Abstract: The integrated quantitative evaluation of movable shale oil is the fundamental basis for optimizing favorable blocks, intervals and lithologic combinations in the study area. The Jurassic shale oil is a key exploration layer series in Sichuan Basin, and currently there is no literature report on complete integrated evaluation and recoverable layer prediction for the mobility of shale oil in Da’anzhai Member. This paper is a case study of reservoirs in Da’anzhai Member. The reservoir space, occurrence mechanism and pore structure characteristics of different lithologic combinations were studied using the microscopic experimental methods such as SEM, low-temperature and nitrogen adsorption. The oil-bearing property and adsorption difference of reservoirs in Da’anzhai Member were analyzed based on the characteristics of source rock. According to the basic analysis of oil-bearing property, dynamic core experiments were further conducted to deeply analyze the mobility of the target reservoir and clarify the influencing factors of mobility. Finally, by analyzing the influencing factors of shale oil mobility, a comprehensive evaluation system and an integrated quantitative method for shale oil mobility in Da’anzhai Member was established based on the fuzzy analytic hierarchy process, sum product method and translational range transformation method. On this basis, the paper selects the major influencing factors of shale oil mobility, optimizes the favorable lithologic combinations in Da’anzhai Member, predicts the corresponding favorable production intervals and movable resources amount, and confirms exploration breakthrough in wells. The research results indicate that shell limestone in Da’anzhai Member is compact, and shale microfractures are underdeveloped; the layered limestone shell shale has the best oil-bearing property, of which the OSI is 121.86 mg/g; the heterogeneous mud shale interbedded with shell limestone has the best shale oil movability, of which the POI is 34 mg/g. Therefore, the exploitable shale oil in Da’anzhai Member is the interbedded/interlayered lithologic assemblage of shale oil, and the high frequency of interlayer between the roof and floor of dense shell limestone in the lower submember 1 of Da’anzhai Member and upper submember 2a of Da’anzhai Member and the submember 2b of Da’anzhai Member are predicted as recoverable strata, which are distributed in Nanchong-Langzhong-Yilong-Pingchang area, Fuling and Santai area. The movable resources of shale condensate oil and gas in Type Ⅰ favorable areas amount to 1.91×10⁸t and 3 232.39×10⁸m³, respectively, showing good prospects.

Key words: lacustrine facies shale oil, occurrence mechanism, adsorption difference, oil-bearing property characteristic, comprehensive evaluation of shale oil mobility

摘要： 可动页岩油综合定量评价是优选研究区有利区块、有利层段、有利岩性组合的基本依据,侏罗系页岩油是四川盆地当前勘探的重点层系,但对其大安寨段页岩油可动性的综合评价和可采层段预测还未见报道。以大安寨段储层为研究对象,通过扫描电镜、低温氮气吸附等微观实验手段,研究不同岩性组合的储集空间、赋存机理及孔隙结构特征;在烃源岩特征基础上,分析大安寨段储层的含油性和吸附差异性;根据基础含油性分析,进一步通过动态岩心实验深入分析目标储层的可动性,并明确其可动性影响因素;最后,通过可动性影响因素分析,依据模糊层次分析法、和积法、平移极差变换法,建立了大安寨段页岩油可动性综合评价指标体系和综合量化方法,筛选了页岩油可动性主要影响因素,优选了大安寨段有利岩性组合,并预测了相应的有利开采层段和可动资源量,通过勘探突破井获得了证实。研究结果表明:大安寨段介壳灰岩致密、泥页岩微裂缝欠发育,含油性最好的纹层状灰质介壳页岩的OSI(即热解游离烃量S₁与有机碳含量的比值)可达121.86 mg/g,页岩油可动性最好的是不等厚泥页岩与介壳灰岩互层,其采油指数达34 mg/g。因此,大安寨段可开采的页岩油为互层型/夹层型岩性组合页岩油,致密介壳灰岩顶底板间夹层频率高的大安寨段一亚段下部和大安寨段二a亚段上部、以及大安寨段二b亚段为预测可开采层段,平面上分布在南充—阆中—仪陇—平昌一带、涪陵和三台地区,Ⅰ类有利区页岩凝析油可动资源为1.91×10⁸t、凝析气可动资源为3 232.39×10⁸m³,具有良好的前景。

关键词: 湖相页岩油, 赋存机理, 吸附差异性, 含油性特征, 可动性综合评价