Shin Chang-Hoon
Research Institute, Korea Gas Corporation (KOGAS), Ansan, 15328, Gyeonggi-do, South Korea.
Sci Rep. 2022 Mar 29;12(1):5321. doi: 10.1038/s41598-022-08135-x.
Non-Darcy flows are a vital event leading to the inaccuracy in flow performance evaluation, particularly in the fractured wells in shale gas and tight oil deposits. The internal flow commonly indicates high flow rates at the early period of production, owing to the large geometric size of hydraulic fracture and high porosity in proppant packs. After that, the production flow rate decays steeply until the Darcy flow regime is attained. Therefore, accurate porous flow analyses from the Darcy to Forchheimer and then turbulent flow regimes are essential for optimal facility designs and economic productions in the unconventional deposits. The Comiti capillary model is recognised as the leading non-Darcy flow correlation for simple packed beds comprising mono-size grains. However, in actual hydraulic fractures, various types of proppants are used simultaneously and generally combined with numerous soil grains of different sizes and shapes. In this study, the Comiti model is modified by incorporating the effective diameters of the porous media and then examined for mixed complex multi-size packs. Subsequently, a novel type of non-Darcy flow equation is presented according to the logarithmic turbulent friction factor based on the physical variables determined only in the Darcy flow regime. The new equation presents accurate results for all the types of proppant packs under wide porosity and permeability ranges. The generalised non-Darcy flow correlation, which can be extensively employed from the Darcy to non-Darcy flow analyses, particularly beyond the Forchheimer regime, is presented for the accurate flow evaluation of the fractured reservoirs.
非达西流是导致流动性能评估不准确的一个重要因素，尤其是在页岩气和致密油藏的压裂井中。由于水力压裂的几何尺寸大以及支撑剂充填层孔隙率高，内部流动在生产初期通常表现为高流速。在此之后，生产流速急剧下降，直到达到达西流态。因此，从达西流到福希海默流再到湍流态进行精确的多孔介质流动分析，对于非常规油藏的优化设施设计和经济生产至关重要。科米蒂毛细管模型被认为是适用于由单一尺寸颗粒组成的简单填充床的主要非达西流关联式。然而，在实际水力压裂中，会同时使用各种类型的支撑剂，并且通常会与许多不同尺寸和形状的土壤颗粒混合。在本研究中，通过纳入多孔介质的有效直径对科米蒂模型进行了修正，然后针对混合复杂多尺寸充填层进行了检验。随后，根据仅在达西流态确定的物理变量，基于对数湍流摩擦因数提出了一种新型的非达西流方程。新方程在宽孔隙率和渗透率范围内对所有类型的支撑剂充填层都给出了准确的结果。为了对压裂油藏进行精确的流动评估，提出了广义非达西流关联式，它可广泛应用于从达西流到非达西流的分析，特别是在福希海默流态之外。
