四川盆地五峰-龙马溪组页岩储层非均质性特征

通过对比焦石坝、长宁和威远气田五峰-龙马溪组页岩产层段的岩矿、物性、含气性以及可压裂性等地质参数及其纵向变化规律，综合分析了页岩储层的平面和纵向非均质性及其对“甜点”优选和储层改造的影响。研究表明，纵向非均质特征在不同地区具有总体一致性：石英含量、有机碳含量和含气量均呈现下高上低的基本趋势；底部深水陆棚沉积层段普遍具有高有机碳含量、高脆性、高孔隙度和高含气量的特征，一系列属性参数的相互耦合和匹配决定了五峰组-鲁丹阶成为“甜点”的主要发育层段。平面非均质特征主要表现为储层品质以及“甜点”发育层段和厚度的区域差异：长宁和威远地区的钙质含量明显高于焦石坝地区，发育钙质硅质混合页岩相；焦石坝地区的水平应力差明显低于长宁和威远地区，且天然裂缝更为发育；长宁和焦石坝地区的“甜点层”发育于五峰-鲁丹阶下部，而威远地区的“甜点层”则发育于鲁丹阶-埃隆阶中部。页岩储层的非均质性决定了“甜点”的分布范围、发育层段和厚度；矿物组成、天然裂缝、岩石力学参数和地应力场的空间变化是进行压裂设计的重要依据。

Heterogeneity characteristics of Wufeng-Longmaxi shale reservoir in Sichuan Basin

Planar and vertical heterogeneity of Wufeng-Longmaxi shale and their influence on “sweet spot”selection and reservoir stimulation were analyzed through comparison of geological parameters including mineral composition，physical properties，gas content and fracability，as well as their vertical varying regularities in Jiaoshiba，Changning and Weiyuan gas fields. The study shows that the vertical heterogeneity is consistent in different regions：Quartz content，TOC and gas content all present the trend of decreasing from bottom to top，and the bottom shale interval deposited in deep-water shelf environment is generally characterized with high TOC，high brittleness，high porosity and high gas content. The coupling and matching of a series of properties and parameters leads to the “sweet spot” mainly developed during Wufeng-Rhuddanian stage. Planar heterogeneity causes the regional variation of reservoir quality：The calcareous content in Changning and Weiyuan regions is obviously higher than that of Jiaoshiba region，and the calcareous-siliceous mixed shale is developed in the former region. Jiaoshiba region is featured with smaller horizontal stress difference and better-developed natural fracture comparing with Changning and Weiyuan regions，which are both more favorable for reservoir fracturing. The“sweet spot”in Changning and Jiaoshiba regions is mainly the interval of Wufeng-Lower Rhuddanian，while the“sweet spot” in Weiyuan region is mainly the interval of Rhuddanian-Middle Aeronian. Heterogeneity of shale reservoir controls the distribution scope，interval and thickness of “sweet spot”. And the spatial variation of mineral composition，natural fracture，rock mechanical parameters and in-situ stress are all the basis of hydraulic fracturing design.