压裂液强制返排及支撑剂回流模型研究

Study on the models for the forced flow-back of fracturing fluid and the backflow of proppant

如何科学合理选择放喷油嘴尺寸,同时准确预测裂缝闭合时间,是压裂液强制返排的核心.根据支撑剂运移和压裂液强制返排机理,同时考虑支撑剂受力、压裂液二维滤失、压裂液压缩性和井筒摩阻,并结合物质平衡原理、岩石力学和流体力学的相关理论,建立了裂缝闭合前后放喷油嘴尺寸选型的支撑剂运移及力学模型和裂缝强制闭合时间计算模型.采用建立的模型,不仅可使放喷油嘴尺寸定量化,同时在不需要冗长的压降数据情况下,就能确定裂缝强制闭合时间.经实例验证,本模型的计算结果稳定可靠,可用于实际分析.

To accurately choose the size of blowout choke and predict fracture-closured time is the key to the flow back of fracturing fluid.Based on the related theories to material balance,rock mechanics and fluid mechanics,the migrating model and mechanic model of proppant for determining the size of blow-off choke and the model for calculating the forced closure time of fracturing cracks are established,in which the force acted on proppant,the two-dimensional water-loss and compressibility of fracturing fluid and the friction of well-bore are considered.Using the established models and the given solution method,not only can the critical size of blowout choke be determined but also the fracture closure time be obtained without a lot of pressure-drop data.The field cases verify that the obtained results using the models are reliable and the models can put into practical application.