砂岩储层酸化的新型螯合酸液体系研制

砂岩储层基质酸化采用常规土酸体系酸化时存在酸岩反应速度快、有效作用时间短、近井带过度溶蚀等问题,且酸化过程中产生的氟硅酸、硅铝酸、氟化钙沉淀,硅胶薄膜扩散及沉淀,会对储层造成严重的二次伤害。为此,研制了一种对岩石骨架溶蚀能力强,同时又能对酸化可能出现的沉淀有效抑制的新型可降解有机螯合酸体系。通过实验对该种新型螯合酸的性能进行了分析,主要考察螯合酸对钙、铁、铝、镁等容易成垢的金属离子的螯合能力,螯合酸缓速性能、腐蚀性能、酸化流动效果及微观扫描电镜分析等。结果表明:该螯合剂与常规无机酸配伍性好,对铁、钙、铝、镁离子螯合能力强,腐蚀速率低,缓速性能好,岩心酸化流动后渗透率提高幅度大,且酸化前后岩心端面扫描电镜结果显示该新型螯合酸酸化能够有效稳定黏土及微粒运移,同时也能够形成明显的溶蚀孔洞。

Development and research of a novel chelating acid system for sandstone reservoir acidification

Conventional mud acidification applied to sandstone reservoir matrix acidification is accompanied by such problems as accelerated acidic/rock reaction rate, limited effective reaction time, and excessive corrosion near wellbore zones. Moreover, the fluosilicic acid, aluminium silicate, calcium fluoride precipitation, and diffusion and precipitation of silicon gel membrane may cause serious secondary damage to reservoirs in the acidification process. In view of this, a new degradable organic chelating acid was successfully developed. This acid can not only effectively dissolve the rock matrix, but inhibit these precipitates. A study was made for testing the performance of this new chelating acid, mainly focusing on the chelating capability to calcium, iron, aluminum, magnesium and other metallic ions which are most liable to scale deposition, the retarded capability, corrosivity, and acidification and flowing effect of the chelating acid, as well as the micro scanning electron microscopy analysis. The results showed the following advantages of the chelating acid: sound compatibility with conventional inorganic acids, great chelating capability to calcium, iron, aluminum, magnesium, and other metallic ions, low corrosion rate, excellent retarded capability, and increasing permeability after coreflood treatment. And from the display results of core end SEM conducted before and after acidification, we found that this newly developed chelating acid is capable of effectively controlling grain and clay migration and solution holes are obviously formed.