湘鄂西页岩非均质性研究——以Ld1井龙马溪组为例

页岩非均质性直接决定了页岩的储层可改造性和含气量,是页岩气勘探开发基础研究的内容之一。以湘鄂西Ld1井龙马溪组页岩为研究对象,在矿物岩石、显微薄片、地球化学和低温N2吸附-脱附实验的基础上,分析了研究区龙马溪组页岩的非均质性。研究发现Ld1井龙马溪组页岩主要发育硅质页岩、混合质页岩和黏土质页岩三大类,三大类页岩在有机质的赋存状态、有机质含量、矿物组成、显微结构和构造、脆性以及微观孔隙类型等方面具有较强非均质性,沉积作用、后期成岩作用和陆源输入是影响页岩非均质性的主要因素。硅质页岩具有有机碳含量高、脆性和孔渗条件好等成藏条件,是后期重点勘探开发层段,但通过FHH分形维数定量研究发现,硅质页岩段孔喉细小且非均质性强,孔隙结构复杂且联通性差,需要进行有效的储层改造才能够适应开采。

Study on shale heterogeneity in western Hunan and Hubei:a case study of the Longmaxi Formation in well Ld1

The study of shale heterogeneity is one of the core research topics in shale gas exploration and development.This paper is based on the Longmaxi Formation from well Ld1 located in western Hunan and Hubei. The shale heterogeneity is analyzed on the basis of shale mineral rocks, micro- slices, geochemistry and low temperature N2 adsorption- desorption. It is found that the shales of Longmaxi Formation are mainly composed of siliceous shale, mixed shale and clayey shale. The three types of shale facies show strong heterogeneity in the distribution of organic matter, organic matter content, mineral composition, microstructure and structure, brittleness and micro- pore type. Sedimentation, late diagenesis and terrigenous input are the main factors influencing shale heterogeneity. Silica shale has high organic carbon content, good brittleness and good pore permeability conditions. However, according to FHH classification theory the pore throat of silica shale is small and heterogeneous, with complex pore structure and poor connectivity indicating that effective reservoir transformation is needed for exploitation.