Research On The Optimized Formulation And Selective Water Plugging Mechanism Of Dual Crosslinked Gel Plugging Agent

As oilfields of china turn into the later stage of high water cut,the phonomenon of producing water in oil well become so seriously that oil production falls sharply and water cut increases to a great extent,what is worse,it sometimes may lead to "flooding".Aiming at the problems of low water-plugging rate and poor selectivity of low permeability-fracture reservoirs,it is proposed to design the selective water-plugging agent with the view of double cross-linked polymer gel to improve the cross-linking degree of blocking agent and increase the choice of blocking agent.It can direct the internal network polymer to firstly crosslink under the conditions of the ground,and then to secondly crosslink external network polymer under the formation of high temperature.eventually forming a high strength double crosslinked gel type selective plugging agent.In this paper,the double cross-linked gel system is selected and researched.The organic chromium crosslinking agent is chosen as the first cross-linking agent.The hyperbranched polyacrylamide is used as the main agent of the first-crosslinking system.The phenolic resin system is used as the second cross-linking agent.The cationic polyacrylamide is used as the main agent of the second-crosslinking system.The plugging formulation is 1000mg/L hyperbranched polyacrylamide + 300mg/L internal network cross-linking agent + 800mg/L stabilizer + 2000mg/L cationic polyacrylamide + 2000mg/L external network cross-linking agent + 150mg/L enhancer,and evaluate the system performance.Finally,the selective water shutoff mechanism of the double cross-linked gel-type plugging agent is analyzed in this paper: 1.The double cross-linked system has more dense mesoporous pores and full structure,and the outer network is filled in the gap of the internal network.Water retention and viscoelasticity is very good;2.Parallel core simulation experiments show that double cross-linked gel can be selected according to the size of the permeability of the fracture,a good selectivity,the main closure of large cracks,the system of water blocking rate is much greater than the oil blocking rate;3.The high sealing performance of the gel system comes from physical blockage and surface adsorption,and the surface wettability of the rock mainly affects the surface adsorption of the gel system.4.The double crosslinked gel has a high degree of swelling in the simulated formation water,The water-swellable gel has a high shrinkage in crude oil.By analyzing the mechanism of the double crosslinking gel system and the final stage of the gelation effect and efficient plugging mechanism,the mechanism of selective water shutoff is discussed,which provides theoretical support for the application of double cross-linked gel-type plugging agent,and provide technical support for hig and stable production.