川中侏罗系自流井组大安寨段二亚段页岩油赋存特征

Occurrence characteristics of shale oil in the second submember of Da'anzhai Member of Jurassic Ziliujing Formation, central Sichuan Basin

张晨雨 刘子驿 王斌 单帅强 陆建林 王保华 左宗鑫

ZHANG Chenyu LIU Ziyi WANG Bin SHAN Shuaiqiang LU Jianlin WANG Baohua ZUO Zongxin

中国石化 石油勘探开发研究院 无锡石油地质研究所, 江苏 无锡 214126 中国石化 油气成藏重点实验室, 江苏 无锡 214126

Wuxi Research Institute of Petroleum Geology, SINOPEC, Wuxi, Jiangsu 214126, China SINOPEC Key Laboratory of Hydrocarbon Accumulation, Wuxi, Jiangsu 214126, China

我国湖相页岩油资源丰富，但开采过程具有一定难度。揭示页岩油不同赋存状态在页岩储层中的赋存情况有助于页岩油资源的勘探与开发。以川中地区侏罗系自流井组大安寨段二亚段(以下简称大二亚段)页岩为研究对象，通过多温阶热解实验的实施、扫描电镜孔隙发育特征的观察以及洗油前后孔径分布的分析，揭示了页岩油不同状态在各介质孔隙中的赋存方式。川中地区大二亚段页岩中热模拟恢复后的页岩油以游离态为主(0.42~10.88 mg/g)，吸附态次之(0.30~1.95 mg/g)。页岩发育的储集空间主要为有机质孔(孔径2~600 nm)、黄铁矿粒间孔(孔径10~700 nm)、介壳粒内孔(孔径20~1 000 nm)、石英/长石粒间孔(孔径4~500 nm)以及黏土矿物晶间孔(孔径4~500 nm)。洗油后氮气吸附—高压压汞结果显示，页岩中孔径在2~30 nm以及60~1 000 nm的孔隙明显增多，页岩油主要赋存于此孔径范围的孔隙之中。同时建立了页岩油赋存状态与岩石中各介质间的关系热图，阐明了大二亚段页岩油主要赋存于有机质和黄铁矿之中。最终采用页岩油各赋存状态含量与洗油前后获取的含油体积拟合的方法，指明了研究区不同状态页岩油聚集的孔径范围。大二亚段页岩油游离态主要聚集于孔径60~700 nm的有机质和黄铁矿孔隙之中，吸附态主要聚集于孔径2~6 nm的有机质孔隙之中。对页岩油赋存特征进行深入剖析，有助于川中地区大二亚段页岩油开采突破。

Although China has abundant lacustrine shale oil resources, their exploitation is challenging. Investigating the various occurrence states of shale oil in shale reservoirs provides value for the exploration and development of shale oil resources. With the shale in the second submember of Da'anzhai Member of Jurassic Ziliujing Formation of the central Sichuan Basin (the Da2 submember) as the research object, the study reveals the occurrence modes of shale oil under different states in various medium pores, through the implementation of the multi-temperature pyrolysis experiment, the observation of pore development characteristics under the scanning electron microscope and the analysis of the pore size distribution before and after oil washing. In the Da2 submember, the shale oil is mainly in the free state (0.42 to 10.88 mg/g), followed by the adsorption state (0.30 to 1.95 mg/g), as revealed by thermal simulation recovery. The reservoir space of shale includes organic pores (pore size: 2 to 600 nm), pyrite intergranular pores (pore size: 10 to 700 nm), shell pores (pore size: 20 to 1 000 nm), quartz/feldspar intergranular pores (pore size: 4 to 500 nm) and clay mineral intergranular pores (pore size: 4 to 500 nm). After oil washing, the results of nitrogen adsorption and high pressure mercury injection demonstrated a significant increase in pores with sizes of 2 to 30 nm and 60 to 1 000 nm, where most of shale oil is stored. Meanwhile, it was demonstrated that the shale oil in the Da2 submember mainly occurs in organic matter and pyrite by establishing a heat map of the relationship between the occurrence state of shale oil and the medium in the rock. Lastly, by fitting the content of shale oil in different occurrence states with the oil volume obtained before and after oil washing, the pore size range for shale oil accumulation in the study area was determined. The free state of shale oil in the Da2 submember primarily accumulates in pores of organic matter and pyrite with pore size of 60 to 700 nm, and the adsorbed state of shale oil mainly accumulates in the organic matter pores with pore size of 2 to 6 nm. In conclusion, this study presents a thorough examination of the occurrence characteristics of shale oil in Da2 submember, and it will support shale oil exploitation efforts in the area.

中国石化科技部项目“四川盆地及周缘构造改造与油气关系研究” P22072;中国石化“十四五”资源评价方法与数据库建设 P23229

https://doi.org/10.11781/sysydz2024061215