低粘吸附型酸化缓速剂分子设计及缓速机理研究

The gelled acid can reduce the speed of the acid-rock reaction rate by its high viscosity which can decrease the transfer of hydrogen. But, the viscosity of the system mentioned above was too high to be injected into the reservoir and also has poor properties of shear resistance and temperature resistance. Besides, after construction, residual acid with high viscosity which was difficult to flow back would cause the secondary damage to the reservoir. Therefore, we design a retarder of acid-rock reaction speed with the effect of adsorption and low-viscosity by varying different absorbing, forming membrane and auxiliary monomers, and adjusting polymerization methods and process. We focus on the properties of reduce the speed of the acid-rock reaction rate, temperature resistance, salt tolerance, acid resistance and shear resistance. We would establish adsorption model by testing the dissolution of rock at different times, analysis the functional groups, element content, adsorption and microstructure of rock surface after reaction. Then, we can get the adsorption behavior of retarder agent on the rock surface, the mechanism of reducing the acid-rock reaction, analysis the damage of the retarder agent on reservoir. By analysis the change law of the viscosity, filter loss of the acid fluid system, and the acidizing effect of different reservoirs and cores with different pore throats, we can get the scope of application of retarder agent. This project provides a new idea for acid retarder agent and the results will provide theoretical guidance and technical support to the development of low-viscosity and adsorption acid retarder agent.

稠化酸依靠粘度阻碍氢离子运移达到缓速，但酸液体系粘度高，注入困难，抗温、抗剪切能力差；残酸粘度高，残渣多，返排不彻底，二次伤害大。针对上述问题，本项目拟通过分子设计，选取不同类型吸附单体、成膜单体、辅助单体，通过调控聚合方式和聚合工艺，聚合出一类分子量较低的低粘吸附型酸化缓速剂，并研究缓速剂的缓速效果，抗温、抗酸、抗剪切能力；通过缓速剂在不同时间点下对岩石的溶蚀速率，溶蚀后岩石表面物质的官能团、元素含量、吸附量、表面形态的变化等实验数据，建立吸附模型，推导缓速剂在岩石表面的吸附行为，提出缓速剂的缓速机理，剖析缓速剂对岩石的伤害情况；探讨低粘吸附型酸化缓速剂的粘度、滤失量及对不同储层、不同孔喉大小岩芯的酸化效果，推断该缓速剂的适应地层。该项目的实施可为酸化缓速剂提供一条新的研究思路，研究结果将为低粘吸附型酸化缓速剂的发展提供理论指导和技术支持。

随着油气田开发的不断进行，致密超致密油气储层占比越来越高，要想实现稳产增产，就必须对储层进行工艺改造。酸化是常用的方法之一，但现用酸液体系存在粘度高，注入返排困难，抗温抗剪切能力差，残渣多，二次伤害大等缺点。本项目从酸岩反应机理出发，依据分子设计原则，选取不同类型单体，通过不同聚合方式和单因素优化法，确定最优聚合条件，制备出三种不同类型的低粘吸附型酸化缓速剂。其中非离子酸化缓速剂最优聚合条件为：AM∶APEG∶OM=30.0∶0.3∶0.1（mol），单体浓度15.0wt%，引发剂加量0.25wt%，反应温度50.0℃，时间6.0h，乳化剂OP-10加量7.0wt%；阳离子酸化缓速剂最优聚合条件为：AM∶APEG∶DMC=20.0∶1.0∶4.0（mol），疏水单体加量0.7wt%，单体浓度25.0wt%，引发剂加量0.3wt%，反应温度50.0℃，时间6.0h；两性酸化缓速剂最优聚合条件为：APEG∶DMAAC-18∶SSS∶AM=2.0∶1.5∶0.5∶96.0（mol），单体浓度30.0wt%，引发剂加量0.3wt%，反应温度50.0℃，时间5.0h。借助红外、核磁、凝胶渗透色谱等对缓速剂分子结构进行表征，三种酸化缓速剂结构与设计相符，且分布宽度指数均小于3，分子量不大。性能评价结果显示：随着缓速剂加量的增大，三种缓速剂均能有效延缓酸岩反应的进行；在90℃的反应温度下，酸岩反应时间可延长至120min；在盐含量为5000mg/L的情况下，依然具有良好的缓速效果，用低粘吸附型酸化缓速剂配制的缓速酸溶液粘度低，大约在15mPa•s左右，有利于酸液泵入和返排；缓速剂在岩石表面的吸附热力学模型符合Freundlich模型，说明缓速剂在岩石表面是多分子层的吸附，而吸附动力学属于准二级动力学控制；吉布斯自由能ΔG和吸附焓变ΔH均小于0，说明吸附过程是一个放热的自发过程；通过缓速机理发现：该缓速剂是通过吸附成膜的方法来实现缓速效果的；测试酸化工作液体系在100℃的抗酸稳定性，发现阳离子缓速剂酸液体系抗酸稳定性好，6h都不会出现沉淀。该项目的研究为目前酸化工艺中存在的部分问题的解决提供了一些研究思路，也为低粘吸附型酸化缓速剂的进一步应用提供了理论支撑。