深部碎屑岩储层溶蚀作用实验模拟研究

Experimental Simulation for Dissolution in Clastic Reservoirs of the Deep Zone

结合渤海湾深层天然气勘探实际,选用渤海湾盆地深埋储层的长石砂岩和灰质长石砂岩,配制与地层有机酸组分相近的反应液,模拟开放-半开放条件下,晚成岩期有机酸溶解作用。通过样品定位对比分析,结果证明：①乙酸对碎屑岩颗粒,特别是钾长石、钠长石、方解石、白云石溶蚀过程中,Ca、Mg、Na、K离子优先释放,Al、Si离子释放较慢。②扫描电镜定位对比分析表明,在实验模拟的高温、开放成岩环境下,乙酸优先溶解方解石,方解石溶出速度大于白云石;钠长石比钾长石更易溶解。③溶解试验反应161h后,孔隙度平均提高2%-3%,证实了乙酸可提高深部储层的次生孔隙空间。溶解量的大小与矿物中可溶物质含量有关（特别是方解石、长石、白云石的含量有关）。④X衍射、能谱分析和扫描电镜资料证实,溶解沉淀物为硅质、铝硅酸盐沉积物,呈块状、粒状产出。由于沉淀时间短,其晶形较差,而且随着反应时间增加,沉淀物数量增加。

The experiment was performed to investigate the effects of dissolution in deep-buried clastic rock of the Bohai Bay Basin. Experiment for dissolution by acetic acid has been performed under the conditions of 130℃ and pH 2.75. The samples used in experiments has been examined by thin section,scanning electron microscope,X-ray diffraction,and energy dispersive x-ray analysis both before and after dissolution. The experimental results are as follows： 1） calcium, magnesium sodium and kalium were preferentially released,but aluminium and silicon was released slowly in clastic rock dissolution. 2） The calcite is most easy to dissolute in different samples. At the same time, albite is more easily to be decomposed than Kfeldspar. 3） After the dissolution process for 161 hours, the porosity of clastic rock could rise about 2%-3% on average. The dissolution amounts is related to the contents of the dissoluble matter（especially calcite, dolomite, feldspar） in the deep-buried classic rock. 4 ） The precipitation of siliceous and aluminosilicate deposits occurs as microcrystal with dissolution. The experiment will help study the relationship between dissolution in deep-buried clastic rock and formation of secondary porosity.