Technology of Lost Circulation Prevention and Control in Deep Coalbed Methane Drilling in Eastern Ordos Basin

The exploration and development of deep coalbed methane have opened up a new field of developing resources in new formations in the Ordos Basin, ensuring the steady growth of the oil and gas equivalent of the Changqing oilfield. However, due to the deep burial of the target layers and the long open hole section of the upper part, the difficulty of drilling and development has increased significantly. It is mainly manifested in technical problems such as the prominent contradiction between borehole wall collapse and lost circulation in the second interval, the low success rate of lost circulation control in the first try in the second interval Ф311.2 mm borehole, and the instability and collapse of the coal-seam borehole walls in the horizontal section. To deal with these problems, the casing program was optimized, thereby separating the borehole wall collapse and lost circulation in different intervals. Two sets of drilling fluids were developed to ensure the stability of the wellbore. An efficient technology was adopted to improve the efficiency of lost circulation control without tripping drill strings out of hole. Meanwhile key technical measures were implemented, forming a set of lost circulation prevention and control technology suitable for deep coalbed methane development in the eastern part of the Ordos Basin. This technology has been applied on more than 10 wells, and the drilling time has been reduced by 36.5%. This technology has been used to successfully drill the longest horizontal section of 2,222 m, contributing to the deep coalbed methane development in China.