吉木萨尔凹陷芦草沟组混积型页岩油可动性实验

Experiments on Mobility of Mixed Shale Oil in Lucaogou Formation in Jimsar Sag

为确定吉木萨尔凹陷芦草沟组页岩油藏储集层孔喉结构及其原油可动性,利用薄片、扫描电镜、高压压汞等划分储集层;通过驱替与核磁共振联测实验,开展页岩油可动性评价,揭示可动油占比、孔径变化规律及其控制因素,建立页岩油可动性定量评价模型。芦草沟组发育粒间孔型、粒间-溶蚀-晶间孔型、溶蚀孔型、溶蚀-晶间孔型和晶间孔型5类储集空间。粒间孔型发育在粉—细砂岩相和砂质白云岩相中,可动性最好;溶蚀孔型主要发育在白云质粉砂岩相中,可动性中等;其他类型主要发育在泥岩相、泥质白云岩相和石灰质砂岩相中,可动性稍差。厘定页岩油可动孔喉下限为20 nm,可动性明显提高的孔喉界限为60 nm和150 nm,试油产能与之对应较好。页岩油赋存特征和孔喉结构共同影响页岩油可动性,粉—细砂岩相和白云质粉砂岩相的孔喉及页岩油赋存均最佳,为芦草沟组页岩油最有利开发岩相。

In order to determine the pore-throat structure and the mobility of crude oil in the shale reservoirs of the Lucaogou formation in the Jimsar sag,the reservoirs were classified by means of thin section identification,scanning electron microscope(SEM),and experiments such as high-pressure mercury intrusion. The mobility of the shale oil was evaluated through a displacement-NMR combined experiment to reveal the movable oil proportion,pore size variation and its controlling factors,and then establish a quantitative evaluation model of shale oil mobility. The Lucaogou formation develops 5 types of reservoir spaces including intergranular pores,intergranular-dissolution-intercrystalline pores,dissolution pores,dissolution-intercrystalline pores,and intercrystalline pores. The intergranular pores are mainly found in the silty-fine sandstone and sandy dolomite,and exhibit the best mobility. The dissolution pores are mainly in the dolomitic siltstone,and exhibits moderate mobility. Other pores are mainly in mudstone,argillaceous dolomite and limy sandstone,and show poor mobility. The lower limit of pore throats for shale oil moving is determined to be 20 nm. When the pore throat size are 60 nm and 150 nm,the movability is significantly improved,which corresponds well to the tested production capacity. Shale oil occurrence and pore-throat structure jointly affect the mobility of shale oil. The pore throats and shale oil occurrence in silty-fine sandstone and dolomitic siltstone are the best,which are the most favorable lithofacies for developing the mixed shale oil in the Lucaogou formation.