Application of Geo-Engineering Integrated Technologies for Ultradeep Longmaxi Shale Gas Life Cycle Management, Sichuan Basin

A huge variation in well performance was observed in Longmaxi shale gas wells, in Yongchuan block, Sichuan Basin. The Longmaxi shale was buried deeper than 3500 m with complex structures, in-situ stress, and natural fracture corridors, which makes well performance very uncertain. Horizontal well length was greater than 2000 m and proppant intensity was higher than 3.5 t/m. To solve these challenges in an ultradeep shale gas play, a multidisciplinary and life cycle management strategy was proposed and practiced. Initially, geology and geophysics (G&G) work using seismic data revealed the exact geological structures with folds, faults, and natural fractures. Then the study turned to 3D high-resolution geological and geomechanics modeling to identify the sweet spots and high drilling and completion risks areas. With the deep G&G understanding, the well drilling and completion design were proposed, executed, and iterated by onsite diagnosis and support to place high-quality hydraulic fractures. Finally, the production strategy was optimized to keep the flow path undamaged during its life cycle. The detailed study and post-fracture well performance indicate that the successful ultradeep shale gas development in the Longmaxi in the Sichuan Basin relies on: Placing the wells where there are fewer faults but more natural fractures Identifying the stages with high screenout and casing failure risks, thereby levering the 3D G&G model Creating the completion design by considering the screenout and casing failure risks Executing the completion design successfully by onsite diagnosis and support, leveraging on the 3D G&G model, microseismic data, and treating pressure trend Enhancing the 3D model accuracy by iterations with observation data Minimizing the propped fracture damage by adjusting the choke size during the production phase With the high-resolution quality management on well drilling, completion, and production management, the well outperformed 100% more than the neighboring wells. The geoengineering integration values were highlighted in both the in-house study and field operations, and this strategy could be duplicated to other candidates approaching their drilling, completion, and production engineering's limits under complex geological conditions.