低用水量、低储层伤害、高返排效率的泡沫压裂是低压、低渗、强水敏煤系储层开发的潜在技术之一，但相关研究与应用主要聚焦于泡沫稳定性与流变性能优化，其压裂增渗特征研究不足。鉴于此，开展了不同泡沫干度(泡沫中气体体积百分比)的N₂泡沫、清水与N₂气体压裂煤系致密粉砂岩的裂缝起裂扩展规律对比研究，并评价了裂缝面形态和导流能力特征。试验结果表明：① 泡沫为气液混合物，其压缩性介于清水和N₂气体之间，且泡沫干度越高，压缩性越强，压裂增压时间越长；② 泡沫呈现高黏、低滤失特性，其岩石破裂压力高于清水和N₂气体，且岩石破裂压力与泡沫干度正相关，泡沫干度越高，岩石破裂压力越高；③ 压裂液排量影响岩石破裂压力，40、20 mL/min排量下，90%干度泡沫的破裂压力分别高于清水15.66、6.08 MPa；④ 泡沫压裂的水力输入能量和声发射能量高于清水，且随着泡沫干度升高，其破裂时的最大和累积声发射能量均越大；⑤纯N₂气体压裂致密粉砂岩的水力输入能量最高，但主要用于气体压缩，其破裂时的声发射能量最低，压后重注压力高，造缝能力弱。泡沫干度提高，无因次裂缝面积和粗糙度均增加，进而泡沫压裂裂缝导流能力高于清水和N₂气体。强水敏储层泡沫流体可替代常规水基高黏压裂液，形成粗糙度和面积更大的高导流裂缝，可为强水敏煤系储层高效压裂增渗开采提供理论指导。

Foam fracturing with low water consumption, low reservoir damage and high flowback efficiency is one of the potential technologies for the development of low-pressure, low-permeability and strong water-sensitive coal measures reservoirs. However, the related research and application mainly focus on foam stability and rheological property design, and the research on fracturing and permeability enhancement characteristics is rare. In view of this, this experiment carried out a comparative study on the law of crack initiation and propagation of N₂ foam with different foam quality (volume percentage of gas in the foam), clean water and N₂ gas fracturing tight siltstone in coal measures, and evaluated the characteristics of fracture surface morphology and conductivity. The test results show that: ① The foam is a gas-liquid mixture, and its compressibility is between water and N₂ gas. The higher the foam quality, the stronger the compressibility and the longer the fracturing pressurization time. ② The foam has the characteristics of high viscosity and low filtration, rock breakdown pressure is higher than that of water and N₂ gas, and the rock breakdown pressure is positively correlated with the foam quality, the higher the foam quality is, the higher the rock breakdown pressure is. ③ The flow rate of fracturing fluid directly affects the rock breakdown pressure, with the flow rates of 40 and 20 mL/min, the breakdown pressures of 90 % foam quality are 15.66 and 6.08 MPa higher than those of clear water, respectively. ④ The hydraulic input energy and acoustic emission energy of foam fracturing are higher than those of clear water, and with the increase of foam quality, the maximum and cumulative acoustic emission energy at the time of rupture are greater. ⑤ The hydraulic input energy of pure N₂ gas fracturing tight siltstone is the highest, but it is mainly used for gas compression. The acoustic emission energy is the lowest when it breaks, and the reinjection pressure is high after fracturing, then the fracturing capacity to induce fracture is relative weak. With the increase of foam quality, the dimensionless fracture area and roughness increase, and the fracture conductivity after foam fracturing is higher than that of clean water and N₂ gas. Foam fluid in strong water-sensitive reservoirs can replace conventional water-based high-viscosity fracturing fluid, and the high conductivity fracture with large roughness and surface area can be formed This study provides theoretical guidance for high-efficiency fracturing and permeability-enhancement of strong water-sensitive coal-bearing reservoirs.