Experimental Studies On Percolation Mechanism In Low Permeability Conglomerate Reservoirs

The glutenite reservoir is a special oil and gas reservoir with abundant reserves.Due to its special pore structure and strong heterogeneity,the recovery rate is low.Because of its seepage pattern is different from ordinary sandstone reservoirs,an in-depth study of the seepage pattern of glutenite reservoirs is of great significance to the development of the reservoir.Taking the Yanjia block of Shengli oilfield as the research object,the basic physical properties of the on-site cores were measured,the pore characteristics of glutenite were studied using a high-pressure mercury porosimeter,and the pore structure and pore size distribution of the glutenite cores were analyzed.The threshold pressure gradient test of oil and water singlephase was carried out using the flow-pressure difference method,the JBN formula considering the threshold pressure gradient was deduced,and the phase permeability curve of the glutenite core considering the threshold pressure gradient was drawn,and the seepage pattern of lowpermeability glutenite reservoirs was analyzed;the experimental study of water displacement on glutenite cores was carried out,and the effects of permeability difference,average permeability,flooding rate,and injection pore volume multiplier on the water drive effect were analyzed.The experimental results show that the Yanjia block of Shengli oilfield belongs to the ultralow porosity and ultra-low permeability reservoirs.The mercury injection experiment found that the displacement pressures of the reservoir are different,and the pore throats are complex and diverse with a large proportion of fine pore throats,the pore fractal dimension is close to 3and the core sortability is poor,and the reservoir heterogeneity is serious.The expression of single-phase minimum and maximum threshold pressure gradient and mobility is regressed from the single-phase threshold pressure gradient study of the core,the core threshold pressure gradient chart was drawn,and the characteristics of the single-phase threshold pressure gradient and seepage characteristics were obtained;relative permeability curves were drawn using the derived JBN formula based on the threshold pressure gradient,it was found that the oil phase threshold pressure gradient on relative permeability curve was significantly greater than that of the water phase threshold pressure gradient,and threshold pressure gradient will cause the relative permeability curve of oil phase to fall faster and the relative permeability curve of water phase to rise slightly;water displacement experiments on glutenite cores revealed that the permeability difference has an important effect on the model,excessive permeability diffrence will cause low-permeability cores to lag or fail to start.The average permeability and recovery are positively correlated,increasing the replacement rate and increasing the injection pore volume multiplier within a reasonable range can improve the recovery rate of glutenite reservoirs.