长庆油田延长组页岩油采用低黏滑溜水压裂面临裂缝延伸距离短、缝网复杂度低、簇间易窜流的问题，导致改造后初期产量高但递减快。针对高滤失导致改造不充分的工程难题，建立水平井多簇压裂数值模拟模型，明确影响改造体积的主要工程参数，分析黏度和排量对裂缝延伸距离及整体改造体积的影响，揭示多簇裂缝起裂、扩展、竞争、滤失力学机理，最后提出变压裂液黏度交替注液造缝扩缝方法。数值模拟分析表明，随着压裂液黏度的增加，裂缝长度增加但裂缝两翼长度的不对称性也增加。适当增加排量可促进裂缝的偏转角度增加和次生微裂缝数量增加，但过高的排量可能导致裂缝扩展不均匀。压裂液黏度高于70 mPa·s时压裂液滤失明显降低，形成了缝宽大、形态简单的主裂缝，在压裂初期提高裂缝缝长；黏度低于30 mPa·s时裂缝多分支扩展，在近井簇间窜流。采用变黏度交替注液策略能有效提高裂缝网络的复杂性和整体改造效果，即先用高黏压裂液压裂形成主要渗流通道，再用低黏压裂液在远井形成复杂缝网，显著提高改造体积。研究成果为优化页岩储层水平井压裂设计提供了理论依据和技术指导，对于页岩油的高效开发具有重要的实际意义。

The Yanchang Formation shale oil in Changqing Oilfield faces challenges such as short fracture propagation distance, low fracture network complexity, and easy inter-cluster flow, resulting in high initial production but rapid decline after fracturing. To address the engineering problem of insufficient fracturing due to high fluid loss, a numerical simulation model of multi-cluster hydraulic fracturing in horizontal wells was established. The main engineering parameters affecting the volume of fracturing were identified, and the effects of viscosity and flow rate on fracture propagation distance and overall fracturing volume were analyzed. The mechanical mechanisms of fracture initiation, propagation, competition, and fluid loss in multi-cluster fractures were revealed, and a method of alternating injection of variable viscosity fracturing fluids for fracture creation and propagation was proposed. Numerical simulation analysis show that increasing the viscosity of fracturing fluid increases the length of fractures but also increases the asymmetry of fracture lengths on both sides. Increasing the flow rate appropriately promotes an increase in the turning angle of fractures and the number of secondary microfractures, but excessively high flow rates could lead to uneven fracture propagation. When the viscosity of the fracturing fluid exceeds 70 mPa·s, fluid loss is significantly reduced, forming main fractures with large widths and simple shapes, thus increasing fracture length in the early stage of fracturing. When the viscosity is less than 30 mPa·s, fractures expand into multiple branches with inter-cluster flow near the well. Adopting an alternating injection strategy of variable viscosity fracturing fluids effectively increases the complexity of the fracture network and the overall fracturing effect. Specifically, high-viscosity fracturing fluids are first used to create the main flow channels, followed by low-viscosity fracturing fluids to create a complex fracture network, significantly increasing the fracturing volume. The research results provide theoretical basis and technical guidance for optimizing the fracturing design of horizontal wells in shale reservoirs, and are of great practical significance for the efficient development of shale oil.