南堡凹陷古近系泥页岩孔隙结构特征

Characteristics of pore structures in Paleogene shales in Nanpu Sag

对南堡凹陷古近系泥页岩采用岩石热解、X衍射矿物分析、扫描电镜观察、氮气吸附测试等实验方法,探讨主要目的层段泥页岩孔隙结构特征。结果表明,南堡凹陷古近系泥页岩具有低孔致密的储层特征,部分样品具有较高的脆性矿物含量,有利于形成裂缝网络;微观孔隙类型主要包括有机质孔隙、粒间孔、粒内孔和微裂缝;微孔和中孔提供了绝大部分比表面积与孔体积,是气体吸附和存储的主要场所;泥页岩孔隙结构主要有细颈长体的墨水瓶孔型、四面开放的平行板型,其中以有利于气体吸附存储的墨水瓶型为主;有机碳含量是控制南堡凹陷古近系泥页岩中纳米级孔隙体积及其比表面积的主要内在因素;石英含量与孔体积有较好的正相关性;脆性矿物对于孔隙有积极的建设作用;有机碳含量是影响页岩吸附气体能力的主要因素。

Using rock pyrolysis, X-ray diffraction mineral analysis, electron microscopy scanning, and nitrogen adsorption tests, this research studied and discussed the pore structures in Paleogene shales in Nanpu Sag. The new results show that Nanpu Sag shale reservoir can be characterized as the follows. It is of low porosity and tight; and part of the samples have high content of brittle minerals, which can be easy to form a fracture network. The microscopic pore types are organic, inter-granular, intragranular and microfracture. Micropores and mesopores provide most of the pore surface area and pore volume, which are the main space for shale gas adsorption and storage. Pore structures include ink-bottle-like and slit-like pores, of which ink-bottle-like pores are the main pores favorable for gas absorption. The TOC content is the main internal factor that controls the volume and surface of nanopores of the Paleogene shale gas reservoir in Nanpu Sag. Quartz has good correlation with pore volume. Brittle mineral has a positive effect for the construction of the pores. Lastly TOC is the main factor affect-ing shale methane adsorption capacity.