关键词: 水力压裂, 裂缝, 强制闭合, 压降分析, 物质平衡原理, 模拟模型

Abstract: A new analytical model for pressure decline under the condition of forced fracture closure was developed on the basis of material balance theory and the former corresponding fracture models,such as PKN and KGD models.The effects of back flow of fracturing fluids just at the moment of shut-in and the continue propagation of fractures were considered in the new model. Furthermore,the problem about the leak off of the new propagated fractures was also considered.The condition of natural fracture closure was adaptable in the model.The calculation results indicate that the value of leak off coefficient obtained from the former models is higher than the real value when the forced fracture closure technique is conducted just at the moment of shut-in,while the new model can provide a true value of leak off coefficient and other parameters.The field cases verified that the calculation results with the new model is reliable and may be put into practical application.

Key words: hydraulic fracturing, fracture, forced fracture closure, pressure decline analysis, material balance theory, simulation model