深水疏松砂岩储层微粒运移损害的控制方法

中国南海深水疏松砂岩油气层钻完井作业中，易发生微粒运移、堵塞，造成储层损害，需要探索微粒运移损害的控制方法。选用南海深水疏松砂岩储层岩样，通过微粒吸附和释放实验以及岩心动态损害评价实验，探讨了纳米材料控制微粒运移损害的作用效果；实验分析了纳米颗粒吸附对岩石表面形貌、粗糙度及电性的影响；利用微粒与吸附纳米颗粒的岩石孔壁之间的相互作用能计算模型，分析了不同离子强度下储层微粒与岩石孔壁之间的总相互作用势能及作用机制。结果表明，纳米颗粒能有效控制深水储层微粒的运移，将其吸附并固定在孔壁表面。随着流体离子强度增加，控制运移的作用效果增强。其中，纳米氧化铝NP-1的作用效果最好，可明显提高深水储层岩心的渗透率恢复值，并且与深水钻井完井液具有良好的配伍性。模型计算结果表明，吸附纳米颗粒后，岩石孔壁与储层微粒之间的总相互作用势能下降，有利于岩石孔壁吸附、固定微粒，原因是纳米颗粒的吸附增加了岩石表面粗糙度及黏附力矩，也影响了表面电荷分布，有利于降低排斥势垒，并使初级势阱加深，提高岩石表面固定微粒的能力。因此，深水钻完井中，可通过加入纳米颗粒、适当提高工作液矿化度来减少微粒运移引起的储层损害。

Control methods for fines migration damage in deepwater unconsolidated sandstone reservoirs

In the drilling and completion operations of deepwater unconsolidated sandstone reservoirs in the South China Sea, fines migration and plugging are prone to occur, causing reservoir damage. Therefore, it is necessary to explore the ways of controlling damages during fines migration. Using rock samples from deepwater unconsolidated sandstone reservoirs in the South China Sea, the control effect of nanomaterials on fines migration damage was investigated by particle adsorption and release experiments and core dynamic damage evaluation experiments; the effects of nanoparticle adsorption on rock surface morphology, roughness and electrical properties were also analyzed; the interaction energy calculation model between particles and rock pore walls adsorbed with nanoparticles was used to analyze the total interaction energy between particles and rock pore surfaces under different ionic strengths and its action mechanism. The results show that nanoparticles can effectively control the migration of deep-water reservoir fines, which are adsorbed and fixed on the surface of pores. The control effect on migration increases with the increasing of fluid ion strength. Among them, the nano-alumina NP-1 has the best effect and can significantly increase the return permeability of deepwater reservoir cores and has good compatibility with deepwater drill-in fluid. Model calculations show that after adsorption of nanoparticles, the total interaction potential energy between rock pore surface and reservoir fines decreases, which is favorable to the adsorption and immobilization of particles on rock pore surface, because the adsorption of nanoparticles leads to an increase in rock surface roughness and adhesion moment, and also affects the surface charge distribution, which is beneficial to reducing the repulsion potential barrier, deepening the primary potential well, and improving the ability of rock surface to immobilize particles. Therefore, reservoir damage caused by fines migration can be reduced by adding nanoparticles and appropriately increasing the salinity of working fluid in deepwater drilling and completion.