提高煤层气井钻井效率的工艺技术

目前煤层气井钻井,特别是探井、参数井,钻井效率不高已成为影响煤层气勘探开发进程的主要因素之一。在分析影响煤层气钻井效率的原因的基础上,针对不同影响因素,着重从简化井身结构、开发保护储层的钻井液体系、优选钻井工艺、完善钻井设备配套等方面进行了探讨。提出了如下技术思路:①开发适用于152.4mm井眼的煤层气井专用绳索取心工具,从而将井身结构缩小一级;②研制能保护上部井壁、有效保护储层、满足获取煤层参数要求的钻井液体系,从而省去技术套管,将三级井身结构简化为二级井身结构;③推广不同循环介质下旋冲钻井工艺技术;④研究适应煤层气井的钻井液泵和固控设备配套方案。为提高煤层气井钻井效率,建议开展以下研究:①优化井身结构;②保护储层的钻井液体系;③优选钻井工艺;④完善钻井设备。

Techniques of improving the drilling efficiency of coalbed methane gas wells

The exploration and production of CBM requires a high efficiency and a low cost in CBM drilling. At present, a low drilling efficiency for the CBM wells, especially the exploratory wells and strat test wells, has become one of the bottlenecks impeding the process of exploration and development. Based on analysis of the reasons leading to a low efficiency in CBM drilling, a discussion was made focusing on technical improvement from many aspects including simplifying the well structure, developing a drilling fluid system to protect the reservoirs, optimizing drilling techniques, and improving drilling equipments, etc. Hereby, the technical measures were put forward as follows:①Special wireline coring tools were developed for the CBM wells with the diameter of 152.44 mm, so as to reduce the borehole by one level from the previous diameter of 215.9 mm. ②A drilling fluid system was studied and developed to protect the upper well wall and reservoirs and meet the requirement of obtaining the coal bed parameter; Thus, the intermediate casing could be omitted and the previous three level casing work could be simplified as a two level one; ③The percussion drilling technique was popularized with different cycling medium. ④A single pump set and solid control devices were worked out to be in line with the CBM drilling equipments. Besides, the following proposals were also presented for further studies on how to enhance the drilling efficiency of CBM wells:the well structure to be optimized, favorable drilling fluids to be developed for the protection of reservoirs, the drilling technology to be optimally selected, and drilling equipments to be completed.