页岩气勘探开发实验技术研究进展与发展方向

Experimental technologies of shale gas exploration and development:Research progress and development direction

页岩气开发的成功得益于全新地质理论的建立及工程技术的进步,其中地质理论的创新离不开实验技术的突破与发展,但随着页岩气进入全面开发的新阶段,对实验方法、基础理论等方面提出了更高要求和技术挑战。为此,针对页岩气勘探开发过程中的关键问题,从页岩矿物组成、岩石物性、孔隙结构、含气性及可压性等5个方面展示了地质实验研究的进展和应用实例,分析了页岩气勘探开发实验研究面临的问题和挑战,并展望了其未来的发展方向和趋势。研究结果表明:①薄片鉴定和X射线衍射是页岩矿物分析最有效的定性定量方法,开展矿物成因实验研究对于揭示页岩成储规律及地质工程甜点段优选有着更重要的指导意义;②页岩物性测试方法多且标准不统一,需要根据研究目的选择适用的测试方法,开展地层条件下的物性测试对储量计算及开发效果评价更有帮助;③页岩孔隙结构表征已形成了从宏观到微观、从定性到定量、从二维到三维的综合评价方法,可指导开发层系划分和水平井靶窗优选;④页岩含气性评价已形成了现场含气量测试、等温吸附、气体碳同位素监测等实验方法,揭示了页岩气赋存状态和解吸规律,可有效指导气井生产制度制订和采收率提高;⑤页岩可压性评价已形成了X射线衍射、多尺度的裂缝网络刻画、三轴力学、差应变法、声波各向异性法及声发射法等实验方法,可指导水平井设计和压裂工艺优化。结论认为,建立跨尺度多方法深度融合的实验体系、加强原位条件下的页岩气储层评价、开展关键参数的动态演化和基于大数据模型的人工智能实验评价等是下一步研究方向,持续完善页岩气实验地质技术体系方可为页岩气高效勘探开发提供更好的理论基础和技术支撑。

The success of shale gas development is attributed to the establishment of brand-new geological theories and the advancement of engineering and technologies.The innovation of geological theories is inseparable from the breakthrough and development of experimental technologies.As the new stage of extensive development of shale gas is ushered,however,higher requirements and technological challenges are raised to experimental methods,basic theories and so on.In view of the key problems in shale gas exploration and development,this paper illustrates the progress and application cases of geological experimental technologies from the aspects of shale mineral composition,petrophysics,pore structure,gas content and fracability,analyzes the problems in and challenges to the experimental research of shale gas exploration and development,and predicts the future development directions and trends.The following results are obtained.First,for shale mineral analysis,thin section identification and X-ray diffraction are the most effective qualitative and quantitative methods,but the experimental study on mineral genesis is of more important guiding significance to reveal the shale reservoir-forming patterns and selecting the geology-engineering sweet spots.Second,for shale physical property testing,there are various methods and the standards are not unified,so it is necessary to select the suitable testing methods based on research objectives,and performing physical property testing under formation conditions is more beneficial for reserve estimation and development effect evaluation.Third,for shale pore structure characterization,a comprehensive evaluation method has been developed from macroscopic to microscopic,from qualitative to quantitative,and from two-dimensional to three-dimensional,which can guide the division of development layers and the selection of horizontal well target window.Fourth,for shale gas content evaluation,experimental methods such as field gas content test,isothermal adsorption and gas carbon isotope monitoring have been established,which reveal the occurrence states and desorption patterns of shale gas and can provide an effective guidance for the formulation of gas well production system and the enhancement of recovery efficiency.Fifth,for shale fracability evaluation,experimental methods such as X-ray diffraction,multi-scale fracture network depiction,triaxial mechanics,differential strain method,acoustic anisotropy method and acoustic emission method have been developed,which can guide the design of horizontal wells and the optimization of fracturing process.The future efforts are proposed to focus on establishing an experimental system integrating multi-scale methods,enhancing the evaluation of shale gas reservoirs under in-situ conditions,conducting dynamic evolution of key parameters,and implementing artificial intelligence experimental evaluation based on big data models.The continuous improvement of the experimental geological technology system for shale gas can provide a better theoretical foundation and technical support for the efficient exploration and development of shale gas.