Characteristics and genesis of fracturing curves for coalbed methane vertical wells in Zhengzhuang Block Southern Qinshui Basin

The Southern Qinshui Basin is a leading region for large-scale commercial coalbed methane （CBM） development in China. Analyzing the characteristics of fracturing operation curves during reservoir stimulation of CBM wells in this area and unraveling their genetic mechanisms offer theoretical insights for CBM development in other regions. This paper focusing on the Zhengzhuang Block in the Southern Qinshui Basin, summarizing the fracturing curve patterns of over 200 vertical CBM wells, classifying the genetic types of different curves, and analyzing their underlying mechanisms. Key findings include: ① based on curve morphology, post-fracturing curves in coal reservoirs are categorized into eight types. “normal" “proppant bridging-induced” “cementing contamination” “fluid loss” “no distinct breakdown pressure” “C-shaped” “fluctuating” and “complex”. ② Geological factors dominate. Construction curves are significantly influenced by geological conditions such as formation porosity, permeability, degree of natural fracture development, differential in-situ stress, rock mechanical properties, and coal seam heterogeneity. Engineering factors act synergistically. Fracturing fluid formulation, pumping rate, proppant placement, cementing technology, and equipment performance interact with geological conditions to jointly shape curve morphology. ③ Engineering measures. Geological characterization: conduct pre-fracturing assessments to guide operational design. Fluid system optimization: develop novel clean fracturing fluids to meet the requirements of diverse geological formations. Process adjustments: rationalize injection rates, pressures, and proppant concentrations; refine cementing procedures to enhance proppant transport. Real-time monitoring: employ multi-method surveillance to track operations and dynamically adjust parameters based on pressure responses.