, the challenges and future development directions of natural gas hydrate drilling are analyzed. It is summarized as below. The exploration and trial production of natural gas hydrate have been carried out in many permafrost areas and oceanic areas around the world, showing a better prospect of natural gas hydrate exploration and development. Natural gas hydrate drilling usually combines with logging-while drilling data (LWD) and employs conventional drilling equipment and water-based drilling fluids. The completion methods employed in natural gas hydrate test wells are different, with having not formed effective completion technology series yet. The characteristics of natural gas hydrate, such as temperature-pressure characteristics, reservoir characteristics, burial depth characteristics, mechanical characteristics and so on, commonly determines the challenges of natural gas hydrate drilling in terms of wellbore instability and narrow safety window of drilling fluid density. In the future, the application of managed pressure drilling, underbalanced drilling, drilling with casing, insulated riser drilling, drilling and completion of horizontal wells in shallow and unconsolidated formations, combination of submersible drilling equipment and economically, environmentally friendly and efficient low-temperature drilling and completion fluid in natural gas hydrate drilling should be further explored.