Abstract:

The Ordos Basin is rich in deep coalbed methane resources, with block X of the Shenmu gas field being a key exploration and development area for the Jidong Oilfield in the basin. The deep Benxi Formation the 8th coal seam is an important production resource in this block, mainly produced through horizontal well drilling and large-scale fracturing operations. The Benxi Formation the 8th coal seam is characterized by complex local structures, brittle and soft coal layers, fast drilling rates, and a tendency for collapse, making trajectory control of the horizontal section difficult and posing a challenge to achieving a high rate of reservoir drilling encounter. Therefore, improving the high drilling encounter rate of coalbed methane horizontal wells and achieving rapid drilling and completion have become key technical challenges in the exploration and development of this domain. To address these challenges, multidisciplinary technical research, including geology, seismic analysis, logging, mud logging, and drilling, were conducted. This research led to the development of a deep coalbed methane horizontal well geological guidance technology, which included fine seismic structural interpretation as the foundation and near-bit orientation gamma imaging analysis as the core. This technology involved several key aspects: precise coal seam structural characterization, coal seam feature prediction, landing trajectory control, overall coal seam determination, geological guidance for the horizontal section, and control of drilling engineering parameters. Through the effective integration and proper application of these technologies, precise well landing and fine-tuning of the horizontal trajectory in real time were achieved. In geological guidance practices in the exploration and pilot test wells of this block, the horizontal well geological guidance technology demonstrated significant results, increasing the coal seam drilling encounter rate from 70.4% in the initial risk exploration well to the current average of 94%. Additionally, this technology ensured smooth and seamless wellbore trajectory, facilitating the successful implementation of casing and cementing operations and shortening the drilling and completion cycle. The efficient drilling and completion of deep coalbed methane horizontal wells have laid a solid resource foundation for subsequent large-scale fracturing and economic production, providing valuable insights for geological guidance in deep coalbed methane exploration in other blocks of the Ordos Basin.

Key words: Ordos Basin, Shenmu gas field, deep coalbed methane, the 8th coal seam, horizontal well, geological guidance