Application validation and high-yield mechanism analysis of the desorption superposition effect method in Fukang...

Multi-seam combined production is crucial for enhancing single-well output in coalbed methane extraction. However, challenges persist in identifying the contribution of individual seams, predicting production capacity, and optimizing seam combinations. The combined effect of desorption behavior across multiple seams remains the core constraint to achieving high yields in combined production. A mathematical model centered on desorption efficiency was developed. Combined with curvature analysis of desorption curves, three critical nodes-including the initiation pressure-were identified, dividing the desorption process into four stages. The rapid and sensitive stages constitute the core contributors to production capacity. Using the FS-24 well in Fukang Area 8 as a case study, the desorption sequence was determined as Seams 39, 41, and 42. When the dynamic fluid level ranged from 699 to 795 m, all three coal seams desorbed simultaneously, directly entering the highly efficient and sensitive desorption phase with excellent compatibility. During this phase, the desorbable volume under well control reached 2.0682 million m³, averaging 5600 m³ per day, demonstrating a significant "superimposed effect" of desorption. This study provides theoretical and practical support for addressing key challenges in combined exploitation.