注入水结垢对储层的微观影响特征研究

Study on Microscopic Influence Characteristics of Injection Water Scaling on Reservoirs

针对尕斯库勒油田N1-N21油藏注水开发引发的储层结垢、注水井欠注等问题,通过室内岩心流动实验,结合核磁共振、SEM、XRD等技术,分析了油藏开发中后期,温压条件的变化和流体的不配伍导致难溶盐过饱和,形成结垢沉淀型储层伤害的问题。结果表明,结垢对岩心渗透率的损害可分为诱导期、伤害期和稳定期,物性较好的岩心渗透率损害较大;NMR曲线显示,垢的充填和堵塞作用使得渗流空间减小,吸附孔喉、部分微孔喉和细小孔喉的数量相对增加,部分渗流通道被堵塞,主要表现为谱峰降低和曲线左移;XRD结果表明,实验中垢型为碳酸钙垢,垢的主要成分为方解石和霰石;SEM显示岩心不同位置压力、流体的流速以及模拟水成垢离子浓度的差异,导致了不同物相及形貌的碳酸钙垢的形成,压力、流速较低的出口端会形成发育较好、粒径较大的半自形和菱形方解石。

Aimed at the problems of reservoir scaling and under-injection of injection well caused by waterflooding in N1-N2~1 reservoirs of Gasikule Oilfield,indoor core flow experiment is made and nuclear magnetic resonance,SEM,XRD and other technologies are applied to analysis on scaling and precipitation type reservoir damage formed by supersaturation of insoluble salts because of the changes in temperature and pressure con-ditions and fluid incompatibility in the middle and late stages of reservoir development.The results show that the damage of scaling to core permeability can be divided into induction period,damage period and stability period.The permeability damage of cores with good physical properties is greater.The NMR curve shows that the filling and blocking of the scale makes the flow space small,the number of adsorption pore throats,some microporous throats and fine pore throats increases relatively,and some flow channels are blocked,which mainly shows that the spectral peak drops and the curve moves to the left.XRD results show that the scale is calcium carbonate one dominated by calcite and aragonite.SEM shows that the difference on pressure at different positions of the cores,flow rate of the fluid and scaling ion concentration of simulated water leads to the formation of calcium carbonate scale with various phases and shapes,and the outlet end with low pressure and flow rate will form well-developed semi idiomorphic and rhombic calcite with larger particle size.