两类产量递减模型在预测页岩气井和致密气井中的应用与对比

Application and comparison of two production decline models in shale gas wells and tight gas wells

产量递减模型是评价油气井与油气藏产量和可采储量的重要工具。它的有效应用不受储集类型、驱动类型、流体类型、压裂类型和开采方式的限制。只要油气井和油气藏的产量进入递减阶段,并拥有一定的生产数据,即可进行有效预测。多年的实际应用证实,Arps于1945年提出了指数、双曲线和调和递减模型,其中双曲线递减模型是一种具有代表性的模型。陈元千等近年提出的泛指数递减也是一种具有实用价值的预测模型。从理论上讲双曲线递减模型的递减指数n值为0~1,实用的有效范围为0~0.5。对于泛指数递减模型的泛指数m,理论上为0~1,有效范围为0.5~1。应当指出,当n=0或m=1时,由两类递减模型均可得到指数递减模型。当n=0.5或m=0.5时,由两种递减模型均可得到具有实用价值的预测模型。本文提出了预测页岩气井和致密气井产量、累积产量、可采储量、递减率、无因次产量和无因次累积产量的关系式。通过实例应用表明,两类模型的预测结果基本上是相同的。

The production decline model is of vital importance to predicting the production rates and recoverable reserves of oil-gas wells and reservoirs.Its effective application is not limited by the ways it is reserved,driven,fractured,and recov⁃ered as well as the fluid in it.In the decline stage of production rates,the production rates and recoverable reserves can be predicted with enough production data.After years of application,Arps,in 1945,created the exponential decline model,the harmonic decline model,and,more importantly,the representative hyperbolic decline model.Moreover,the pan exponential decline model is practically valuable.Theoretically,the decline exponent n of the hyperbolic decline model ranges from 0 to 1 and the model is practical when n falls between 0 and 0.5.However,the pan exponent m of the pan exponential decline model can be valued at,in theory,between 0 and 1.The model is feasible when m ranges from 0.5 to 1.For n=0 or m=1 of the corresponding models,the exponential decline model can be obtained.For both n=0.5 and m=0.5,practical models can be built.The formulas of production rates,cumulative productions,recoverable reserves,decline rates,dimensionless pro⁃duction rates,and dimensionless cumulative productions of shale gas wells and tight gas wells,and dimensionless cumula⁃tive productions are proposed.According to application cases,the two models made similar predictions.