Visible Simulation Of The Optimum Position Of Plugging Agents In Different Rhythmic Formations

During the water flooding in unconsolidated sandstone reservoirs, water channeling is easily found as a result of the heterogeneity, which leads to the invalid circle of injected water and low sweep efficiency. Profile control and water shutoff, as an important measure to improve the spread, has played a pivotal role. But field tests showed that successive decline of incremental oil effect emerged after multi-cycle operation, because of the overlapping of plugging agents. So research on the optimum position of plugging agents in different rhythmic formations has great significance for field production.To guide the experiments of physical simulation, 3D conceptual models of geology were founded using ECLIPSE to observe the existing patterns of oil and water in formations with different rhythm and permeability contrast. The results showed that: for positive rhythmic formations, the distribution of remaining oil was concentrated, mainly in formations with medium and low permeability; while for reverse rhythmic formations, it was much more scattered in low-permeability formations at the bottom and second half of the upper formations with high permeability, as a result of gravity; for composed rhythmic formation, remaining oil patterns in depended heavily on the zone allocation. Afterward, explorations of effects with different plugging position were also launched as well.Before the experiments of physical simulation were carried out, a new cheaper and easier-made visual plate-like model, which could be unloaded and used for recycling, was designed based on the existing one. And matching technology was also optimized, which provided a much easier way for macro visible simulation research. With the new model, experiments were carried out to observe the flow line and distribution of oil and water during water flooding process. In view of the results of numerical simulation, physical simulation of different plugging position was also done to observe the micro oil fraction and summarize the regulation of profile control and water shutoff. The results showed that: for positive rhythmic formation with high permeability contrast, multi-cycle operation with different plugging position should be taken in the order of “from shallow to deep” and “from formation with high permeability to medium”; but for formation with medium permeability contrast, deep plugging position in oil reservoirs was the best choice; while for low permeability contrast formation, the chosen position of plugging agents was thought to be near oil well in consideration of economy situation. Gravitational differentiation was beneficial to improve the sweeping efficiency in reverse rhythmic models. When the contrast of permeability was over the force of gravity, the best way to improve oil recovery was separate-zone production; while non-operation method could be considered, as the contrast was low. For composed rhythmic formation, when high permeability zones were at both ends, the plugging agents should be first put into the deep position in the bottom zone with high permeability, and then shallow position was plugging in the top zone with high permeability at the right time; While high permeability zones were in the middle, profile control and water shutoff operations should be carried out simultaneously in both zone in the order of “from shallow to deep”. Finally, the feasible technologies of plugging at fixed point were discussed to provide theoretical basis and reference for field tests.