Abstract Proppant selection in hydraulic fracturing operations is a crucial decision that influences the productivity and performance of stimulated wells. In hybrid completion designs, proppants of various sizes and materials are often mixed and incorporated into the pumping schedule. Optimization of mixing proppants of various sizes and materials has the potential to maximize proppant pack conductivity and to enhance the reservoir production performance. In this work, an experiment/simulation-integrated workflow, which combines the discrete element method (DEM) and lattice Boltzmann (LB) modeling with laboratory penetrometer experiments, was adopted to investigate the effects of proppant mixtures of different sizes and materials on the fracture conductivity. The DEM was used to simulate proppant compaction and rearrangement. Proppant embedment was determined by a load-embedment correlation obtained from the penetrometer experiments. The pore structure of the proppant pack was extracted from the DEM model and then imported into the LB simulator as internal boundary conditions of flow modeling to determine the time-dependent conductivity of the proppant-supported fracture. The integrated workflow demonstrates that the conductivity of a mixed-sized proppant pack is not simply the arithmetic average of the conductivities of the pure proppant packs. The selection of proppants with close sizes has a minor impact on the fracture conductivity when proppants develop to multilayers; whereas mixing with a much finer proppant size will downgrade the fracture conductivity significantly. It is demonstrated that proppant size combination has a lesser effect on the fracture conductivity compared to proppant material combinations. This study also suggests that the application of combinations of sand and premium proppants and modification of proppant injection schedule in the fracturing treatment design can mitigate fracture closure and improve fracture conductivity. This study investigated fundamental mechanisms of proppant mixture at the pore scale, which have significant implications to the optimization of hydraulic fracturing and proppant placement designs.

中文翻译：

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使用实验/模拟集成方法研究支撑剂混合物的电导率

摘要 水力压裂作业中支撑剂的选择是影响增产井产能和性能的关键决策。在混合完井设计中，各种尺寸和材料的支撑剂通常混合并纳入泵送计划。各种尺寸和材料的混合支撑剂的优化有可能使支撑剂充填层的传导性最大化并提高油藏生产性能。在这项工作中，采用将离散元法 (DEM) 和格子玻尔兹曼 (LB) 建模与实验室针入度实验相结合的实验/模拟集成工作流程来研究不同尺寸和材料的支撑剂混合物对裂缝的影响电导率。DEM 用于模拟支撑剂压实和重排。支撑剂嵌入是通过从渗透仪实验中获得的载荷-嵌入相关性来确定的。从 DEM 模型中提取支撑剂充填层的孔隙结构，然后将其导入 LB 模拟器作为流动建模的内部边界条件，以确定支撑剂支持的裂缝随时间变化的导流能力。集成的工作流程表明，混合尺寸的支撑剂充填层的电导率不仅仅是纯支撑剂充填层电导率的算术平均值。当支撑剂发展为多层时，选择尺寸相近的支撑剂对裂缝导流能力影响较小；而与更细粒度的支撑剂混合将显着降低裂缝导流能力。结果表明，与支撑剂材料组合相比，支撑剂尺寸组合对裂缝导流能力的影响较小。该研究还表明，在压裂处理设计中，砂和优质支撑剂的组合应用以及支撑剂注入计划的修改可以减轻裂缝闭合并提高裂缝导流能力。本研究在孔隙尺度上研究了支撑剂混合物的基本机制，这对水力压裂和支撑剂放置设计的优化具有重要意义。该研究还表明，在压裂处理设计中，砂和优质支撑剂的组合应用以及支撑剂注入计划的修改可以减轻裂缝闭合并提高裂缝导流能力。本研究在孔隙尺度上研究了支撑剂混合物的基本机制，这对水力压裂和支撑剂放置设计的优化具有重要意义。该研究还表明，在压裂处理设计中，砂和优质支撑剂的组合应用以及支撑剂注入计划的修改可以减轻裂缝闭合并提高裂缝导流能力。本研究在孔隙尺度上研究了支撑剂混合物的基本机制，这对水力压裂和支撑剂放置设计的优化具有重要意义。