Research On Heat Resistance And Salt Tolerance Of Composite Profile Control System

The geng 83 block of Jiyuan oilfield is a low porosity and permeability, more developed fracture reservoir. From the view of development of dynamic reservoir, the water break into the oil well fast, and the water cut increase sharply until water-flooded after water breakthrough on the main direction of crack. The oil wells of side direction have a small effective degree and low capacity. In order to improve the water-flood efficiency and increase water swept area and realize the target of precipitation and increasing oil, combine with the geologic feature and high formation water salinity of geng 83 block the laboratory research of composite profile control system is carried out. The high intension preformed gel particle and weak gel which have a good injectivity and adjustable gelled time are selected to serve as composite profile control system. The formulation optimization and performance evaluation are separately carried out to improve their temperature and salt resistance.Performed gel particle is a monomer polymerized product. The effect of each component on water absorption of preformed gel particle has been researched. The optimized formulation is screened out, initiator:0.04%, crosslinker:0.04%, flexibilizer: 10%, acrylic acid:2.5%, monomer gross:30.0%, neutralization:20%. The performance evaluation of the optimized formulation performed gel particle is carried out. The swell multiples of performed gel particle are respectively 100 times and 15.8 times in pure water and simulation formation water. Water-retaining property keeps above 80% after placing 120 days under the condition of reservoir. The stemming ratio of gel particle reaches up to 99% through sand packs physical simulation experiments, and the stemming ratio keeps around 91% after prolonged injecting 30PV simulation formation water.Weak gel synthesised by low concentration of polymer and crosslinking agent, the crosslinking colloid has flow capacity and viscosity. Designing orthogonality and level experiments, the research of each component of weak gel is carried out, and the optimized formulation is polyacrylamide 0.15%, utotropin 0.03%, resorcinol 0.015%, auxiliary crosslinking agent 0.03%, ammonia chloride 0.3%. Aiming at evaluating the optimized formulation of weak gel, this weak gel has a good temperature and salt resistance and shearing resistance. Weak gel viscosity remains above 70% under the condition of simulation reservoir. The stemming ratio of weak gel reaches up to 97% through sand packs physical simulation experiments, and the stemming ratio keeps around 93% after prolonged injecting 30PV simulation formation water.To research the injectivity and sealing effect of profile control system, the injection modes and slug combinations are researched. When the gel particles are injected first, the injectivity of profile control are better. While the plug is 0.5PV gel particle and 0.5PV weak gel, the sealing effect of composite profile control system is best.Six water injection wells on crack main direction are selected from geng 83 block. The field tests of composite profile control system are carried out. The injection pressure is obvious rising after profile control. The water absorption index curves move up, and their slopes turn large. The results indicate that profile control system plugs effectively to fracture. According to the dynamic data of responding oil well, the effective well occupy 48.9%, daily incremental oil is 15.8t/d, cumulative incremental oil reaches 4025.4t, and the increasing oil and decreasing water obtain a good effect.