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虽然砂岩酸化已经在近十年取得很大进展,但仍面临挑战。它们包括:多种同时存在的地层伤害;不确定的岩石矿物学特征;多流体和抽吸阶段;流体和地层矿物间的复杂化学反应;高温下快速的动力反应。其他因素:酸液区域覆盖率不够;活性酸穿透深度有限;酸岩反应引起岩石胶结变差;酸液乳化作用和形成酸渣;腐蚀以及环保问题。这些因素导致砂岩酸化作业的成功率低,特别是在对酸敏感、富含黏土及碳酸盐的高温砂岩地层。文章回顾了工业中的一些实践并提出一种可提高砂岩酸化作业成功率的新方法。该方法需要用地球化学模拟器通过为地层选择最安全的流体、优选用酸量及射孔段以及一种可以简化酸化作业和降低地层伤害的酸液来“设计成果”。间歇反应研究表明,新的流体同铝硅酸盐的反应比常规无机酸的反应慢得多,从而防止了二次、三次沉淀。岩心流动实验表明新流体防止近井筒地带的弱胶结问题通常出现在使用HF酸化体系的砂岩高温酸化作业中。现场岩样实验和地球化学模拟证实了室内研究结果,特别是对于富含黏土和碳酸盐的砂岩地层的研究。大量的室内研究也表明了该流体能减小乳化作用和酸渣形成趋势;减小对设备的腐蚀;更加环保(其pH值几乎为中值)以及更好地适应地层条件。
Although sandstone acidification has made great strides in recent ten years, it still faces challenges. They include: multiple simultaneous formation damage; uncertain rock mineralogy; multiple fluids and aspiration stages; complex chemical reactions between fluids and formation minerals; and rapid dynamical reactions at high temperatures. Other factors: Insufficient coverage in the acid zone; limited penetration depth of active acid; deterioration of rock cementation due to acid rock reaction; acid emulsification and acid formation; corrosion and environmental issues. These factors lead to a low success rate of sandstone acidification operations, especially in high temperature sandstone formations that are acid sensitive and rich in clay and carbonate. The article reviews some of the practices in industry and suggests a new approach to improve the success rate of sandstone acidification operations. The method requires geochemical simulators to “design outcomes” by choosing the safest fluid for the formation, preferably with acid and perforated sections, and an acid that simplifies acidification and reduces formation damage. Batch reaction studies have shown that the new fluid reacts with aluminosilicates much more slowly than conventional mineral acids, preventing secondary and tertiary precipitations. Core flow experiments show that the new fluids prevent the weak cementing of the near wellbore zone usually occurs in high temperature acidification of sandstone using HF acidification systems. In-situ rock samples and geochemical simulations confirm laboratory results, especially for clay and carbonate-rich sandstone formations. Numerous laboratory studies have also shown that this fluid can reduce emulsification and sourdough formation trends; reduce corrosion of equipment; make it more environmentally friendly (its pH is almost median) and better adapt to formation conditions.