中国页岩油资源丰富,截止至 2022 年底,中国陆相页岩油预测储量达到 29.74 亿t,但在如此规模的储量下只有可采页岩油才具有经济价值.吉木萨尔凹陷芦草沟组页岩油储层根据矿物组分及源储比可分为夹层型、纹层型及混积型 3 种类型.但由于三类储层孔隙结构特征及流体赋存状态差异较大,导致在相同的压裂手段下产能差异甚远.为明确吉木萨尔凹陷芦草沟夹层型、纹层型储层孔隙结构特征及其约束下的流体可动性差异,本文通过XRD、铸体薄片、扫描电镜、氮气吸附等方法对孔隙结构特征进行研究,利用核磁共振离心技术对纹层型、夹层型储层样品页岩油可动性进行定量评价,采用T1-T2 谱方法明确不同储层类型页岩油赋存状态,最终结合孔隙结构特征参数对页岩油储层流体可动性的主控因素进行分析.结果表明,纹层型储层碳酸盐岩类矿物含量较高,储集空间以碳酸盐岩晶间孔、黏土矿物层间缝及有机质孔为主,干酪根含量较高,游离油组分含量极低,可动流体饱和度均值仅为 7.97%;夹层型型长英质含量较高,储集空间以晶间孔、长石粒内溶孔为主,流体组分以可动油为主,其次为束缚油、干酪根,不含可动水,可动流体饱和度均值为29.26%.孔隙结构特征参数中最大孔喉半径大小是控制页岩油储层可动流体饱和度的主要因素,两者呈指数正相关,相关系数可达 0.9521.通过本次研究,明确了吉木萨尔凹陷芦草沟组夹层型、纹层型页岩油储层的主要储集空间类型分别为粒间孔、粒内孔.从单峰夹层型储层到双峰纹层型储层可动流体饱和度逐渐减小,但均随着最大孔喉半径的增大而呈指数增加,表明最大孔喉半径对页岩油储层可动流体饱和度有较大的影响.

China is rich in shale oil resources.By the end of 2022,the predicted reserves of continental shale oil in China have reached 3 billion tonnes,but only recoverable shale oil has economic value under such reserves.The shale oil reservoirs of the Lucaogou For-mation in the Jimusar Sag can be divided into three types:interlayer type,lamina type and block type according to mineral composition and source-reservoir ratio.However,due to the large difference in pore structure characteristics and fluid occurrence state of the three types of reservoirs,the productivity difference is high using the same fracturing method.In order to clarify the pore structure character-istics of the Lucaogou interlayer and laminated reservoirs in the Jimusar sag and the difference of fluid mobility under their constraints,this paper studies the pore structure characteristics by means of XRD,casting thin sections,scanning electron microscopy and nitrogen adsorption.Nuclear magnetic resonance centrifugation technology was used to quantitatively evaluate the mobility of shale oil in laminated and laminated reservoir samples.The T1-T2 spectrum method was used to clarify the occurrence state of shale oil in different reservoir types.Finally,the main controlling factors of fluid mobility in shale oil reservoirs were analyzed by combining characteristic pore structure parameters.The results show that the carbonate content of laminated reservoirs is high,and the reservoir space is domi-nated by carbonate intergranular pores,clay mineral interlayer fractures and organic matter pores.The fluid component is dominated by kerogen,and the free oil component content is extremely low.The average value of movable fluid saturation is only 7.97%.The felsic content of the interlayer type is higher,the reservoir space is mainly composed of intercrystalline pores and dissolved pores in feldspar grains,the fluid composition is mainly movable oil,followed by bound oil and kerogen,and there is no movable water.The average saturation of movable fluid is 29.3%.The pore throat radius in the characteristic pore structure parameters is the main factor controlling the movable fluid saturation of shale oil reservoirs.The two are exponentially correlated,and the correlation coefficient can reach 0.95.Through the study,the main reservoir space types of the intergranular pores and intra-granular pores in the Lucaogou Formation and the laminar shale oil reservoirs in the Jimsal Depression are determined.The mobile fluid saturation decreases gradually from unimodal interlayer reservoirs to bimodal laminated reservoirs,but increases exponentially with the increase of the maximum pore throat radius.The results show that the maximum pore throat radius has a great influence on the mobile fluid saturation of shale oil reservoir.