定时爆破释放型微胶囊的设计合成及其应用研究

Fracturing and profile control and water shutoff are important technical means of improving oil recovery in low permeability reservoirs. However, the existing fracturing fluid and profile plugging agents generally have the problem of gel breaking and gelling time uncontrollable, resulting in the crude oil recovery difficult to be improved. This project draw lessons from timing bomb blasting principle and propose a new idea to prepare ammonium presulfate, which is applied to not only fracturing fluids but also profile plugging agents, into timed-release microcapsules. In this way, the gel breaking time of fracturing fluids and the gelling timing of profile plugging agents will be controlled. Polyaniline or polypyrrole is used as the shell materials of the microcapsules. Petroleum resins, nanometer inorganic particles and water-disintegrable resins are used as the dopants of the shell materials. A series of microcapsules containing ammonium persulfate cores with timed-release properties were synthesized by continuous titration method. The release time of the microcapsules can be controlled precisely by changing the sizes, morphologies, shell thicknesses, shell composition, pH values and temperatures. The interface and interaction principle between dopants and polyaniline (or polypyrrole) is revealed before and after releasing of the microcapsules. The formation and timing-release mechanism of the microcapsules are also studied. Finally, the timing gel breaking type fracturing fluids and timing glue type profile plugging agents are obtained, which can meet the needs of a variety of oil wells.

压裂和调剖堵水是低渗透油藏提高原油采收率的重要技术手段，但现有的压裂液和调剖堵水剂普遍存在破胶和成胶时间不可控的问题，导致原油采收率难以进一步提高。本项目借鉴定时炸弹的定时爆破原理，将用作压裂液破胶剂和调剖堵水剂中聚合引发剂的过硫酸铵制备成定时爆破释放型微胶囊，实现压裂液定时破胶以及调剖堵水剂定时成胶。拟以聚苯胺（或聚吡咯）为壳材，石油类树脂、纳米无机颗粒、遇水可崩解材料为壳材掺杂物，通过连续滴定法合成一系列定时爆破释放型过硫酸铵微胶囊，通过尺寸、形貌、壳厚、壳组成以及温度、pH值等参数的调控实现过硫酸铵起始释放时间的精确控制。揭示微胶囊释放前后掺杂物与壳材界面的组成变化规律及相互作用原理；阐明微胶囊的形成和定时爆破释放机理，为定时爆破型微胶囊的理性设计奠定坚实的理论基础。最终研发出可用于多种油井环境的定时破胶型压裂液和定时成胶型调剖堵水剂。

我国原油储量中低渗透油藏占据较大的比例，这将成为我国今后相当长一段时间内的主要勘探开发资源。而低渗透油藏的自然产能处于较低的水平，一般很难达到工业油流的标准，所以需要通过压裂或调剖堵水等技术改造才能对低渗透油藏进行有效开发。过硫酸铵作为破胶剂和聚合引发剂被广泛使用在压裂液和调剖堵水剂中。然而，在压裂液中过早加入过硫酸铵会导致提前破胶，无法携带支撑剂；过晚加入则导致破胶不彻底，给油井带来永久性伤害。过硫酸铵直接加入调剖堵水剂中会导致成胶过快，形成的凝胶受岩石构造、岩石渗透系数等因素的影响，无法被送入油层深部，从而降低调剖堵水剂的作用效率，进而影响原油采收率。若借鉴定时炸弹的定时爆破原理，将用作压裂液中的破胶剂或调剖堵水剂中的引发剂“过硫酸铵”制备成定时爆破释放型微胶囊，可以有效解决上述问题。本项目以过硫酸铵为芯材，利用具有较好热力学稳定性、较高机械强度和致密的聚苯胺或聚吡咯为壳材，通过新颖的无溶剂连续滴定聚合法、原位聚合法等新颖方法合成了一系列定时爆破释放型微胶囊。同时，通过在聚苯胺或聚吡咯壳中掺杂石油树脂、纳米SiO2颗粒等掺杂物，使微胶囊的起始爆破释放时间可通过调节掺杂树脂的种类、氢氧化钠溶液浓度、温度以及掺杂物添加量等进行精确调控，以期满足不同油井条件的使用要求。在合成上述定时爆破释放型微胶囊的基础上，深入研究了掺杂物在聚苯胺（或聚吡咯）壳中的分布规律、掺杂物与聚苯胺（或聚吡咯）相互作用的原理，以及定时爆破释放型微胶囊的形成及控释机理、理化性质等。最终研发出了可用于多种油井环境的定时破胶型压裂液和定时成胶型调剖堵水剂，并为其实际应用奠定坚实的理论基础。