Study On New Method For Controlling The Formation Damage Associated With Fines Migration In Deepwater Unconsolidated Sand Reservoirs

Reservoir damage caused by fines migration is one of the main reasons leading to the reduction of oil and gas production in deepwater unconsolidated sandstone reservoirs.Therefore,there is an urgent need to propose a new method to control the reservoir damage associated with fines migration in deepwater unconsolidated sand reservoirs.In this paper,based on the latest research progress in the field of nanomaterials,the experiments designed to evaluate the effect of nanoparticles on the formation damage associated with fines migration was introduced,the interaction mechanism between fine particles and formation pore walls adsorbed by nanoparticles was explored,and the mechanism of nanoparticles controlling fines migration was revealed.The nanoparticle which is suitable for controlling fines migration damage in deep-water unconsolidated sandstone reservoir was optimized as reservoir protective agent.A set of drill-in fluids suitable for protecting deepwater unconsolidated sandstone reservoirs was constructed.By means of XRD and SEM,the mineral composition,microstructure and pore permeability characteristics of deepwater unconsolidated sandstone reservoirs in the South China Sea were analyzed.The results showed that the lithology of the reservoir is lithic quartz sandstone with good physical properties.The reservoir is a typical high porosity and high permeability reservoir.The cementation of rocks is relatively unconsolidated.The skeleton mineral of rock is mainly quartz.Kaolinite and quartz microcrystalline mineral particles are distributed on the surface of pore and skeleton.The results of flow velocity sensitivity experiment showed that the reservoir was strong velocity sensitivity.The mechanism of reservoir damage is that the mineral particles are easy to fall off and migrate under the effect of various kinds of external factors.An experimental method for simulating the adsorption and release process of formation fine particles on the rock wall surface was optimized.The control effect of nanoparticles on formation fines migration was evaluated.The experimental results showed that nanoparticles can effectively control the migration of fine particles in reservoir rock channels.Formation fine particles can be adsorbed and fixed on the rock pore walls treated by nanoparticles.Among them,the quartz sand porous media treated by SDNP-1 had the highest adsorption efficiency,which indicated that it has a better effect on controlling the migration of formation fines.Based on the basic principles of colloidal chemistry and mechanics,the surface element integration method was used to establish the interaction energy analysis model between the formation fine particles and the rock pore walls treated by nanoparticles.The determination conditions were given,whether formation fine particles were adsorbed or released.Scanning electron microscopy(SEM),atomic force microscopy(AFM),Zeta potential measuring instrument and other instruments were used to test and analyze the effects of nanoparticles adsorption on the morphology and electrical properties of rock pore wall surface.The effects of nanoparticles adsorption on the heterogeneity of rock pore wall surface was discussed.On this basis,the total interaction potential between the formation fine particles and the rock surface adsorbed by different nanoparticles under different ionic strength conditions was quantitatively calculated and compared.The microscopic mechanism of nanoparticles controlling fines migration was revealed.The results showed that the total potential energy of formation fine particles and rock pore walls decreases,the repelling barrier decreases or even disappears,and the attractive potential energy increases,which promotes the adsorption and fixation of formation fine particles.Nanoparticles can form an adsorption layer on the rock surface,enhance rock surface heterogeneity,provide high surface activity characteristic adsorption points for reservoir particles,and effectively control formation fines migration reservoir damage.Based on the analysis of the reservoir damage mechanism and protection measures of deep-water unconsolidated sandstone reservoirs,the nanoparticle SDNP-1 was used as a reservoir protection agent to optimize a set of drill-in fluids that can better protect deepwater reservoirs.