鄂尔多斯盆地中部长6和长8储层特征及酸敏机理

Reservoir characteristics and acid sensitivity mechanism of Chang 6 and Chang 8 reservoirs in the central of Ordos Basin

运用铸体薄片、X衍射、扫描电镜、能谱、等离子发射光谱仪等分析测试技术,对鄂尔多斯盆地中生界延长组湖盆中部长6和长8储层酸敏特征及机理进行分析的结果表明,长6和长8储层的敏感性为改善—弱酸敏性。绿泥石膜的溶蚀作用是造成改善型储层的主要原因;绿泥石与盐酸的反应过程中,反应残余的绿泥石晶片堵塞喉道,这是形成弱酸敏型储层的主要原因。对酸敏残液分析结果表明,在一定时间内不可能形成Fe(OH)3沉淀及堵塞喉道。因而,在储层酸化过程中应注入足量的酸化液,使残余物发生完全反应。但酸化液不宜在地层中滞留时间太长,否则易形成沉淀,从而降低渗透率。

The reservoir characteristics and acid sensitivity mechanism of Chang 6 and Chang 8 reservoirs in the Mesozoic Yanchang Formation of Ordos Basin were analyzed by using some methods such as casting body slice image analysis,XRD, SEM, EEDS and ICP-AES. The results showed that there was amendatory weak damage resulted from acid sensitivity in Chang 6 and Chang 8 reser- voirs. The corrosion of chlorite membrane resulted in the evident improvement of microscopic pore structures. In the reaction process of chlorite with hydrochloric acid, remnant chlorite fell off from the wall of pores and jammed the throat, which is the main reason for weak sensitivity of the reservoirs in these regions. The sensitivity test showed that the remnant chlorite was impossible to form Fe（OH）3 precipitation in the simulative system. In the fracturing process, the adequate standard acidizing fluids should be injected into fractured wells in order to ensure the complete reaction of chlorite. The standard acidizing fluids only stay short time to avoid increment of acid value of fluid and forming precipitation.