我国南方古生界高过成熟页岩吸附特征与页岩含气性评价

The term "Shale Gas" refers to self-sourced, self-reservoired and unconventional occuring in both adsorbed and free gas accumulated in organic rich mudstones or shales，while the adsorbed gas and adsorption plays key role in the shale gas formation and potential evalution. The fundamental geological and geochemical conditions of Palaeozoic marine shales distributed widely in Southern China are compatible with that of these gas shale plays in Northern American，and primary investigation suggests these shales are great potential of shale gas resources. However, due to the lack of fundamental research and the complexity of geological and tectonic history as well as their high to over maturity, the shale gas potential evalution and industrial exploitation in these shales are much behind the industry exploitation need. Therefore, there is urgent need for carrying out some fundamental studies regarding to the geological background and geochemical properties of the high & over maturity shales，and to develop the theory of shale gas occurrence and reservoir formation mechanism(s) that can be useful the shales exploration in China. This proposal will focus on the methane adsorption property and their controlling factors, to investigate the major adsorption components and their micropore structures and distribution, and to find out the adsorption mechanism(s) and adsorption capacity of major adsorption componenet. By doing so, we will be able to assess the controlling geochemical factors on the shale adsorption property and to determine the correlation between the adsorption amount and shale gas capacity both qualitatively and quantitatively. And therefore to provide scientific information for the gas potential evalution of these high & over matured Palaeozoic shales.

页岩气是指自生自储、以吸附和游离态储集于富有机质泥页岩中的非常规天然气，其中，吸附气和吸附作用是页岩气形成和资源评价的关键所在。我国南方广泛分布的古生界泥页岩与北美地区页岩气产区在有机碳含量和厚度等方面具有良好的可比性，初步认为具备页岩气形成和储集成藏的有利地质地球化学条件，资源潜力巨大。然而，由于我国在页岩气研究基础薄弱，特别是对于南方古生界复杂的地质构造演化及高过成熟度背景条件下页岩气赋存特征等缺乏必要的基础性研究，影响制约着南方古生界页岩含气性和页岩气资源潜力的评价以及实际勘探开发。因此，迫切需要开展我国南方古生界高过成熟页岩吸附特征研究，确定页岩主要吸附单元的显微孔隙结构及分布，探讨页岩主要吸附单元的吸附机制和吸附容量，综合评价影响页岩吸附性能的地球化学因素，定性和定量评价页岩吸附容量及特征与页岩含气性相关性，为南方古生界高过成熟页岩气资源评价提供科学依据。

通过探讨中国南方古生界寒武系、志留系和二叠系海相页岩及其干酪根的吸附容量及其与有机质丰度、可溶有机质、成熟度及吸温度、粘土矿物含量等的相关性，并结合页岩孔隙结构和比表面积分析，综合研究了南方古生界页岩吸附性能及其控制因素和相关的吸附机制。论文取得主要认识和结论如下：.1、南方古生界页岩的甲烷吸附量在0.7~4.33 cm3/g STP之间，不同时代、不同地区样品吸附量相差很大；但总体上南方古生代页岩的吸附容量与美国页岩气产区页岩具有可比性。.2、南方古生界页岩甲烷吸附容量与有机碳含量之间整体具有正相关性，显示有机质是页岩吸附能力的主要影响控制因素，但相关系数随地层时代及分布区域有显著变化。.3、可溶有机质吸附及对页岩吸附容量的影响与地层时代与成熟度有很大的关联；湿度和温度同样对页岩吸附容量的影响很大。 .4、古生界页岩干酪根具有较强的吸附能力， 吸附容量在9～35cm3/g STP之间，并明显受干酪根类型影响，其中III型干酪根比II型干酪根的吸附量要大；不同时代的干酪根吸附能力相差较大的原因，可能是成熟度的原因，即不同成熟度的干酪根孔隙发育程度不同。.5、粘土矿物种类及含量对页岩吸附能力的影响作用比较复杂，总体上粘土矿物含量与页岩吸附容量之间无明显相关性，显示粘土矿物不是页岩吸附作用的主要载体。.6、页岩的比表面积和孔体积都与甲烷吸附量具有正相关关系，且平均孔径越小，比表面积越大，越利于页岩甲烷的吸附。.7、自行开发研制了超高压气体吸附解吸附分析仪，设计最大压力为高达70MPa，并设计编写了仪器操作和数据分析软件， 并显示出积极的科学研究与工业用途。