Hydrodynamic geological effect during the waterflooding of seriously heterogeneous reservoirs

Hu12 Block of the Huzhuangji Oilfield is a typical strongly heterogeneous reservoir. The hydrodynamic geology effect was studied by comparing experimental results of cores before and after waterflooding. The experimental results show that the chemical force of acidic medium accelerates the dissolution of plagioclase, generating new kaolinite crystals in small pore throats at the same time. The chemical force has less impact on carbonate minerals. The physical force of the injected water caused the reduction of the total content of argillaceous minerals and the loss of quartz grains of silt to very fine sizes, which occurred in layers with good physical properties and developed channeling paths. In terms of changes in pore-throats, waterflooding resulted in the increase of the large pore-throats and improvement of percolation conditions, also gives rise to the reduction of pore throat sorting and the aggravation of micro-heterogeneity of reservoir. With respect to variations in reservoir macroscopic parameters, waterflooding leads to the drop of overall average effective porosity by 4.63% and the rise of overall average effective permeability by 8.93%. The physical property changes of reservoirs of different original properties take on obvious “Matthew Effect”.