Transient flow of geofluids caused by a well production in a subsurface formation is a phenomenon of enormous importance in hydrology, geosciences and engineering. Geofluid transient flow has been proved to be a nonlinear physical process dominated by QPG (quadratic pressure gradient). Much research has indicated that neglecting a QPG term in flow models by assuming small pressure gradients can cause significant errors in predicted pressures. Despite the existence and importance of QPG, limited research on nonlinear QPG models has been performed when compared with the traditional linear flow models. On the basis of the previous linear and nonlinear QPG models, a comprehensive geofluid flow model for a well in a subsurface formation was established and solved. A general solution method for this model and its general solutions were obtained for vertical and horizontal wells in ordinary, fractured and fractured-vuggy formations. Next, flow regimes and typical transient flow characteristics were thoroughly analyzed by using a series of standard type curves. Then, the differences in type curves between linear and nonlinear QPG models were qualitatively and quantitatively studied. Afterwards, model validations and production predictions were performed. This comprehensive model contained various specific modeling situations. Some modeling situations that were reported in the previous studies were well-reviewed in this paper. The other previously unreported modelling situations were firstly studied and exhibited in this paper. At the end, the existing problems pending to be solved were put forward and future work on nonlinear QPG models was suggested. This paper is very helpful in understanding the QPG-dominated transient flow behavior more profoundly.

在地下地层中，由于井的生产而引起的地流体的瞬时流动是在水文学，地球科学和工程学中极为重要的现象。地流体瞬变流已被证明是一个以QPG（二次压力梯度）为主的非线性物理过程。许多研究表明，通过假设较小的压力梯度来忽略流量模型中的QPG项，可能会导致预测压力出现重大误差。尽管QPG的存在和重要性，但与传统的线性流模型相比，对非线性QPG模型的研究仍然有限。在以前的线性和非线性QPG模型的基础上，建立并求解了地下地层中一个井的综合土流模型。对于普通，压裂和压裂孔隙地层中的垂直井和水平井，获得了该模型的一般求解方法及其一般求解。接下来，使用一系列标准类型曲线彻底分析了流动状态和典型的瞬态流动特性。然后，定性和定量地研究了线性和非线性QPG模型之间的类型曲线差异。之后，进行了模型验证和生产预测。该综合模型包含各种特定的建模情况。在先前的研究中报道的一些建模情况在本文中得到了很好的回顾。本文首先研究并展示了其他以前未报告的建模情况。在最后，提出了有待解决的现有问题，并提出了非线性QPG模型的未来工作。本文对于更深入地了解QPG为主的瞬态流动行为非常有帮助。