页岩中原生水特征及其对含气性的影响

The content and occurrence of connate water in shales have significant influence on the evaluation of the free gas, adsorbed gas and dissolved gas in shales. For the weakness of correlated fundamental research as well as the lack of date and theoretical model of connate water in shales, it has become one of the most important reasons restricting the evaluation and forecast of the shale gas potential in china. In this research, three scientific problems associated with connate water in shales are supposed to be solved basing on the three series of Palaeozoic high-maturity shales in south china: (1) the content, occurrence and the main controlling factor of connate water in shales; (2) the influence of bound water in shales on the gas content; and (3) the model of dissolved gas in the limit geological conditions. The aims of this research are to evaluate the content and the main controlling factor of connate water in shales quantitatively, to establish the correlation between the content of connate water and the content of adsorbed gas in shales, as well as to establish the model of dissolved gas in limit geological conditions. The results of this research will provide scientific basis to the evaluation and forecast of the potential of shale gas in the three series of Palaeozoic shales in south china.

页岩中原生水的含量及赋存状态对页岩中游离气、吸附气和溶解气的含量均具有重要的影响。我国相关基础研究薄弱，缺乏相关数据与理论模型，成为制约页岩含气性评价与资源潜力预测的主要因素之一。本研究以我国南方上扬子地区三套很高成熟度的古生界页岩（下寒武统、下志留统、上二叠统）为研究重点，通过对典型样品的研究，重点突破与页岩原生水相关的三个关键科学问题：（1）页岩中原生水的含量、赋存状态及主控因素；（2）页岩中束缚水对其吸附能力的影响；（3）限定地质条件下页岩水溶气模型。本研究的预期目标是：定量评价三套页岩典型样品中原生水的含量及主控因素、建立页岩中不同赋存状态原生水含量与页岩含气性的相关关系和建立限定地质条件下页岩水溶气模型，相关成果将为南方古生界三套页岩含气性评价与资源潜力预测提供科学依据。

地质条件下, 页岩储层普遍含水, 页岩原生水的含量和赋存状态对页岩含气性具有重要的影响. 随着中国页岩气快速的勘探与开发, 近年来对中国南方上扬子地区下古生界下寒武统与下志留统页岩开展了大量地球化学与储集物性的研究, 但对两套高成熟度页岩中原生水的特征及其影响因素缺乏研究. 本研究对取自该地区的FY1井下寒武统牛蹄塘组和YQ1井下志留统龙马溪组的页岩样品, 进行了页岩原生水含量的测试, 研究了页岩原生束缚水与页岩TOC含量、孔隙度及孔隙结构等参数的相关性, 探讨了影响页岩原生束缚水特征的主要因素. 结果显示: FY1和YQ1页岩样品原生束缚水含量分别为4.17 mg/g - 5.29 mg/g和 3.28 mg/g - 5.06 mg/g, 原生束缚水饱和度分别为30.52% - 42.72%和32.87% - 45.51%, 均处于超低含水饱和度状态. 两套页岩样品的原生束缚水含量与其TOC含量、孔隙度、微孔与非微孔的孔容和比表面积均呈正相关性, 而页岩原生束缚水饱和度与这些参数均呈负相关性. 研究表明, 高成熟度页岩层中不含有原生自由水, 只含有原生束缚水, 并且原生束缚水在微孔中主要呈填充态, 而在非微孔中主要呈吸附态. 高成熟度页岩中有机质孔具有束缚水的能力, 在相同地质环境下, 页岩中有机质孔原生水饱和度低于无机质孔, 页岩有机质控制了页岩孔隙度和孔隙结构的差别, 随着页岩TOC含量增加, 页岩中亲水性孔隙增加, 亲水性/疏水性孔隙比例减小, 因此造成了页岩束缚水的含量增加, 束缚水饱和度减小.