页岩气藏多段压裂水平井基质-裂缝网络渗流特征研究

The commercial development of shale gas reservoirs is a key pathway of remitting the energy gap of our country, and the technology of multi-stage fractured horizontal well is the key issue for effective implementation of this pathway. But, the knowledge of flowing characteristics of matrix-fracture network becomes the major bottleneck of acquiring reservoir parameters and assessing the fracturing effect of multi-stage fractured horizontal well in shale gas reservoirs, due to the multi-mechanisms of shale gas flowing and complex fracture networks. This item takes the flowing characteristics of fracture networks of multi-stage fractured horizontal well in shale gas reservoirs as the research object，and plans to carry out basic scientific researches for matrix-fracture network flowing model of shale gas and the influence law of fracture network for flowing characteristics. The specific contents are: First, a flow model of shale matrix including multiple flowing mechanisms is presented and verified by its experimental data; then，based on this, the characterization parameters for fracture network flow of multi-stage fractured horizontal shale gas wells is explored, a matrix-fracture network flow model is established, and verified by production data; At last, the influence of reservoir parameters, fracturing characterization parameters and stimulated reservoir volume for flowing characteristics are analyzed, and an evaluation method for these parameters is proposed. The aim of this item is to uncover the characterization method and influence rule of fracture network for multi-stage fractured horizontal well in shale gas reservoirs, and the results can offer the theoretical basis and technical supports for acquisition of reservoir parameters and assessment method for fracturing effectiveness of multi-stage fractured horizontal well in shale gas reservoirs.

页岩气藏的商业化开发是缓解我国能源缺口的重要途径，而多段压裂水平井技术是这一途径得以有效实施面临的重大问题。然而，页岩气流动包括多种流动机理，而且压裂形成复杂裂缝网络，对基质-裂缝网络渗流特征的认识成为获取多段压裂水平井储层参数和评价压裂效果的主要瓶颈。本项目以页岩气藏多段压裂水平井基质-裂缝网络渗流特征为研究对象，对页岩气的基质-裂缝网络渗流模型以及裂缝网络对渗流特征的影响规律进行基础科学研究。具体内容为：首先建立考虑多种流动机理和储层结构的页岩气藏基质渗流模型，并进行实验验证；在此基础之上，探索页岩气藏多段压裂水平井裂缝网络参数的表征方法，由此建立基质-裂缝网络渗流模型，对其进行生产数据验证；最后，分析裂缝网络表征参数、压裂改造体积和储层参数对渗流特征的影响，并提出其评价方法。本项目旨在揭示裂缝网络表征方法及其对页岩气藏多段压裂水平井渗流特征的影响规律，为页岩气藏多段压裂水平井储层参数

页岩气藏存在多种渗流机理和复杂的孔隙结构，导致页岩气藏多段压裂水平井缺乏合适的渗流模型和储层参数评价方法。围绕该难题，本项目研究了页岩孔隙尺度渗流机理、岩心尺度渗流模型及其评价方法、储层尺度多段压裂井连通性和地质储量的评价方法。在渗流机理方面，我们通过修正Boltzmann方程，为Extended Navier-Stokes提供了物理基础；提出了适合Extended Navier-Stokes的动量本构关系。从而为建立页岩微纳米尺度孔隙气体渗流模型提供了统一的理论基础。此外，还解决了含启动压力梯度渗流控制方程存在的矛盾，为页岩基质中液体流动提供了理论基础。在页岩岩心尺度方面，提出了基于压力脉冲法和颗粒岩心动态吸附测试，通过压力导数法分析页岩岩心渗流模型的方法。该方法能够区分不同双重介质模型、气体吸附模型，同时也为页岩岩心渗透率测试提供了更加准确的分析手段。在储层尺度参数评价方法，建立了页岩气藏多段压裂水平井裂缝连通干扰试井模型，提出了同时确定地质储量和孔隙压缩系数的流动物质平衡方法和考虑吸附相体积的流动物质平衡方法。为更加精确评价页岩储层参数提供了手段。