Research On Recognition Of High Permeable Channel In Water Flooding Sandstone Reservoir

The formation structure of heterogenous unconsolidated sandstone reservoirs has changed distinctly after the long-term high speed water-flooding. The effects of injected water to pore structure, rock skeleton granule, bond and reservoir fluids, make formation permeability increase and pore throat radius increase, thus high permeability or terribly high permeability zones come into being in reservoir, namely preferential percolation path. In reservoirs existing preferential percolation path, injected water cyclically produces inefficiently along water channel, so that the utilization efficiency of the injected water is lower, meanwhile the pore volume swept by water driving is reduced, and the improvement of oil recovery and development benefit is seriously affected.From reservoir property variation to dynamic development, the forming mechanism of high permeable channel in sandstone reservoir by waterflooding has been analyzed, as well as the impact of different factors on the formation of high permeability channel. Different roles that geological static and dynamic development play in sandstone waterflooding are recognized.On the basis of selecting main factors, while considering the varying parameters, the conceptual model is established. According to the given range of parameters, the criterions of high permeable channel are determined. By setting the range of different factors and using single factor design, the impact of permeability ratio, vertical and horizontal permeability ratio, oil viscosity, water injection rate, injection-production spacing and injection-production ratio on the high permeability channel are analyzed. By using orthogonal experimental design, the relative weight of major factors is quantitatively analyzed, providing a comprehensive reference for subsequent identification.According to the simulation results of single factors, the single-factor and multi-factor prediction models of high permeable channel formation have been established, with the given scope of the model. For values of different factors, the desired injection PV to form high permeable channel can be calculated. According to the actual stage of reservoir development, whether the high permeable channel has been formed and the degree of development could be roughly judged.While in the association analysis of oil and water, splitting dynamic data by traditional stratigraphic coefficient method has been improved using seepage resistance method, and different dynamic system analysis methods of tracing high permeability channel direction has been proposed, such as correlation analysis, rank correlation coefficient method, multiple linear regression method. In practical application, comprehensive use of various methods should be made to ensure more accurate results.Taking the actual field as example, the high permeable wells are identified by using fuzzy recognition and streamline numerical simulation, the directions of high permeable channels are determined by using production dynamic system analysis method, the developing layers of high permeable channels are recognized by using injection and production profile, the high permeable channels in the main sandstone layers are identified and described, the relevant parameters of high permeability channels are calculated by stream-tube method. All the mentioned above could finally form a set of high permeable channel identification method, which is relatively complete.