Research On Injection Parameter Optimization Of Self-generating Foam Plugging In Edge Water Reservoir

In the late stage of water flooding in the A oilfield,some blocks have entered the medium-high water cut-off stage,and inefficient or ineffective recycling of injected water is becoming more and more serious,therefore it is increasingly difficult to control water and stabilize oil.Although,the previous profile control work has slowed down the water-cut rate to a certain extent,the effect is getting worse after rounds of operation,so it is necessary to carry out water plugging work in oil well immediately.Considering the difficulties in water plugging on the offshore platform in the H block of the A oilfield,such as limited work space,the difficulty of fresh water supply and replenish the foam gas source,the technology of self-generating foam is proposed to block off water.The technology of self-generating foam is a compound of the self-generating gas and foam to plug the high permeable layer and control the water channeling,so as to achieve the goal of controlling water and stabilizing oil production.Self-generating foam technology is an oil recovery technology proposed in recent years,generally using CO2 as the gas phase,and the technology was mainly used for water profile control with steam stimulation or steam flooding in heavy oil reservoirs.However,there is little research on the influencing factors of plugging performance and injection parameters of self-generating N₂ foam system.The study investigates the research and application of self-generating foam systems in domestic and foreign oil fields,optimizes and evaluates the self-generating foam systems that is applicable for the working site,and the system formula is determined as:23.26%of NH₄Cl+30%of NaNO₂+0.1%of C₆H₈O₇·H₂O+0.6%of COSL-3 foaming agent+0.3%of HS-type HPAM foam stabilizer.Experiments are conducted to simulate the plugging performance of self-generating ordinary foam and self-generating enhanced foam,finding that compared with the self-generating ordinary foam system,the self-generating enhanced foam has better plugging ability and a selective plugging effect in heterogeneous formation,and mainly blocks the middle and back parts of high permeability formation.In view of the serious formation heterogeneity and edge water in Block H of the A oilfield,an experimental apparatus is designed to optimize the injection parameters of the self-generating foam system,such as slug combination,slug size,and injection volume,et al.The optimized injection parameters are:pre-slug+self-generating enhanced foam;optimized injection volume is 0.05PV pre-slug+0.3 PV self-generating enhanced foam;and the optimized injection cycle is three cycles.The experiment shows that the self-generating enhanced foam's comprehensive enhanced oil recovery rate could reach 24.85%.Finally,the experiment adopts the parallel sand pack pipes model and the three-dimensional visualization model to study the water plugging effect of the self-generating foam system under different formation conditions and different well conditions,providing some theoretical guidance for the field application of self-generating gas foam system.