Experimental Study On High Strength Gel Water Shutoff Technology

The Bohai oilfield has the characteristics of loose core porosity,serious heterogeneity,high viscosity of crude oil,high average permeability and so on,so it is easy to form the flow through water flooding which restricts the water flooding recovery seriously.Water plugging and profile control is an effective technique to solve the flooding channeling in high permeability.It is widely used in continental oilfield which is very important to improve the development effect of water flooding reservoir.Compared with the continental reservoir,Bohai reservoir is not only more serious reservoir heterogeneity,but also easy to cause damage to the reservoir rock structure,which further exacerbated the reservoir heterogeneity,because of the single well injection production intensity.Therefore,it is difficult to adapt to the conditions of Bohai reservoir by the existing water shutoff and profile control technology.In this paper,The performance evaluation and water plugging effect and optimization of process parameters of water plugging agent was studied through instrumental analysis,chemical analysis and physical stimulation techniques,guided by physical chemistry,polymer materials and reservoir engineering theory,based on Bohai reservoir characteristics and fluid properties.The results show that the high strength gel plugging agent of starch graft copolymer can form the gel system with high strength,but the gelling environment has a great influence o n it..Compared with the conventional conditions,the gel effect of water plugging agent in the porous media is poor.However,even the formulation of water plugging agent can form a high strength gel system in porous media,the gel effect in the simulation of the actual formation environment of artificial core is still not ideal.Therefore,in order to obtain the best water plugging formula to meet the water shutoff conditions of the SZ36-1 reservoir in Bohai oilfield,a lot of experiments are carried out.Finally,the optimum formulation of the water shutoff agent is determined by the viscosity,permeability and displacement experiment:”4% starch+4% acrylamide+0.036% crosslinking agent+0.012% initiator+0.002% sodium sulfite”.Through the experimental research and technical and economic analysis of the core displacement,the optimal combination of the "profile control and water shutoff" : 0.05PV-0.075 PV profile control agent(Cr3+ polymer gel,Cp=3500mg/L,polymer: Cr3+=120:1-180:1)+ water shutoff agent[0.025 PV Lead slug(4%starch)+0.025PV-0.075 PV Plugging agent+0.025 PV Protective slug(4%starch)+0.05 PV Displacement plug(0.15%polymer solution)].The plugging mechanism of starch graft copolymer water shutoff agent was studied by the experiment of flow rate at last.