Preparation And Properties Of High Strength Polyacrylamide Composite Gel

At present,oil and natural gas resources have been developed on a large scale,and the water content of area where oil production is relative easier has become higher and higher,so that the development of low permeability reservoirs has become a key point.Refracturing technology is widely used in oil fields,but with more and more times of fracturing,the validity period becomes shorter,and the production increment of each fracturing decreases,the effect of refracturing becomes worse.Turnaround fracture technology can solve this problem.The turnaround fracture technology is to inject temporary plugging agent into the formation to form temporary plugging layer.By increasing resistance,the fracturing fluid will flow from high permeability area to low permeability area as result the low permeability area can be fractured.This technology is simple and effective,meanwhile plugging agent with high strength are needed to ensure the performance.In this paper,acrylamide monomer,starch,and laponite are used as main raw materials,and N,N-methylenebisacrylamide(MBA)is used as a cross-linking agent to prepare starch grafted polyacrylamide strong gel and polyacrylamide-laponite composite gel.At the same time,degradable starch graft polyacrylamide composite gel was prepared by using ester crosslinking agent.The rheological properties,compressive properties,tensile properties and adhesive properties of the composite gel were measured using HAAKE Rheometer,texture analyzer and adhesion testing device,and the microstructure of the composite gel was observed by scanning electron microscope.The results showed that the addition of starch and laponite effectively enhanced the viscoelasticity,tensile/compressive properties and adhesion properties of the composite gel greatly,and high strength starch grafted polyacrylamide composite gel and polyacrylamide-laponite composite gel have been prepared.As the concentration of the main agent acrylamide monomer increases within a certain range,the viscoelasticity,compressive strength,and tensile stress of the composite gel increase.the tensile properties of composite gel could be effectively enhanced by adding starch and laponite.Especially the addition of laponite,can make the composite gel stretch to 10 times its original length without breaking.In the composite gel system,the optimal amount of crosslinking agent is 0.3% of the main agent,and the optimal amount of initiator is0.2%.For the degradable starch grafted polyacrylamide composite gel,the concentration of the main agent,the reaction temperature and the p H value of the gel base fluid have a certain influence on the degradation time of the gel.The degradation time of the composite gel formed by 4% acrylamide,4% starch and cross-linking agent PEGDA200 at 70 ? is about 10 days.