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.

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