基于合金注入与大视域图像技术的致密储层孔隙与喉道表征

致密油气是我国油气资源的重要组成部分，对其孔喉结构的研究有利于推进致密油气地质理论的丰富和完善。以鄂尔多斯盆地三叠系延长组致密储层为例，通过高温高压合金注入装置，结合大视域图像拼接技术与图像孔隙提取方法，建立了致密储层孔隙结构表征新方法。结果表明，将合金注入致密储层孔隙中可以较好地反映孔隙连通性特征，使孔隙形貌和结构更加容易辨别。大视域图像拼接方法解决了孔隙分布非均质性强、小视域观察代表性差的问题。鄂尔多斯盆地延长组致密储层主要发育粒间孔、粒内孔和粒间—粒内混合孔，其中粒间孔最为发育。孔隙缩小型喉道、缩颈型喉道、管束型喉道、片状喉道和弯片状喉道是其发育的5种喉道类型，其中弯片状喉道最为发育。石英和长石的孔隙明显大于其他矿物孔隙，对致密储层面孔率的贡献率达74%,是致密油气重要的赋存空间。

Pore and throat characterization of tight reservoirs based on the methods of alloy injection and large-field image stitching

Tight oil and gas is an important part of China’s oil and gas resources, and the study of related pore-throat structure is conducive to the enrichment and improvement of tight oil and gas geological theory. Taking the tight reservoir of the Triassic Yanchang Formation in the Ordos Basin as an example, combined with large-field image stitching method and image pore extraction method, this paper established a new method for pore-throat structure characterization of tight reservoir with high-temperature and high-pressure alloy injection. Results show that the alloy injected into the pores of tight reservoirs can reflect the characteristics of pore connectivity better, and the pore morphology and structure are easier to be identified. The large-field image stitching method solves the problem of strong heterogeneity of pore distribution and poor representativeness of small-field observation. The tight reservoirs of the Yanchang Formation in the Ordos Basin are mainly composed of intergranular pores, intragranular pores, and intergranular-intragranular mixed pores, among which the intergranular pores are mostly developed. There are five types of throats, including pore shrinkage throat, neck constricted throat, bundle throat, sheet throat and curved sheet throat, among which the curved sheet throat is mostly developed. The porosity of quartz and feldspar is significantly larger than that of other minerals, contributing 74% to the surface porosity of tight reservoir, and is an important occurring space for tight oil and gas.