Simulation of Multi-Component Gas Flow and Condensation in Marcellus Shale Reservoir
本文研究了马塞勒斯页岩储层中的多组分气体流动和冷凝现象。马塞勒斯页岩形成了超过463万亿立方英尺的可回收天然气，是提供清洁能源和环境可持续性的关键。然而，由于近期天然气价格低迷，许多运营公司已放缓在干气区域的活动，转而关注液体丰富区域的油气生产。为了应对这种生产计划的变化，必须详细研究气体冷凝库的发展和饱和动态。研究表明，气体冷凝在页岩气储层中的相行为与常规气体冷凝显著不同，受到页岩孔径分布、气体吸附和水蒸气饱和度的影响。本文提出了一种新型状态方程，考虑了流体-流体和流体-固体相互作用的粘附和凝聚力，并利用该方程开发了马塞勒斯页岩气储层中气体冷凝流体的组成模型。通过使用CMG（GEM）模拟器，本文研究了气体冷凝的动态变化，并对不同气体组成的饱和度剖面进行了敏感性分析。研究结果表明，页岩气储层中的气体冷凝行为与孔壁效应和吸附层效应密切相关，这对生产策略和刺激设计具有重要影响。
CMG软件应用情况
在本研究中，使用了CMG的GEM模拟器来研究马塞勒斯页岩气储层的气体冷凝动态和饱和度变化。通过该软件，研究者能够模拟不同操作条件和储层特性对气体冷凝库发展的影响，并进行敏感性分析，以优化气体生产策略。
Abstract
The Marcellus shale formation, with more than 463 trillion cubic feet (Tcf) of recoverable gas in Pennsylvania and West Virginia, will play a critical role in providing clean energy, environmental sustainability, and increased security for our nation. However, due to recent low gas prices, most of the operating companies have slowed down their activities in dry gas areas and refocused their attention in oil and condensate production from liquid-rich regions. This change in production plans requires detailed investigation of gas condensate bank developments and saturation dynamics in shale gas reservoirs that change greatly with reservoir conditions. An advanced level of understanding of the parameters affecting gas condensate phase behavior is necessary in order to make accurate predictions of these changes.
One of these parameters is the phase behavior of gas condensate in shale gas reservoirs that is significantly different than that of gas condensate as bulk in the PVT cell. It is highly affected by shale pore size distribution, gas adsorption, and water vapor saturation. Critical properties of gas condensate are also significantly influenced by shale pore size distribution, leading to changes in viscosity and formation volume calculations. In addition to that fluid composition, natural and hydraulic fractures, reservoir anisotropy, rock compressibility and number of horizontal wells and their operating conditions could also significantly impact the condensate bank development and dynamics. To quantify the importance of each one of these parameters and their interactions on dynamics of condensate bank development, an experimental design technique, Plackett-Burman design, will be practiced for two different cases (single well cylindrical model and actual Marcellus shale gas reservoir with heterogeneous porosity and permeability field). Detailed uncertainty analysis of different parameters has a significant impact on implementing the best production strategies such as bottom-hole pressures and hydraulic fracture spacing. Commercial simulators are unable to provide reliable predictions of condensate production rates and saturation dynamics due to lack of correct physics controlling production mechanisms in shale gas reservoirs.
In this study we will introduce a new equation of state, including the cohesive and adhesive forces due to fluid-fluid and fluid-solid interactions, and use that to develop a compositional model for gas condensate fluids in Marcellus shale gas reservoirs. A new correlation to adjust critical properties of gas condensate will also be developed based on shale pore size distribution to incorporate into the compositional simulator, CMG (GEM), to investigate the dynamics of gas condensation, and to perform sensitivity analysis on saturation profiles for different gas compositions of Marcellus from “super-rich” to liquid-rich areas.
Based on our study, critical properties and phase behavior of gas condensate are distinctively different under the influence of wall effects and adsorption in organic nanopores, and also have significant effect on production strategies and stimulation design for Marcellus shale gas reservoirs. This study takes a unique approach that can be applied to commercial simulators as a modification to currently applied models without requiring rewriting or development of a new generation of simulators.
作者单位
西弗吉尼亚大学工程与矿产资源学院 阿卜杜拉·埃拉敏（Abdallah Elamin）
