Study On Damage Mechanism And Simulation Model Of Sandstone Reservoir

Formation damage is a phenomenon that productivity declines and even losses caused by human factors happens from opening the reservoir to production. It occurs in various stages of reservoir development, including production, drilling, hydraulic fracturing, workover and so on. Therefore, in order for effective exploitation of oil and gas reservoirs, it is necessary to select and establish suitable laboratory experiment and mathematical model to understand, evaluate, diagnose, treatment, control and prevent of formation damage.This paper focuses on the damage caused by drilling fluid, clay hydration expansion, particle migration and inorganic scaling in sandstone reservoir, mainly carried out the following works:(1) On the basis of the analysis of drilling damage mechanism, this paper established a cake model, a damage radius model, and a damage permeability model. Combined with the Furui horizontal well skin factor model, this paper solved the degree and range of drilling fluid damage of horizontal well in non-uniform reservoir.(2) Based on the clay hydration expansion mechanism analysis, combined the empirical formula of critical salinity with the clay hydration expansion damage equation, the degree of damage can be determined.(3) Based on the analysis of particle transport mechanism, this paper established a particle migration model. By analyzing the torque balance of individual particles, a continuity equation that considering particle retention, strain and release was established. This model can solve the concentration of particles at different times and locations and can also solve the particle migration damage when combining with Carman-Kozeny model and Civan permeability decline model.(4) This paper describes the inorganic scale damage mechanism for two aspects:the formation of inorganic scale and influencing factors of inorganic scale precipitation. By using Oddo-Tomson SI method, the maximum amount of calcium carbonate scaling prediction equation, scaling radius model and permeability decline model, the damage of calcium carbonate scaling can be simulate.(5) A case analysis of kinds of formation damages for well M in a Middle East oilfield was conducted. By using numerical reservoir simulation methods, this paper simulated the production of well M before and after damage.