Guo Chaohua, Wei Mingzhen, Liu Hong
Key Laboratory of Tectonics and Petroleum Resources (China University of Geosciences), Ministry of Education, Wuhan, China.
Department of Geological and Petroleum Engineering, Missouri University of Science and Technology, Rolla, MO, United States of America.
PLoS One. 2018 Jan 10;13(1):e0188480. doi: 10.1371/journal.pone.0188480. eCollection 2018.
Development of unconventional shale gas reservoirs (SGRs) has been boosted by the advancements in two key technologies: horizontal drilling and multi-stage hydraulic fracturing. A large number of multi-stage fractured horizontal wells (MsFHW) have been drilled to enhance reservoir production performance. Gas flow in SGRs is a multi-mechanism process, including: desorption, diffusion, and non-Darcy flow. The productivity of the SGRs with MsFHW is influenced by both reservoir conditions and hydraulic fracture properties. However, rare simulation work has been conducted for multi-stage hydraulic fractured SGRs. Most of them use well testing methods, which have too many unrealistic simplifications and assumptions. Also, no systematical work has been conducted considering all reasonable transport mechanisms. And there are very few works on sensitivity studies of uncertain parameters using real parameter ranges. Hence, a detailed and systematic study of reservoir simulation with MsFHW is still necessary. In this paper, a dual porosity model was constructed to estimate the effect of parameters on shale gas production with MsFHW. The simulation model was verified with the available field data from the Barnett Shale. The following mechanisms have been considered in this model: viscous flow, slip flow, Knudsen diffusion, and gas desorption. Langmuir isotherm was used to simulate the gas desorption process. Sensitivity analysis on SGRs' production performance with MsFHW has been conducted. Parameters influencing shale gas production were classified into two categories: reservoir parameters including matrix permeability, matrix porosity; and hydraulic fracture parameters including hydraulic fracture spacing, and fracture half-length. Typical ranges of matrix parameters have been reviewed. Sensitivity analysis have been conducted to analyze the effect of the above factors on the production performance of SGRs. Through comparison, it can be found that hydraulic fracture parameters are more sensitive compared with reservoir parameters. And reservoirs parameters mainly affect the later production period. However, the hydraulic fracture parameters have a significant effect on gas production from the early period. The results of this study can be used to improve the efficiency of history matching process. Also, it can contribute to the design and optimization of hydraulic fracture treatment design in unconventional SGRs.
两项关键技术的进步推动了非常规页岩气藏（SGRs）的开发：水平钻井和多级水力压裂。为提高油藏生产性能，已钻了大量的多级压裂水平井（MsFHW）。SGRs中的气流是一个多机制过程，包括：解吸、扩散和非达西流。MsFHW的SGRs产能受储层条件和水力裂缝特性的影响。然而，针对多级水力压裂SGRs的模拟工作很少。其中大多数使用试井方法，这些方法有太多不切实际的简化和假设。此外，没有考虑所有合理输运机制进行系统的工作。而且，使用实际参数范围对不确定参数进行敏感性研究的工作也很少。因此，对MsFHW进行详细而系统的油藏模拟研究仍然是必要的。本文构建了一个双孔隙度模型来评估参数对MsFHW页岩气产量的影响。利用巴尼特页岩的现有现场数据对模拟模型进行了验证。该模型考虑了以下机制：粘性流、滑移流、克努森扩散和气解吸。采用朗缪尔等温线模拟气解吸过程。对MsFHW的SGRs生产性能进行了敏感性分析。影响页岩气产量的参数分为两类：储层参数，包括基质渗透率、基质孔隙度；水力裂缝参数，包括水力裂缝间距和裂缝半长。回顾了基质参数的典型范围。进行了敏感性分析，以分析上述因素对SGRs生产性能的影响。通过比较可以发现，与储层参数相比，水力裂缝参数更敏感。储层参数主要影响生产后期。然而，水力裂缝参数对早期产气有显著影响。本研究结果可用于提高历史拟合过程的效率。此外，它有助于非常规SGRs水力压裂处理设计的设计和优化。
